I run A/C, I get burned...

[91lxttrim]

Here in AZ it has been in the 100's and I have to run the A/C, but when I do it feels like it is putting so much stress on the crank!

When I use the a/c the oil pressure is a little lower, the car runs hotter, and when I take off from a stop and don't have the RPM's high enough I get a BAD rod knock. You know the kind when the engine bogs on itself when you let the clutch out... It makes my skin crawl when I hear that.

While I'm driving at any speed around 2000 rpm, my oil pressure is at 40-50 psi. At idle after warming up to full operating temp it's at 20-25 but when the a/c is on it's more like 20 and a little under. What if it starts to dip below 20 after a while? Am I just driving myself crazy by worrying too much?

I also have a T-trim to install but now I'm rethinking it. It would just be more stress on the crank.

BTW the block has approximately 50-75,000 miles on it. I'm not sure since I bought the car used and discovered cross hatching in the cylinders when I did the HCI.

Thanks for any input.

 

[fiveohh94gt]

i'm having similar problems, i just posted in the 94-95 tech section

 

[91lxttrim]

I'll check your replies...

 

[91lxttrim]

bump

 

[Cman88]

Here in AZ it has been in the 100's and I have to run the A/C, but when I do it feels like it is putting so much stress on the crank!

When I use the a/c the oil pressure is a little lower, the car runs hotter, and when I take off from a stop and don't have the RPM's high enough I get a BAD rod knock. You know the kind when the engine bogs on itself when you let the clutch out... It makes my skin crawl when I hear that.

While I'm driving at any speed around 2000 rpm, my oil pressure is at 40-50 psi. At idle after warming up to full operating temp it's at 20-25 but when the a/c is on it's more like 20 and a little under. What if it starts to dip below 20 after a while? Am I just driving myself crazy by worrying too much?

I also have a T-trim to install but now I'm rethinking it. It would just be more stress on the crank.

BTW the block has approximately 50-75,000 miles on it. I'm not sure since I bought the car used and discovered cross hatching in the cylinders when I did the HCI.

Thanks for any input.

You SHOULD have cross hatching on the cylinders. Lack of would indicate a worn engine. I don't really have much to offer in terms of advice on the A/C thing. My Mustang's A/C needs to be recharged (and to have the leak repaired)... I wouldn't think 20psi of oil pressure at idle is an issue however. The noise you describe on take off certainly doesn't sound good however.

 

[352Ford2]

20psi at idle is more than enough. How hot is it running? it is because your ac condesor is rejecting heat with the ac on and increasign the temp of the incoming air to cool your rad.

do you have an electric fan, if so do you have it wired to come on automaticaly with the ac?

the main thing I would look into the sound though (preigintion?)

 

[91lxttrim]

I have the Black Magic Extreme(?) elec. fan and yes I wired it to the a/c so it switches on when the a/c comes on. I think a new rad is in order.

As far as the oil pressure, I bought an oil pressure warning light a while ago (not installed yet) and the sending unit for it is rated at 18 psi. So when I'm sitting at idle and the pressure, according to the gauge, goes below 18 psi, isn't that warning light going to be going off all the time? What's the lowest acceptable oil pressure?

I think I'm going to put the SC on this weekend and if if and the a/c are too much I will definitely get the rad. I was thinking since the a/c and SC will be on different sides of the crank pulley they might balance each other out. (jk)

352ford2 --- It definitely sounds like a knock but it only did it the one time when i let the clutch out too fast without enough gas. Nice quote BTW! That movie rocks!

 

[352Ford2]

What weight oil are you running? How is the oil pressure before the engine heats up? If your oil is getting too hot it could be thinning out too much. I hate to ask this, but when was the last time you changed your oil? Old oil can cause press issues
You need to get a real gauge (pick one up at shucks for a few bucks) and see how low it is, before you make guesstaments off the factory gauge.

