84 corvette at, 90,000 miles, VG condition This evening I took my college age son out to dinner. Drove around campus for a while then took him home. as I left his house I noticed the check engine light , the red bar at the coolant temp guage and a temp of 289. I was 8 miles from home so I drove carefully. As I drove the temp dropped and the lights went out. When I got home the temp read 214. Too hot to check raditor. No leaks anywhere. Some fluid was pushed out of coolant resv. not much, enough to get the area wet. Where should I be looking ?

 

The only advice I have for you is to not ever let it get to 289 again!
It does not matter how careful you drive it, or how close it is to home. Pull it off the road and shut it down.

You stand a very good chance at cracking or warping a head at those temps. Anything over 260 is asking for trouble.

 

I just checked the radiator..FULL...no leaks! any clue?!

 

After a heat cycle of this magnatude, I'd replace the T-Stat ASAP.

If your engine is stock, go back with a stock temp T-stat or check the stampings on the old unit.



PS remember to fully burp or pack the coolant.

 

Is the fan working?

 

I'll be checking the fan today.

 

After a 289 heat cycle, I would think your oil is toast. Change it immediately. Follow the above posts .....change or check t-stat, full coolant system change & replace with fresh 50/50 mix of antifreeze and distilled water. Check or change top and bottom hoses. Check or change radiator cap. Pull the radiator and do a complete cleaning.
Burp or pack...your choice when replacing coolant.

 

thanks for the advise....will follow.

 

Check for debree between the radiator and condensor. Could be full of leaves and junk.

 

SOUNDS LIKE THE FAN RELAY IS BAD.
When I first got my 86, the thing would only cool off when I was moving. That meant that the fan wasn't turning. I replaced the fan relay, and it has worked fine for 14 years.

 

How do you burp/pack coolant on these things? The high point looks like its in the radiator hose near the alternator. TIA

 

I wondered about that myself. I replaced the thermostat today. Interesting.... The oil I changed 2 weeks ago looks and smells ok, the tranny fluid the same. It was only a quart of coolant low.No leaks. Hoses look ok. I did order a new fan relay just in case. I'm going for a test run tomorrow.

 

Hi AZ I am dealing with a similar experience. Did the motor actually get hot? In my case I dont think it did. Mine went to 240 on the gauge. It spiked up there in less than a minute under light load. I will be suprised if it could acually have gotton that hot that fast. It is looking like the sensor. I replaced the water pump (leaking) and need to remove all air from the system. Do you see any indication that yours acually got that hot?

good luck
Dave

 

I just had my head gaskets replaced. (89 Vette). I don't have overheating problems anymore. Head gaskets are a common problem with these older C4's. Just make sure you do it right. Do BOTH heads, get both heads checked for cracks, warp etc. Some fool, (previous owner), only changed 1 head gasket in mine, it just ends up blowing out the other one. It was actually rotted from lack of antifreeze also. Hope this doesn't happen to you.

 

nothing is wrong with your oil. 289 is nothing for oil.
coolant is another story.
sounds like a bad stat, or fan, or head gasket.

 

Crepitus,
If you changed the coolant in your engine, you will have air pockets in the heads until you can get the thermostat open and enough water flow from the water pump. If you got a spike, it was because you had extremely low coolant, and an air pocket near the sensor, and you are measuring the steam temp in that area.

 

Thanks i think your right.

 

just changed stat,relay,fan motor,switch and hoses..pump not working, That's neat also fan won't work .relay connector looks cooked. looks like past owners trbl coming back. will replace connector also. any idea where to buy a relay connector with pigtails?
Thanks

 

What do you mean the Pump is not working??

I have the same car, I had the same issues, I had to replace the pump and have the radiator boiled out completely. then I had to flush the block about 6 times before the rusty water would stop coming out.

Stock Thermostat and new hoses with the system properly maintained and the heat temps never see 220°

 

You need to get a multi meter and use it to fix your fan wiring. Stop blindly throwing parts and money at this thing. Obviously you're not getting voltage to the fan. Buy the 84' GM shop manual for exact wiring diagrams. If you can read a diagram you'll know which wires to start testing for voltage and continuity and how the fan system is outlined.

Your main fan should turn on at about 229 degrees, and whenever the AC is turned on. You said the fan is still inoperable even after you blindly threw in a new fan and relay without testing first. So obviously that's the first thing you need to fix, your fan issue. Without your fan, your temps will just continue to rise while standing still. You always test the wiring and relays before you just go out and blindly dump money on unneeded parts for this very reason. And most places won't accept returns on electrical parts for this same reason. In all likelihood, all you simply have a break in the fan wiring causing your overheating, and every part you went out and bought was an unecessary waste of money.

Knowing WHEN the car gets hot is 90% of the story. A car that runs hot only while sitting still but not while driving indicates a lack of airflow through the radiator which is the purpose of a fan. Below 30 mph, the fan is the only thing keeping your car cool by sucking air through it. If it's not working, there is nothing to keep the temps from rising until you start to move again and air is flowing through the front of the car and radiator. Which sounds like what you are describing. Above 30 MPH the fan becomes useless. At that point the incoming air through the front takes over, exceeding what the fan can ever put out. By you saying the temps dropped massively from 289 to 212 simply by driving tells us a few things:

Your water pump is fine. If it wasn't circulating coolant the temps would have remained high while driving since the water would just be standing still. But since the temps dropped by an amazing 76 degrees just by driving, this means the cooler water in the radiator was circulated to the engine where it was needed and where the Gage temp sender is, hence the massive drop in temps. This also tells us that the thermostat must be opening. If the stat was stuck closed, the upper radiator hose would feel noticeably cooler than the lower, also hard to squeeze, and no circulation.

Do not let the car get this hot again. You're lucky you didn't blow the head gaskets. Shut the car off earlier, since the temps will continue to spike some more after the engine is off.

Raise the front of the car to change the high point to the radiator. Top off radiator. Start the car and have somebody raise and hold the engine rpm to 1500-2000 while you add more. With raised rpm's the coolant level in the radiator will drop. Top it off again and reinstall the cap BEFORE letting the rpms back down or coolant will spill out. Repeat for the next several days after normal driving until level remains and air bubbles expelled.