!990 Runs Warm
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Instructor
Joined: Oct 2000
Posts: 130
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From: Clifton Park New York
!990 Runs Warm
My 90 has run warm from almost day one. It has 30K miles on it and I relpaced the thermostat with a 180. I put in a Hypertech chip (Street) and I thought it would turn on the fans sooner. The primary fan comes on fairly early, but the secondary hardly ever comes on. I read the service manual and there is several criteria that has to take place before the ECM says turn on. The car doesn't run warm while driving, it is more when it is at an extended idle. I just purchased an automatic kit for the secondary fan. It consist of a thermal switch and a harness. I am assuming that the thermal switch goes somewhere in the block and the harnes goes to the negative leg of the fan relay. Again I am just guessing but I believe it will override the ECM and turn it on at a predetermined temp. My real question is has anyone ever used that additive that you mix in with your water? It is suppose to tranfer heat better. Is it safe for the alum parts?
Thanks
Thanks
Safety Car
Joined: Jan 2006
Posts: 3,566
Likes: 4
From: Mt Laurel NJ
St. Jude Donor '06-'07
Not to ask a dumb question, but have you ever changed the antifreeze? How about removing the shroud that covers the radiator? C4 corvettes draw air from under the car, and can pickup trash , leafs, and plastic bags that lodge around the radiator. Do a search, there are many threads on this subject.
Randy
Randy
Race Director
Joined: Oct 2001
Posts: 19,653
Likes: 428
From: Melbourne Florida
Cruise-In IV Veteran
You don't mention when the chip turns your fans on and off...with a 180* t-stat it should be around 190 and 182*....
I run a 160* t-stat and my fans are set to go on at 198 and off at 192*...these settings are from a previuos t-stat and I've never gotten around to changing them...in traffic or at extended idle my fans come on and drive the temp down to 196* ...that is as hot as it gets...
I also run one gallon of anti freeze, 2 bottles of water wetter and the rest distilled water...I may cut back to 1/2 gallon of anti freeze since down here freezing is not an issue...plain old distilled water is the best cooling agent by far but I want a little anti freeze in the system for the lubricating properties...
I run a 160* t-stat and my fans are set to go on at 198 and off at 192*...these settings are from a previuos t-stat and I've never gotten around to changing them...in traffic or at extended idle my fans come on and drive the temp down to 196* ...that is as hot as it gets...
I also run one gallon of anti freeze, 2 bottles of water wetter and the rest distilled water...I may cut back to 1/2 gallon of anti freeze since down here freezing is not an issue...plain old distilled water is the best cooling agent by far but I want a little anti freeze in the system for the lubricating properties...
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
My 90 has run warm from almost day one. It has 30K miles on it and I relpaced the thermostat with a 180. I put in a Hypertech chip (Street) and I thought it would turn on the fans sooner. The primary fan comes on fairly early, but the secondary hardly ever comes on. I read the service manual and there is several criteria that has to take place before the ECM says turn on. The car doesn't run warm while driving, it is more when it is at an extended idle. I just purchased an automatic kit for the secondary fan. It consist of a thermal switch and a harness. I am assuming that the thermal switch goes somewhere in the block and the harnes goes to the negative leg of the fan relay. Again I am just guessing but I believe it will override the ECM and turn it on at a predetermined temp. My real question is has anyone ever used that additive that you mix in with your water? It is suppose to tranfer heat better. Is it safe for the alum parts?
Thanks
Thanks
BTW I never use water wetter but some swear by it.
I don't think those analog gauges are very accurate.
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Racer
Joined: Dec 2004
Posts: 470
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From: Phoenix Arizona
Pay close attention to the temperature on a 90. I have a 90 and it overheated to the point of a blown head gasket.
Check for cold spots on the radiator (blocked by deposits) also make sure there is no air in the closed system. Also avoid prolonged stand still
idle. Have you checked the relays on the drivers side of the radiator housing they have failed on mine.
Hope this helps
Check for cold spots on the radiator (blocked by deposits) also make sure there is no air in the closed system. Also avoid prolonged stand still
idle. Have you checked the relays on the drivers side of the radiator housing they have failed on mine.
Hope this helps
Tech Contributor
Joined: Aug 2006
Posts: 9,933
Likes: 103
From: Peoria Arizona.. Resident Gold Cylon
? How about removing the shroud that covers the radiator? C4 corvettes draw air from under the car, and can pickup trash , leafs, and plastic bags that lodge around the radiator.
Randy[/QUOTE]
Randy is correct the C4 is a known street hoover. Do an R&R on the rad and do a good cleaning. I bet your dealing with sediment issues as well as restriction. Another rare possiblity is extreme impellar wear on the water pump. But that is a long shot.
Randy[/QUOTE]
Randy is correct the C4 is a known street hoover. Do an R&R on the rad and do a good cleaning. I bet your dealing with sediment issues as well as restriction. Another rare possiblity is extreme impellar wear on the water pump. But that is a long shot.
Advanced
Joined: Sep 2005
Posts: 64
Likes: 1
From: Columbus Ohio
Something to check even if the radiator looks free of debris is the spaces within the fins. My 90 was a Florida car in its early life and when I got it in 2005 it would overheat very easily. I cleared the obvious debris but it still ran hot. Then I pulled the radiator and found that the bottom 1/3 was clogged with sand. A garden hose backwash helped but alot of the grains were stuck. I ended up putting it in a bathtub full of very hot water and when the aluminum expanded the majority of the sand dropped out. It worked well but the wife was a bit upset. 
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
High pressure hose works good if the bathtub is too dirty to put your parts in 
Spray it slowly from teh backside, over and over and over, youd be surprised how "clean" its not. Hold it up and see how much light you can see through it to judge progress....Then take a shop vac and slowly go over the face (front) of the radiator, that will get sand too. Do NOT press hard withthe vac, youll flatten the fins.
Using a small white bristled scrub brush (steal it from the kitchen
) on the front of the condenser is perfect for cleaning the fins out too, start at the top and firmly but gently run the brush from top top bottom. Then shop vac it out too, clean as a whistle. Condenser is important, if air cant get through there its not going to get much air to the radiator.
Last edited by cv67; Apr 29, 2007 at 08:16 PM.