Overheating problem
Thread Starter
Cruising
Joined: Dec 2016
Posts: 14
Likes: 0
Overheating problem
Hi everyone, I'm a new owner of a '90 C4. It started overheating when driving in stop and go driving. Had it flushed, put in a 180 degree thermostat, blew out the fins of the radiator and it still runs 240 plus. The coolant is boiling inside the motor I can hear it. Will a high flo water pump make any difference? It doesn't take long for it to heat up. Is there a fix for this? Thanks for the advice and help.
Racer
Joined: Jun 2017
Posts: 311
Likes: 24
From: Ohio
Congrats on your new C4! I would recommend checking in between the radiator and a/c radiator (not sure what its actually called) for leaves, as they tend to build up there as well as in front of the a/c radiator.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Are the lower air dams in place and in good condition? Those pieces direct air from under the front of the car and up into the AC condensor and radiator.
Have you replaced the radiator hoses? Could be that the lower hose is weak and collapsing. That will cut down the flow of coolant nad create high temps quickly.
What about the fans? Are they working? They should come on before the 240+ indicated temp you see. And is that temp as seen on the digital display rather than the analog gauge?
It could be that the water pump is failing; the impeller fins may have corroded to the point where they do flow enough coolant. A high flow unit probably won't help just to try to lower temps. For a stock engine and "normal" driving, it really isn't necessary.
Have you replaced the radiator hoses? Could be that the lower hose is weak and collapsing. That will cut down the flow of coolant nad create high temps quickly.
What about the fans? Are they working? They should come on before the 240+ indicated temp you see. And is that temp as seen on the digital display rather than the analog gauge?
It could be that the water pump is failing; the impeller fins may have corroded to the point where they do flow enough coolant. A high flow unit probably won't help just to try to lower temps. For a stock engine and "normal" driving, it really isn't necessary.
Zen Vet Master Level VII
Joined: Mar 2016
Posts: 5,218
Likes: 1,174
From: Southlake, TX
You can spend a fortune on cooling components and clogged air flow will restrict it all.
Last edited by billschroeder5842; Jul 25, 2017 at 07:36 PM.
Thread Starter
Cruising
Joined: Dec 2016
Posts: 14
Likes: 0
Overheating Problem
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
Thanks Mike, I did do this and found a bird's nest and other stuff. Also had the coolant system flushed and scoped. We saw an obstruction in the back passages. turned out to be part of the intake gasket. Also replaced the single core radiator with a DeWitt dual core radiator and new water pump and 180 degree t-stat. Put new coolant in with some Purple Ice additive, tried burping the air bubbles but it puked out all the coolant. mostly water now. We did get most of the bubbles out and I was able to drive it in stop and go traffic all afternoon without getting over 200 degrees. I'm a Happy Camper!
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Thread Starter
Cruising
Joined: Dec 2016
Posts: 14
Likes: 0
over heating
Are the lower air dams in place and in good condition? Those pieces direct air from under the front of the car and up into the AC condensor and radiator.
Have you replaced the radiator hoses? Could be that the lower hose is weak and collapsing. That will cut down the flow of coolant nad create high temps quickly.
What about the fans? Are they working? They should come on before the 240+ indicated temp you see. And is that temp as seen on the digital display rather than the analog gauge?
It could be that the water pump is failing; the impeller fins may have corroded to the point where they do flow enough coolant. A high flow unit probably won't help just to try to lower temps. For a stock engine and "normal" driving, it really isn't necessary.
Have you replaced the radiator hoses? Could be that the lower hose is weak and collapsing. That will cut down the flow of coolant nad create high temps quickly.
What about the fans? Are they working? They should come on before the 240+ indicated temp you see. And is that temp as seen on the digital display rather than the analog gauge?
It could be that the water pump is failing; the impeller fins may have corroded to the point where they do flow enough coolant. A high flow unit probably won't help just to try to lower temps. For a stock engine and "normal" driving, it really isn't necessary.
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
I wouldn't trust the gauge. If I thought my car were overheating, first thing I would do, for future reference, is to hit multiple points of the radiator with an infrared thermometer to see if there are hot and cold spots indicating a blockage. I'd also make sure that the ECM sees the same temperature as is being reported by hitting the sensor that reports to the ECM, not the gauge sensor, and it should be about the same temp. That way you know it is accurate.
Thread Starter
Cruising
Joined: Dec 2016
Posts: 14
Likes: 0
C4 overheating
I wouldn't trust the gauge. If I thought my car were overheating, first thing I would do, for future reference, is to hit multiple points of the radiator with an infrared thermometer to see if there are hot and cold spots indicating a blockage. I'd also make sure that the ECM sees the same temperature as is being reported by hitting the sensor that reports to the ECM, not the gauge sensor, and it should be about the same temp. That way you know it is accurate.
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
Trust but verify. If the sensor is sending bad values, well, Garbage In, Garbage Out. I believe the one you want is under the TB. IIRC, there is another one for the gauge but that is irrelevant. I would scan the ECM so we know what it THINKS the temp is, scan the sensor and see if it is close.
Intermediate
Joined: Jul 2015
Posts: 48
Likes: 2
From: 130 km west of Stockholm
Some more information:
Make sure the cooling system is pressurised. This is done by the radiator cap and it increases the boiling point.
If the radiator hoses become stiff when the engine is warm (but not boiling) the cap probably is ok.
A good mix of antifreeze and water also increases the boiling point compared to just having water in the cooling system.
And don´t rely on the temp gauge. Boiling is boiling but don´t trust the gauge for it. I have a feeling that they can show anything except the real engine temperature.
I had about 200 F yesterday on the Tuner Pro and the engine had ran for like 20 minutes so that temp reading can´t be to far from the reality but gauge showed just above the 100 F mark. There´s no way that the engine can have just 100 F after 20 minutes of idling, even with my 160 F thermostat.
Is problems with the gauge a well known issue? I´m thinking that it might have similar problems with that resistor that the tacho has on the -90 and forward Vettes. I have repaired the tacho but I might need to repair the temp gauge as well.
Make sure the cooling system is pressurised. This is done by the radiator cap and it increases the boiling point.
If the radiator hoses become stiff when the engine is warm (but not boiling) the cap probably is ok.
A good mix of antifreeze and water also increases the boiling point compared to just having water in the cooling system.
And don´t rely on the temp gauge. Boiling is boiling but don´t trust the gauge for it. I have a feeling that they can show anything except the real engine temperature.
I had about 200 F yesterday on the Tuner Pro and the engine had ran for like 20 minutes so that temp reading can´t be to far from the reality but gauge showed just above the 100 F mark. There´s no way that the engine can have just 100 F after 20 minutes of idling, even with my 160 F thermostat.
Is problems with the gauge a well known issue? I´m thinking that it might have similar problems with that resistor that the tacho has on the -90 and forward Vettes. I have repaired the tacho but I might need to repair the temp gauge as well.
Last edited by Robban_C; Sep 6, 2017 at 03:41 AM.