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Mysterious Oil Leak

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Innerpiece, Feb 22, 2001.

  1. Innerpiece

    Innerpiece 1/2 ton status

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    Location:
    Mississippi (Yee Haw)
    I have an 87 Silverado Blazer with a 305 TBI, TH700 Tranny (i think), NP 208 that has a mysterious oil leak.

    It seems to be coming from middle rear of the block, higher up than the bell housing of the tranny. I leaks a little all of the time, but seems to leak more at higher rpm or if I'm moving. it drips down either side of the bell housing, the rear of the oil pan, the tranny cooling lines, the starter, and onto the front driveshaft. I'm loosing maybe 2-3 ounces a day (it's not real bad, but annoying)

    I've checked and worked on the valve covers (they're dry all around and I'm sure they're not leaking). I've checked the oil pressure sender and the distributer and I'm pretty sure they aren't leaking, but they are hard to get at. I dont think it's the rear seal because the oil seems to be coming from further up the block. I'm sure it is engine oil. I don't think its the head as I have good compression, no oil in the coolant or vice versa.

    What else is there back there to leak??? Any suggestions would be much appreciated. It's for sale BTW
     
  2. Smitty

    Smitty 1/2 ton status

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    Sounds like the gasker at the rear of the intake manifold (some of the engines just use RTV). If it's leaking you might also want to check to see if your PCV valve is working. This area usually stays sealed pretty well until crankcase pressure starts to rise. If you're losing 2-3 ounces a day it should be easy to narrow down if you have one of those extendable mirrors.

    Smitty
     
  3. TX Mudder

    TX Mudder 1/2 ton status

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    Probably won't help you, but I kept thinking my valce covers and rear main were leaking - replaced both more than once.
    Turns out the mech oil pressure guage line had a leak, a very small and annoying one.
    -- Mike
     
  4. ragtop

    ragtop Registered Member

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    Ten Mile, TN
    I've got the same problem. Had the rear main replaced when I had the tranny rebuilt and didn't help. Mechanic said was either rear seal on manifold (just a b**** to unbolt everything to remove/replace) or oil pressure sending unit (he'd seen several of these develop leaks). I'm putting off till warmer/dryer weather. Other than valve covers, there's nothing else back there to leak!

    Ragtop - '88K5 [​IMG]
     

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