My '89 6-speed coupe is experiencing MASSIVE overheating and I don't know what the problem is.

The car overheated on me the first time late last summer. It didn't bother me so much since I was putting it away for the winter anyway. During the winter, I changed the thermostat, the upper hose, flushed the rad, and put in new GM coolant (the green stuff). I just took it out today, and while idling the temperature climbed to normal, with the fans cycling on and off as they normally should. But when I got the car on the road, the temperature started to climb very high (130C or about 270F). Both fans were on, but they weren't dropping the temperature. I turned around and headed back home. When I hit the driveway, I turned the car off immediately and popped the hood. There was coolant all over the passenger side under hood - no doubt from the coolant overflow bottle which was bubbling pretty baddly.

I should also mention, while the car was idling, there was considerable white smoke pillowing out the exhaust pipes, accompanied with a weird smell. This smoke went away as the car warmed up, so I figure it's probably a combination of both moisture in the exhaust system and in the gas tank - the car was stored with very little and VERY old fuel in it all winter (a mistake, I know). I thought that it might be a sign of burning coolant, but there's nothing in the oil.

I'm totally stumped, and what's worse my cousin wants to use the car for his wedding in 2 weeks.

HELP!!! Anybody have any ideas at all?

 

It sounds like a closed thermostat. Try removing it and taking it in the house. Next put the thermostat in a pot of water and heat the water. Look and see if the thermostat is opening and closing.

You are sure the main cooling fan comes on , right ?

Vic

 

Do a cylinder leak down test. I am think you have a blown head gasket.

 

Check and clean BETWEEN the two radiators...it gets loaded with crap and will overheat your car when you drive.

Check this thread out...

http://forums.corvetteforum.com/zerothread?id=265835

 

White smoke out the exhaust usually means blown head gasket. Look for water in your motor oil. If the antifreeze is in the oil it will start to eat up ther engine bearings so drain the oil out quickly and start you valve job.

 

Check thermo- just to be safe,Do you have an air pocket in the block?
This will cause it to overheat as Well.
Is your radiator cap bad?
What mixture are you running(50/50-70/30 etc)??
Not being mean,just wanna help.
Matt

 

Hey guys, thanks for the quick responses. In answer to some of your replies:

Vic'89:

The thermostat is new, and I know it works 'cause I tested it before I put it in the car. It's a 160 degree 'failsafe' unit too, so if it does fail, it should fail in the open position. To top it all off, I took a tip from the TPIS Insider Hits book and drilled 2 holes through it also.

And yes, the main cooling fan comes on like clock work - at 107-108 C. The boost fan also comes on when the temperature gets REALLY high (which is normal).

Corvette0096:

I hadn't thought about a leak-down test. Is that something I can do at home? If not then I'll need to figure out a way to get the car to a shop.

JonM:

I had the rad out of the car when I changed the thermostat, and I vacuumed all the leaves and dirt out from the rad tray using a ShopVac. I know it's clean.

weekendwrench:

The white smoke has me concerned too. But would burning coolant contribute to an overheating condition? And if the car was buring coolant, why would the smoke stop as the car warmed up? I've also heard that when coolant and engine oil come in contact, they form a milky-mocha colored gel-like substance. The car doesn't have any of that.

BTW, I've also checked the plugs and they all looked fine, so I'm not totally convinced that the car is burning coolant.

A neighbour of mine thinks I should take the rad out of the car (again) and have it checked by a local shop. He believes that it's either the rad or the water pump. I personally believe the pump is fine.

So while I appreciate all of your posts, I'm still stumped...

Any additional thoughts would be greatly appreciated.

Thanks again guys.

 

Hi 6sp.89

I'm pretty sure that the thermostat is OK (re. an earlier reply to Vic'89). As for an air pocket, when I filled the car with coolant, I had the front end of the car about 3 feet off the ground in an effort to get the rad as far above the engine as possible in order to eliminate any chance of air getting trapped in the system. I don't think there was any air in it. Funny thing is, when I started the car, I got the 'LOW COOLANT' light on the dash, but it turned off then came back on a couple of times for the first minute or so, then turned off and didn't come back on.

