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98 vette which only has headers installed is having an issue with temps getting high rather quickly. Just from the point of starting up to casual driving after warm up, the temperatures hit 220. Then on the freeway, temps reach 230 upwards of 240 and hover there until I take the foot off the gas.
I pretty much had it checked and changed everything to do with the cooling system that I could think of.
Coolant pressure test was done and came out good.
Leak down test came out good. No symptoms or signs of a blown or leaky head gasket.
Replaced radiator around a year ago.
Replaced thermostat with 180 degrees a couple of months ago.
Air dam is still intact
Fan relays were good and verified to run at proper temps.
No leaks from the coolant system either or cracked hoses.
Reservoir cap replaced with a 18psi one
Water pump was replaced same time as the radiator and was working without issue.
System was burped yesterday as much as possible to get air out.
I have a lip years back and my temps were running 210-220 with 225 being the highest. It was only a couple of months ago where my temps were sitting high while driving and hover around 225-235 within 30 minutes.
Even had an incident happen twice where I was driving, the coolant tank would start spewing out coolant. The second time, the coolant spewed out everywhere and seen where it was coming out of the first coil pack on the passenger side.
98 vette which only has headers installed is having an issue with temps getting high rather quickly. Just from the point of starting up to casual driving after warm up, the temperatures hit 220. Then on the freeway, temps reach 230 upwards of 240 and hover there until I take the foot off the gas.
I pretty much had it checked and changed everything to do with the cooling system that I could think of.
Coolant pressure test was done and came out good.
Leak down test came out good. No symptoms or signs of a blown or leaky head gasket.
Replaced radiator around a year ago.
Replaced thermostat with 180 degrees a couple of months ago.
Air dam is still intact
Fan relays were good and verified to run at proper temps.
No leaks from the coolant system either or cracked hoses.
Reservoir cap replaced with a 18psi one
Water pump was replaced same time as the radiator and was working without issue.
System was burped yesterday as much as possible to get air out.
Stumped as to what else could be the problem.
How does the engine maintain temperature running at idle/parked? Have you tested the coolant for the presence of combustion gas? Any codes?
When parked or idling, it fluctuates between 210-225. Have not tested for combustion yet, will add that to the to do list. No codes were popping up on the DIC.
I would take the thermostat out completely and see if your temps change drastically. If they do you know the thermostat is at least part of the problem. Can always test in a pan of boiling water if you want to verify it's working.
Has the condenser and radiator been blown out lately? Those can fill up easily in a year.
Also, when even typical burping doesn’t work there’s two additional options.
1. have the coolant removed with a vacuum system. It will replace the coolant 100% no air bubbles.
2. Bleed the coolant from the front coolant crossover. Just loosen the passenger side fitting enough so fluid starts flowing out steadily and then retighten.
Most often the culprit is air in the system or debris/blockage in the condenser and/or radiator.
Last edited by vette4fl; Mar 28, 2024 at 10:10 PM.
I have a lip years back and my temps were running 210-220 with 225 being the highest. It was only a couple of months ago where my temps were sitting high while driving and hover around 225-235 within 30 minutes.
Even had an incident happen twice where I was driving, the coolant tank would start spewing out coolant. The second time, the coolant spewed out everywhere and seen where it was coming out of the first coil pack on the passenger side.
OK I'm just saying, 90% of the time when I see cooling issues on C5s, the car has an aftermarket front lip on it. At speeds, the car relys solely on airflow for cooling. And obstruction of airflow will be my prime suspect.
Good idea to look into. Recently had my radiator out and was amazed at how much crap was embedded in the condenser, especially in the top corner areas. I spent an hour or so with a tiny pic digging tiny rocks and grass out of the fins. A lot of this stuff is so wedged in it won’t blow out with compressed air at a safe level…
Good idea to look into. Recently had my radiator out and was amazed at how much crap was embedded in the condenser, especially in the top corner areas. I spent an hour or so with a tiny pic digging tiny rocks and grass out of the fins. A lot of this stuff is so wedged in it won’t blow out with compressed air at a safe level…
my condenser was like seized and frozen over or something. 😂 23 years old will do that. No air was getting through. Also make sure you have the all the necessary radiator shrouds. I bet you’re missing a piece
Oh, one other thing…. There are 3/4” thick sections of foam between the sides of the radiator and condenser. If these pieces are missing, the air can travel out the sides past the radiator.
