1989 Corvette Overheating At Idle Solution

[Superc63]

Hey,

So, the symptoms of my overheating issue were essentially it would overheat (I mean temps of 220+) at idle (no white smoke or antifreeze smell from exhaust, oil clean). It would reach these temps after maybe 2 or 3 minutes of idleing. If I were driving it in stop and go traffic, it would be quicker. I could lower the temps by placing the trans in neautral and bringing my RPM up to 1600...even if at a dead stop (made me think it is not an air flow issue). Car ran at a steady 198ish while cruising or on the highway. I replaced the waterpump with a normal voulme water pump from AUtozone for like 40 bucks. I still had the issue...and on top of that, I was losing coolant. Also, my coolant would look all rusty and what not after a very brief time. (I made the mistake of using straight water for coolant. I did this while I was troubleshooting my overheating problem.)
So, solution one, I put one of those Flowkooler high volume water pumps in and in the process, I figured out where I was loosing coolant, I did not tighten the water pump mounting bolts much nor did I use Mr. Gasket on the gaskets. I did not make the same mistake with the Flowkooler. I drained my rusty water and flushed the system just before installation of the new pump. I used 50/50 Antifreeze for coolant to refill it. The actual antifreeze looks great after a couple hundred miles. Apparently using straight water or too much water was causing corrosion and making the coolant look horrible after like 100 miles.

I let the Vette idle in my driveway for about 10 minutes, max temp was about 198 or 199. That was about 3PM Saturday. Now, around 5:30 Sat evening, I get the bug and I am outside literally cleaning out the area under my plenum near the Fuel Pressure Regulator. I disconnected the vacuum line to access this area.

Monday morning, I drive to work, 30 miles mixed driving. The car is exhibiting the same overheating symptoms and on top of that, blue smoke in the exhaust at idle...and a lot of blue smoke if I rev it up. I get to work and start looking around. Evantually, I notice I left my Fuel Pressure REgulator vacuum line hanging. I hooked it back up. I just let the car idle in the driveway for about 10 mins. I reached 200. So, looks like my initial overheating issue was misinstallation on a cheap waterpump and using water for coolant. Second overheating issue was disconnected vacuum hose between plenum and fuel pressure regulator. I am surprised that hose made such a difference.

I just wanted to share so in the future, anyone with a L98 experiencing unexplained overheating issues knows to check that.


Cheers,
Chris

 

[boomdriver]

Another tip regarding water only....DON;T DO IT !

running straight water cools better. It transfers heat better because its thinner. BUT...straight water suffers or causes electrolysis and that will destroy the aluminum in the system very very quickly. As electricity flows thru the block the charge travels thru the water and this allows electrons from the aluminum to be carried away with it in a chemical reaction driven by the electrical charge. The end result is an aluminum head that has the water passage eaten thru into the combustion chamber like someone poured acid in there....There will be pits and holes at random spots where ever there is aluminum. The solution is a zinc anode to take the abuse of the electricity much like the zinc blocks that are mounted on the hull of a ship or power boat....for the same reason. There are zinc anodes attached to radiator caps that drop in the radiator for those that want that extra oz of protection against electrolysis. The use of the proper mix of anti-freeze & water prevents this chemical process from taking place. The only other concern is antique anti-freeze that eventually turns acidic from time. Thats why/how dexcool came to be with 5/50 protection against corrosion. Its got an est life of 5 yrs before it breaks down chemically and goes acidic. The standard green is only good for about 1 yr. This is based on cycles & time, but many many people run the same green for a decade without incident.

 

[Superc63]

Update, I Was Wrong

So, it seems like that new water pump and reconnecting that fuel pressure regulator only worked for like 20 mins. This morning, I drove into work (twice, forgot my ID) and by the end of the 1.5 hours of driving, the temp would climb pretty quickly at idle. Also, I have white (with a very slight bluish tint) smoke coming out the exhaust at idle...even after 1.5 hours of driving.

So, I have concluded I need head gaskets. Bummer. Oh well. I'll get to it sometime this winter.

Total since I started having the engine warm up at idle until it got bad enough for me to conclude it is a head gasket was probably about 600 miles of driving.

Cheers,
Chris

 

[boomdriver]

Wheres the proof?

any loss of coolant?

any foam/gel on dipstick, pcv or oil filler cap?

any spark plugs fouled from water?

your temps are nothing strange. The fans are not even supposed to come on until it hits 226 degrees...unless a/c is on.

A little white smoke can be from the cats, from moisture in the exhaust...from water in the fuel.

Before drawing a conclusion you have to prove it (justify) tearing the engine apart. Get some evidence before getting the tools out.

