Hello from a new member. I joined Covette Forum to tap into your knowledge to try to solve a problem with my '96 LT4 cooling system.

I replaced the water pump, everything went fine. When I filled the system back with 50/50 DexCool, I filled at the pressure tank, and kept the bleed valve on the thermostat housing open until coolant ran out. I started the engine, and continued to add coolant until it would accept no more.

The engine overheats. I have allowed it to get to 217 degrees (180 degree thermostat), which is the limit of my comfort level. I have swapped out the thermostat, checked the old one and it seems to work fine, so does the new one.

I noticed that the upper radiator hose seems empty. This is the one that goes into the top of the thermostat housing from the top of the radiator. This hose has an upward bend, so I took it loose from its support, and pushed it down so any trapped air would flow out. I also squeezed it to force air out. I was able to get some more coolant in by doing this.

I also removed the small fill hose on the top left of the radiator to check the radiator level. The radiator is full. I can't find any more areas where air would be trapped, though.

None of the manuals for my Vette mention that it takes an act of God or sacrificing my only daughter to get the system full. Anybody have any word of wisdom?

Also, the articles I've read are contradictory about which direction the coolant flows. I am thinking it flows INTO the thermostat housing from the radiator. Is this correct?

Thanks for any help you guys can give me.

Bruce Smith

 

In the LT1 the coolant flows from the thermotat to the radiator. I assume the LT4 is the same. Seems your doing it right by bleeding the air out of the system. Are you sure your radiator is OK?

 

Just changing to a lower temp thermostat will not make your engine run cooler. Once it is open the temp will keep rising until the fans come on. I have an 89 L98 and the fans don't even come on until it reaches 228 degrees, not sure when they come on for an LT4.

 

217 is not hot for a C4....
Have you checked between the rad and the condenser for an accumulation of road debris?

 

Ditto what everyone else said. 217 is not too hot, not even close. If it was running 217 while going down the highway under light load it might indicate something, but 217 under any other conditions is to be expected. I believe the stock setting don't have any fans coming on until close to 230.

Jason

 

 

One test you can try is to force the fans on by wire jumping the switch - then check the engine does not go above 200 degrees.

These engines all run hot and so 220-230 in traffic is 'normal' - however when the fans are running it should get it down to below 200. You can have the temp at which the fans turn on adjusted with a programmer if you want but we just get used to seeing 220+ temps

 

1. I can see water circulating in the reservoir with the pressure cap off--you might verify that.
2. Did you get a good quality water pump and made sure that you got the coupling connected between the drive and the water pump?
3. Others report having someone hold the rpm at around 2000-2500 with the cap off and getting the system to take more water--don't let rpm drop until you put the cap back on or you will get a hot bath.
4. The AC turns on the fans and I don't normally get over 200, but I had to replace the plastic mickey mouse radiator because of two failures with less than 50K miles.

Hope this helps.

 

With most of all that has been said.

217 is not hot at all. I know it freaks you out a little, if you have never had a C4 before. I think all of us have been there.
Your fans should kick on at 228 degrees, or if you just turn on the AC, they will come on while the AC remains on.
Turn the car on and let it idle with the cap off of your coolant resevoir, and you can see if the coolant is moving, if it is, at least you know your water pump is working. The level should drop if you have air in the system, just keep adding coolant until full.

 

I just went through the same thing w/my LT1 the cooling systems are similar. Fans will come on low at 228° and drop you to 217° or so. If you get to 238° The fans will kick up to High. One of my relays was not correct so I was not getting anything until 238° kind of makes you nervous... If you run your A/C the fans will stay on to help cool the system.. So if your not comfortable over 210° turn on the A/C. otherwise you sound normal...

 

Problem solved. Thanks for the suggestions. I used them all. Filled the coolant system while running the engine at 3500RPM, then put the cap on quick. That got enough coolant in so that the cylinder heads didn't overheat. Took it out for a run, which got all the air out.

 

I had tons of heating problems with my 93. Replaced everything easy and in the end realized that the radiator was filled with road grime. It was a solid brick of dirt.
Replaced it and everything's fine.

 

Has anyone had success with putting in a cooling fan kit from Ecklers NOT the manual switch kit but the automatic switch kit that comes on at 195 F and shuts down at 180 F (Ecklers part # 25-113335-1) . Would appreciate any positive feedback. Already back flushed system and changed thermostat 180F. Thanks Hammer

 

You can get re flash your prom to set the fans to come on at any temp you want

No idea how to do it on a 94

On my 93 I have An ostrich plugged into where my chip goes. I can attach a USB cable to it, use the appropriate $da2 definition file on tuner pro RT and tune the available tables on my laptop computer. One of the tables has values for cooling fan 1 on off points and cooling fan 2 on/off points.

You can make the car run a lot cooler this way.

It runs hot for emissions purposes .

I have mine running cool for forced induction purposes - don't want detonAtion under boost

 

DIZWIZ24, THANKS but I have no Idea what "re flash your prom" means? I'm not so tech savvy. The car runs great on open road speeds (freeway it runs at 175 -179 for hours out here in the country it runs 175-190 F depending on how many small towns I have to go through) the temp will increase in the length of a stop light by 15-20F if I have been in stop and go traffic for more than 10 minutes . RPM will start to surge from 750 to 900 the up to 1100 then up to 1200 RPM at this point the engine will shake like heck and shut down. Yes checked for obstructions between radiators changed to lower thermostat etc. Was specifically hopping that someone had installed an after market cooling fan kit with positive results . I know these LT1 engines are supposed to run "hot" but mine runs great when it is constantly moving THANKS ACAR94

 

with my 96, I did exactly what you did, started it, let it come up to temp, shut it off, let it cool, added more coolant; started it up etc.; took four to five cycles before all the air purged itself from the entire cooling system, then all was well.

 

Your problem is something besides a cooling problem. Out on the road your temps are actually a bit lower than what is considered normal. In stop and go traffic the temps will go up as the fans do not turn on until about 229. The RPMS should not fluctuate and go up like they do. That is the problem you need to work on. It has nothing to do with the cooling system.

 

Like you, I'm not used to seeing coolant temps ramp up that high...even though it's apparently normal to do so.

In any case...I've adjusted fan #1(the smaller one?) to run continuously. With combination of heavy stand still traffic/+90 degree day & A/C not running...it's never gotten higher than 215.

 

From what I have read the fans are not designed for continuous running and will not last.
What is wrong with letting the car run the way it was designed to run? A normal operating temperature of 210 is fine, and if your fans come on at 229 and the temps go down everything is good.

 

Hello to all, I am a noob who has fallen in love with my 84 c4. I knew nothing of the temperature fluctuation in corvette's and I have spent a lot of money having a new radiator, fan and investigation done on why my temp was going up during stop and go traffic. My baby runs beautifully on the freeway 160-170 while we're moving but I saw 228 in thick traffic and started to sweat. My mechanic has most recently told me that I have a leak in my heads and the unrestricted pressure is causing the temp to fluctuate. Should I trust that my cooling system is designed to fluctuate and just make sure that she is full of coolant like I do every morning or have my head gaskets replaced and be prepared to see the same variations visually. I really like my car and being only three years older than her I would really appreciate if some of you older vett-erans could share some of your wisdom with me.
Cognac510