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car overheats when ac is turn on?

This is a discussion on car overheats when ac is turn on? within the General Help forums, part of the LSx Technical Help Section category; Need help on a 1998 LS1 that is overheating when ac is turn on and driving it in the City. ...

  1. #1
    Junior Member arnoldonsite2's Avatar
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    black with blue flames
    1998, ls1 pontiac formula

    car overheats when ac is turn on?

    Need help on a 1998 LS1 that is overheating when ac is turn on and driving it in the City. Temperature drops back to normal if i drove it in the highway...as soon i get off the highway and drove back in the city to a stop and go...the temp started to climb again and I have to turn off the ac so it does not overheat.
    1) So far i cleanned out the front condenser to make sure it was not clogged, but that did not help.
    2) I check the fan and both turns on.
    3) check the coolant is up on the neckline....no bubbling or steam coming out.
    4) Finally i flushed out the radiator.
    After all these the temperature is still rising and only happens when the AC is on. If the AC is off i can go anywhere for miles without no overheating. Only happens if I turn on the AC.

    Can anyone give me an advise to what i should do next?
    Last edited by arnoldonsite2; 07-31-2008 at 07:33 PM. Reason: adding

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    Member tpilews's Avatar
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    You could install a manual fan switch. I had one on my '98 ta, worked great.

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    Junior Member arnoldonsite2's Avatar
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    black with blue flames
    1998, ls1 pontiac formula

    I do have manual switch, brah! Switch I bought from SLP.

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    Blown, Stroked, & Sprayed

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    Junior Member arnoldonsite2's Avatar
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    black with blue flames
    1998, ls1 pontiac formula

    you think my 160 thermostat could have gone bad? I have not replaced it, the last time it was replaced was maybe 4 years ago. But thing is, it does not overheat when the AC is off.

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    Blown, Stroked, & Sprayed

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    Thought you had the stock one. Maybe not.

    Have you checked between the condensor and radiator to make sure nothing got stuck there?

  7. #7
    Bone it like you own it FORD RECOVERY EXPERT's Avatar
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    also check t see if #2 fan is engaging. if not, maybe your fan switch doesnt operate both, or #2 fan motor is bad...

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    Junior Member arnoldonsite2's Avatar
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    black with blue flames
    1998, ls1 pontiac formula

    yes...the 2 fan kicks in..
    This afternoon I took the radiator cap off and started the engine cold, while watching the radiator coolant gets hot enough to test if the thermostat would open up and it did. I can see the coolant circulating, as soon I switch the air conditioning on, thermostat closed and coolant started overflowing, I closed the raidiato cap. Now I can also feel the hose and the coolant were not circulating.
    Why would the thermostat closed immediately? Maybe this was the cause of overheating, the thermostat had never openned up again to circulate the coolant in the radiator and the car started to overheat again.
    Does anyone have any answer?
    Last edited by arnoldonsite2; 08-01-2008 at 07:49 PM.

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    Senior Member Orcus79's Avatar
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    Two possibilties, but I may not be certain. The heater hoses are reversed, or your t'stat isn't operating right (like duh). There is/may be a control valve located on one of the heater hoses connected to a vacuum line. Try diconnnecting that and see what happens. Next step I can think of would be a new thermostat.

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    Any luck, I am having the exact same problem....
    Last edited by CitationZ06; 08-03-2008 at 06:56 PM.

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    Track Whore 570SX's Avatar
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    Quote Originally Posted by Ed Blown Vert View Post
    Have you checked between the condensor and radiator to make sure nothing got stuck there?
    +1. your problem exactly describes either bad fan(s) or too much debris in/on/around the fins. get between the rad and condenser and clean, get behind the rad and clean, etc. i only have a rad, no condenser, but i hit it from the rear with a garden hose every once in a while to remove bugs, dust, dirt and the like from the fins to keep maximum cooling capability. when you have a rad + condenser you gotta get in between though.
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