Engine Coolant Leak || KOER Test issues - Need Input

Killing Hours

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May 23, 2018
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Hello again stangnet-

So I'm chasing my tail again trying to make sense of a weird cooling & code reading issue. I'll split them into separate questions. Looking for input and ideas from the know it alls. (Looking at you @jrichker @TOOLOW91) :O_o:

COOLING ISSUE:

Info:

Stock gauge (yes, I know it's crap.. get an aftermarket etc etc etc)
New SVE radiator (3 row aluminum blah blah blah)
New Motorcraft thermostat
New lower hose
Headgaskets replaced last month
Lower intake gaskets replaced last month (Felpro 1250 - Intake ports cut correctly and sealed with Ultra Black)
Have done a leak down test on the cooling system with no noticeable drop in the needle and no puddling anywhere that we could see
Used the tester for exhaust leak and didn't change color

Symptoms:

So initially I noticed the the temp rising higher (from slightly below the middle mark to mid-way between the middle mark and 3/4 under hard pulls) than normal so I started paying more attention to the temp and to narrow down my cooling issue. Naturally, I had a bit leaking from the lower intake on the driver side just behind the distributor hole. Ok... lower intake is probably leaking both into and out of the motor due to bad gasket.

Well, made the decision to go ahead and replace and while already that far in... go ahead and replace the head gaskets while I was in there and replace head bolts with ARP for a bit of insurance.

Did the replace, sealed it all up according to guides etc... sealed all the ports, torqued all the bolts etc etc etc... and ... womp womp... still has the same exact issue. This time however, it started exhibiting a different problem. On a cold start, the thermostat seemed to stay closed until the temp went to the 3/4 mark before opening then would cool back to mid mark and back to the initial problem I started with. (running warmer than normal)

So then that got me to thinking that maybe the issue was with the thermostat... so I replaced it with a Motorcraft. While I was in there, I went ahead and replaced what looked like a cheap thin oreillys radiator to the SVE one and also changed out the bottom hose just to be on the safe side..

The car ran great after I burped it and didn't seem to show any leaks the first few drives after changing it all and I thought it must have been a bad thermostat and/or bad/clogged radiator.

But today at work, I noticed a smallish puddle on the driver side front (near the lower hose/radiator cap/reservoir area). This *could* just be overfill and I haven't verified that yet through multiple days of driving and sitting... but here's the biggest kicker to all of this.

Though I know the stock gauge isn't accurate by any means... it has been showing consistently the same behavior on cooler days vs. warmer days. On cooler days, the temp usually runs right on the mid mark.... but in the afternoons when it warms up to around 70+F... it consistently runs below the the mid mark.

Cooler days = Car runs warmer
Warmer days = Car runs cooler

I'm at a loss as to where to even begin looking next other than a poor functioning water pump or something else I'm not aware of. Maybe a clog or bad build up in the motor? Thoughts?

-----------------------------------------------------------------------------------------------

KOER Test:

So in an effort to pull codes, I've run the KOEO (Off) test and pull a codes:
63 - Throttle Position Sensor or circuit
67 - Air conditioner clutch switch circuit (clutch switch was jumpered so most likely the cause)

When I went to run the engine ON test, I get the RPM drop & rise... but then the CEL light just stays solid and the test doesn't go any further. No RPM rise, no nothing... just solid CEL. Not sure what that means... I couldn't find anything online related to it. I very well could have a short somewhere but just wanted to ask to see if there was something else I was doing wrong. (Yes, I pulled the jumper on the clutch switch after the car started to simulate pushing and releasing the clutch)

Any insight would be appreciated. Thanks!
 
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Hey general, been awhile but I have been lurking. ;)

I probably should have pan tested to ENSURE it was actually opening at 190.... but (obviously using the stock gauge).. it appears the thermostat is indeed opening and keeping the temp it's supposed to... in warm weather... just not the same temp in cooler air. Really throwing me for a loop with that.

