Running hot...what to do?
Thread Starter
Instructor
Joined: May 2004
Posts: 184
Likes: 0
From: San Francisco Ca
Running hot...what to do?
I've had the problem the last couple of days that my car is running extremally hot...usually well over 200, especially at ideal. Is there a way to cool the car better?
Team Owner
Joined: Sep 2001
Posts: 62,141
Likes: 1,729
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Elaborate. What are the circumstances/conditions when its running hot and what temperatures are you getting.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
I wish you had been a little more specific. Well over 200 doesn't tell us a lot. How different are the temps from when you felt they were "normal"?
The obvious things come to mind:
Debris blocking the radiator
Fan not working properly
Low coolant level
Jake
The obvious things come to mind:
Debris blocking the radiator
Fan not working properly
Low coolant level
Jake
Melting Slicks
Joined: Jun 2004
Posts: 3,032
Likes: 4
yeah... what temps and what conditions... if you're sitting in bumper to bumper traffic on a 100 degree day, temps could possibly hit 230 or higher... i think 250 is what the manual lists as a 'danger zone' right?
Racer
Joined: Jul 2004
Posts: 308
Likes: 0
From: Christiansburg VA
Now granted I haven't had my C4 long...
At idle with the climate control off:
220+
At idle with the climate control on (fan on):
198-200
I too plan on lowering the fan activation setting eventually; however, from what I understand, this is what GM originally designed the cooling system to operate at.
I'm sure my temps may be a bit high..I could probably use a flush and debris cleaning.
I agree with what's stated above...check your overflow tank and make sure you check thoroughly for leaks. Also when the car is cool, you can take off the cap and make sure it's topped off as well.
At idle with the climate control off:
220+
At idle with the climate control on (fan on):
198-200
I too plan on lowering the fan activation setting eventually; however, from what I understand, this is what GM originally designed the cooling system to operate at.
I'm sure my temps may be a bit high..I could probably use a flush and debris cleaning.
I agree with what's stated above...check your overflow tank and make sure you check thoroughly for leaks. Also when the car is cool, you can take off the cap and make sure it's topped off as well.
Thread Starter
Instructor
Joined: May 2004
Posts: 184
Likes: 0
From: San Francisco Ca
ok sitting at idle it will go almost all the way to the warning at 250...but when i get going and get more air into the radiator the temp drops well off to about 207 (takes a couple of minutes but it gets there...) is this somthing that I should be worried about...or should I go out and change the radiator or what?
Pro
Joined: Feb 2003
Posts: 599
Likes: 0
From: anderson sc
yea ok to play it safe, STOP DRIVING IT NOW TILL YOU FIGURE OUT WHAT THE CRAP IS WRONG WITH IT. i had my low coolant light come on and go off for a week. turns out now it wont hold water better than rag in a waterfall. i got a blown head gasket and abusted radiator. and a $1700 bill to get it all fixed. my advice, drive it to a radiator shop tomorrow and tell em to fix it. who cares if it's 300 for aflush. leak fix or whatever. beats $1700. 
Team Owner
Joined: Sep 2001
Posts: 62,141
Likes: 1,729
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Still need more details, is this happening every time you drive it? How long after startup does it reach these temperatures?
Is the AC on or off?
Verify that the thermostat is opening at 195 as it should. Check to see if the main fan comes on at 228F.
Dont start throwing money at a problem until youve had a chance to troubleshoot.
Is the AC on or off?
Verify that the thermostat is opening at 195 as it should. Check to see if the main fan comes on at 228F.
Dont start throwing money at a problem until youve had a chance to troubleshoot.
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Le Mans Master
Joined: Mar 2004
Posts: 8,700
Likes: 298
From: Ft. Lauderdale Fl
Running hot
You don't say how hot it is running. The easy quick fix and the cheapest is to add Waterwetter or 40 Below. What I would do is follow all the posts. Check for obstruction between radiator and condenser.
Check the hoses for one that is toasted.
Complete radiator flush.
Etc.
Check the hoses for one that is toasted.
Complete radiator flush.
Etc.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
OK, what year C4 do you have??
Since coolant temp climbs in traffic but drops when moving it sounds like the fan isn't comming on. Possibly the ECM isn't sensing coolant temp properly (you did mention that with A/C On temps drop, indicating that the ECM is bringing on the fan when the pressure switch opens).
On an L98 ('85-'91) the ECM's coolant temp sensor is located in the intake base below the TB. If this sensor is open the ECM will see low coolant temps and not bring on the fan when temps climb.
Since coolant temp climbs in traffic but drops when moving it sounds like the fan isn't comming on. Possibly the ECM isn't sensing coolant temp properly (you did mention that with A/C On temps drop, indicating that the ECM is bringing on the fan when the pressure switch opens).
On an L98 ('85-'91) the ECM's coolant temp sensor is located in the intake base below the TB. If this sensor is open the ECM will see low coolant temps and not bring on the fan when temps climb.
Advanced
Joined: Feb 2003
Posts: 97
Likes: 0
From: Richmond CA
My LT1, with stock TStat, never went to 250F, even with bumper-to-bumper traffic on the hottest days. It will get to the 230+ mark. It did, however, get to 250 when I 1st bought it but that was due to the previous owner who did not reset the computer for the 180 TStat when the dealer replaced his 160. After I reset the computer, I never went to 250.
last weekend, as part of doing my wires/plugs,TB bypass, TB clean and IAC replacement, I also put in a 160 Hypertech tstat, and set the computer for 160. At highway speeds, I'm getting anyway from 177 to 185. In really hot weather, like the last few days here in N. california, I'm hitting the 211 mark in stop-go-traffic.
If I was in your shoes, check to ensure the coolant is still "serviceable". Then burp the system, via the 2 vent screws, or 1 screw if you have the TB coolant bypass done. Failing that, maybe your waterpump is no longer doing its job.
last weekend, as part of doing my wires/plugs,TB bypass, TB clean and IAC replacement, I also put in a 160 Hypertech tstat, and set the computer for 160. At highway speeds, I'm getting anyway from 177 to 185. In really hot weather, like the last few days here in N. california, I'm hitting the 211 mark in stop-go-traffic.
If I was in your shoes, check to ensure the coolant is still "serviceable". Then burp the system, via the 2 vent screws, or 1 screw if you have the TB coolant bypass done. Failing that, maybe your waterpump is no longer doing its job.
Race Director
Joined: Jul 2004
Posts: 16,795
Likes: 62
From: Lake Havasu City, AZ
I agree with the earlier posts. First check the radiator for obstruction.
Water wetter might get you 10 degrees but your issue needs to find more cooling than that.
It does sound fan related so follow the posts
Water wetter might get you 10 degrees but your issue needs to find more cooling than that.
It does sound fan related so follow the posts
Drifting
Joined: Nov 2002
Posts: 1,593
Likes: 0
From: Mobile AL
St. Jude Donor '05
I agree. Probably a fan problem, which is easy to check. Pull over when temp is that high, leave it in park with engine running and open the hood. Fan running? Coolant system flush and fill. Fan not running? Check fuse, relay and fan.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Really should verify the gage first. You'll need a scanner, but verifying that the gage is accurate can save you some headaches. Otherwise, both fans should be on with the a/c on. With it off, the primary should switch on at 219 and the secondary at 228. Signal is from the Coolant Temp Sensor.