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  1. #1

    Overheating but coolant's cold?

    I recently bought an '89 Grand Prix with a 3.1. My problem is, it overheats. When it overheats it starts running rough and dies. If I feel the radiator, it's not even warm. I tried burping the system by letting the car idle in my driveway with the radiator cap off. I filled the radiator to the top and watched it. The coolant was bubbling and it dropped about two inches. I refilled it and it just sat there bubbling. I checked the temp gauge periodically and after about 15 minutes the car was starting to overheat and I shut it off. The radiator was cold and I stuck my finger in the coolant and it was cold. The thermostat housing was hot. I took off the water pump to replace it but it was nice and tight with no play and no visible damage. Before I did this I ran a water through the radiator with a hose and it came out both sides and the engine so I don't think the rad is plugged. Any ideas? I'd like to get this car going so I don't have to drive my gas guzzling '68 GP to work every day. Thanks, Jimmy.
    1968 Pontiac Grand Prix-455, awaiting 9inch swap<br />1989 Pontiac Grand Prix-3.1<br />1995 Grand Prix-Awaiting 3400 swap<br />1962 Chevrolet Corvair-164ci flat six+4speed<br />1975 Honda CB750-Vintage race replica project

  2. #2
    Lurker DiscoStudd's Avatar
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    Overheating but coolant's cold?

    You said the thermostat housing was hot, but was the upper radiator hose hot? Did you change your thermostat?

    Kevin B.
    2004 Chevy Impala 3400 V6 - Color: Victory Red

    1999 Chevy Tahoe 5.7 Vortec V8 - Color: You guessed it, Victory Red!

  3. #3

    Overheating but coolant's cold?

    I tried it without the thermostat and with a new one. It made no difference. The hose was hot without the thermostat and it wasn't hot with a new one, but when I had the thermostat out I was driving, not just idling. Jimmy
    1968 Pontiac Grand Prix-455, awaiting 9inch swap<br />1989 Pontiac Grand Prix-3.1<br />1995 Grand Prix-Awaiting 3400 swap<br />1962 Chevrolet Corvair-164ci flat six+4speed<br />1975 Honda CB750-Vintage race replica project

  4. #4

    Overheating but coolant's cold?

    Hot much is it overheating? What's it saying on the guage?
    <br />[size=7pt]2003 Impala LS&nbsp; _&nbsp; Series II 3800 _ Completely stock with 5x,xxx miles[/size]<br />Leather and roof, clean as a whistle.<br />http://gmwbody.com

  5. #5

    Overheating but coolant's cold?

    It goes all the way to the top, I think it's 260, and the light comes on.
    1968 Pontiac Grand Prix-455, awaiting 9inch swap<br />1989 Pontiac Grand Prix-3.1<br />1995 Grand Prix-Awaiting 3400 swap<br />1962 Chevrolet Corvair-164ci flat six+4speed<br />1975 Honda CB750-Vintage race replica project

  6. #6

    Overheating but coolant's cold?

    Sounds like a stuck thremostat, or plugged intake to the radiator. If it worked fine without a thermostat, it shouldn't hurt the engine too run without.. just take longer to warm up.

    <br />92 Grand Prix GTP 3.4DOHC 5spd
    <br />88 Fiero Formula Convertible 3.4DOHC 5spd
    <br />84 Fiero T-Top 3.4DOHC 5spd
    <br />Gee there seems to be a pattern there.

  7. #7

    Overheating but coolant's cold?

    It didn't work fine without a thermostat, it still overheated just as quickly. I noticed that if I run the car even for just a minute, then pull up on the lever to take off the radiator cap, air starts to shoot into the overflow container. Also, when the engine was running with the cap off, What looked like steam was rising out of the radiator, even though the coolant was cold.
    1968 Pontiac Grand Prix-455, awaiting 9inch swap<br />1989 Pontiac Grand Prix-3.1<br />1995 Grand Prix-Awaiting 3400 swap<br />1962 Chevrolet Corvair-164ci flat six+4speed<br />1975 Honda CB750-Vintage race replica project

  8. #8

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    Overheating but coolant's cold?