Heres a link to a comprehensive post on the subject.
so you are saying temps rise while moving when they should be going down??
sounds like you have some type of obstruction
Yes, once it idles and warms it reaches 190. As soon as I start driving around temps creep up to 220. Once I hit freeway, those temps creep up to 230-235. This is just within 30-40 minutes of casual driving after starting the car.
Originally Posted by vette4fl
Has the condenser and radiator been blown out lately? Those can fill up easily in a year.
Also, when even typical burping doesn’t work there’s two additional options.
1. have the coolant removed with a vacuum system. It will replace the coolant 100% no air bubbles. https://youtu.be/13ekPSv66iI?si=qS6AGoU0DeuCIcyW
2. Bleed the coolant from the front coolant crossover. Just loosen the passenger side fitting enough so fluid starts flowing out steadily and then retighten.
Most often the culprit is air in the system or debris/blockage in the condenser and/or radiator.
Yes, I made sure to clean it out every chance I get. I will check today to see if anything is up there. I haven't drove the car in over a month since it was at my mechanic's shop sitting until I was able to get a new PCM for it. They the coolant bubbling over was because the fans weren't turning on. So had the new PCM installed, but the temps are still hitting higher than normal.
Originally Posted by Dads2kconvertible
I would take the thermostat out completely and see if your temps change drastically. If they do you know the thermostat is at least part of the problem. Can always test in a pan of boiling water if you want to verify it's working.
Thermostat was verified working by my mechanic.
Originally Posted by FourG63 97GST
OK I'm just saying, 90% of the time when I see cooling issues on C5s, the car has an aftermarket front lip on it. At speeds, the car relys solely on airflow for cooling. And obstruction of airflow will be my prime suspect.
Mine is a flat lip with no opening. I was going to eventually switch it to the ZR1 style lip.
Originally Posted by Lawandorder
Replace the condensor
That I will check, my AC wasn't working when I got the car back as of Yesterday.
Originally Posted by vette4fl
Oh, one other thing…. There are 3/4” thick sections of foam between the sides of the radiator and condenser. If these pieces are missing, the air can travel out the sides past the radiator.
Heres a link to a comprehensive post on the subject.
That I don't remember seeing on the sides of the radiator. I am going to check that today as well and see.
Originally Posted by jim993
A frequent cause of overheating is after the cooling system has been opened or drained for any reason is that air is still trapped in the heads.
Here is the Factory Service Manual procedure to remove trapped air from the heads:
If all else doesn't solve it, then that would be a serious amount of air in the system. I had the car burped multiple times by mechanics prior to me dropping it off a month ago to see if it would solve the heating issue. Only thing I can assume is they were doing it all wrong.
Mine is a flat lip with no opening. I was going to eventually switch it to the ZR1 style lip.
ok, then go ahead replace radiator, condenser, burp it, swap the motor. when it's still overheating you can circle back to the front lip that blocking airflow to the radiator
ok, then go ahead replace radiator, condenser, burp it, swap the motor. when it's still overheating you can circle back to the front lip that blocking airflow to the radiator
I already replied to you about this previously. I have had that lip for years with no issues of overheating or temps reaching above 220. This only started months back with temperatures hitting high. I have had high temperatures before but that was due to no front air dam.
If you are still fixated on that, by all means continue to.
Oh, one other thing…. There are 3/4” thick sections of foam between the sides of the radiator and condenser. If these pieces are missing, the air can travel out the sides past the radiator.
Heres a link to a comprehensive post on the subject.
I already replied to you about this previously. I have had that lip for years with no issues of overheating or temps reaching above 220. This only started months back with temperatures hitting high. I have had high temperatures before but that was due to no front air dam.
If you are still fixated on that, by all means continue to.
220 is not high. For a c5 that is actually normal operating temp. I would WANT the car to get to 220 to properly heat cycle everything. Even 235-236 is NORMAL. Also check your cooling fans. Make sure they are coming on in two different stages low and high.
Can Figure Out Cooling Issue