The attached image shows the place it rides in warmer temps. This is how it always rode prior to me noticing the temp fluctuations. In colder air... it will ride up to the middle mark or ever so slightly above that.

Something else that came up in a conversation with a mechanic friend of mine this evening was how it also idles differently between the hot vs. cold air. In warm air... it holds a perfect 850 - 900 rpm... but on a colder day (50ishF), it idles around 650 - 700.

In that conversation we went back to the ACT, MAF, MAP, O2 (all relatively new with the exception of the MAP & MAF) etc etc etc and their roles in the A/F map and the code being thrown for 63 (TPS) with the key off. We're tossing the idea that there could be a short somewhere and that's reeking havoc on everything. Going to chase this electrical demon down for the time being to eliminate that as any sort contributing issue. Just really annoying and stumped with the reverse order of things. Would expect the opposite from the cooling system.

If that doesn't resolve some issue, will definitely have to get an aftermarket gauge to log numbers and re-approach it with hard data.

Any other input/advice/suggestions I'm all ears.
 

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Not saying this has anything to do with your problem but I've had 2 SVE aluminum radiators and my problems didn't stop until I threw away the junk 16# cap that comes with it and replaced with a good 13# one.
 
Not saying this has anything to do with your problem but I've had 2 SVE aluminum radiators and my problems didn't stop until I threw away the junk 16# cap that comes with it and replaced with a good 13# one.

I had wondered that exact thing when I put the SVE in there. The position of it makes it extremely tight to get to on mine because of the wire looms & the neck sitting down lower than the previous radiator. However, the symptoms were present before the new radiator and after so I'm assuming it's not the radiator or cap at play.

Thanks for the input though, I've got one of those pressure release caps that was on the old I'll throw on there tonight and give it a few runs to just see what happens.
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For reference, I took a couple of pics this morning on the way to work. (50ish F)
 

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Hello again stangnet-

So I'm chasing my tail again trying to make sense of a weird cooling & code reading issue. I'll split them into separate questions. Looking for input and ideas from the know it alls. (Looking at you @jrichker @TOOLOW91) :O_o:

COOLING ISSUE:

Info:

Stock gauge (yes, I know it's crap.. get an aftermarket etc etc etc)
New SVE radiator (3 row aluminum blah blah blah)
New Motorcraft thermostat
New lower hose
Headgaskets replaced last month
Lower intake gaskets replaced last month (Felpro 1250 - Intake ports cut correctly and sealed with Ultra Black)
Have done a leak down test on the cooling system with no noticeable drop in the needle and no puddling anywhere that we could see
Used the tester for exhaust leak and didn't change color

Symptoms:

So initially I noticed the the temp rising higher (from slightly below the middle mark to mid-way between the middle mark and 3/4 under hard pulls) than normal so I started paying more attention to the temp and to narrow down my cooling issue. Naturally, I had a bit leaking from the lower intake on the driver side just behind the distributor hole. Ok... lower intake is probably leaking both into and out of the motor due to bad gasket.

Well, made the decision to go ahead and replace and while already that far in... go ahead and replace the head gaskets while I was in there and replace head bolts with ARP for a bit of insurance.

Did the replace, sealed it all up according to guides etc... sealed all the ports, torqued all the bolts etc etc etc... and ... womp womp... still has the same exact issue. This time however, it started exhibiting a different problem. On a cold start, the thermostat seemed to stay closed until the temp went to the 3/4 mark before opening then would cool back to mid mark and back to the initial problem I started with. (running warmer than normal)

So then that got me to thinking that maybe the issue was with the thermostat... so I replaced it with a Motorcraft. While I was in there, I went ahead and replaced what looked like a cheap thin oreillys radiator to the SVE one and also changed out the bottom hose just to be on the safe side..

The car ran great after I burped it and didn't seem to show any leaks the first few drives after changing it all and I thought it must have been a bad thermostat and/or bad/clogged radiator.