 

[gmjunkie]

Wheres the proof?

any loss of coolant?

any foam/gel on dipstick, pcv or oil filler cap?

any spark plugs fouled from water?

your temps are nothing strange. The fans are not even supposed to come on until it hits 226 degrees...unless a/c is on.

A little white smoke can be from the cats, from moisture in the exhaust...from water in the fuel.

Before drawing a conclusion you have to prove it (justify) tearing the engine apart. Get some evidence before getting the tools out.

220* ain't nut'n on these cars,Hell the secondary cooling fan won't even kick on unless your running less than 55 MPH w/AC on,Cooling Diagnostic Trouble set,or Engine Temp Exceeds 235*!!!
You have another problem,Leaking Injectors,Faulty Fuel Pressure Regulator,Faulty PCV Valve,Faulty Valve Seals,Partially Plugged Cat,Worn Piston Rings,Weak Ignition System,just to name a couple!

 

[Superc63]

I'm not sure of the best way to post youtube videos, so here is the link. This shows what I think is excessive steam which would indicate coolant getting into the combustion chambers through a bad gasket or worse (cracked head or block).

Suspected Bad Head Gasket - YouTube

I do not have any signs of coolant in the oil yet.

Do you guys think this looks like a head gasket?

Cheers,
Chris

 

[John Robinson]

All this started when you replaced the water pump as I understand it. Boomdriver and GMJunkie have given you some very good possibilities for you to check before you start removing the heads. Check the vacuum hose routing and make sure that they are all connected to the right place. Think about what changes in the engine when the temp gets to normal operating temp. The thermostat opens (did you replace with a new one)(Is it in backwards) You used a high flow water pump the second time (is it a high volume pump because it use's higher pressure)(or is it because it has a high volume) The thought here is if it uses pressure to achieve more cooling then when the engine gets to temp for the thermostat to open if it doesn't open or is in backwards then the coolant system could be forcing water into the combustion chambers through the intake or throttle body. You can try removing the pressure cap and then bringing the car up to temp by idling it and see if that reduces or eliminates the smoke. While you have the pressure cap off have it tested to be sure it is working. Just for the sake of conversation lets suppose the cap is rated at 10# pressure. What that means is it will hold a pressure in the cooling system of ten pounds and at lets just say 12# pressure it will relax and relieve the pressure in the system to prevent over pressuring the system. If you have ever seen a pressure cooker working it is very much like what happens with the cooling system. This is not a put down but something was introduced when you replaced the water pump with a non OEM water pump so focus your attention on those things you did and how they affected this situation.

 

[gmjunkie]

I'm not sure of the best way to post youtube videos, so here is the link. This shows what I think is excessive steam which would indicate coolant getting into the combustion chambers through a bad gasket or worse (cracked head or block).

Suspected Bad Head Gasket - YouTube

I do not have any signs of coolant in the oil yet.

Do you guys think this looks like a head gasket?

Cheers,
Chris

Are you loosing Coolant?~??
Do you have any mis-firing?~?? (I couldn't tell from the Video!)

 

[John Robinson]

Junk I have a question for you on this. If the PCV valve was plugged would it cause the back pressure to force oil up past the rings? As I see it that would explain why this starts after the engine gets to temp because that is when the oil is hot and thinned out but more importantly it has had time to build up pressure in the crankcase.

 

[gmjunkie]

Junk I have a question for you on this. If the PCV valve was plugged would it cause the back pressure to force oil up past the rings? As I see it that would explain why this starts after the engine gets to temp because that is when the oil is hot and thinned out but more importantly it has had time to build up pressure in the crankcase.

Yeah,It could!
Also,Sludge Plugged drainback holes in the heads can too!~!!
I've had to clean out allot of them on the SB's,Oil level in the valve covers get so high it sucks oil past the valve seals!~!!

 

[K & B Special Products]

I see no one has suggested cleaning the trash that's picked from the road out of the bottom of the radiator. That's the first thing to do. The second is to put in a lower temp thermostat. It will work great wnen the car is moving. GM ser these cars up to run at 220 degrees to help lower emissions. 220 does not help performance & longevity like 180 degrees does.

 

[John Robinson]

I see no one has suggested cleaning the trash that's picked from the road out of the bottom of the radiator. That's the first thing to do. The second is to put in a lower temp thermostat. It will work great wnen the car is moving. GM ser these cars up to run at 220 degrees to help lower emissions. 220 does not help performance & longevity like 180 degrees does.

