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cooling problems

This is a discussion on cooling problems within the LT1 forums, part of the Vehicle Specific category; car heats up when idling at a light or in traffic (almost got to the red), cools back down when ...

  1. #1
    Junior Member
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    white
    1995 z28

    cooling problems

    car heats up when idling at a light or in traffic (almost got to the red), cools back down when moving.

    checked all 3 relays by switching them one by one into the fog light position and checking, fog lights worked with all 3. fluid is fine.

    put a new thermostat on it. cranked it and let it sit, thermostat opened up, top tube got hot. everythings a go there. temperature was still creeping up. fans were not coming on! turned the a/c to max and the fans came on and the temperature started dropping back down. turned the a/c back off, and the fans kept going, and the temperature went right back down to where it normally is! what the hell??

    yesterday was a nice day and i was driving around for a while with the tops off and no a/c, first time ive done that for more than a short trip to town... guess this is why i never noticed it. normally im using the a/c so the fans are on and its a non issue. so what does this mean, i have to turn the a/c on and back off whenever the temp gets too hot?

    what do i check next? this is the first car ive owned with electric fans...

  2. #2
    LS1ROC
    Guest
    You may posibly have a bad fan switch. Or the wire for it could be screwed up. A lot of times overheating lt1's will suffer from air pockets in the cooling system .there is a little bleeder screw there to help with that. Did you bleed the air out after the thermostat install?Another thing could be that the themostat is stuck open. This CAN cause overheating. do you have access to a scanner?

  3. #3
    Mine was doing that for a few days before it finally started boiling the coolant in under 2 minutes flat... turned out that the thermo was going bad and finally went... but you seem to have ruled that out... good luck

  4. #4
    Junior Member
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    white
    1995 z28

    Quote Originally Posted by LS1ROC
    You may posibly have a bad fan switch. Or the wire for it could be screwed up. A lot of times overheating lt1's will suffer from air pockets in the cooling system .there is a little bleeder screw there to help with that. Did you bleed the air out after the thermostat install?Another thing could be that the themostat is stuck open. This CAN cause overheating. do you have access to a scanner?
    the fans are coming on with the a/c, so it rules out the fans themselves and the power wires. was going to replace the PCM temp sensor today, but the lackeys at advance auto sold me the wrong sensor

  5. #5
    Quote Originally Posted by LS1ROC
    You may posibly have a bad fan switch. Or the wire for it could be screwed up. A lot of times overheating lt1's will suffer from air pockets in the cooling system .there is a little bleeder screw there to help with that. Did you bleed the air out after the thermostat install?Another thing could be that the themostat is stuck open. This CAN cause overheating. do you have access to a scanner?
    I'm having heating problems as well. My heater doesn't crank out much heat anymore. As far as I can tell, coolant is cycling through it and the fan is working fine. Is there a way to bleed air from the heater core? (The only bleed screws I'm aware of are the 2 intelligently placed above the opti.)

    The car also runs slightly hotter than it used to while on the highway under normal driving.

    Any ideas?

  6. #6
    LS1ROC
    Guest
    First you must answer this for me.....Have you altered the cooling system at all?Thermostat?Drained the coolant?Anything?And have you checked the coolant level at all? 9 times out of ten heater problems will be be linked to the cooling system problems.

  7. #7
    Hark_Z
    Guest
    My car had the exact same symptons. They traced it to the waterpump where the bearing was shot and it leaked coolant out of the 'weephole'. Your car leakin coolant ever??

  8. #8
    Quote Originally Posted by Hark_Z
    First you must answer this for me.....Have you altered the cooling system at all?Thermostat?Drained the coolant?Anything?And have you checked the coolant level at all? 9 times out of ten heater problems will be be linked to the cooling system problems.
    Quote Originally Posted by LS1ROC
    My car had the exact same symptons. They traced it to the waterpump where the bearing was shot and it leaked coolant out of the 'weephole'. Your car leakin coolant ever??
    Haven't done any mods to the cooling system as of yet. I was planning on changing the coolant about the same time that this problem seemed to crop up. I checked the coolant level, and it's fine as best as I can tell.

    Is it normal for the radiator to be an inch or two low after the engine cools? I always thought that as it cooled, it drew more from the reserve tank. Is this an indication of a defective radiator cap?

    I'll have to look hard at the pump. I assumed that wasn't likely the culprit since the engine temp didn't increase in too serious a way. I'll check out the weep hole to see if there are any signs of leakage. The pump would make sense since the heater gets warm, indicating that there is coolant but that it isn't getting the "super hot" water coming from the engine.

    Thanks guys!
    Last edited by my5thNewUsernameHere; 11-24-2005 at 05:34 PM.

  9. #9
    LS1ROC
    Guest
    When You Start The Engine Cold For The First Time ,take The Cap Off The Radiator And After You Start It ,check The Level, It Should Be Full To The Top And Then Your Overflow Should Say Full Cold .if Its Not Full Fill It Up We Have To Get This Right Before Jumping To Mechanical Problems. If You Say It Is 1 To 2 Inches Low ,i Assume You Mean The Radiator And No This Is Not Normal. For Optimum Cooling It Needs To Be Full.write Back After Doing The Cold Temp Level Check. One More Thing , Is Your Air Dam Underneath The Radiator In Good Shape?

  10. #10
    Quote Originally Posted by LS1ROC
    When You Start The Engine Cold For The First Time ,take The Cap Off The Radiator And After You Start It ,check The Level, It Should Be Full To The Top And Then Your Overflow Should Say Full Cold .if Its Not Full Fill It Up We Have To Get This Right Before Jumping To Mechanical Problems. If You Say It Is 1 To 2 Inches Low ,i Assume You Mean The Radiator And No This Is Not Normal. For Optimum Cooling It Needs To Be Full.write Back After Doing The Cold Temp Level Check. One More Thing , Is Your Air Dam Underneath The Radiator In Good Shape?
    Here's what I did last: I checked that the overflow tank was at full cold. I started the engine, and I topped off the radiator until it was warm and dumping coolant into the reserve tank. I then capped it and let it run for about 2 more minutes. When I checked it again a few hours later, the level in the radiator was down again slightly (1"-2") and the reserve tank was relatively unchanged.