But today at work, I noticed a smallish puddle on the driver side front (near the lower hose/radiator cap/reservoir area). This *could* just be overfill and I haven't verified that yet through multiple days of driving and sitting... but here's the biggest kicker to all of this.

Though I know the stock gauge isn't accurate by any means... it has been showing consistently the same behavior on cooler days vs. warmer days. On cooler days, the temp usually runs right on the mid mark.... but in the afternoons when it warms up to around 70+F... it consistently runs below the the mid mark.

Cooler days = Car runs warmer
Warmer days = Car runs cooler

I'm at a loss as to where to even begin looking next other than a poor functioning water pump or something else I'm not aware of. Maybe a clog or bad build up in the motor? Thoughts?

-----------------------------------------------------------------------------------------------

KOER Test:

So in an effort to pull codes, I've run the KOEO (Off) test and pull a codes:
63 - Throttle Position Sensor or circuit
67 - Air conditioner clutch switch circuit (clutch switch was jumpered so most likely the cause)

When I went to run the engine ON test, I get the RPM drop & rise... but then the CEL light just stays solid and the test doesn't go any further. No RPM rise, no nothing... just solid CEL. Not sure what that means... I couldn't find anything online related to it. I very well could have a short somewhere but just wanted to ask to see if there was something else I was doing wrong. (Yes, I pulled the jumper on the clutch switch after the car started to simulate pushing and releasing the clutch)

Any insight would be appreciated. Thanks!

Code 63 - Throttle Position Sensor (TPS) signal too low.

Revised 02-Jul-2009 to update TPS setting procedure & add 10 pin connector layout.

Vref missing (5 volt reference voltage supplied by the computer), bad connections or damaged wiring, TPS sensor failed, TPS sensor way out of adjustment. Use a DVM to check for 5 volts on the Orange wire. If it is missing, look for +5 volts at the Orange wire on the EGR or MAP/Baro sensor located on the firewall near the center of the car. If there is +5 volts on the MAP/Baro sensor, but not on the EGR, clean the #2 & #5 pin on the white 10 pin connector. If there is +5 volts on the EGR but not on the TPS, look for bad wiring inside the engine fuel injector harness.

See the graphic for the 10 pin connector circuit layout.
?temp_hash=3ef2497fff29a7a9daee955cf93e5805.jpg


Setting the TPS voltage
You'll need a Digital Voltmeter (DVM) to do the job.

Wire colors & functions:
Orange/white = 5 volt VREF from the computer
Dark Green/lt green = TPS output to computer
Black/white = Signal ground from computer

Always use the Dark Green/lt green & Black/white wires to set the TPS base voltage.

Do the test with the ignition switch in the Run position without the engine running.

Use the Orange/white & Black white wires to verify the TPS has the correct 5 volts source from the computer.
Setting the TPS: you'll need a good Digital Voltmeter (DVM) to do the job. Set the TPS voltage at .5- 1.1 range. Because of the variables involved with the tolerances of both computer and DVM, I would shoot for somewhere between .6 and 1.0 volts. Unless you have a Fluke or other high grade DVM, the second digit past the decimal point on cheap DVM’s is probably fantasy.

Since the computer zeros out the TPS voltage every time it powers up, playing with the settings isn't an effective aid to performance or drivability. The main purpose of checking the TPS is to make sure it isn't way out of range and causing problems.

The Orange/White wire is the VREF 5 volts from the computer. You use the Dark Green/Lt green wire (TPS signal) and the Black/White wire (TPS ground) to set the TPS. Use a pair of safety pins to probe the TPS connector from the rear of the connector. You may find it a little difficult to make a good connection, but keep trying. Put the safety pins in the Dark Green/Lt green wire and Black/White wire. Make sure the ignition switch is in the Run position but the engine isn't running.

Always adjust the TPS and Idle with the engine at operating temp. Dive it around for a bit if you can and get it nice and warm.

When you probe the leads of the TPS, do not use an engine ground, put the ground probe into the lead of the TPS. You should be connecting both meter probes to the TPS and not one to the TPS and the other to ground.

