I had the system pressure tested and the tech reported all ok, but I am on the road and have some problems I want to correct. FYI - I am from BC, Canada and taking it to Az for the winter. I am leaving it with a relative until I get back down

The car has been running normal on the hwy, but in stop & go traffic the temp gets uncomfortably high. So far the fans come on and keep it from over heating. When I shut it off, I smell antifreeze and when I open the hood there is a very slight amount of coolent that has seeped out of an undetermined point on the high fill reservoir.

I drained the coolant out of the overflow reservoir and filled the "high-fill" reservoir as per the owners manual. That included opening the bleeders until coolant flowed freely. This hasn't helped.

If anyone has any exoerienc what is causing this problem, pls give me some ideas what to consider doing to correct this.

Many thanks for any information.

 

What year is the car? And what are the temps?

 

Bob, please give the temps you hit that you are concerned about and some details of your Vette, ie. year, mods etc.

 

Is the over flow reservoir excessively filling the after driving by it self?

And if you have a LT1 with the opti, have you run your hand under the water pump to see if there is any coolant there at all. It should be dry and if the weep hole is slightly leaking a pressure test might not show it up during a static test. It might only leak when hot and under operating conditions.

Which temp gauge are you looking at, digital? If so and your past 230* there probably is something to talk about. Under 220* might be OK in traffic depending on time and outside temperature.

But as said you need to add much detail to get some accurate answers.

 

It sounds as though you have an LT1. If that's the case;
The temps run high. The digital gauge will read ~200 with the A/C on because the fans run all the time the A/C is on. With the A/C off the temps will normally run 220 give or take 15F in traffic as the fans cycle on/off and high/low. This is on the digital gauge.
But you smell antifreeze and that's another concern.
My '95 LT1 smelled of antifreeze for about a year. Only occasionally and never very strong. I dreaded the heater core replacement but waited for full failure to tackle the job. Then one 'high rev' situation blew out the 'flow control' valve. It limits the pressure that the water pump puts on the heater core during high revs. The flow control valve is located in the rubber hoses under the 'high-fill' reservoir and slightly forward of that tank. The valve is just a plastic insert in the hose. Mine was evidently dribbling for that year because after replacing it, there was no more antifreeze odor.
So feel around those heater hoses under the 'high-fill' reservoir to see if the flow control valve is leaking. Of course, the reservoir may be cracked. Especially check the neck where the overflow hose attaches. If the coolant is building in the lower overflow, you have either a bad pressure cap or a crack in the neck/hose leading to the lower overflow that permits air back into the upper tank rather than sucking liquid up from the lower tank.
And hope it isn't the heater core.
Good luck and hope this helps.

 

Many thanks for all the replies. I will check all the ideas suggested

I have a low milage 1994 LT1. Only around 50K original miles and very clean all around

Yes the lower reservoir has "excess" coolant even after the engine is cold overnight... so when cool it isn't returning to the high fill reservoir. I'm spending a few more days in Las Vegas before heading to Phoenix and will try to get to the bottom of the problem.

Again many thanks for all the responses. You have helped alot.

Bob

 

I believe there should always be coolant in the lower tank. If you look at the stick, it has mrkings for two levels, cold and hot. DexCool doesn't like to mix too much with air so I think they designed it this way.

It is not unsual for the lt1 to run in the 200's. The fans come on at 228. GM designed these to run hot for emission purposes. Plus the engine coolant is reverse flowed to keep the heads cooler. This makes temp readings warmer. Be sure you are looking at your digital gauge, this is the more accurate of the two.

You're good unless you're seeing temps north of 240. Is your A/C and heat working properly?

 

Since there is 'excess' coolant in the lower reservoir, there is an air leak in the overflow system. I've had cracked nipples just under the upper tank pressure cap as well as cracked overflow tubing that caused this problem. It could also be a defective cap that doesn't allow 'back-flow' of coolant from the lower tank to the upper tank during cooling.
Also check that the fluid level in the lower tank is above the lower hose end and that the fitting is not cracked or leaking.
Good luck.

 

Had the same problem with my 89. I had a mess in front of the radiator. Pulled the radiator and filled a 5 gal bucket 3/4 full of leafs, gum wrapers, paper, etc. Now it will not even atempt to overheat.

 

Start with the simple, the thermostat. See if it's opening before driving yourself nuts.

I have an situation right now with my car that it would run hot. The T-stat, brand new mind you, was sticking closed.

$10 and an hour later, and wham, no heating problems.

Second, debris caught between the radiator and AC can cause over heating. I had that problem too, sucked up a home depot bag. Same symptoms.

Cars run hotter at idle. ARe the fans both coming on?

 

To canadabob (I get it, Bob from Canada)
Just want to add or clarify that the level in your over flow tank should be the same everyday when its cold and not increasing everyday. The level should rise a half inch or so (or to the hot line approximately) when engine at operating temperature. And then when cools should draw back down to where it stared (to the cold line).

I agree with the cap theory if your coolant level is increasing.

 

Well I have replaced the water pump, belt, cap and sensor along with a flush and new coolant. There's no debris blocking the radiator, but it still wants to run warm in traffic and shows 233 to 235 even with the fans on. Right now the car is with a relative in Az and I'm up in BC.

Is a new radiator the final cure??? Or is it stll something elsle??

Here's a long list of ideas from a blog I found. Anyone have any experience with #4 or #7 ?? The others all chcck OK.
My description suggests insufficient airflow if car not moving. Possible causes for overheating from shop manual for conditions " engine temp lamp on or temp gauge shows hot".

1) Loss of coolant.
2) Loss of system pressure.
3) Belt tension too low.
4) Timing retarded by malfunctioning ignition control system.
5) Damaged coolant pump drive assembly.
6) Radiator fins obstructed.
7) Cooling system passages blocked.
8) Recovery reservoire hose pinched or kinked.
9) Cooling fans inoperative.
10) Thermostat stuck in closed position.
11) Malfunctioning coolant pump; eroded or broken impeller blades.
12) Incorrect radiator.
13) Missing or damaged radiator upper air deflector and/or center air deflector.
Other things that come to mind:
Engine coolant temperature sensor malfunction ( located on underside of water pump) Cooling fans inoperative.
You may be able to check some of the simpler items yourself.
Also check if you're losing or are missing coolant.

 

I don’t see where you have stated that you replaced the stat with a “LT1” stat (did I miss it). The radiator could of course be a problem with that age if it is the original. Perhaps a radiator shop might be able to do a flow test and see if it seems to be satisfactory. But with the vette, it needs all the cooling it can get and sub par radiator might cause a problem.

Also wondering how fast it gets to 233, in what driving condition and outside air temperature?

 

If you didn't replace the thermostat, or replaced it with an incorrect thermostat, it could cause the higher temperatures (the LT1 thermostat is unique as it has an extra 'plate' which opens/closes the internal circulation chamber).

We had a weird thing happen on our 1994 -- the thermostat's lower plate became slightly seperated from the main plunger (the lower 'plate' has a 'cap' which firmly slips over the main plunger), causing the internal passageway to be closed more than normal when the thermostat was closed, and prevent the thermostat from openning as much as it should when it was opened.

This caused a 15-20 degree rise in typical operating temperatures.

Once the thermostat was replaced (ACDelco), and new anti-freeze installed (good ol' green stuff -- Texaco brand), the temps are now 194-196 while driving and maybe 200-205 at a light (whereas previously they were 215-220 while driving).