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Bad radiator?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by spin2win, May 5, 2006.

  1. spin2win

    spin2win Registered Member

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    I have an ’89 Blazer that is stock and the motor has nearly 200k miles on it. My brother gave it to me with a bad transmission. I have fixed that with a 700R4 from Bowtie Overdrives and I’m now running a trans temp gauge and a trans cooler behind the radiator. Tires are 31” BFG ATs and the diff is a 3.73.

    Around town (45 mph or less) the truck runs very cool. Engine temp is below 175 and the transmission oil is pretty consistent at ~150 degrees. I’m usually running in overdrive turning 1000 – 1500 rpm at these speeds.

    On the highway things are not as good. Driving 65 – 70 mph, I’m turning north of 2000 rpm. The engine temp starts to creep up to 175 and the trans temp is usually between 150 and 200. Any sort of hill and the engine temp goes higher, 185 or so, and the trans temp hits 200 or a bit above this.

    I live in Seattle, and it is not hot here. Ambient air temps are 65 – 70 degrees for the readings quoted above.

    My concern is the transmission temp. I would really prefer it stayed ~150 degrees in the pan where the temp sending unit is. My current thought is that the radiator is going bad.


    What do you guys think?
     
  2. ryan22re

    ryan22re 1/2 ton status

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    sure the converter is locking up?
     
  3. spin2win

    spin2win Registered Member

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    Yeah, it seems to be. I get a 300 - 400 drop in RPM as it locks up. When it is locked, applying the brakes just enough to turn on the brake lights unlocks the converter.
     
  4. ryan22re

    ryan22re 1/2 ton status

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    put the trans cooler in front of the radiator. how is it mounted behind the rad? or is it just in the rad?
     
  5. spin2win

    spin2win Registered Member

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    It's mounted behind the radiator. Moving it to the front would double its effective cooling capacity, but even that seems like it would leave the trans running hot.
     
  6. Thunder

    Thunder 3/4 ton status

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    If you have the stock thermostat your engine temp should be around 195. 180 to 195 is what the ECM likes to see for best performance.
    But your trans temps are too high.
    With 200K on that engine I would definatly replace the radiator.
    Drain the radiator and take a look down the fill hole with a flashlight. If the cooling tubes have white deposits around the openings they are clogged and its time for a new rad.
    You should also move the cooler infront of the radiator where it belongs.. No good mounting cooler behind the rad. Mounting a cooler behind the radiator can acually heat up the fluid.
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Not to counter, but to add to the clogged radiator comment. The lower portion of a radiator can be clogged up with nothing visibly wrong from looking inside it. This is why antifreeze is spec'd to be changed at regular intervals. Most owners do NOT do this.

    If it's an old radiator, it's probably bad regardless. If nothing else, it will be less efficient than a new one.

    I've seen someone chase a cooling problem all over the motor because the radiator was "new" not too long ago. Got to the point of changing the cylinder heads (!) before actually trying the radiator, since it "looked" good. A lot more money spent for a $150 problem. :)
     
  8. spin2win

    spin2win Registered Member

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    Ok, going to move the trans cooler to the front of the radiator when I change it. LMC seems to have new radiators for about $280. Anyone know of a better price?
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    I don't think I paid more than $150 for mine at Schucks maybe a year ago. (3 core tall one)
     
  10. Thunder

    Thunder 3/4 ton status

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  11. rick88blaze

    rick88blaze 1/2 ton status

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    That's where I got mine from and haven't had a problem since. Even when I lived in Las Vegas, Nv it didn't overheat in the summer even with the AC on full blast. :D

    Rick
     
  12. spin2win

    spin2win Registered Member

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    OK, so I upgraded to a 4-row radiator from www.radiator.com. $230 delivered next day FedEx ground, easily $100 cheaper than anyone else.

    I also moved the trans cooler to the front of the radiator. Over all I’m seeing a 45 degree trans temp reduction. 70 MPH on level interstate has the trans right at 150, where it was about 185 prior. Climbing up highway 2 in Washington over 4000’ Stevens Pass at 60 MPH in 3rd has me running at 190 - 200, quickly cooling below 150 after cresting the top.

    I’m not running carpet, so this as been a real improvement to the comfort level inside the cab.

    Thanks guys for all your incite.
     
  13. 4xcrazy

    4xcrazy 3/4 ton status

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    wow, i don't think there's been a day in the life of my truck, that it has EVER seen temps THAT low, even when you were having "problems":crazy: well,,,,maybe during winter:p:

    Not sure what the trans temps have seen, but i'm pretty certain it's never been that low, unless i was in SoCal area :D . Heck my motor USED to run around the 220-235 mark for awhile, no problems. I did however end up dropping a new 4 core rad and heavy duty clutch in it, and now it will ride around the t-stat of 195, maybe alittle hotter when demanding situations occur, which is where it's supposed to be anyways.
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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    I'd put a good t-stat in there (personally 195*) as if you ask me, 150* is too cold to run the engine. If anything, pointless to run that cold, but you don't want the engine temps swinging that much regardless.
     
  15. spin2win

    spin2win Registered Member

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    Ok, to clarify, I quoted transmisison temps. Goal of the whole project was to get the transmission temps down around 150.

    The ENGINE runs pretty steady at 175 or so, maybe moves 5 degrees?
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    Gotcha, the temps were right at engine levels in the last post from you, so I assumed that's what you were talking about, since you mentioned it in the first one. All good then. :)
     

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