The TPS is a variable resistor, much like the volume control knob on a cheap radio. We have all heard them crackle and pop when the volume is adjusted. The TPS sensor has the same problem: wear on the resistor element makes places that create electrical noise. This electrical noise confuses the computer, because it expects to see a smooth increase or decrease as the throttle is opened or closed.

TPS testing: most of the time a failed TPS will set code 23 or 63, but not always. Use either an analog meter or a DVM with an analog bar graph and connect the leads as instructed above. Turn the ignition switch to the Run position, but do not start the engine. Note the voltage with the throttle closed. Slowly open the throttle and watch the voltage increase smoothly, slowly close the throttle and watch the voltage decrease smoothly. If the voltage jumps around and isn’t smooth, the TPS has some worn places in the resistor element. When the throttle is closed, make sure that the voltage is the same as what it was when you started. If it varies more than 10%, the TPS is suspect of being worn in the idle range of its travel.


Code 67
Revised 18-Mar-2017 to include warning about the necessity of having a 5 speed O2 Sensor wiring harness when bypassing the wiring for test purposes

Cause of problem:
Clutch not depressed (5 speed) or car not in neutral (5 speed and auto) or not in park (auto) or A/C in On position when codes where dumped. Possible neutral safety switch or wiring problem. This code will prevent you from running the Key On Engine On tests.

External evidence from other sources claims that a code 67 can cause an idle surge condition. Do try to find and fix any issues with the switch and wiring if you get a code 67.

What the NSS (Neutral Safety Switch) does:
5 speed transmission: It has no connection with the starter, and the engine can be cranked without it being connected.
Auto transmission: It is the safety interlock that prevents the starter from cranking the engine with the transmission in gear.
What it does for both 5 speed and auto transmission cars:
The computer wants to make sure the A/C is off due to the added load on the engine for the engine running computer diagnostic tests. It also checks to see that the transmission is in Neutral (5 speed and auto transmission) and the clutch depressed (T5, T56, Tremec 3550 & TKO)). This prevents the diagnostics from being run when the car is driven. Key On Engine Running test mode takes the throttle control away from the driver for several tests. This could prove hazardous if the computer was jumpered into test mode and then driven.

The following is for 5 speed cars only. Do not do this unless you are sure that you have a 5 speed O2 Sensor harness!!!! Smoke, sparks and expensive pain in the wallet may ensue if you don’t.
The NSS code 67 can be bypassed for testing. You will need to temporarily ground computer pin 30 to the chassis. Computer pin 30 uses a Lt blue/yellow wire. Remove the passenger side kick panel and then remove the plastic cover from the computer wiring connector. Use a safety pin to probe the connector from the rear. Jumper the safety pin to the ground near the computer.
Be sure to remove the jumper BEFORE attempting to drive the car!!!

a9x-series-computer-connector-wire-side-view-gif.71316
 
@jrichker Thanks for the reply... I do appreciate it as I'm sure you're busy... but the codes are not the issue themselves (obviously an issue, just not towards my pointed questions). I've learned to look for your guides and go through step by step to ensure resolution or to exclude etc... BUT... the crux of the questions are....

1: If the cooling system cools better in warmer air vs. colder air... would that indicate something electrical or mechanical?
(I don't believe there is anything electrical that interacts in any way shape or form with the thermostat but I could be wrong or uninformed)

When I went to run the engine ON test, I get the RPM drop & rise... but then the CEL light just stays solid and the test doesn't go any further. No RPM rise, no nothing... just solid CEL. Not sure what that means... I couldn't find anything online related to it. I very well could have a short somewhere but just wanted to ask to see if there was something else I was doing wrong. (Yes, I pulled the jumper on the clutch switch after the car started to simulate pushing and releasing the clutch)

2: If the clutch is depressed (no jumper) and 67 is still present from the engine OFF test but still doing what is expected (not starting the car) would that somehow stop the Engine Running test from completing?