I can’t remember if that supercharger uses engine oil if so this is going to make it worse, I would be looking at aftermarket oil pans and oil coolers after you fix the issue at hand

I always diagnose cooling system issues though how the system works. Ideally you want the coolant in the engine to be at the exact temp the thermostat is (it is their to regulate temp, when it gets hot, it lets hot coolant out and cool water from the rad in.) For this to work the coolant in your rad has to be cold. If the temp in your rad gets to the temp of your thermostat, you are done, the system is maxed out. Whether than means putting in a larger rad (capacity, surface area/vol ratio, heat transfer properties, etc depending on what lacks) or a fan that pulls more air.

How much coolant are you running? Coolant doesn’t transfer heat as well as water does, so I run only about 20% coolant.


and yess it is the sweetest movie ever

 

[91lxttrim]

I just changed my oil last weekend to see if it would that would change the oil pressure at idle but it's pretty much the same. I'm running straight 30w just because I bought a case when I did my HCI install and ran that through for the first 500 mi. Next oil change maybe I'll up it to some 10w40.

I have an Autometer full sweep oil pressure gauge. At idle my oil pressure goes up and down about 5-7 psi. (20-27) when hot. For the first 10 min after I fire it up it's around 50-60 at idle.

I still have to replace the water temp gauge this weekend with another Autometer one. I bought the tach pod cause I was running out of room and don't want to use any of the real estate in the dash vents for gauges, and open the box for the tach pod and they forgot to include the brackets. Autometer is mailing them to me so I have to wait for that to install the gauge.

I'm running about 70% water to 30% coolant and half a bottle of Water Wetter...

 

[352Ford2]

it does sound like that oil is thinning out too much, I would be worried, you really don't want to hurt a bearing or two. the black magic is a pretty good fan (i am asumming you have Part# 175) and pulls a fair amout of air.

does it over heat only in stop and go traffic, or will it run hot cruiseing on the freeway or pulling a grade?

 

[91lxttrim]

It's more in stop and go traffic but once it gets up there, it takes a while to come down and when it does it only goes down a little. But if the a/c is on it will never go as low as when it's not on.

The first day I used it i drove it on the freeway and was above half on the stock gauge the whole time. I'm installing the Autometer gauge tonight.

 

[352Ford2]

well if it does come back down sounds like airflow isn't that bad, I would get a bigger rad, performance rad makes some affordible ones. if your going to put the supercharger on you need to deal with the oil issues, try puting in some diffrent/better oil, and if you have to a bigger oil pan and oil cooler
here is a cheap option if you are hard up for cash, get a winshild washer motor and tank from the junkyard, mount it and have a push button to spray water on the fins of your rad, its hillbilly but it might save your engine untill you can fix it properly.

 

[brandonshady]

1 time occurance

I had my A/C on, no traffic/hwy - dawg'n out a ricer... I know I was over a 100 for bout 5 min. When we came up on some spotted traffic, I looked at my gauges & saw the temp. about 85% to RED !!! My autometer's were not hooked up till today, so no exact reading could be made.

Wierd thing... I babied her home, and pulled off hwy as soon as I saw the gauge up. My resevoir was empty, so I put some gas station water in till I got home. Next day I popped the cap off & rad was at about 1/2 full. When I parked it, I could see the rad water spraying from the top hose connection.

Today while we were installing the gauges, I pulled the hose off to check for a crack... nothing. Re-tightned the hose down & filled with water to top. Ran around city 20 min. & got back on it on the hwy for about 25min total. Temp. never went up... any idea's???? Total drive time on occurance, was less than 15min from crank to house.

 

[Cman88]

I had my A/C on, no traffic/hwy - dawg'n out a ricer... I know I was over a 100 for bout 5 min. When we came up on some spotted traffic, I looked at my gauges & saw the temp. about 85% to RED !!! My autometer's were not hooked up till today, so no exact reading could be made.

