L98 Overheating/Coolant Problem
Thread Starter
Intermediate
Joined: Jun 2008
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L98 Overheating/Coolant Problem
Hi,
I have recently been trying to solve the overheating problem with my 1987 Z52. I cleaned out all of the leaves and had a 180-degree thermostat installed. She ran well for about two weeks, but temperatures started to creep back into the 240s (in traffic) culminating with a 270+ degree overheating episode several days ago.
After the car cooled down, I filled the radiator and reservoir with coolant and drove home with no problem. The next day I had the radiator flushed, after which the car is very hesitant when accelerating, idles far higher (and rougher) than normal, and I'm very perplexed.
Did I blow a head gasket or damage the heads? Is it possible the new thermostat is not operating properly? Beyond the recent problem with the engine, what do I do to lick the oveheating problem for good?
Thanks,
Conrail4022
I have recently been trying to solve the overheating problem with my 1987 Z52. I cleaned out all of the leaves and had a 180-degree thermostat installed. She ran well for about two weeks, but temperatures started to creep back into the 240s (in traffic) culminating with a 270+ degree overheating episode several days ago.
After the car cooled down, I filled the radiator and reservoir with coolant and drove home with no problem. The next day I had the radiator flushed, after which the car is very hesitant when accelerating, idles far higher (and rougher) than normal, and I'm very perplexed.
Did I blow a head gasket or damage the heads? Is it possible the new thermostat is not operating properly? Beyond the recent problem with the engine, what do I do to lick the oveheating problem for good?
Thanks,
Conrail4022
Instructor
Joined: Sep 2004
Posts: 216
Likes: 4
From: Linton Indiana
If, during the 270 degree overheating session you lost a lot of water, there is a good chance you might have warped something, like a head. Could you tell where the water escaped from? That car came out with aluminum heads which are a little more prone to warp than the old cast iron ones, but it also could have blown an intake gasket or a head gasket. When you put the new coolant in did it stay or leak back out? Also you might check your radiator hoses to make sure they're ok.
Instructor
Joined: Sep 2004
Posts: 216
Likes: 4
From: Linton Indiana
Let me say also that these engines are always going to run a little warmer than other cars because of the way the Corvette gets it's air to the radiator. The air is hot down by the highway and the Corvette gets its air from the bottom of the car which doesn't help. The best thing you can do is keep the cooling system clean and good belt and hoses.
Pro
Joined: Nov 2005
Posts: 602
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From: North Bay Ontario
Can't say for certain whether you have a head gasket problem, but I'd be thinking that way especially with the recent high operating temps that you have described...my limited experience with a blown head gasket and the associated warped head on a Chrysler 2.2, found that temps seemed increase when idling, and when the leak worsened, there was excessive pressure in the cooling system causing it to puke the anti-freeze. Check for white smoke coming from your exhaust (either bank) and/or moisture or a sweet smell at the tail pipes.
Le Mans Master
Joined: Sep 2006
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From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
you might just check your throttle position sensor. I found that in rainy weather my 86 adcted like that and it turned out that the TPS wasn't sealed around the edges where the back was glued on.
So if it got wet during the flush procedure, it might be at fault.
Also, if your mechanic isn't familiar with corvettes, just a simple filling won't do it. it has to be burped.
So if it got wet during the flush procedure, it might be at fault.
Also, if your mechanic isn't familiar with corvettes, just a simple filling won't do it. it has to be burped.
Last edited by coupeguy2001; Sep 1, 2009 at 12:50 AM.
Thread Starter
Intermediate
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Thanks for all of the replies. After the overheating, the coolant level in the radiator was close to normal, but there was nothing at all in the reservoir. I added more coolant to the radiator as well as the reservoir and drove home with no problem. The next day, I briefly started the car, and after it cooled a bit (not completely), I opened the cap and a fair amount of the anti-freeze did come out. I wasn't sure if that was because I hadn't let it cool down enough or if I over-filled the radiator the day before.
The Throttle Position Sensor could have gotten wet (I couldn't watch the procedure and the car didn't have this problem before the flush). Also, how do you burp the system? I had this done at Jiffy Lube, so perhaps the system hasn't been burped either.
Thanks again,
Conrail4022
The Throttle Position Sensor could have gotten wet (I couldn't watch the procedure and the car didn't have this problem before the flush). Also, how do you burp the system? I had this done at Jiffy Lube, so perhaps the system hasn't been burped either.
Thanks again,
Conrail4022
Safety Car
Joined: Nov 2004
Posts: 4,991
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From: The Pines South Jersey
what you described is proper - the rad drank up the reservior - keep that at the proper level the next few times you drive and let it cool down. that is essentially burping it.
Let's hope that 270 was a false reading.
Let's hope that 270 was a false reading.
Le Mans Master
Joined: Jun 2006
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From: One day you're a Comet...the next day you're dust... Arkansas
Continue to add coolant only to the over flow tank. If you add water add only distilled water. I can tell you 90% of the the Jiffy Lube guys will screw you up.
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Thread Starter
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Thanks for all the help, guys. The other day, I tried starting the car. Beforehand, I opened the radiator cap and it spewed out some coolant--however, it had not been burped since the flush/refill. It took three tries as it was very hesitant to turn over. I drove it around the block twice. At first it was ok, though the acceleration was certainly not normal--barely noticeable "missing" as I used the throttle. This became more apparent as I went up a small hill.
