1996 LT1 Overheating Nightmare
Thread Starter
Cruising
Joined: Mar 2007
Posts: 13
Likes: 0
From: SoCal California
1996 LT1 Overheating Nightmare
I purchased my Torch Red 96 LT1 in August of 2007 (after selling my 84) and never had an issue until recently. This experience has become increasingly frustrating as my Vette is currently my DD.
Some days the car runs perfect. I drove over 100 miles from San Diego to Los Angeles with the engine temp floating around 200.
As I pulled into Burbank the engine temp shot up from 200 to past 260 in a matter of Seconds. I let the car sit for 15 minutes, started it back up and it was like nothing ever happened. The "Low Coolant" light comes on, however the reservoir is almost full and bubbling like crazy. Overheats are completely sporadic. There is no oil visible in the coolant. The fans come on automatically at 230.
Things I have done over the past week (None of which fixed it)
1. Replaced the water pump.
2. Had the system professionally bled and flushed. (Multiple times)
3. Replaced the 160 thermostat.
4. Replaced the radiator cap with a 16psi.
When the engine is not overheating the car runs very strong which leads me to believe it is not a head gasket issue.
Any advice from the Vette experts?
(At the day spa)
Some days the car runs perfect. I drove over 100 miles from San Diego to Los Angeles with the engine temp floating around 200.
As I pulled into Burbank the engine temp shot up from 200 to past 260 in a matter of Seconds. I let the car sit for 15 minutes, started it back up and it was like nothing ever happened. The "Low Coolant" light comes on, however the reservoir is almost full and bubbling like crazy. Overheats are completely sporadic. There is no oil visible in the coolant. The fans come on automatically at 230.
Things I have done over the past week (None of which fixed it)
1. Replaced the water pump.
2. Had the system professionally bled and flushed. (Multiple times)
3. Replaced the 160 thermostat.
4. Replaced the radiator cap with a 16psi.
When the engine is not overheating the car runs very strong which leads me to believe it is not a head gasket issue.
Any advice from the Vette experts?
(At the day spa)
Race Director
Joined: Jan 2005
Posts: 10,641
Likes: 13
From: Slidell Louisiana
Have you cleaned the front of your radiator? Since air comes in from the bottom debris can block airflow to the radiator, leaving you with marginal cooling.
If nothing is blocking the radiator I'd pressure test the cooling system.
Mike
If nothing is blocking the radiator I'd pressure test the cooling system.
Mike
Melting Slicks
Joined: Oct 2004
Posts: 2,662
Likes: 8
From: Knoxville Tennessee
If you are getting bubbles in your overflow tank you could have a cracked head, a blown head gasket or a crack in the cylinder block. I had trash covering almost half my radiator on my '92 and it would slowly heat up in traffic or when stopped. Continous bubbles coming from the radiator usually indicate the first three possibilities listed.
Bernie
Bernie
Burning Brakes
Joined: Feb 2009
Posts: 785
Likes: 3
From: Richmond Virginia
They're notorious for it-debri in front of the condenser and between condenser and radiator. I'm also wondering if as you say "200 to 260 in a matter of seconds"-- about a air pocket ( I know it's been checked) coolant shouldn't/wouldn't jump 60 degrees in a matter of seconds. Are both analog and digital gauges close to the same even when it overheats ??
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
Just a thought....You said you replaced the 160 thermostat. Did you make sure the one you replaced it with is for a vette? The LT1 has a reverse flow cooling system and takes a special thermostat. Just any old 350 thermostat won't work.
Thread Starter
Cruising
Joined: Mar 2007
Posts: 13
Likes: 0
From: SoCal California
Watching the temp gauge climb was similar to watching an analog speedometer climb at wide open throttle. It usually happens when going up any kind of grade. The bubbling in the reservoir only happens when the engine has overheated. On "good" days there is no problem whatsoever.
Going to check on the radiator. I appreciate the feedback.
Going to check on the radiator. I appreciate the feedback.
Last edited by -Bell-; Dec 28, 2009 at 05:21 PM.
Drifting
Joined: Nov 1999
Posts: 1,502
Likes: 12
From: Yorktown Heights NY
The most important item othr than the radiator is the thermostat.
If you don't have the special LT-1 thermostat with the long cylinder and round valve plate on the end, the water doesn't circulate properly into the block, instaead it recirculates mostly through the radiator and water pump....can definately cause your symptoms.....I know why from a personal experience
Also, make sure they bleed air from the bleed valve on the thermostat gooseneck
Lastly, check to see if both fans are running when you get too hot.
There are three fan relays and when one goes, the fans will ot come on properly. If I remember right it goes from one fan on to both low and then both high. Three stages!
The three relays are located on the driver side of the radiator shroud. I have had one of the connections actually overheat and not work properly.....
Good Luck on finding the problem
If you don't have the special LT-1 thermostat with the long cylinder and round valve plate on the end, the water doesn't circulate properly into the block, instaead it recirculates mostly through the radiator and water pump....can definately cause your symptoms.....I know why from a personal experience
Also, make sure they bleed air from the bleed valve on the thermostat gooseneck
Lastly, check to see if both fans are running when you get too hot.
There are three fan relays and when one goes, the fans will ot come on properly. If I remember right it goes from one fan on to both low and then both high. Three stages!
The three relays are located on the driver side of the radiator shroud. I have had one of the connections actually overheat and not work properly.....