    Is your water pump working?
    -2007 Saturn Sky Redline M5<br />-2007 Chevrolet Silverado Classic 2500HD 6.0/A4<br />-2006 Chevrolet Impala SS<br />-1996 Chevrolet Camaro Z28 Hardtop M6<br />-1996 Chevrolet Beretta 3400<br />-ASE Master Technician with ASE Advanced Engine Performance and Under Car Certification

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    Overheating but coolant's cold?

    Sounds to me like you have a leaking head gasket. Is the exhaust white or smell sweet? you may also have some air in the engine, try reving it up
    a few times to see if it will burp its self, or use the bleading screw if it has one.

  10. #10

    Overheating but coolant's cold?

    I had an 89 cutty that did the same. It would read all the way on the temp guage. There would be pressure in the radiator from the hot coolant expanding, but the coolant at the opening was FREEZING cold. The housing was HOT, the tube got colder enroute to the radiator. The radiator obviously did not cool the tranny fluid and it was boiling and smelled horrible. This was the dead of winter. I could run it and it would read full temp for a couple of mins, and then would drop almost all of the way, AND THEN the heat would blow hot. The time intervals from full hot to dropping became longer and longer. I drove around like that for about 3 weeks and the bitch never died. I replaced the radiator with new, replaced the water pump, and the thermostat twice. I never did find out what was wrong with it.
    <br />92 coupe and 93 vert LQ1&#039;s<br /><br />I own 2 so I have one to drive when the other breaks

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    Overheating but coolant's cold?

    I would say either water pump is plugged up with crap, rad is plugged up, internally collapsed hose, LARGE AIR bubble in the system, or your thermostat is in upside down somehow... 8)
    Kenny K

  12. #12

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    Overheating but coolant's cold?

    Have you tried opening the bleeders with the car running to bleed any air out? If you can't get it completetly bled out within a few minutes, air is getting in there somehow, then you most likely have a bad head gasket.

  13. #13
    1990lumina's Avatar
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    Overheating but coolant's cold?

    Also try it with the heat cranked on full hot. I had a nice air ock in my RX-7 after I replaced the oil cooler "O" rings and this air lock would not pass until I turned the heater on...then everything went back to normal.
    Jeff L. :: 2nd Canadian to win COTM The Preservation for POS W-bodies Canada Chapter
    2004 Acura TSX | 2.4L I4 iVTEC; 5 Speed Auto | 1 of Many Made In '04 | 89,XXXKM
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    1985 Mazda RX-7 S | 1.1L 70ci 12A Twin Rotor RE; 5spd | 1 of 63,105 Made in '85 | 130,XXXKM

  14. #14
    Quote Originally Posted by TGPilot View Post
    I would say either water pump is plugged up with crap, rad is plugged up, internally collapsed hose, LARGE AIR bubble in the system, or your thermostat is in upside down somehow... 8)

    He is almost absolutley right but I had to become a member just to get my two cents in. Usually if you are moving down the road and a car overheats its because you have air in system, bad thermostat, or plugged radiator. Reason is you have flow over the radiator. , so fans are out of the equation) A water pump never goes bad unless there is allot of noise or leakage. One exception is a very rusted and dirty system where the blades that pump the water have rusted off. There is only one car I have ever seen that happen and that is a ford taurus late 90s. For simple sake a pump is a pulley, bearing and blades. So assume you have flow. Now here is the kicker!! all of the new systems ESPECIALLY GERMAN cars all need to be bled. That means no Matter if you get the car hot once or do work on it they have air pockets in the cooling system. That is because most are now a open system instead of closed. that means they have no radiator caps and have overflow tanks instead. Simply fill up the overflow tank while the engine is running with the CAP OFF. And wait for the bubbles to come up. If that doesn't help and there is no difference moving or down the road with overheating change the radiator. Hope this helps GOOD LUCK

    PS. The smart car companies know this and half a bleed valve on top of the engine by the water inlet port. ( On top of thermostat typically) Ie Lexus, Nissan,
    Last edited by MobileManMecanics; 05-15-2011 at 11:43 PM.

  15. #15
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    5.5 year old thread......
    Jay
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