However while stopped briefly at a traffic light, the temperature climbed quickly from 220 to 261 before it held steady for about 15 seconds, then went back down to 222.
By this point, anything that might have been on the throttle position sensor should have dried up (unless it really worked its way in there).
So, am I looking at a blown head gasket here? If so, how much would this cost to have repaired/is it possible for a novice DIYer to do without monkeying up?
Conrail4022
However while stopped briefly at a traffic light, the temperature climbed quickly from 220 to 261 before it held steady for about 15 seconds, then went back down to 222.
By this point, anything that might have been on the throttle position sensor should have dried up (unless it really worked its way in there).
So, am I looking at a blown head gasket here? If so, how much would this cost to have repaired/is it possible for a novice DIYer to do without monkeying up?
Conrail4022
Le Mans Master
Joined: May 2006
Posts: 9,226
Likes: 9
From: Irvine Ca
The rise in temps could be alarming (the uphill incident). That could mean that you have a blown head and super heated temps are blowing into your cooling res......that is extreme....let's back off that for a little while.
How old is the water pump??? It could be on it's last leg.
Have you ever had your Rad boiled out? there could be a blockage....(Not likely)
What electronic wire got too hot during the 270° episode. This is what I'd like to be looking for....some wire or sensor is now having an issue with a ground or something that may have been brought on by the over heated condition.
Apparently the coolant sensor has a LOT to do with the CPU etc.
Sorry, I'm not much help....but sometimes asking the right question nets you the correct answer
How old is the water pump??? It could be on it's last leg.
Have you ever had your Rad boiled out? there could be a blockage....(Not likely)
What electronic wire got too hot during the 270° episode. This is what I'd like to be looking for....some wire or sensor is now having an issue with a ground or something that may have been brought on by the over heated condition.
Apparently the coolant sensor has a LOT to do with the CPU etc.
Sorry, I'm not much help....but sometimes asking the right question nets you the correct answer
Team Owner
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
The ECM will adjust the RPM higher as the water increases.
SO someone else flushed the radiator? Which means they may have tampered with the TB stop or other components.... Seems that you need a FSM and start from the beginning.
The next day I had the radiator flushed, after which the car is very hesitant when accelerating, idles far higher (and rougher) than normal, and I'm very perplexed.
Last edited by JrRifleCoach; Sep 6, 2009 at 01:15 PM.
Thread Starter
Intermediate
Joined: Jun 2008
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Thanks again for your replies. I will take it to my Corvette shop, and hopefully get the problem licked. The one thing I can say I feel good about is that the oil is not milky at all--so I'm hopeful its not the worst, but I'll let you know when the verdict comes down.
Conrail4022
Conrail4022
Drifting
Joined: May 2006
Posts: 1,428
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From: Chewelah Wa
You might try taking the radiator out and cleaning the fins. I had to use a pressure washer on mine, and you would not believe the stuff that came out, dog hair, sand, etc. You have to be careful if you do this or you will damage the fins. I tried everything to keep my car from overheating, and this was the cure. I had the same problems you are having.
Safety Car
Joined: Jan 2008
Posts: 3,939
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From: Vero Beach Florida
Check closely along the intake to head area for an intake leak, this can raise coolant level temp very fast. Also make sure your fan is comming on at the right temp setting should be 228 without AC running.
Drifting
Joined: May 2006
Posts: 1,428
Likes: 7
From: Chewelah Wa
Other things that keep my car below 200 degrees, even on the hottest of days:
185 degree thermostat w/ 2-1/8" holes drilled in it
Main fan comes on at 208 degrees (adjustable thermostat switch)
Throttle body bypass (don't really know if this affects water temp)
Repaired air dam (had been curb slapped)
Water Wetter additive
Squeaky clean radiator and condensor
I also have the stock oil cooler
185 degree thermostat w/ 2-1/8" holes drilled in it
Main fan comes on at 208 degrees (adjustable thermostat switch)
Throttle body bypass (don't really know if this affects water temp)
Repaired air dam (had been curb slapped)
Water Wetter additive
Squeaky clean radiator and condensor
I also have the stock oil cooler
Melting Slicks
Joined: Apr 2003
Posts: 3,110
Likes: 6
From: Red Sox Nation! RI
Kind of sounds like you have an air pocket in your cooling system or possibly another bad thermostat - maybe a cheap one?
When the temp is up around 180, try squeezing the top hose with a rag. See if it's hard (water backed up) or if you can compress it. See if temps come down. If you fill the radiator, run it, fill it and keep the overflow tank up where it belongs, your water level should be ok. I just worked on a Porsche that had a similar problem and it took a few cycles to get the stat & temps back to where they belong.
Check your dipstick for signs of coolant in the oil. Go to Autozone or Advance Auto and get their free rental radiator pressure tester. It's quick and easy. I f you see a noticeable loss of pressure, then you may have a head/gasket problem.
When the temp is up around 180, try squeezing the top hose with a rag. See if it's hard (water backed up) or if you can compress it. See if temps come down. If you fill the radiator, run it, fill it and keep the overflow tank up where it belongs, your water level should be ok. I just worked on a Porsche that had a similar problem and it took a few cycles to get the stat & temps back to where they belong.
Check your dipstick for signs of coolant in the oil. Go to Autozone or Advance Auto and get their free rental radiator pressure tester. It's quick and easy. I f you see a noticeable loss of pressure, then you may have a head/gasket problem.
