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maaaky
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Oct 3, 2007, 4:00 PM
Post #1 of 9
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corvette runs hot
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 my 88 corvette automatic runs hot. after new thermostat no change with radiator cap off and warmed up to 200 degrees there is virtually no movement of fluid in radiator.. has been as hot as 245-250 degrees. with ac on it runs cooler cause of fan.
highway driving is 190-215 degrees,
any help will be appreciated. maaaky
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way2old
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/ Moderator
Oct 3, 2007, 5:04 PM
Post #2 of 9
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Re: corvette runs hot
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Best guess without having hands on it is a weak water pump or cooling fan. Your symptoms are classic for a weak pump or a bad cooling fan. As you drive, the air is moving through the radiatoe and cooling the engine. At idle there is not enough air movement to cool engine. Water pump is same way. Need to have hands on to properly diagnose. As I said, this is best guess.
Being way2old is why I need help from younger minds
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maaaky
New User
Oct 3, 2007, 5:50 PM
Post #3 of 9
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Re: corvette runs hot
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thanks for reply, weak or bad water pump is what i was thinking cause usually you can see the water being pulled down the radiator and the fluid running out the radiato from the other side.
i can watch the thermostat open on the temp. rises to 195-197 then opens , temp drops to 180's and then starts climbing again to high temps.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 4, 2007, 9:02 AM
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Re: corvette runs hot
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To add some thoughts: These cars had cooling problems since the style change of 1968. You should have a closed cooling system which means the radiator is always full and would always spill some anti-freeze just taking the rad cap off. Cap must have two rubber gaskets to allow for expanded coolant to go to a tank (recovery) and then be drawn back in when it conracts - that thru the little flapper - nickel size. Cap is critical in purging out air and only drawing back coolant.
If you can see the coolant drop and flow it's too low! These cars need every last mm of radiator to behave.
Your performance seems ok at speed or when A/C aux fans are on. Isn't the main fan a fan clutch set up? I'm asking because I don't recall for sure. The fan clutch is junk after a few years for this car. Only buy GM OE part or the best one Hayden makes. If you don't mind the roar and slight loss of power go for a non thermostatic one that pulls air whether it needs to or not.
Note: Cap is the pressure regulator. Bet system was designed for a 15lb cap which at sea level raises the boiling point to about 257 Fahrenheit - that with just plain water. You get a little (not much) higher with ethylene glycol anti-freeze in there which in this car I would reduce the concentration to about -20F instead of the usual -34F as anti-freeze is lousy at transferring heat. Some vehicles specify this reduction - especially overtaxed ones like in boats. That also means use an anti-rust additive and change the coolant lots more often than a regular vehicle. If you really do use the car in sub zero temps adjust as needed for those expected temps.
Sorry for the long post but I'm most concerned that you can see the level drop in the radiator. In that there is a problem,
T
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Guest
Anonymous Poster
Oct 4, 2007, 10:30 AM
Post #5 of 9
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Re: corvette runs hot
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thanks for the reply tom
but shouldn't i see some kind of turbulence in thre radiator with the cap off and up to temp(thermostat open).
seems to me being a mechanicla pump and belt driven it should pump in an open or closed loop system.
going to check the fans again also.
thanks again i appreciate all the help i can get
maaaky
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 4, 2007, 10:39 AM
Post #6 of 9
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Re: corvette runs hot
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Gotta be fast here right now - bear with me. Yes, you would notice turbulance and even spilling out some while running but not go so low that you can see it coming out of the tubes inside the rad. You do see that filling it up after you have drained it and are waiting for all the air to come to the top.
Should have said before to just put a good new cap on it - I don't really care how old it is. From cold and full you should feel the upper rad hose stay cold and warm to hot as t-stat opens. THERE SHOULD BE PRESSURE IN THE SYSTEM NOW AND FEEL THAT AT THE UPPER HOSE and if not that's a problem. Then find out why as if it can't hold pressure there is another problem - just report back on that.
Water pump is working all the time - not just when t-stat is open. If it has been changed it may not be what the car called for. I've never seen an impeller stop pumping but it's possible. When t-stat is closed the pump mixes all coolant in engine to be of even temp thru a by-pass system. Chev does that thru the water pump itself - others use heater or a separate hose.
soory to be fast here but I gotta go now! Hit back and I'll catch any new observations or questions in a few hours or so,
T
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Guest
Anonymous Poster
Oct 5, 2007, 4:41 PM
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Re: corvette runs hot
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hi way2 old and ted,
was our anniverary so mamma wouldn't let me work on the vette yesterday. but today i did a lot of checking and the cooling system works fine with the air on. with the air off it get's hot idling, aux cooling fan comes on at 238 degrees but regular cooling fan doesn't come on as it does when ac is on.
so now i am looking at the switches and sensors that feed the ecm.
i'll keep you posted, again thaks. maaaky
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Guest
Anonymous Poster
Oct 5, 2007, 4:44 PM
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Re: corvette runs hot
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sorry tom didn't mean to use ted
maaaky
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way2old
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Oct 5, 2007, 5:03 PM
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Re: corvette runs hot
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I understand the momma thing. Keep us posted. Sure sounds like you got it going towards you now. See ya. HAPPY ANNIVERSARY Mrs.maaaky 
Being way2old is why I need help from younger minds
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