I posted a few weeks ago and received lots of help and I appreciate it very much! However, my car is still running hot. It only happens when I'm sitting in traffic or stopped for a period of time with the engine running. My husband has cleaned and flushed the radiator, cleaned the debris from in front of the radiator, and replaced the fan on the inner portion of the car (closest to the motor - I think the secondary fan). He had already replaced my thermostat. My A/C is definitley pouring out colder air than before and the car is even running somewhat cooler, but, I was stuck in traffic and my car's temperature sky rocketed! I had to pull over and let it cool off (about 280 degrees). I added antifreeze the next morning before starting back to work and it has been running pretty good since, but still has a tendency to go above 240 or more. I panic at the thought of being stuck in traffic because I know my car will overheat! Help please! :confused:

 

If you had to add antifreeze then that may mean the radiator needs to be packed. Fill it full when cold replace the radiator cap then start it up and let it warm. I've done this w/o putting the cap back on and it still works the same, I just don't want to take the cap off when it get's too warm. When it's warm (100*) take off the cap and raise the RPM's to 2500 and hold there while you top off the radiator. I put the cap back on while the RPM's are raised. Other than that I'm drawing a blank.

 

I didn't know what year Vette you were referring to until I pulled your profile and since I've got an 86 and yours is an 87, here's what I think is happening.

If everything is in good working order, and the radiator has been packed, you have a two fold issue:

One is airflow and the other is thermostat opening temp. You need improve both to lower the operating temps of the engine.

Merely installing a lower temps stat, like a 180 or 160 degree, won't do the trick because all that will do is allow the coolant to begin to cycle through the radiator at a lower temp. You need to couple the lower temp stat with a lower temp turn on of the fan.

Then, not only will coolant begin to flow through the radiator at a lower temp but the fan will begin to remove the unwanted heat from the coolant at that lower temp.

There are a several ways to address the problem.

One is to have the PROM reburned to make the main fan (the one on the engine side of the radiator) to activate at a lower temp.

Another is to install a switch in the cylinder head - to replace the one that's currently there - which will turn on the fan at a lower temp.

Another is to replace the small auxillary fan (on the bumper side of the radiator) with a larger fan that pushes more CFM. You can either tie it to the main fan circuitry or install a toggle switch on the dash as I did.

Another is to make the mods recommended in the TPIS Insider Hints catalog of blocking the bypass hole (lowest hole, passenger side of the water pump) but this requires the removal of the water pump. Then you install a Robert Shaw (AutoZone) lower temp stat and drill four .125 holes in it to serve as a bypass. This is what I did and I also included a PROM reburn which turns on my main fan at 180 F.

Now even in this extreme Texas heat, my engine rarely crosses 200 F.

In addition, I recently replaced my aux fan (because it threw a blade and vibrated like crazy) with a Derale 16" fan as a 'pusher' controlled by a toggle switch mounted to the dash to lower the temps during idle/AC on conditions. This improved the airflow through the radiator when the car is idling with the AC on and now it only reaches 206 F under those MOST stenuous conditions.

High engine temps are a common concern with Vette owners and you'll find lots and lots of posts from others on this same issue. The Vette is a ground feeder and has terrible airflow through the radiator at idle and low speed.

A buddy of mine spent of $500 for a oversized radiator trying to address his high temps on his 86, but now realizes it was a waste of money since I'm running the same engine with a stock radiator and have solved my high temp problems.

BTW, slightly retarded ignition timing will cause higher coolant temps too, so that is something to check.

Hope this helps.