The sequence I tried (incase something catches your eye):

1. Hook up OBD1 reader to test port
2. Turn key
3. Write codes
4. Turn key off
5. Turn key on and start
6. Pull clutch switch jumper out when the motor catches
7. Motor dips rpm as it's supposed to and comes back to normal idle
8. OBD1 reader holds solid light instead of blinking codes

obviously I'm getting that code on the engine OFF test because I didn't pull the jumper there, would that cause the engine ON test to fail unless I clear all codes?

--------------------------------------------

I'm really starting to think there must be some sort of wiring issue somewhere which isn't the end of the world... just time to track down the fault... BUT... I wouldn't think an electrical issue would mess with a mechanical system (the cooling) in the way I'm observing.

Thank you again for your time and effort.
 
Your gauge temp pics look normal.
I couldn't get the SVE cap on, ears are too big.
It's a fine radiator, but I put the old Stant cap back on.
Your temp runs that high? I know the gauge itself says "normal" but I've never seen that high on the gauge in my car. Mine runs on the L or A all the time.
 
Your gauge temp pics look normal.
I couldn't get the SVE cap on, ears are too big.
It's a fine radiator, but I put the old Stant cap back on.

It is fairly normal (the temp) and doesn't go 3/4 hot anymore (changed thermostat to motorcraft. Assuming old tstat it was sticking until forced open) But the issue of running different temps with differing ambient air temps is still happening. It's just really odd and flies in the face of any cooling issues I've dealt with previously on any car/truck.

Also, I'm not a fan of that cap nor how low it sits... PITA to get off at times... especially if it's hot.

Your temp runs that high? I know the gauge itself says "normal" but I've never seen that high on the gauge in my car. Mine runs on the L or A all the time.

Do you run yours with a thermostat in? Confirmed readings with aftermarket gauge? Kinda curious now...

While researching this issue and trying to narrow down my particular problem before posting about it, I read from a few posts where people said theirs "typically" ran right around the mid mark which mine has always done. It's just fluctuating by a few degrees in cold air vs. hot air which is the confusing part. 190 is 190 regardless of ambient air and the tstat should open and close based on coolant temp without any other influence as far as I'm aware but I could be missing something or unaware of something... hence the post. :)
 
Do you run yours with a thermostat in? Confirmed readings with aftermarket gauge? Kinda curious now...

While researching this issue and trying to narrow down my particular problem before posting about it, I read from a few posts where people said theirs "typically" ran right around the mid mark which mine has always done. It's just fluctuating by a few degrees in cold air vs. hot air which is the confusing part. 190 is 190 regardless of ambient air and the tstat should open and close based on coolant temp without any other influence as far as I'm aware but I could be missing something or unaware of something... hence the post. :)

Yes, I have a thermostat. Never been a fan of not using one. I use one marked 192. And yes I used to have Autometer gauges for everything. Can't remember the exact number but it always matched up as close as I could estimate on the gauge. Someone in here once gave a very detailed explanation of the relationship between thermostat temp vs actual coolant temp vs actual engine temp. Someone will direct you there.
 
T-stat sets the lower temp limit, not the upper temp limit. They are not accurate but are repeatable. A 192 will start to open at around 188 & fully open at 196.
Removing a t-stat will cause the engine to take a lot longer to warm up. In the winter, it may never warm up.
 
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T-stat sets the lower temp limit, not the upper temp limit. They are not accurate but are repeatable. A 192 will start to open at around 188 & fully open at 196.
Removing a t-stat will cause the engine to take a lot longer to warm up. In the winter, it may never warm up.

Fully understand... and is why this issue is perplexing me.

I was responding to his statement... "Mine runs on the L or A all the time." ...which seems a bit low to me based on what others were saying their stock gauge would show (middleish needle mark) while running theirs.

