View Full Version : How HOT is HOT?

04-12-04, 08:15 AM
Recently purchaced an 89 with 140K miles (with new motor and tranny less than 30k) drove the car from GA. to the new home in TX. Car has had no real issues just gas and drive it's a great Sunday driver until till last week. I havent driven in stop and go traffic since I have had it but, the first freeway rush hour had me sitting at a park watching the ducks till the traffic died down. The car runs about 190 with or without the AC at highway speeds, heats to about 225 at a red light and zoomed to about 250 on the freeway sitting in traffic on a cool day to boot. I have replaced the radiator and there was no help. When should I be worried and are there any other things to check or do? Yep the thermostat does open and both fans are working,radiator and resivor are full.

04-12-04, 10:08 AM
I had almost the same issue with my vette when I purchased it. Would cool when moving and go up to 240-250 when idling. I changed all the gaskets on the heads, and the intake changed. At the same time, I put a cooler fan switch kit in and now run a 180 degree stat. Now at cruising in 60 degree weather, my car runs at 175-180 and oil temp is about 10 degrees higher. Fans kick on at 204 and go off at 179. In short, check for loose bolts and worn gaskets used on complete intake and heads. Also add water wetter to the radiator( cheap and does work ). If all else fails-put in the cooler fan kit, I did for the hell of it, makes me feel better about the temps I run. Also have someone check the temp sensor and switch for fan- I changed mine due to the age. One less thing to worry about. Hope this helps.

04-12-04, 05:03 PM
It is normal for a vette to run hot, but I dont think it should be running quite that hot (not over 250) unless its a hot day.

You say your stat is opening and I assume the space between your condensor and radiator is clear, and the main fan comes on at 228F.

So if those arent the problem, you either are going to have to change to a lower temp thermostat, or change the fan settings. Preferably both if you want the problem eliminated.

It is possible, though unlikely, that your water pump is going out, so check the front of it to see if water is leaking out the weephole.

DO NOT let it get over 250 for extended periods, pull her over and cut the engine, aluminum heads are not supposed to be allowed to get so hot for long. You could blow a head gasket.

04-12-04, 06:29 PM
Make sure the relays are kicking the fan(s) on at he right time/temp.
A buddy's 89 was doing this and the relays were sticking.

Good luck, let us know what you come up with.

04-12-04, 07:00 PM
Most early C-4s run quite hot!!!! Here are a few things to check,The gauge,does it show the bottom of the range when the engine is cold? If so, is it really as hot as you think it is. Have someone check it with an accurate thermometer,One of those inferred(sp) guns works really well!!!! Its not uncommon to have the upper radiator hose temp. 235 to maybe as hot as 240 degrees. If all checks OK, You could try a lower temp. fan switch. This really isnt part of your problem but make sure you use the BEST motor oil you can find(synthetic Mobil-1) is the choice I made!!!!:w

04-12-04, 07:24 PM
250 is not normal, not for any corvette. Have you ever pulled and cleaned the radiator? If the fan and thermostat are operating normally, this procedure will cure almost all overheating problems. I highly recommend it, as it will instantly lower your coolant temp back to normal operating temperatures.

Here is the link:


04-13-04, 12:17 PM
Don't discount the water pump, even if it's not leaking.
I replaced mine as a matter of caution, I had about 140k at the time, and I noticed
a 10 degree drop on average....no joke!!
It's gonna go ...sooner or later, based on the age of your car , probably sooner at the
worst possible time.
The key to these babies is to be PRO-ACTIVE!!

04-16-04, 09:56 AM
Thanks for the various idea's on things to check. I belive I am going to start with the cheapest and work my way up from there. A new 160 stat and water wetter. By the way I had the radiator replaced 2 weeks ago before the post due to a small leak under a pressure test. dont really want to try for the head gaskets first but that coulsd be up the line. By the way is there a bleeder on the coolant system for an 89 and where might it be?

Thanks again

04-16-04, 02:45 PM
Just remember to burp the system when you change thermostats, and be careful getting the thermostat out, the small screws on the housing get brittle over the years and can break while you pull them out.

04-16-04, 09:04 PM
Might be a good idea to explain burp! the way to fill is to leave the cap off and when the thermostat opens rev to about 1500 rpm the water will dropthen fill to the cap while holding revs up when full replace the cap. this gets all air out!

04-16-04, 09:37 PM
Have you ever pulled and cleaned the radiator? If the fan and thermostat are operating normally, this procedure will cure almost all overheating problems.
Here is the link:

I did this to my 84 vette today. Fairly simple job and was definitely worth the time. There was a lot of debris, leaves, grime, etc. between the radiator and condensor. The radiator was pretty caked with all kinds of grime, mostly wet leaves that worked their way into the radiator fins. Lucky for me, I had an extra new spare radiator that I replaced mine with so I didn't bother cleaning my old one. I, too, highly recommend any c4 owner to do this if you haven't done so already. My temps used to run anywhere from 205-235, now they struggle to even hit the 200 mark at a stand still. Needless to say I'm happy and had to share the good news.:w

04-16-04, 09:39 PM
Oh yea, forgot to mention the noticeable power increase. With the temps running cooler she feels more peppy and healthy.

04-17-04, 12:09 AM
I recommend a Robert Shaw 180, as it flows more water than a Stant. 180 is plenty cool. Remember that the thermostat opens and closes, like an on/off switch.

Did you have a good system flush when the rad was changed?

I'd surely look at the plugs and the oil for symptoms of coolant leakage before pulling any heads!

And......don't call me Shirley!

04-17-04, 03:29 AM
My '85 has never been hotter than 230 even in stop and go summer traffic.

Let's elliminate a couple of simple things here first.

Were your temps that high before you had the radiator work done????

Start your Vette and let idle with hood up and AC off until temps reach 228 or so. Does your fan(s) start up when the car reaches this temp???

IMO 250 is way too hot!!! Once your temps reach approximately 228 the fans should turn on and cool down the engine to approximately 200. The fans then stop and the cycle starts all over again.

I always believe in checking the simple stuff first.

Good Luck