    I believe that the Air Dam is in good shape, but I'll double check it tomorrow.

    Another other idea that my uncle cited during our Thanksgiving dinner was the possibility of a blown head gasket. I doubt this is the case because I'd be having lots of performance issues and/or leaks if I was losing that much coolant that fast to a bad gasket.
    Last edited by my5thNewUsernameHere; 11-24-2005 at 05:46 PM.

  11. #11
    Senior Member 5.0THIS's Avatar
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    red
    95 Z28

    Quote Originally Posted by my5thNewUsernameHere
    Another other idea that my uncle cited during our Thanksgiving dinner was the possibility of a blown head gasket. I doubt this is the case because I'd be having lots of performance issues and/or leaks if I was losing that much coolant that fast to a bad gasket.
    Drain the oil and look at it. You'll know real quick wether or not you have a blown head gasket.

  12. #12
    Quote Originally Posted by 5.0THIS
    Drain the oil and look at it. You'll know real quick wether or not you have a blown head gasket.
    Just did an oil change about a few days ago, looked fine, no water.

    My dad's car had a blown gasket and you're right, it stuck right out in the oil. The car also ran like crap and you could even smell the coolant in the exhaust fumes.

  13. #13
    LS1ROC
    Guest
    Keep filling the radiator while its cold until it won't take anymore. And make sure your not overfilling the system by watching the full cold and full hot lines. Be sure and bleed air from the system as you work with this. Also do one more thing for me. Start the car and let it warm up completely. Turn the heater on and give it a minute. Feel both the inlet and outlet hoses of the heater core. If one hose is alot hotter than the other, the heater core may be stopped up. Some temperature difference is normal but you will probably know whats right and whats wrong. If the inlet hose is extremely hot your heat should be hot. Any questions on this just ask.

  14. #14
    Quote Originally Posted by LS1ROC
    Keep filling the radiator while its cold until it won't take anymore. And make sure your not overfilling the system by watching the full cold and full hot lines. Be sure and bleed air from the system as you work with this. Also do one more thing for me. Start the car and let it warm up completely. Turn the heater on and give it a minute. Feel both the inlet and outlet hoses of the heater core. If one hose is alot hotter than the other, the heater core may be stopped up. Some temperature difference is normal but you will probably know whats right and whats wrong. If the inlet hose is extremely hot your heat should be hot. Any questions on this just ask.
    Hey, I'm going to try and resurrect this thread from the dead....

    The weather was nice enough today so I drove the car for the first time since I last replied. Since it was relatively cold today, I can now say for certain that it's not blowing as hot at it needs to. From what I recall the heater core hoses going in and out were both relatively hot and at the same temp, but I'm going to check this again.

    If the heater core is jammed up, how would you expect the rest of the cooling system to act?

  15. #15
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    1995 Trans Am 6 Speed

    Quote Originally Posted by LS1ROC
    Keep filling the radiator while its cold until it won't take anymore. And make sure your not overfilling the system by watching the full cold and full hot lines. Be sure and bleed air from the system as you work with this. Also do one more thing for me. Start the car and let it warm up completely. Turn the heater on and give it a minute. Feel both the inlet and outlet hoses of the heater core. If one hose is alot hotter than the other, the heater core may be stopped up. Some temperature difference is normal but you will probably know whats right and whats wrong. If the inlet hose is extremely hot your heat should be hot. Any questions on this just ask.
    Replace the radiator cap with a new GM one. Could be the seal is shot. It take pressure to keep the coolent moving. Check for leaks from the water pump, again, pressure is going to force its way out somewhere and that's what the weep hole does when the water pump shift seals start to go.

    If it turns out to be the water pump, plan on replacing the Opti-Spark as well. As the water pump goes, so goes the Mr. Opti.

  16. #16
    12.36@109 Red on Red WS6's Avatar
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    Quote Originally Posted by my5thNewUsernameHere
    Hey, I'm going to try and resurrect this thread from the dead....

    The weather was nice enough today so I drove the car for the first time since I last replied. Since it was relatively cold today, I can now say for certain that it's not blowing as hot at it needs to. From what I recall the heater core hoses going in and out were both relatively hot and at the same temp, but I'm going to check this again.

    If the heater core is jammed up, how would you expect the rest of the cooling system to act?
    Are you using DEX Cool or the green stuff? First thing I would do is flush the heater core.

  17. #17
    Quote Originally Posted by seppburgh
    Replace the radiator cap with a new GM one. Could be the seal is shot. It take pressure to keep the coolent moving. Check for leaks from the water pump, again, pressure is going to force its way out somewhere and that's what the weep hole does when the water pump shift seals start to go.

    If it turns out to be the water pump, plan on replacing the Opti-Spark as well. As the water pump goes, so goes the Mr. Opti.
    The radiator cap idea does seem like a potential cause of the problem and it's a cheap and easy fix so it can't hurt either way.

    I don't think it's the water pump because there really doesn't appear to be any coolant loss as far as I can tell, though I do need to look a bit closer at the weeps for sanity's sake.

  18. #18
    Quote Originally Posted by Red on Red WS6
    Are you using DEX Cool or the green stuff? First thing I would do is flush the heater core.
    Using the DEX...I'm going to try the cap first. Hopefully that will help. Regardless, I plan to flush the entire system in the spring.

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