I've got an 89 convertible, and about a year ago it started running hot. By "hot" I mean over 225 deg F and gradually would creep up toward 260 deg. Before it always ran between 190 and 225 deg F.

The first thing I suspected was a faulty thermostat, so I pulled it out completely to see if the flow was restricted. There was no change, so I replaced the radiator with a brand new, OEM spec radiator and still, there was no change. Next, I replaced the water pump, thinking it wasn't getting full flow and there is still no change. I also put a new 190 deg F thermostat back in it at this time.

It will get hot sitting at idle. In fact, in about 10 minutes it was fast approaching the 260 deg F mark at which point I shut it down.

Some other info that may or may not be important:

This car sits most of the time. It only gets driven maybe a 2-3000 miles/year (if it is running good).

The coolant that came out when this fist happened was very "rusty" looking. I tried flushing the block with radiator and cooling system "flush" that I purchased at Walmart three times back to back.

The cooling fan comes on at about 225 deg F and goes back off at about 200 deg F. One thing that doesn't seem right however, is it goes of with the ignition switch.

The heater doesn't seem to be blowing warm air.

I am completely at a loss of what to do next.

What in the world is going on? I've got to get this resolved.

 

My 89 had the same problem overheating. I will tell you what I learned on here.

1) your cooling fan should kick in at 226 or 228 I forget, if it doesn't. go to step 2.

2) I am going to assume you know how to pull check engine codes. If not use a paper clip here are the instructions (http://www.digitalcorvettes.com/foru...ad.php?t=22897)

When you are codes mode the coling fan should kick in. If it doesn't it's probably the main fan relay. The aux fan relay is useless and the same exaclt relay. It is located driver side offset to the left of radiator, its held in by these crappy plastic clips. The main fan relay you want to replace is on wheel well driver side. If you have a 6 speed there will be 2 relays and the fan relay is thone closer to passenger side.

prairie pirate - I also have a convertible in Dark Red Metallic with beige top, she is on the verge of 39k miles.

***** I suck with cars this info is what I leaned from the many great minds this site has to offer*****

 

Thanks guno89, fortunately the cooling fan works just fine. It comes on about 225 deg F and cools it down to around 200 deg F and then kicks back off. That is the very first thing I checked.

 

Most probable cause with everything working and crappy looking coolant with a plugged up heater core is a leaking head gasket at #7. It's a common issue with the '89, and it often started somewhere around 20,000 to 25,000 miles becoming really obvious at 50 - 60.000 miles. Pull that plug and look for rust on the threads or an electrode that looks different than all the rest. Crank the engine by hand and see if any coolant comes out of the hole. Check compression. Fix it before it wears a groove in the deck which will ruin the block.

 

Thanks, I'll have a look at the #7 plug. I also read in another forum to suspect a faulty injector causing it to run lean and hot.

 

Pirate, I'm experiencing the EXACT same problem... just pulled my 89 vert out of storage and began tinkering. It had been running hot last summer and the 'low coolant' light was coming on once in awhile so I was paying close attention to coolant issues when I fired it up yesterday...

Just sitting in my garage idling for a couple minutes the temp quickly shot up to 235 deg and kept going. the rad fan kicked in, to no effect. I have the aux fan wired to a toggle switch, turned that on... still climbing.

I hopped in and took it for a spin to see if airflow would help it cool down, it just kept climbing to 250-260 at which point I headed for home and shut it down! The coolant looks good, except for some little black specs floating in it... but the rad is full and COLD when I shut it down, rad hoses were both cool.


I just changed the heater core last year, and the rad was just in to have a new tank put on (cracked) the year before that... I was going to change the tstat next and then move on to the water pump if that didn't fix it.

Did you find out what the problem was, anything with the plugs?

Anyone else have a suggestion as to where to start?

C.

 

Yep, that sure sounds like what mine was doing! The only difference was my coolant was definately getting hot, and you could hear it "hissing" after I shut it down. Which made me think it was getting exhaust gas in the cooling system.

Well, I'm sorry to say that my situation does not have a happy ending. At the suggestion of SunCR (above), we inspected the #7 plug, which lead us to pressure testing, and it soon became obvious that I do indeed have a blown head gasket. The heads are in the machine shop this morning and my fingers are crossed that they are not ruined!! They looked OK, but you never know.

Further more, once we got it apart, we discovered that it had more than likely been blown for quite a while, and I never noticed it until it started overheating. It definately was not your typical blown head gasket that brings up visions of white smoke bellowing from the exhaust and coolant leaking.

Good luck with yours, I hope it is something more simple! And thanks SunCR for the advice, it steered me in the right direction.

 

well, crap. That's no good eh?

Guess I'll start pulling the plugs and do a compression test this week. I have a feeling this is going to have mayzwell disease written all over it tho.. mayzwell pull the motor and rebuild it while I'm in there... while I'm at it, mayzwell stroke it to a 383... mayzwell cleanup the engine bay and detail it... mayzwell give it a paint job...

Thanks man, good luck with your rebuild.

 

These cars are bottom feeders...meaning, they are fed air from under the front bumper. Check to see how much road junk is built up and blocking the flow of air over your radiator. You'll be surprised at how much junk ends up in there. After you clean up all the large trash, back flush the radiator core by running a garden hose through the fins on the fan side. This will clean up all the crud built up on the fins themselves, which also impedes air flow and radiant cooling.

 

Still shouldn't heat up to +240f while idling in my garage for 5 minutes should it? it was only 70 degrees outside, if that...

 

no, it shouldn't...but I always subscribed to the "rule out the easy stuff first" method...check your bottom and top radiator hoses and see if they're both hot; maybe your thermostat is stuck closed or clogged up with crud.

 

I just bought an 89 that was doing the same thing. After replacing the thermostat and taking the car for a ride, I realized that the radiator had busted as well. After removing the radiator, i couldn't believe all of the crap that was lodged in front of it. I cleaned all of the crud out, replaced the radiator and still periodically got some overheating. I suspected head gaskets and intakes. They both were leaking. The head gasket had just blown through on number 7. I took the heads to a machine shop to have them checked and both were cracked right next to the center head bolt. That explains the broken radiator and the violent bubbles I was getting in it. Almost forgot, mine would get really hot in about 5 minutes as well. It was blowing the coolant back out of the block.

 

I just cleaned out the rad area 2 summers ago, and it's maybe got 1000 miles on it since. I checked both rad hoses when I came back from my little run the other day, both were still cold. Rad was still cold...

I dunno, I'm going to pull the plugs and do a compression test and pressure test the cooling system this weekend and see what the scoop is.

 

pulled the plugs tonight, i don't think theres any obvious signs of water on them. they may be a bit oily if anything... I'm running platinums with the 4 electrodes.

I did notice some oil pooled on the drivers side of the intake manifold. Can't tell if it's fresh oil or not. This would be an indication of a leaking intake manifold I'm guessing? Would this cause the overheating I'm seeing?

next step is to pull the tstat and see if that fixes it, unless anyone else has a better idea?

Thanks for any input!

 

p.s. - sorry for hijacking your thread Pirate... just didn't see the sense in starting another one if we're both seeing the same problem. Lemme know if you want me to take my problems elsewhere!

 

Thermostat stuck closed

 

Bingo. New 195 tstat, floats between 180 and 200 on the road, 229 is the highest it gets sitting in the driveway.