Wierd thing... I babied her home, and pulled off hwy as soon as I saw the gauge up. My resevoir was empty, so I put some gas station water in till I got home. Next day I popped the cap off & rad was at about 1/2 full. When I parked it, I could see the rad water spraying from the top hose connection.

Today while we were installing the gauges, I pulled the hose off to check for a crack... nothing. Re-tightned the hose down & filled with water to top. Ran around city 20 min. & got back on it on the hwy for about 25min total. Temp. never went up... any idea's???? Total drive time on occurance, was less than 15min from crank to house.

If you had a leak in the hose, then you will have two problems.. One, lower pressure reduces the boiling point of the coolant and thus will cause the engine to run warmer. Two, the loss of coolant will reduce the effectiveness of the cooling system, also causing the engine to run warmer...

 

[brandonshady]

Good catch CMANN88...

I checked for leaks, but did not find any. I saw them after a hard run, but figured it was overspray from resevoir. I went and bought a pressure check tool today. We tested & found the leaky hose right away. I replaced thermo, all w/p hoses,Top & bottom rad hose... Now she is pressure checking good. Huge rust build up in rad... After about 3 flushes, I got tired of the mess & ran the hose direct in rad with draincock pulled & heater running. Once water turned clear & no deposits - re-filled & she is screamin again.


Literally got on hands & knee's: "Yes it's not a cracked head or bad head gasket".

 

[Cman88]

Good catch CMANN88...

I checked for leaks, but did not find any. I saw them after a hard run, but figured it was overspray from resevoir. I went and bought a pressure check tool today. We tested & found the leaky hose right away. I replaced thermo, all w/p hoses,Top & bottom rad hose... Now she is pressure checking good. Huge rust build up in rad... After about 3 flushes, I got tired of the mess & ran the hose direct in rad with draincock pulled & heater running. Once water turned clear & no deposits - re-filled & she is screamin again.


Literally got on hands & knee's: "Yes it's not a cracked head or bad head gasket".

If the radiator was full of rust, you might want to keep an eye on things. You might need to replace it if its real bad. Do you run low coolant/water ratios? Might want to watch out if so. Coolant is good for more then just cooling the engine. People often seem to overlook these benefits.

 

[HISSIN50]

Actually, coolant isnt good for cooling the engine - it's benefits are lubrication of moving components, rust-inhibiting, freeze protection and so on. Water is 2.6 times more effective at wicking heat away than coolant.

 

[Mustang5L5]

Well if you are running the A/C then it's most likely hot as hell out. The heat of the day and the heat of the engine will thin the oil out a lot and cause the lower pressure. The car will run hotter as a result of the A/C and the knock you heard may have been clutch chatter from not enough RPM's.

I know my 5.0 was a total dog with the A/C on and even my new '03 GT runs like ass with the A/C on. It makes all sorts of funky noises and it tough to drive. I try not to use the A/C unless i really NEED it as a result.

I've driven other cars that you can't even tell when the A/C is on or feel such a loss of power....but in both my Mustangs running the A/C is such a huge loss of power.

 

[Cman88]

Actually, coolant isnt good for cooling the engine - it's benefits are lubrication of moving components, rust-inhibiting, freeze protection and so on. Water is 2.6 times more effective at wicking heat away than coolant.

Coolant alone isn't good for cooling an engine, correct.. However, it is used to increase the boiling point of water (along with the pressure created by a sealed system) and thus will "help" in keeping the engine cool.

 

[brandonshady]

Oh forgot to add - rad was pulled & replaced along with other parts installed today. No way I was leaving that sludged up piece in there, especially after all new hoses, thermo.

I like to run mean green... bout 70%anti/30%water mix. I know alot say 50/50 or 60/40. I run straight water & a trans flush cond. for about a week every so often. Then i go back to 70/30 mix. This was a newly purchased car & is showing signs of neglect. Thats why I was leaning towards a craked head/gasket when I saw muddy looking fluid in rad.