If the upper stock gauge temp is 270... and the lower 130... = total 400 / 2 = 200 (middle mark on stock gauge roughly)

If his was running that low, his tstat is either really low (160ish???) OR stuck open not bringing the coolant temp up and keeping it around the 190ish range. (I would assume his tstat to be 180 - 190)

Don't be too concerned with the gauge. The stock temp gauge is little more than a glorified dummy light. Personally, I'd leave the stock T-stat right where it is unless you run into any legitimate cooling problems. Stock coolant temps generally run anywhere from 190F-210F in normal operating range. Lowering the operating temperature will affect your fuel economy, contribute to engine wear, increase emissions output, shorten your oil change duration and have a negative impact on your ECU function. You might get away with a 180F T-stat, but like the old saying goes....if it ain’t broke, don't fix it.

Quoted from HERE

I'm within the "optimal range" as quoted from above just before your response HERE ... but I'm just trying to understand the relationship between warmer ambient air and cooler running car or vice versa. Just doesn't make sense to me other than the engine producing more heat in cooler (denser) air that can't be dispelled as well as in warmer air. It's always been the reverse on any vehicle I've ever had cooling issues on.
 
Fully understand... and is why this issue is perplexing me.

I was responding to his statement... "Mine runs on the L or A all the time." ...which seems a bit low to me based on what others were saying their stock gauge would show (middleish needle mark) while running theirs.

If the upper stock gauge temp is 270... and the lower 130... = total 400 / 2 = 200 (middle mark on stock gauge roughly)

If his was running that low, his tstat is either really low (160ish???) OR stuck open not bringing the coolant temp up and keeping it around the 190ish range. (I would assume his tstat to be 180 - 190)
You don't have to assume what tstat I have....I said 192 in the post. So no the tstat is not really low and no it's not stuck open. I bought this car brand new 31 years ago. I build my own stuff. I also had a shop that almost every Fox body in my area came to for mods back then. I'm not trying to convince you of anything or even resolve your problem. I was just trying to give you an example of what every Fox I've ever worked on shows. I've never seen a car run straight out on the gauge like that and I've installed literally scores of them (just like others in here). I know 12.8 people will chime in and say they've seen them run exactly like yours. I have no issue with that. Just trust me when I say I haven't. In the old days, I'd run outside, drive down the road and take a pic to post. I do not feel the need to prove things anymore. I'm starting to remember why I took such a long hiatus from message boards. I'll stop trying to help and go back to reading.
Now that I got that out......carry on :eek::D
 
You don't have to assume what tstat I have....I said 192 in the post. So no the tstat is not really low and no it's not stuck open. I bought this car brand new 31 years ago. I build my own stuff. I also had a shop that almost every Fox body in my area came to for mods back then. I'm not trying to convince you of anything or even resolve your problem. I was just trying to give you an example of what every Fox I've ever worked on shows. I've never seen a car run straight out on the gauge like that and I've installed literally scores of them (just like others in here). I know 12.8 people will chime in and say they've seen them run exactly like yours. I have no issue with that. Just trust me when I say I haven't. In the old days, I'd run outside, drive down the road and take a pic to post. I do not feel the need to prove things anymore. I'm starting to remember why I took such a long hiatus from message boards. I'll stop trying to help and go back to reading.
Now that I got that out......carry on :eek::D

@Wayne Waldrep I appreciate the post. It's a perspective that I didn't have before and runs counter to what I've always known and experienced myself. (gives me a broader toolbox of things to think about when dealing with issues) Not sure where the wires are being crossed up here... but I was merely expressing what I've known just as you've expressed what you've known.

I also apologize, I was in the midst of a phone nearly bricking on me while I was trying to keep up with this thread as well as clients driving me insane. I was also trying to keep the topic on the pointed questions rather than spiraling into a discussion about the gauge itself. It's been stated all over these boards that the stock gauge isn't accurate. I fully comprehend that and it would lend itself to your experience. (I also should have had it as one other possible cause being the inconsistent stock gauge from one vehicle to the next when I responded that it was either a low tstat or stuck open. Didn't mean to imply you were lying or anything)

However, if by calculating the value of the middle hash mark comes out to be roughly the 200 degree mark, then my gauge would seem to be reporting a somewhat accurate reading based on a 190 tstat.