As for the mixture, it's about a 70/30 coolant-to-water mix. In fact, it's probably closer to 80/20...

If you have any more ideas, I'm all ears...


[Modified by TheCorvetteKid, 4:13 AM 5/6/2002]

 

Have you made sure that the coolant is circulating? Water pump is moving the water?

 

Hi again Corvette0096

I think that the pump is working fine. When I first filled the system with coolant, I tried to 'pack' the system as described in the service manual. I had my brother in the car holding the engine at 1500rpm (so that I could concentrate on filling the rad). When I took the rad cap off, the coolant level had dropped significantly as the pump began to pull coolant into the block.

Is there any other way that I can tell if the pump needs replacement (appart from the obvious like leaks and such)?

I'll be honest, I'm dreading the possibility that it may be something as serious as a blown head gasket (or worse, a cracked head). It's not so much the cost of such a repair, but the time. Like I said, I need the car in 2 weeks for a wedding.

 

Certainly sounds like blown head gasket which was common on the 89 due to galvanic corrosion of the head gasket. The first time you overheated is because the gasket blew. Pull the #7 plug (for some reason that is where most blow). If you have rust on the plug threads that's a good indication that you're sucking coolant. Also, the coolant will look like crap within a very short amount of time. You can also go to a radiator shop and have them check the coolant for the presence of combustion gasses.

 

ABSOLUTELY! You will not believe how much crap accumulates there, and it will block airflow enough to overheat your car. You MUST remove the radiator to clean the front, but it's relatively simple. Do this before spending any more money.

 

Once the water dropped you topped it back off? Here is what i do. I take the thermostat out and fill the rad till the water level reaches the point there the thermostat sits in the manifold replace housing and hose and fire it up. Crank the heater on and let the car reach operating temp.15 min or so come out after things have cooled down top it off again.

 

Hi again guys,

Thanks for the great response to the posting - I appreciate you all taking the time out to lend your advice.

I think I've decided on my next step. I'm pulling the rad out of the car tonight and getting it tested and/or flushed first thing in the morning. If the rad is blocked or clogged, then I think I know where my problem might be (it's the original rad BTW). If the test shows that the rad is fine, then I'll consider changing the waterpump before putting everything back together. If that doesn't solve the problem, then I'll have no choice but to get the car flat-bedded to a shop (I'm not prepared to rip the heads off of the car right now).

I'll also check the plugs. I checked them when I changed the thermostat, but I don't mind checking them again - especially the #7 plug.

I don't know if I mentioned this in an earlier posting, but the car's temperature tended to increase the faster I drove. When I slowed the car down, the temperature started to come back to normal range. Does this mean anything?

As for the white smoke, is there a chance it could be a combination of REALLY old gas and condensation in the tank? I stored the car with almost no gas in it and no fuel stabilizer for the entire winter (I know, I know, bad move). I only recently filled the tank with a jerry-can and repeated trips to the gas station (the gas that was in it was probably well over a year old - I think I only used the car once last year and the gas that was in it was already pretty old). I originally thought that the smoke coming from the exhaust was coolant, but I read somewhere that when a car is burning coolant, the smoke should smell 'sweet'. This smoke does not smell sweet! Nor does it have a sulfer-like smell. It's hard to describe, but it's a very VERY irritating smell (it also irritates the eyes too). Funny thing is, the smoke goes away once the car gets moving. You'd figure if the car was burning coolant, the smoke would get worse as your drove right? Maybe it's just dry valve seals?

Oh, I also forgot to mention that when I was driving the car around, it wanted to stall-out on me almost every time I came to a stop. I was attributing it to the old gas and condensation in the tank.

Any thoughts on some of this stuff?


