C4 Cooling Issue

[Jim P.]

I just recently purchased a C4 LT1 convertible as a driver. I have already driven it over 1,000 miles without a problem. However when I am at a stop light the coolant temperature rapidly climbs to where it is while driving at about 220 degrees to the low 240s and then drops again when you start driving. The temperature gauge looks like it is almost in the overheat zone. The coolant looks to be in good condition. This has been on days where the temperature is in the 70s here in Houston. I am concerned that in the summer with the a/c on and I get stuck in a traffic jam it will overheat. I was thinking of installing a supplemental electric fan.

Has anyone else had this problem? Any suggestions of what to try before going the electric fan route, or if that is a good idea a fan make or model that someone else has used in this application and how to put it in.

Thanks for your help.

[Edward J.]

Re: C4 Cooling Issue

Jim, The best way to approach this is with a scan tool and watch the coolant temp with scan tool, the electric fan turns on at about 230 degrees or slightly lower. this would be the easiest way to start. while watching the temp you'll be able to note the temp at which the thermostat opens, I believe that later years had a dual speed fan. If you do have a scan tool or know someone that does it will make life easier and your not throwing parts at the problem.

Make sure to check the level of coolant first. check when cold. these year Corvettes like to run in the 220/230 range in traffic and cool down while on hwy. Also note that when the A/C is on the fans will run all the time once the pressure is meet.

[Keith B.]

Re: C4 Cooling Issue

That's the analog reading. whats the digital reading? They use different sensors. Ones in the water pump other in the head. Can't remember which is which. Also did you check for debris in front of the raditor above the air dam?

[Jim P.]

Re: C4 Cooling Issue

Keith - Right the digital reading are the specific temps that I gave. The analog looks like it is almost at 260, but the scale is difficult to interpret.

Edward - by scan tool do you mean what some refer to as a temperature gun?

[Jim T.]

Re: C4 Cooling Issue

Jim, One day when driving my 96 LT4 on the interstate and not using the A/C and having to stop on the interstate for accident ahead I noticed the temp gauge moving up at idle. I turned on the A/C and the temp came down just fine. Leaving the congestion I turned off the A/C. Driving in Houston and turning on the A/C when necessary would be an easy solution to the temps you see. I don't think you have any cooling problems.

[Joe L.]

Re: C4 Cooling Issue

Jim, One day when driving on the interstate and not using the A/C and having to stop on the interstate for accident ahead I noticed the temp gauge moving up at idle. I turned on the A/C and the temp came down just fine. Leaving the congestion I turned off the A/C. Driving in Houston and turning on the A/C when necessary would be an easy solution to the temps you see. I don't think you have any cooling problems.

Jim------


Gordon Killebrew, C4 technician extraordinaire, used to say that with a C4, if it starts to overheat, don't turn the A/C off, turn it ON.

[Joe L.]

Re: C4 Cooling Issue

I just recently purchased a C4 LT1 convertible as a driver. I have already driven it over 1,000 miles without a problem. However when I am at a stop light the coolant temperature rapidly climbs to where it is while driving at about 220 degrees to the low 240s and then drops again when you start driving. The temperature gauge looks like it is almost in the overheat zone. The coolant looks to be in good condition. This has been on days where the temperature is in the 70s here in Houston. I am concerned that in the summer with the a/c on and I get stuck in a traffic jam it will overheat. I was thinking of installing a supplemental electric fan.

Has anyone else had this problem? Any suggestions of what to try before going the electric fan route, or if that is a good idea a fan make or model that someone else has used in this application and how to put it in.

Thanks for your help.

Jim-------



A couple of things:

1) LT1's have dual cooling fans. Make sure both are operating correctly per the operating parameters detailed in the Factory Service Manual. I don't think you'd be able to add any supplemental fansand supplemental fans should not be necessary anyway.

2) When coolant is changed in an LT1, bleeder valves must be opened as described in the Factory Service Manual in order to purge air from the system. If this is not done, air pockets can become trapped in the system and result in overheating. Not everyone that changes coolant in an LT1 knows that this has to be done.

[Edward J.]

Re: C4 Cooling Issue

Keith - Right the digital reading are the specific temps that I gave. The analog looks like it is almost at 260, but the scale is difficult to interpret.

Edward - by scan tool do you mean what some refer to as a temperature gun?

Jim a scan tool is used to aid the tech. with dia. it plugs into a connector under the dash and can read the data provided like engine coolant temp. and some scan tools have bi-directional controls to do things such as turning on the cooling fans and checking there operation. the Temp. gun will also aid the dia. od things like the radiator efficiency and can be pointed at the thermostat housing to watch the engine temp.

[Jim P.]

Re: C4 Cooling Issue

Edward is there a particular scan tool that will fit the plug on the 1994? I was thinking of getting one, anything you would recommend.

Thanks everyone I will check these things particularly the easy one like turning on the a/c.

[Edward J.]

Re: C4 Cooling Issue

Jim, go onto Ebay I bet you can find one the is reasonably priced. If it has bi- directional control capability that's a plus. It will take some time to get a handle on how it works and what you looking at when viewing the data stream. for what your going to be using it for you will not need anything special.

[Larry M.]

Re: C4 Cooling Issue

Jim------


Gordon Killebrew, C4 technician extraordinaire, used to say that with a C4, if it starts to overheat, don't turn the A/C off, turn it ON.

Having owned a new 1987 Z51 car here in New Orleans, I can agree with that. My car always ran hotter when I turned the AC off. That is why I always ran with it on.

The Z51 option had both a puller and a pusher fan (dual fans…..independently activated).

Larry

[Pat M.]

Re: C4 Cooling Issue

I completely agree with Jim T., Joe and Larry - turn the AC on in those conditions. Works on my 96 every time.

[Keith B.]

Re: C4 Cooling Issue

I would like to agree and disagree at the same time on using the AC to help keep it cool. In the seven years and counting daily driving my 94 I never once had to turn the AC on JUST to help with cooling problems.

[Larry M.]

Re: C4 Cooling Issue

I would like to agree and disagree at the same time on using the AC to help keep it cool. In the seven years and counting daily driving my 94 I never once had to turn the AC on JUST to help with cooling problems.

[Duke W.]

Re: C4 Cooling Issue

That's pretty much the way all modern cars work. One or more electric fans, only, that engage at something like 220-230. The reason engines usually run cooler with the AC on is that the fans are also energized by a pressure switch in the AC system that engage the fans to condense the refrigerant, and some cars have two speed fans - low speed engaged by the AC system and high speed when coolant temperature engages them.

Duke