You asked:
"Your temp runs that high? "

Yes it does run that high... but that would be the appropriate place for it to run. (Just under the middle mark) Just like you, I'm not trying to convince you otherwise... you've seen first hand that is not that case... however... sitting that low on everything you've seen makes me think either I'm one of the rare ones... or something else is afoot. (Hence I asked if you ran a tstat, stuck open. It was a legitimate question because they are variables in the system)

Please don't horde your experiences and knowledge... it's how those of us who mostly lurk come to understand different things to think about and/or test.

------------------------

Back on track though, I got to thinking about a way to ask the question to hopefully eliminate the potential of spiraling and the best I could come up with is this:

if we assume for the sake of discussion some things:

A) The stock gauge is accurate
B) The middle mark is 200F
C) Normal driving conditions
D) 50F ambient air causes the system to run at 200F
E) 70F ambient air causes the system to run at 190F

With these variables assumed for the sake of this topic... how is it possible for this to happen? (I'm simply trying to understand this concept)
--------------------------

The only way it makes any sense to me is that there is a wiring issue somewhere that is somehow affected by ambient temperature and causing the fluctuations I'm seeing. Maybe a crack or leak internally that only manifests itself in cooler conditions?
 
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@Killing Hours All good here. Thanks for responding. I was looking on YouTube about Fox related battery stuff and think I stumbled across a @mikestang63 video he did a good while back. Not certain it's the same Mike but the names are very similar. I was watching his code dump and noticed his temp gauge. Just for reference, if you watch his vid all the way to the end his gauge shows almost the same as mine. He's dead on top of the "A" and the line beside it. Mine is just a tad below that line he is on top of. And you are correct that a stock gauge is variable...lol. If mine runs half way I start checking for low coolant. As long as it isn't causing a problem I wouldn't worry about it. Higher than that and yes...start checking.

Vid link:
View: https://www.youtube.com/watch?v=HDXrkKS4jTE
 
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Agree 100%. It's not causing any issues that I can tell at the moment, but since I'm in the process of rebuilding my wifes instead of mine, I'm trying to ensure I don't destroy mine while hers isn't ready. (I'm not ready to yank and rebuild mine yet. Mama comes first sadly)

It's just weird because I've never once encountered a cooling system that rose in cool air and dropped temp in warmer air. Guess there's a first for everything.
 
I'm not sure where this discussion is going, or coming from for that matter. It appears to me this is a 'overanalyzing' situation or maybe 'I just want to be safe' thing. It is a fact that the factory gauge is inaccurate, there is also the sending unit that is grounded to the intake through the threads and then a ground wire at the back of the engine on the drivers side head to the firewall that I believe is important in relation to the gauges. Throw in heat resistance in related wiring and you can get the differences in gauge readings. The thing to do to ease your mind is to install a mechanical temp gauge and make notes of temps in different situations and compare it to the stock gauge.
 
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@Wayne Waldrep Ok... now see, I didn't believe it was THAT far off between vehicles. That's a massive difference from car to car then. I'd read over and over again that they weren't accurate... but that's much further than I'd have ever imagined. Thanks again for your input. Taught me more about the car that I didn't know.

@General karthief The discussion isn't going any further. I've yet to have one person (here or elsewhere) offer up any other sort of explanation for it what I'm observing nor can I find anything online. It must be a wiring issue is where my mind is geared. (with the TPS throwing a code and the engine test not completing correctly, I defiantly think something is not right in the wiring harness somewhere)

Thanks for the explanation of the two grounds. I put a new ground on head --> firewall last year but will go back and clean up and re-seat it all just to be sure. Also thanks for posting THIS link about the 3G, I wired mine up last year with the same LMR kit and followed the same video... starting to wonder if that is playing any role.

Night gents.
 
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