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Overheating with A/C on

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 87K54WD, Jul 18, 2001.

  1. 87K54WD

    87K54WD 1/2 ton status

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    Just wondering if you fellas had any ideas. The truck runs well below the 210 mark with the AC off. However, when the A/C is on during stop n go traffic, it shoots way past the 210 mark. Nothing in the red zone but still too hot to me. When crusing down the freeway with the A/C on, it stays below the 210 mark as well. Just happens when I come to a stop in traffic for too long. Truck stays at 210 or below in stop n go traffic with the A/C off. Is this normal and just part of the stop n go b.s. What the hell makes the truck get so hot just because the A/C is on. Does the A/C put that much of a strain on a 350? As a side note, about how much hp do you lose with the A/C on?
     
  2. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    I would check the clutch fan. It could be bad. Also the radiator could be plugged. On the inside but also on the outside (through the fins). If it is dirty enough on the outside air will not flow through properly and set off the clutch fan like it should.

    My .02,
    JH

    '83 GMC Jimmy 4x4 ZZ4 Crate Motor
    '83 Chevy P/U 4x4 Sand Drag Racer, 578 RWHP
    '94 Impala SS
    '01 Chevy 2500HD w/8.1L & Allison Auto
     
  3. 2Dogs

    2Dogs 1/2 ton status Premium Member

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    I think that is about normal for the truck. I quit worrying about mine doing the identical things when I saw the operating temperatures in my Vette.
    Radiator hoses and clean fluids do become more important if you choose to operate it like that.
    Sometimes I will turn off the AC in stop and go also....

    Dave

    If You Drink Don't Park, Accidents Cause People.

    91 K5 - in the process of 4" lift with D60/14FF plus LOTS of extras. ETF August 1.
     
  4. newyorkin

    newyorkin 1 ton status

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    Don't forget, your A/C condensor and tranny cooler (if equipped) mount in front of the radiator, which means warm/hot air blowing over your radiator. When vehicle is stopped with A/C on, it's relying 100% on the fan to suck just that warm air through them, and isn't getting the additional volume pushed through from driving.

    Also, you may want to pull the radiator and check it for clogged/bent fins and possible pinhole leaks at the hose necks. While it's out, blast some compressed air or the garden hose through the condensor from the engine side out (watch it with garden hose, though. If it has enough pressure, it can bend the fins).
    I pulled my radiator to solder a leak a few weeks ago, and found the way the PO had installed the tranny cooler allowed it to leak, and eventually the constant small layer of fluid collected dust and formed a nice layer of sludge over the bottom corner of the radiator and A/C condensor. I blasted the crap out of the radiator and condensor, installed a bigger tranny cooler with good fittings, and the truck runs at least 10-20 degrees cooler, and doesn't warm up in traffic like it used to. I'm trying to do a cooling system service write-up on my website, but it ain't workin out yet....

    Definately check out your fins for blockage, though. Heck, 210 is probably fine though.

    Dave,
    Don't hold me to it, but I believe the heads, head gaskets, and other small items are different on the 'Vette, and it can tolerate higher temps than the Blazer can. I never owned/wrenched a Vette, though, so don't quote me, I may be talking through my arse on that... I know a service tech at a Pontiac dealer once told me 220 is normal for my wife's '89 grand Prix (about when the electric fan kicks in), because it was designed with tighter tolerances and expected/intended to run hotter.

    Ratch
    <a target="_blank" href=http://k5.8m.com>k5.8m.com</a>
    **K5 - What more is there to life?**
     
  5. 2Dogs

    2Dogs 1/2 ton status Premium Member

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    Yup they are all different castings and flow systems. But the differnces I see in the temps make me think that my Blazer is running cool and I no longer worry (as much) when the temp gauge moves on the Blaze.
    I do like the oil temp gauge on hte Vette tho. It doesnt have an oil coller where the Blazer does... Kinda weird.

    Does my 91 have aluminum heads?

    As long as it doesn't boil over (balzer never has) I think you are safe.

