Strange Overheating Problem

[fyassine]

A week ago my heater core started to leak in the car, so I bypassed it by placing a tube between the two hoses that normally went to the heater core. Had no issues with the car running hot.

The tube sprung a leak so I cut one of the heater core hoses to make a U and connected each end to the ports coming out of the engine that are supposed to go to the heater core.

Since doing that, when I am at a stop the temp will rise from the N all the way to M and almost seem to want to go further. The fan will definitely kick on and maybe take it down in between the O and R. Once I take off and the air hits the engine and it returns to the N in normal. The only time it really heats up is when I am at a stop.

Things I have tried and using:
-Completely burped the system
-Checked and made sure the fan is coming on when it needs to
-Using stock type 195 temp thermostat.
-Checked port where I bypassed the heater core for leaks, none.

I am looking for advice on what to check and find out if by bypassing the heater core this is normal behavior or not.

 

[HISSIN50]

The low speed fan wont come on naturally until around 208*F. I don't know what letter that equates to on a stock gauge.

If installing a manual fan switch(es) (connect Pin 14 on the CCRM to fused 12 volts for low speed fan. For high, ground pin 17 on the CCRM) helps, you know the issue.

Because the cooling system works ok except when you're idling/stationary, I'd make sure the fan comes on at the correct temp (the ECT is calibrated, etc) and see about a fan switch. If there was an issue with the plumbing you had done, you should see issues at all times (not just when ambient air flow diminishes).

Good luck.

 

[fyassine]

It does seem as if the fan is coming on when it needs to and actually does cool it down. Some how it feels as if the rest of the system is not doing it's job so that fan has to kick on to compensate more frequently than I remember.

I keep thinking this has to be related to that heater core bypass as it was the last thing I did before this problem started.

I haven't replaced the thermostat (cheap autozone one) in almost a year or so. Do you think it will do any good to replace it maybe even with a 180?

 

[HISSIN50]

Even if it isn't the fix, doing the t-stat is a great idea - grab a Mr Gasket 180 if you can. Your stat might have some restriction issue (not opening all the way). The Mr Gasket is balanced and has a jiggle valve, both of which can help sort out a situation like yours.

If this occurs while stationary, the fan is really what does cool the car down (temps should creep up when the fan's off since there's no ambient air-flow to cool the coil).

I'd ensure the ECT was not disturbed (it's the fan switch, in essense). Otherwise, I'm not having any great brainstorms. The fact that the system cools alright at speed and under load (when demand is highest) suggests that in and of itself, it's ok. There's just not enough heat rejection while stopped, which still points to the fan.

Bump for thoughts from others.

Good luck.

 

[QUIKSVT]

The low speed fan wont come on naturally until around 208*F. I don't know what letter that equates to on a stock gauge.

208* DOESN'T register on the stock guage, the needle is still buried to the cold side... When the stock guage reads straight up, your probably running roughly 430-470 degrees celsius...

 

[ProKiller]

208* DOESN'T register on the stock guage, the needle is still buried to the cold side... When the stock guage reads straight up, your probably running roughly 430-470 degrees celsius...

what? that makes absolutely no sense. 430* C is 806* F. that engine would have melted a long time ago. even if that was a typo, and you meant fahrenheit, that is still too hot.

my only other thoughts would be a bad head gasket. if you over heated at one point and slightly warped the heads, your HG maybe on the way out. that's what happened to me once. how fast does it heat up when your at a stop? if its really quick then think about saving for a HG failure.

 

[20new5.0]

I have a stock temp gauge and mine seems to stay pretty steady around the o and r during normal driving regardless if i'm stopped or not. If i'm stuck in traffic it might go up a little bit, but I would consider that normal?

 

[94gts]

my car does the same thing, but i have nothing bypassed. sometimes it looks like it is going to overheat then the fan kicks in. same thing once moving, the temp stays way way down. it hasnt given me any problems yet....

 

[fyassine]

I appreciate the suggestions. I think the game plan I am going to take on this one is pretty much leave it alone.

I will just ride around with everything I need in the trunk just in case something happens while I am driving.

 

[HISSIN50]

I appreciate the suggestions. I think the game plan I am going to take on this one is pretty much leave it alone.

I will just ride around with everything I need in the trunk just in case something happens while I am driving.

The best thing I'd recommend is to get a real gauge - factory gauges are hysteretic by design, and there isn't much in the way of graduational steps. Then you'd know once and for all what gives.

Just MHO.

And regarding QuikSVT's post, some facetiousness from his sig spilled over into his entertaining post.

 

[fyassine]

Well I am back and going against my game plan after this started to worry me.

I ended up replacing the thermostat and found some strange things.

I've noticed that when it is up to temp (for the tstat to open) the upper radiator hose doesn't seem to have much pressure as I can squeeze the hose completely when this thing should be flowing like a river.

I've tried 2 Tstats last night (180 & 195) neither of which made any difference to the heating issues or pressure through the hose.

A part of me thinks this has something to do with the bypassed heater core but a lack of pressure at the upper hose almost seems like maybe a water pump issue?

 

[HISSIN50]

If there's no spring in the upper hose (some cars have them in the upper hose and some don't. We do have them in the lower hose for cavitation concerns but not in the upper as I recall) then it is possible to give the hose a good squeeze.

Any idea of actual running temps?

 

[mo_dingo]

It does seem as if the fan is coming on when it needs to and actually does cool it down. Some how it feels as if the rest of the system is not doing it's job so that fan has to kick on to compensate more frequently than I remember.

I keep thinking this has to be related to that heater core bypass as it was the last thing I did before this problem started.

I haven't replaced the thermostat (cheap autozone one) in almost a year or so. Do you think it will do any good to replace it maybe even with a 180?

The car is operating completely normal. Before I got my tweecer, the car would run at O-M all the time. This is not overheating, probably around 210-220 which is perfectly normal. After the tweecer, I set my high speed fan to come on at 195 and that keeps the gauge at O all the time (~205 actual). That is colder than normal operating temperature but I like it that way, only a preference.

I would stop worrying about it until you get a real guage and even then, don't worry, as nothing is wrong.
Scott

 

[fyassine]

I finally got a real gauge on it and see that it hangs around ~215 and will hit near if not right on 230 when at a stop or in stop and go traffic.

Since I am now using this gauge as opposed to the normal meter, at what temp should I start to pull over or kill the engine at, aka the red zone on the normal meter?

 

[WHITE94COBRA]

I wouldnt want it past 230, but I believe cause for concern comes at around 245 250. My car runs at 180 - 215 at all times, And I did all the band aid fixes, I even got a fluidyne radiator only to find out my temp sending unit for the stock guage was a POS. I also would be looking at a HG, since that 230* is high for our cars.

 

[HISSIN50]

I finally got a real gauge on it and see that it hangs around ~215 and will hit near if not right on 230 when at a stop or in stop and go traffic.

Since I am now using this gauge as opposed to the normal meter, at what temp should I start to pull over or kill the engine at, aka the red zone on the normal meter?

I'd redo your diagnostics now that you have a real gauge. Let the car idle in the driveway and note when temps start to stabilize, as well as when the fan's low and high speed is coming on.

Good luck.