Yes the trash can be a factor as you say if you truly have an overheating problem. From what we are being told about the temp the op was seeing it appears that his car was not having an overheating problem and in fact was perfectly normal. I really am surprised that the perception is that the colder the engine runs the better. Perhaps this is a case of two much knowledge is harmful. My 06 Pontiac runs 225 degrees without a hitch. If GM had not put two ways to read the temperature in these cars this would be a non issue. What do you suppose the operating temperature is of all the cars with idiot lights instead of a gauge. You guessed it about the same as the Corvette but because you can't see what it is you don't make a fuss over it. Oh an if that is the case then lower engine longevity is not proven when we look at the number of cars regularly going 200K or more with out the engine failing. As for lowering the thermostat again the ECM is programmed to manage the engine within certain perimeters and when you start changing those perimeters you start to degrade the whole system. As others have said the old school knowledge were we could adjust a carb or the timing and sharpen up the performance are gone. With the new generation of cars. they require a whole new way of thinking. Look at it this way. You want to build a wall with 6 sections equally spaced between the studs so it will fit precisely between other walls. you get the lumber and cut the pieces you are going to use to build the wall. The distance between the walls you want to build another wall in dictate the size of the 6 sections you need to build to complete the partition. If you are careful and ad hear to the exact dimension needed you will be able to build the wall and it will fit the whole perfectly. But if you cut the pieces a few thousandths short each time the new wall will not fill the hole and so the the overall integrity is compromised. That is the danger you run when you start to modify what the hundreds of engineers have designed. Believe me when I tell you for daily driving they have given you the best performance and all around drive ability available.

 

[K & B Special Products]

I respectfully disagree. The ECM is designed to work perfectly well at temps below 225 & engine longevity will not be affected, either.

 

[John Robinson]

I respectfully disagree. The ECM is designed to work perfectly well at temps below 225 & engine longevity will not be affected, either.

I respect your opinion but am a little confused. You stated in your first post that running higher engine temperatures reduced the life of the engine. I responded to that by pointing out that we now have engines that go over 200k that are running at temperatures in the 225 degree range. Which indicates that higher temp do not reduce longivity of the engine Now your position seems to be that lower temperatures do not effect the longevity of the engine. Yes you are right that the ECM can work at lower temperatures because it does so regularly. How it does it is by being in open loop until the temperature reaches a predetermined point and then it goes into closed loop. Unfortunately I am unable to find any reference in my FSM about what the temperature is when that happens.

lOOP STATUS - Tech 1 ~isplays Open or Closed -
"Closed Loop" displayed indicates that the ECM is
controlling fuel delivery according to oxygen sensor
voltage.

In "Open Loop," the ECM ignores the oxygen
sensor voltage and bases the amount of fuel to be
delivered on TP sensor, engine coolant, and MAP
sensor inputs only.

This information is from my 93 FSM Looking at this information it appears at some point if the coolant temp is forced to be below the ECM threshold for closed loop it would revert back to running in open loop or limp home mode.

 

[Superc63]

So, a few folks have asked, yes I am definitly loosing coolant...but no puddles. I went though an entire overflow tank worth in about 60 miles.

I don't know why it is not steaming until the thermostat opens. I did not install a new thermostat. I think the installation of a high volume water pump made my slightly leaking head (or possibly intake) gaskets much worse.

I had similar symptoms before I installed the high volume water pump(thats why I installed it)...but not nearly as severe (I thought it was condensation in the exhaust and I thought I had slight leaks at my original water pump installation because I could go a few days without having to top the coolant off).

I do not think I have leaky rings. I had an 88 with bad rings. I could pull the dipstick out and start the engine and you could see steam blowing out the tube. If I revved it up, oil would shoot out the tube (even cold oil). I found a 90 at a used car dealer doing the same thing. Used car dealer told me it was bad gas.

My 89, there is no steam coming out that dipstick tube.

I did check the PCV valve. It is not gummed up and rattles around pretty freely. I will replace evantually.

I didn't clean out the area in front of the raditor. I can kind of see in there and I see leaves...but the being partially blocked wouldn't cause all that moisture in the exhaust.

The engine will go up to 230+ if I am not careful. When it reaches 220, I'll put it in neautral and bring my RPMs up to like 1600 to drop the temp back down. That worked enough for me to get home without letting my temp get much over 230.

Thanks for all the help!

I definitly enjoy reading all your posts.

Cheers,
Chris

 

[John Robinson]

Thanks for the update. You might try going to an Advance Auto Parts Store and having them put a pressure tester on the system. If it does not hold pressure and there are no leaks from any of the hoses you might then be right about the heads or intake. From your video I would expect if it was putting that much water through a cylinder it would be misfiring badly. I can't tell from the video if the smoke is actually coming from the exhaust pipes. I have seen that before on my 93 when it blew a radiator hose and then again when it blew a heater hose. In both cases the water was going onto a hot exhaust and then rolling out of the back of the car.

I am still holding out hope that you don't have a head problem.

