Z'mnypit

iTrader: (58)

The last two times Ive driven my car its started to run hot while the AC is on. Nefer before has this happend until 2weeks ago. I can go out for a drive and with the AC on the temps will climb to the 210+ range, even going down the interstate the temps will still be 200* or so and I know that cant be good. The temps should not stay that high while doing 80mph. I thought maybe the fans wasnt kicking on so I pulled my file and sure enough the fan settings were set at stock. I had forgot to change them back while messing with my tune. So I started the car outside turned the AC on hig and let it sit for over 20mins and the temp never did go over 178-179* so I thought problem solved. Got in it sat took off and as soon as I get to moving and crank the AC up the temps start rising, I can turn it off and the temp will start to drop. Even at night with its 72* outside the temp will still climb up to 200 or so with the AC on going down the interstate. Theres nothing blocking the air flow to the radiator. My trans cooler is there but its been there for over two years. I cut out the styrofoam(spelling) behind the billet grill to help cool it a little bit but nothing. Any suggestions?

Thanks!

BIG_MIKE2005

iTrader: (116)

I had a car that did this before. It ended up bein the heater core cloged up. Try checking that.

A-Dub

iTrader: (6)

Interesting heater core comment, the heater core is not involved in A/C operation, its not even open during A/C operation (unless you have the temp **** turned to full red).

I know you checked your fan settings, but it sounds like your second fan isn't kicking in when the a/c comes on. Check the relays and the fans themselves.

Z'mnypit

iTrader: (58)

Thanks for the comments so far! ive check the fuses but havent checked the relay. But why would it only run hot when the AC is on? Even running down the interstate?

JohnnyC

low coolant level can cause this

radz282003

iTrader: (1)

Running the A/C places an additional load on the engine, resulting in it working a little harder, and running a bit warmer.

Z'mnypit

iTrader: (58)

Not 50*+ warmer... its always ran about 185-190 with the AC on. I have a 180* thermo and with the AC off it would run around 175*

Ill check the coolant but last time I checked it before I pulled the cap all the way off it was already coming out and the motor was cold so it was full. Want hurt to double check though...

jimmyblue

iTrader: (11)

Same problem here, I even created a thread in
Advanced to look for ways to improve. Basically
we have a small rad and fans, fed hot air off the
condenser, have a nice day. Upgrading the radiator
and fans seems like the ticket. We're pretty much
stuck with an air stream sucked right off the
blacktop, which is lousy hot to begin with.

2000TransAmWS6

iTrader: (12)

^yeah, basically the condenser is trying to cool off the refrigerant, and the radiator is trying to cool off the coolant. you've got 2 very hot liquids running through radiators that are inches apart from eachother.

waSStock

would a low freon level cause the condenser to be hotter?

Sigforty

Have you tried to blow out your condensor or radiator? You will be surprised at the dirt and crap that gets stuck in those fins. I just had to do this with both my vette and my blazer as they both were running hotter than usual.

Quickin

Mine did the same thing and your year car might be ready also. I tried everything possible associated with the cooling system, this is what it was and now I can drive around in 95* heat in traffic as long as I like with the A/C on MAX and it never even gets near the 210 mark. And I had the same exact problems/symptoms as you.

Only things that can cause you to overheat AFTER you turn the A/C is a bad compressor that doesn't spin freely and dragging the **** outta your engine or a clogged condensor.

Gotta take the radiator out first to do the fix.

https://ls1tech.com/forums/general-maintenance-repairs/491395-overheating-solved-you-d-never-guess-how.html

Hope thats the problem.

Z'mnypit

iTrader: (58)

Thanks! Ill start trouble shooting this weekend..

NoMoreLS1

iTrader: (65)

I was just going to say that.

Viper

iTrader: (6)

I replaced my heater core 2 weeks ago due to the same symptoms, now it's runs 100% fine. And I agree, what's the heater core have to do with it when it's not on during A/C use? Don't know, but it fixed it. I did a writeup on it https://ls1tech.com/forums/showthrea...ht=heater+core

Full-Force

iTrader: (11)

I do not think F bodies have heater control valves. So in that case water is running through the heater core all the time so if its plugged then your water in not circulating right.

Viper

iTrader: (6)

That would explain why I saw smoke rising from the center vent on the dyno and smelled coolant.

Although this is my 3rd motor, and obviosuly everything was new tyhus flushed, it never occurred to me to 'flush' the heater core. After reading many posts, it too is victim to dex-cool sludge. And it's nothing you see by looking at the heater core. I pulled mine out and laid it next to the 'new' one, and you'd be hard pressed to tell them apart. Must have to cut it open to see the damage.

Z'mnypit

iTrader: (58)

PROBLEM FIXED! only one fan was kicking on. I put the car on my lift and let it idle with the AC on. Sure enough when it got up to temp it wouldnt stop there so I looked under the car and only one fan was kicking on. The relay in the fan #2 was bad. Replaced it and all goog now. It will stay under 180* even with the AC on. Thanks for all the replies.