[Modified by TheCorvetteKid, 11:38 PM 5/6/2002]

 

One thing I noticed in your posts is that you said your mixture was close to 80/coolant & 20/water. Thats way too rich on the coolant. You really only need 50/50 in "Southern Ontario". I have 60/40 up here and its more than enough to protect from freezing. The problem is that pure "coolant" is not very good at extracting heat so you need the water mix to help pull heat out.
As for the white smoke, is it possibly just the normal "vapour" that all cars produce as the "cat" converts the exhaust and releases water vapour before it heats up. I'm with you on the smell, its probably from the stale fuel.
Remember, always look for the simple things first, you might be worring over nothing. Good luck. :cheers:
BTW, are you going to the Big Wasaga Beach weekend in August, lots and lots of Vettes will be there.

 

It is possible that condensation is causing the white smoke but... I recently had the same problem, I pulled the plugs cranked the motor over and wham, lots of water from one cyl. There was no water in the oil As it turns out, my heads were worn from a galvanic reaction and water started entering the combustion chamber, not much, but enough to make it get real hot and to cause some condensation.

I chose to Look on the bright side, now I get to do some performance mods on the top end, the only problem is that I am moving across country in July and the car needs to be back togther by then.

Good luck,
Joe

 

Hey gang, it's The Kid again,

Well, the rad's out now. I shined a light into the filler neck to see if there was anything in there I didn't notice before. There was some build up, but nothing I would consider abnormal. I guess the rad shop tomorrow will tell the tail...

I'll post the results tomorrow.

Funny thing though - when I pulled the MAF and air horn off of the throttle body, there was liquid in the air horn's pleats! It smelled like water and gasoline. I opened the throttle plates and shined a light into the plenum and I could see little droplets of what appeared to be the same stuff (there wasn't any of this liquid forward of the MAF). My dad thinks that it's just the condensation from the drastic change in temperature of the motor (from extremely overheated to garage ambiant temperature). That may be true 'cause most of this liquid was on the upper surface of the air horn. I sprayed a throttle body cleaner into the plenum to get rid of the stuff, but I left the air horn untouched - I want to get a second opinion. Anybody think there's reason for concern here? :confused:

1-MORTOY:

You're probably right - maybe an 80/20 ratio is a bit too high. Seeing as I have to fill the system with coolant again, I'll use a 50/50 or 60/40 ratio. Hopefully that'll help things.

As for Corvette Weekend at Wassaga Beach - I'd love to go this year, but It'll depend on whether the car is working properly or not. You know, I've lived in Ontario my entire life, and I've never been to Wassaga Beach, let alone on Corvette Weekend. Keep your fingers crossed and maybe that'll change this year.

joalyons:

I never thought about cranking the motor over with all the plugs removed to look for water entering the chambers. I'll definitely try that next - thanks! BTW, what cylinder was it that was taking in coolant? An earlier posting by SunCr says that cylinder #7 is prone to problems (drivers side, closest to the firewall).

Thanks for the posts guys.

P.S. This is going to sound like a REALLY stupid question, but can anybody explain to me how to loosen the belt tensioner?!? There's a 15mm nut on the front of the tensioner, but I'm not sure wheter to turn it clockwise or counter-clockwise? it seems to me that you would have to turn it clockwise to drop the pulley away from the belt, but normally that would tighten the bolt. Am I loosing my mind here?



[Modified by TheCorvetteKid, 3:00 AM 5/7/2002]

 

I believe a 1/2" breaker bar will plug in nicely and give you enough leverage to raise the tensioner up off the belt. Saves on buying a 30.00 serpentine belt tool, at least it worked on my 84.

 

OK, I think I might know part of the problem here. Check your lower radiator hose. It should have a rigid spring inside of it that keeps it from collapsing as the water pump creates suction. If that spring collapses or becomes soft, the hose rigidity under suction will be compromised. It might flow just fine under low RPM, but when the speed increases (and the water pump spins faster), the soft hose collapses thus blocking the flow of coolant.

I'm not positive that this is your problem, but I HAVE seen this condition before caused by a lower hose with a collapsed spring. Check this out, it would be a total bummer to have the car flatbedded to a shop for a $15 hose. Good luck, let us know what you find out.

 

Could it be anything cat-related (broken cat, clogged exh-pipe)? I had that kind of a problem in my -89 earlier