Good Luck on finding the problem
Intermediate
Joined: Aug 2009
Posts: 42
Likes: 1
that sounds very similar to my '95 that i bought in July. The over heating was inconsistent. It would get pretty warm in traffic and then cool down once i got up to highway speed. I pulled pressure test with the radiator and it looked ok. then one day i guess pushed it far enuff that it really started to smoke. I pretty much did everything you have and then once it started smoking, i pulled the plugs and then the heads.
In fact now i am really thinking about replacing the thermostat back to a 180 degree and changing the fan programing since it never gets above 190 even in traffic.
Good luck to ya
In fact now i am really thinking about replacing the thermostat back to a 180 degree and changing the fan programing since it never gets above 190 even in traffic.
Good luck to ya
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Melting Slicks
Joined: Feb 2008
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From: Palm Beach
Melting Slicks
Joined: Jul 1999
Posts: 3,214
Likes: 101
From: Decatur, Alabama
A good shop willo have a 'sniffer' to detect any exhaust leak into the coolant. water pump drive pin could have been installed wrong ..unlikey. spend the 25 to 50 bucks for a real shop to check for head leaks with the right tools....not just a pressure test, then we can get into real diagnostics....right now, we're spittin in the wind. and yes, the wrond thermostat will do exactly what your describing too,
Le Mans Master
Joined: Mar 2004
Posts: 8,700
Likes: 298
From: Ft. Lauderdale Fl
Could have sucked up a plastic bag/news paper etc. There is a 1" x 1" peep hole. Take a flash light and take a look. Its located on the right side of the radiator shroud. Might be time to pull the radiator and clean out the debris.P.S. I know you said you changed the t-stat but it sounds like yours is stuck (not opening)(wrong new thermostat? or bad new thermostat)
Last edited by runner140*; Dec 29, 2009 at 07:58 AM. Reason: additional information
Team Owner
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From: Riverside County Southern California
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Clean the radiator+shroud. I have a similar problem with my 95. It heats up fast in traffic and during the summer I watch the temp gauge more than the road. The radiator is old/beat (15 years old) I have a Dewitt's Aluminum Rad on order.
Race Director
Joined: Jan 2005
Posts: 10,641
Likes: 13
From: Slidell Louisiana
Rereading his pulling into Burbank makes me think that you may be onto something......I didn't even think fan because I'd notice they weren't running in traffic however, OP might not...but the anytime going up grade has me pondering........
But fans are an easy check....
I believe easiest check is to turn AC on, pop hood and see if fans are running....(is there easier way to force them on????? )
Mike
Last edited by aboatguy; Dec 29, 2009 at 03:58 PM.
Team Owner
Joined: Mar 2001
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From: Boston, Dallas, Detroit, SoCal, back to Boston MA
you can jumper the relay(s)
I've also hooked them up direct the to battery.
if it's intermittent, then it might be a little harder to tell
but certainly next time it overheats
kill the engine, then turn the key ON and see if they come on.
I've also hooked them up direct the to battery.
if it's intermittent, then it might be a little harder to tell
but certainly next time it overheats
kill the engine, then turn the key ON and see if they come on.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Low Coolant Light and over heating tells me air in the system which happens the LC sensor is exposed to air. If the pressure testing gauge won't hold, there's s leak somewhere.
Why the coolant level became low to cause low coolant has to be discovered too. Overflow reservoir bottle should remain at the proper level with coolant.
Burp, pressure test for any leak would be my first moves rather than jumping to the more extreme possible causes. Logical, sequential, basic stuff first - K.I.S.S.
Last time I had an issue like yours I traced to a sticking stat. I went with a Fail-Safe version so, should IT fail, it would do so in an OPEN position, preventing over heating.
Jake
West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day Parade 20 May 2010!!!
Why the coolant level became low to cause low coolant has to be discovered too. Overflow reservoir bottle should remain at the proper level with coolant.
Burp, pressure test for any leak would be my first moves rather than jumping to the more extreme possible causes. Logical, sequential, basic stuff first - K.I.S.S.
Last time I had an issue like yours I traced to a sticking stat. I went with a Fail-Safe version so, should IT fail, it would do so in an OPEN position, preventing over heating.
Jake
West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day Parade 20 May 2010!!!
Race Director
Joined: Jan 2005
Posts: 10,641
Likes: 13
From: Slidell Louisiana
QUOTE=BrianCunningham;1572575755]you can jumper the relay(s)
I've also hooked them up direct the to battery.
if it's intermittent, then it might be a little harder to tell
but certainly next time it overheats
kill the engine, then turn the key ON and see if they come on.[/QUOTE]
IMO jumpering or directly powering them is not easier than turning AC on. Either I'm getting lazy in my old age or you are an over achiever 
I've also hooked them up direct the to battery.
if it's intermittent, then it might be a little harder to tell
but certainly next time it overheats
kill the engine, then turn the key ON and see if they come on.[/QUOTE]
IMO jumpering or directly powering them is not easier than turning AC on. Either I'm getting lazy in my old age or you are an over achiever
Melting Slicks
Joined: Aug 2008
Posts: 2,082
Likes: 50
From: Palmdale CA
QUOTE=BrianCunningham;1572575755]you can jumper the relay(s)
I've also hooked them up direct the to battery.
if it's intermittent, then it might be a little harder to tell
but certainly next time it overheats
kill the engine, then turn the key ON and see if they come on.
I've also hooked them up direct the to battery.
if it's intermittent, then it might be a little harder to tell
but certainly next time it overheats
kill the engine, then turn the key ON and see if they come on.
IMO jumpering or directly powering them is not easier than turning AC on. Either I'm getting lazy in my old age or you are an over achiever
[/QUOTE]The guy all ready has an overheating problem!
