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Thread: Spirit R/T running hot on highway

  1. #1
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    Spirit R/T running hot on highway

    Trying to daily my R/T in this heat has me worried. I have a 35 mile drive to work, and the car is running hotter then I'm used to. With the A/C on it will get up to about 3/4 on the gauge, at which point I will turn the A/C off and run the heater on defrost to help bring temps down. I have a manual switch on the fan and have been running it constantly, but it doesn't help keep the temp from creeping up. But at low or no speeds I have no trouble keeping cool, in fact today I had the a/c on and the car idling for almost 30 mins in the parking lot, and temps were low and fine. Car is stock except for exhaust.
    I've installed a new water pump, new 180 degree thermostat, new radiator cap, new lower hose, and fresh anti freeze, about 60% water, 40% antifreeze. Cooling system seems fine, no leaks, builds pressure, etc.

  2. #2
    turbo addict
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    Re: Spirit R/T running hot on highway

    How old is the radiator, Possible that it has built up some calcium inside and is restricting flow.
    Ian Adams Function>Form 1990 shadow scrapped, too rusty:( 1991 Spirit R/T Scrapped, parts sold:( 1989 Turbo Caravan Daily beater with built-[I]ish [/I]​engine slowly evolving into weekend turbo beater.

  3. #3
    Moderator Turbo Mopar Staff Force Fed Mopar's Avatar
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    Re: Spirit R/T running hot on highway

    Sounds like a bad radiator.
    Rob M.
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  4. #4
    ...if you know what I mean... Turbo Mopar Contributor csxtra's Avatar
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    Re: Spirit R/T running hot on highway

    Do you have the plastic airdam under the core support? That helps by creating a low-pressure area behind the radiator to increase airflow through the radiator at highway speeds. Without it, the radiator may not be getting enough airflow at highway speeds with the A/C on. Also make sure that there are no ways for air to get around the radiator without going through it (most likely not a problem if you still have the stock A/C condenser and intercooler in their original locations.)

    Otherwise, I agree with Rob, might be time to get the radiator looked at.
    Warren Hall
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  5. #5
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    Re: Spirit R/T running hot on highway

    Quote Originally Posted by shackwrrr View Post
    How old is the radiator, Possible that it has built up some calcium inside and is restricting flow.
    AFAIK it's the original rad with 80,XXX miles on it. Guess I should look into a cleaning.

  6. #6
    boostaholic Turbo Mopar Contributor
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    Re: Spirit R/T running hot on highway

    Quote Originally Posted by shackwrrr View Post
    How old is the radiator, Possible that it has built up some calcium inside and is restricting flow.
    +1. A lot of folks mistake flushing the cooling system with cleaning the radiator. Just because the old coolant was flushed out, and new put in, doesn't mean the radiator is "clean". Sediments build up in the bottom of it, and can seriously plug it up, and reduce cooling capacity tremendously. Only way to really "clean" it is to have a radiator shop do it professionally. Since new radiators really aren't available for our intercooled applications anymore, cleaning is probably the best bet.

  7. #7
    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    Re: Spirit R/T running hot on highway

    Put a scanner on it and read the what the Coolant Temperature Sensor is actually seeing before you panic too much. Not saying there is not a problem, but it wouldn't hurt to confirm.
    Mike Marra
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  8. #8
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    Re: Spirit R/T running hot on highway

    Quote Originally Posted by 83scamp View Post
    +1. A lot of folks mistake flushing the cooling system with cleaning the radiator. Just because the old coolant was flushed out, and new put in, doesn't mean the radiator is "clean". Sediments build up in the bottom of it, and can seriously plug it up, and reduce cooling capacity tremendously. Only way to really "clean" it is to have a radiator shop do it professionally. Since new radiators really aren't available for our intercooled applications anymore, cleaning is probably the best bet.
    True true. I know a good old skool rad shop so that's where I'll be going.

  9. #9
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    Re: Spirit R/T running hot on highway

    Buy or borrow a temp/ coolant temperature gun and check the actual temp into and out of the radiator. My car did the same thing. In fact, the gauge went all the way overt the "H." When I checked the actual coolant temp, it was fine. I had a combo of a bad gauge and electrical problem.

  10. #10
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    Re: Spirit R/T running hot on highway

    Here's a bit of an update: this past Friday the car got a real trial by fire, as in 90+ degree temps, traffic, and extra running around. The first thing I did was turn off my manual fan switch, as I was using it all the time and realized that it was probably impeding flow on the highway. As I was driving home from work I first drove with the windows down, and the gauge remained around the half way mark. Then I put the a/c on and decided to go for broke
    The needle rose to about 3/4 on the gauge, but never overheated or went up to the full hot mark. On the way home I ran some errands and got stuck in local traffic, including having to wait for 3 trains at a rail road crossing. That was pure bliss. Lol. But again no over heating and only went as high as 3/4 on the gauge. On Saturday I installed a plastic air dam from a 4th gen Firebird, and it fit like it was made for the car! All I had to do was drill some holes, and I used self tapping screws to mount it. Well that air dam made all the difference in the world! I took the car out and cruised up to 90 mph with the a/c cranking, and the needle only got a titch above the half way mark. And this was in 90+ degree weather again. I haven't even had to touch the manual fan switch. Def an easy improvement and hopefully this will get me through the rest of the summer.

  11. #11
    Supporting Member II Turbo Mopar Contributor DOHCRT's Avatar
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    Re: Spirit R/T running hot on highway

    4th gen Firebird is what years?


    Vic in Phoenix
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  12. #12
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    Re: Spirit R/T running hot on highway

    Quote Originally Posted by DOHCRT View Post
    4th gen Firebird is what years?
    1993-02. Camaro uses same air dam.

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