    Dave

    If You Drink Don't Park, Accidents Cause People.

    91 K5 - in the process of 4" lift with D60/14FF plus LOTS of extras. ETF August 1.
     
  6. Itali83

    Itali83 1/2 ton status

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    87K54WD, Remember that the factory guages are JUNK!!!!!!! I just replaced mine with mechanical autometer guages. Witht the factory guage9with a new sending unit) it would read 210-220 with no a/c all the time. Now with my new acurate mechanical guages, my truck runs no hotter than 190. Just a thing for you to think about.
    Ben 87 Jimmy
    <font color=blue>Rust=Bad</font color=blue>
     
  7. K5 NUTT

    K5 NUTT 1/2 ton status

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    1) By cleaning out the evap i've seen 50 to 100 psi drop of high side pressure.

    2) 10 to 12 degrees drop across the top and lower radiator is healthy...anything else will cause problems.

    3) Compressed refridgerant leaves the comp as a HOT gas...that turns to a warm liquid when it exits the condensor...therefore like any add on trans cooler etc you are adding load not to the engine but the cooling system...yes check your clutch fan..engine off it should have some resistance to spin it...check the front of it to see if the silicone is leaking out near the bi-metalic spring...if so replace it right away as it is a fluid coupling and any loose of the fluid equals less cooling. Installing a helper fan on the front of the condensor is the only way to combat this problem if all the formentioned items are okay...you can run a relay and tap into the low psi switch to trigger the fan...or a toggle switch if you so desire.

    4) Can't give you an honest estimate on the HP drain figure...i can tell you that on a semi the clutch fan alone drains 20 HP to run it. And figure in that or half for the comp. And yes the factory gauges have never been noted for being accurate!

    Azblazer

    1979 K5 350 TBI
    1976 K5 Chalet
    If it ain't got arizona pinstriping.....you ain't wheelin the pee outa her!
     
  8. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    Dave,
    Your Vette is probably the LT1, correct? My Impala SS is the same engine. It uses reverse flow cooling. The temps will read higher on an LT1 than on a regular small block.

    If the clutch fan is operating properly on a reg. small block it will keep the temps at no more than 210 normally. Only 230 if it is really, really hot, towing a trailer. That fan will pull about 3500CFM or more when it is fully engaged.

    My .02,
    JH

    '83 GMC Jimmy 4x4 ZZ4 Crate Motor
    '83 Chevy P/U 4x4 Sand Drag Racer, 578 RWHP
    '94 Impala SS
    '01 Chevy 2500HD w/8.1L & Allison Auto
     
  9. BowtieBlazer

    BowtieBlazer 1/2 ton status

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    There is always the option of adding an electric fan...I'm about to myself because down here in South Louisiana temperatures get plenty high. In sitting traffic heat indecies may reach 140deg so having an electric fan pushing that extra air through the condensor could do wonders

    1985 GMC C-10 Shortbed
    1984 Chevy K-5 Blazer
    1982 Chevy C-10 Longbed
     
  10. WakeBoard&4X4er

    WakeBoard&4X4er 1/2 ton status

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    Last summer I was running at about 225-235 then i flushed the block, new Rad Cap, and new thormsate. After that found that the Rad a had a small whole get a new Rad, Today it is 100 Deg F here and the Heat index is over 115 and my K5 never get over 180. Just an idea.
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    If the radiator is suspect, (as in looks old) it can never hurt to have it flow tested. I had an overheat problem, and although the radiator APPEARED fine inside, flow was blocked about 50%!!! A local radiator shop flow tested the thing for free. Of course they made money off of it, but I was standing right there when they tested it.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
    No anti-theft measures on your truck? No pity when its stolen
     
  12. 88streetblaze

    88streetblaze 1/2 ton status

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    i am just curious why the temps would read higher on the reverse cooling in the lt 1's. if i understand right then the lt-1's send the water from the radiator to the heads first which keeps them cooler. and the temp sending unit is in the heads so wouldn't it read cooler?
     

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