 

[Hib Halverson]

If you have to refill the overflow bottle after 60 miles, you're not leaking coolant, there's no coolant in the oil and bluish/white smoke comes out the exhaust; I'd be looking for any leak from the cooling system into the combustion chambers, intake ports or exhaust ports. This could be bad intake gaskets, bad head gaskets, cracked intake manifold or a cracked head.

If you don't have bad rings now you will soon...with that much coolant going through the engine, you'll have coolant in the cylinders after you shut the engine down. That will rust or pit the bores quickly.

Once you tear the motor down, it will be obvious if the problem is gaskets. If it's not gaskets and you can not see cracks in the intake or heads, you'll need to have the manifold and the heads pressure checked.

That much coolant going through the engine will usually clean up the cylinder where the leakage is so pull your plugs and take a look at them. If you have one that's running cleaner than the others, that might be your bad cylinder, but...in the end, with that much coolant being used, you might as well start tearing the motor down.

Earlier in this thread some information was posted about straight water as coolant. Some of that information was inaccurate.

It is true that water-based coolants can have trouble with aluminum corrosion due to "electrolysis", however, running straight water for a short period of time--a few days or a few hundred miles--is not going to cause a catastrophic failure of aluminum parts exposed to water, however, long term use of straight water will damage the system.

That said, there is simple solution to corrosion in systems cooled with straight water and that is Red Line Water Wetter, the active ingredients of which are 1) a package calcium-based corrosion inhibiters similar to that in "Dexcool and 2) a surfactant (or "wetting agent") which improves heat transfer from the cooling jacket walls to the coolant. I use straight water and Red Line Water Wetter as coolant for all my Corvettes and most of my other cars. I do so because water is a better coolant than 50/50 mixes of water and antifreeze. Of course, there are limitations to this: 1) you can't do it if the car is parked overnight or stored where the ambient temp is below freezing and 2) it's not advised in high-performance duty cycles above 8000 feet altitude. I change coolant every 2-3 years. I have done this for over 20 years.

Dexcool (the name GM coined for its Texaco-developed antifreeze which uses a calcium-based corrosion inhibiter and is dyed orange) is good for about 5 years in most engines and duty cycles. Older style antifreeze, which uses a sodium-based corrosion inhibiter and is dyed, green, yellow or blue, is good for about 3 years. It is best to change the coolant on a time rather than a distance basis, that is, with Dexcool, if, in five years, you only drove 100 miles, you still should change the coolant.

Antifreeze does not "break-down chemically over time." The corrosion inhibiters loose their effectiveness over time as they work. When their ability to inhibit corrosion is decreased, corrosion begins and, in the case of aluminum parts, its driven, in part, by electrolysis.

 

[Superc63]

Update

Hello,

Thanks much for all the help and explanations!

So, I ended up taking the Vette to a mechanic a month ago(I read some horror stories about threads getting trashed in the heads and didn't want to risk it). Turns out, I had a blown head gasket leaking coolant into the #7 cylinder. I have pics. I will post later. The gasket was blown towards the firewall side of the cylinder. Also, #7 combustion chamber had a crack right between the intake and exhaust valve. So, when I tested the coolant system for pressurization, there wasn't any extra...probably because that cylinder wasn't making much if any compression. It was basically just burning the coolant and passing it through. Weird symptoms. It was making lots of steam though!

Anyhow, I picked up a used set of heads and had them refurbed and installed. All seems good now. I spent some time and restored my valve covers while they were off...that was well worth the effort! I also had the radiator replaced (there was so much rusty crud in the old one that it weighed about 30% more than the new one!). Now, the car runs anywhere from about 190 to about 201 under all conditions.

I am a little disapointed in the overall job. I think the folks that refurbed the heads didn't put new valve stem seals in because I have the puffs of blue smoke at startup and sometimes at intial acceleration. I might bring it back to the mechanic tomorrow and see what he has to say. I almost don't want to push it because the smoke is little more than a nuisance and all else is great!

Despite the little puffs of blue smoke, I am still very excited to have my Corvette back on the road! It seems more powerful than I ever remember it and the temp is no longer a concern! I put about 400 miles on it in the past week. I averaged 18.75MPG on the first tank (although the computer said 25.5, its been wrong for as long as I owned it!).

Cheers,
Chris

 

[Superc63]

Pics of Bad Head Gasket for #7 Cylinder

Here's the pics of what ended up being my problem.

Bad Gasket:

Steam Cleaned #7 Cylinder

I don't have a pic of the crack between the intake and exhaust valve in the head...but I do have a pic of the used replacement head pre refurb...the crack on the original head is literaly right in the middle of the two valves and it goes horizontal so there was no way the valves were ever sealing:

Cheers,
Chris

 

[Superc63]

And Heres Before and After Shots