Jake

 

Hi Pamela: You said your husband cleaned the front of the radiator. You didn't say if he removed it from the car. Removing it from the car is the only way it can be cleaned properly. This takes some time but its sure worth it. Some of the material that colects between the fins is very difficult to dislodge even when its out of the car. He may have to straighten some of the fins. They are delicate so care must be taken. He must have a whole bucket of patience to complete job correctly. my operating temp lowered almost 20 degrees. I now can drive in slow hot summer rush hour traffic is Atlanta without temp going above 220. I have added a swich to turn on the fans without the a/c on if I get in a accident back up thats 5 or 6 miles long it helps also. But cleaning the radiatior, out of the car was what cured my problems.. Good luck Rich

 

If you removed the radiator from the car and cleaned it and the fans come on when they are supposed to, you have a bigger problem. Once an engine hits about 265* there is no cooling it down any futher as the coolant is boiling and it will shoot very quickly to high temps.

Time to check for clogged radiator (internal), and problems like head gasket leaks.

Good Luck

Pete

 

Thanks so much for the detail. I will take home for my husband to use as a guideline. I read that you are retired from the Chicago Police Department, very commendable. My husband is with the Memphis Police Department.

Thanks again for your help...hope this works!


[Modified by Pamela, 6:51 PM 6/28/2002]

 

Petel is right on the money. Your cars was designed to run get up to 230 before the fans even think about turning on. If your car can not cool itself then, or after, then you do have a bigger problem. Putting in lower temp stat may help, but you have not fixed the problem. If the car runs cool while driving then that takes the head gasket out for the most part. I've had several head gasket leaks on cars in the past and all would over heat no matter what. Then again you did have to add antifreeze, HUM? It sounds more like a rad. problem. I'd tell you how to check the rad. for flow, but the truth is at the nice old age of 16 you should just replace it anyway. They run like $100 at NAPA, or advance.

 

Temps that high suggest a problem with the cooling system, more than inadequate airflow. You may have a water pump going out or a bad thermostat. It is also possible you have a bad temperature sensor.

 

You have a cooling system problem as they have said.

You must flush the radiator, hell run coolant through the block too something is blocked.
Your t-stat may not be opening at all, time to go to a 160 if its opening correctly.
I didnt notice whether he wired the fans together with a fan switch or not, but if theyre coming on at all, the car shouldnt be touching 250 degrees. If he didnt wire them together, time for you to get the chip reprogrammed to have them come on early.

If it gets 255 again, you gotta stop it and let it cool.

 

Year before last, I left my car idling with the A/C on while I went into AutoZone - had a passenger - and it was 104 degrees F. ambient.

When I came out my coolant temp was at 260. As soon as I drove away the temps immediately began to drop and stablized at 220 as I drove along the city streets at 40 MPH.

That got me to thinking; that the biggest difference was airflow through the radiator. That even the stock and aux fans couldn't cope with August Texas temps.

So when my aux fan finally gave up the ghost, I installed a 16" Derale Tornado instead of just replacing the dead one with another stock one.

Two things happened:

My normal, non A/C temps rose 10 degrees F but my idling A/C temps never reach 210 F.

I believe the larger fan acts as a partial restriction to airflow during normal idling with A/C off so instead of the coolant temps remaining at 180 they are now 190. But with both fans running and the A/C "on" while the engine is idling, temps don't cross 210 F.

So, for me, the difference is airflow through the radiator.

Even with a stock radiator, I believe airflow is the real key to controlling temps.

BTW, I put up a (too) long post on another board on this point. It seems that lots of folks get nervous when their coolant temps cross 200 F,. but I don't agree. I wish I could get my coolant temps to maintain 220 - two twenty - under all conditions, during both cold and hot weather.

Ingested air temps down; coolant temps up: that's what I strive for.

Just my thoughts.

Jake

 

It might just be air in the system. I don't know what year or engine you have. On my 92 LT1 there is a bleeder valve on the top of the lower radiator hose that goes into the thermostat neck.

I filled with the valve open until some coolent came out. Then tightened it.

Then I ran the car with the cap off and watched the steam of coolent flow by. No air bubles or burbs so no air.

Then I gently topped it off, waited a sec to make sure it stayed that way and put the cap on. Then I filled the reserve to the right mark.

90 degrees with ac on and stop and go, I hit 215. But I also have the Mezier electric water pump that flows full speed even at idle, so that helps a bit I am sure.