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ARGH! Overheating still!

Discussion in '1982-Present GM Diesel' started by Danno, Jan 20, 2002.

  1. Danno

    Danno 1/2 ton status

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    Changed the coolant, changed the thermostat, and tried to change the water pump today (got the wrong one! ARGH!). The old water pump seems to be OK, so I'm thinking I got a bad new thermostat.

    Had to drive the truck to a friend's place to use his garage. Pulled the thermostat before I left so it wouldn't overheat, never got over 150F (10% grade in the mountians).

    Am I thinking straight here? This is driving me nuts... It HAS to be the thermostat. ARGH!

    On a positive note, I no longer have all that A/C crap cluttering up my engine compartment. At least now I can reach everything a little easier.

    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     
  2. 6.2 man

    6.2 man 1/2 ton status Premium Member

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    I knew a guy who had a small hole in his water jacket going to a cylinder that cause overheating ...I think 150 with out a thermostat is high !!!
     
  3. Danno

    Danno 1/2 ton status

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    That was going up a pretty good grade for a long period of time, foot to the floor on the go pedal. It took about 45 seconds after that climb leveled out for the temp to drop back to 100F.

    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     
  4. Tybee

    Tybee 1/2 ton status

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    What about the clutch on your cooling fan?

    1984 GMC Jimmy 379 diesel, 700R4, 3.73s, 31x10.50 x 15
     
  5. Danno

    Danno 1/2 ton status

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    It seems to be working OK, as far as I can tell. I can't spin the fan easily by hand when the engine is off.

    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     
  6. Rollingthunder

    Rollingthunder Registered Member

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    When did this problem start? Make sure that everything on your exhaust system is ok. Pipe size, # of bends, and damaged (kinked or crushed) pipes can cause a problem. Did you flush the WHOLE system with noncorrosive cleaning agent. Scale deposites, produsts of corrosion, products of chemical compatibility, and petrolium contaminants can all form or get into your cooling system and mess things up. You don't want to run the engine over 200 degrees because the additives in coolant break down, but you also don't want to run the engine under 100 degrees because carbon will form on your rings and it will also wear 8 times a much. Engine wear is also 8 times greater when ran without a thermostat. Normal engine temp is 180 to 200 degrees. 210 is pushing it. Your cap could not be holding pressure. If your cap is working properly it should have 15psi in the coolant system and the boiling point will increase 3 1/2 degrees for every pound. Therefore, if you have no pressure then it will heat up quicker. The pressure also makes the water pump work properly. The fan clutch will always run, even if it isn't working properly. When the fan clutch goes out, it goes into dummy mode which means that it will lock and only spin the speed that the engine is running so it will halfway still cool the engine. A working fan clutch alternates the speed that that the fan turns to give you more cooling or less thanks to the wonderful thermostat on the end of it. If you have more questions just e-mail me and I can probably help you. I am in college for Diesel Service Technology. bassturtle_82@yahoo.com
     
  7. Danno

    Danno 1/2 ton status

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    I'll reply here for everyone to see, then email you.

    I bought this truck in June last year. It's got about 200,000 miles on it (tires are a little over stock, so I'm estimating it's got that many miles on it), and it ran around 200F - 210F when I bought it.

    It's been slowly running hotter and hotter, only by a couple degrees or so, since I've owned this truck. Then suddenly, it wanted to run over 220F.

    I've bought a new 195F thermostat, and installed it. I've had the coolant flushed twice now (didn't run any cleaners through it, didn't know if those were actually safe or not). I was going to change out the water pump, but once we got down to the pump (after pulling the accessories off the front of the engine), it appeared to be functioning OK, and the bearings didn't appear to be loose or leaking anywhere.

    I didn't think about the exhaust causing these problems... I'll take a look at that the first chance I get. I'm down the the flu right now, so no crawling on the ground for me right now.

    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     
  8. Danno

    Danno 1/2 ton status

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    I think I know what\'s wrong!

    The truck might not be overheating at all. In fact, it may be A-OK.

    In addition to this alleged overheating problem, I've also got a charging system that is putting out 16V (or at least claims to via the voltmeter in my dash). If this truck is truely running at 16V, wouldn't that cause high readings from my temp sensor?

    If that's what's wrong, I'm going to beat my head on a rock.

    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     
  9. Danno

    Danno 1/2 ton status

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    Problem solved.

    It was my dumb luck... I did in fact get two new thermostats that were defective in a row. Third time's the charm!

    Ahhhhh....

    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     
  10. K10ANDYKHAMNIC

    K10ANDYKHAMNIC 1/2 ton status

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    Re: Problem solved.

    dont buy parts from there anymore ...
     
  11. Danno

    Danno 1/2 ton status

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    Re: Problem solved.

    No kidding... First bad parts I've ever bought at a NAPA.

    I ended up using a Robert Shaw 370-180 thermostat that Autozone carries. Truck has never gone over 200F, even while carrying a load of tires through the mountians. Normally runs around 190F-200F in city and on the highway in OverDrive.

    I highly recommend this thermostat.
     

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