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HELP! Baffling coolant leak

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by rdoty, Feb 20, 2013.

  1. rdoty

    rdoty New Member

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    I've got a 94 Silverado K1500 4WD with a frustrating coolant leak. I've got it under pressure (15psi) and there's almost no drop over time (1 hr). I can see drips of coolant near the transmission but couldn't find the source. The baffling part is this: There are two struts to the bottom of the bellhousing and where they attach to the bellhousing both bolts have a drop of coolant on them. The struts themselves are not wet. Then laying there on my back I notice a drop of coolant appear on one of the transmission coolant lines! It appears that the lines at one time had battery acid on them because they look corroded. But the coolant drip is definately coming from one of those lines.
    Do those lines have coolant in them or transmission fluid? Also, why would the strut attachment bolts have fluid on them? There is no spray of coolant. It's as though coolant is coming from inside the bellhousing.

    Answers please!!!
    #1
  2. j cat

    j cat Active Member

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    since this is a small leak on a 1994 I would use some bars stop leak. pre mix 1/4 of the stop leak in some distilled water just enough to allow the material to loosen up . then pour into the radiator , not the coolant recovery bottle. drain some coolant out so this can be done.

    If this is a crack or freeze plug leak this should work. even if its a small gasket leak.

    I am assuming that you have properly maintained the coolant system and you have no corrosion and the correct amount of coolant concentration. 50% min . best to use 65% for max corrosion protection with distilled water and NO scale build up.
    #2
  3. trentkoger

    trentkoger New Member

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    The early 90s K model pickups had terrible radiators in them and they would leak through to the tranny cooler that is mounted on them this sounds like part of your problem.
    #3
  4. j cat

    j cat Active Member

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    if the coolant enters the transmission he would see transmission problems very quickly. it would take very little coolant to kill the transmission .
    #4
  5. shibby2oo8

    shibby2oo8 New Member

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    Bet you a millon dollars it the intake gaskets.
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  6. Conlan Rose

    Conlan Rose Super Moderator

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    I own one of these 90's trucks and yes the leak can be anywhere.... check the radiator, hoses, clamps, freeze plugs, gaskets, every thing. If you have stock dex cool it should be easy to find if you clean the engine because it is bright orange.
    #6
  7. rdoty

    rdoty New Member

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    Well, it took a couple of drops of coolant on my forehead and glasses but it's not coming from the transmission cooler lines (duh!) but from somewhere above. Did have a local guy tell me that it couldn't be the head gasket because those would leak inward so it has to be the manifold gasket. It's so tight back there that I can't see anything even with a mirror. One big question....is there anyplace else that it could be coming from other than the manifold? Just want to be 95% sure before I turn somebody loose on this.
    #7
  8. j cat

    j cat Active Member

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    you turn that loose on some one , an they start taking that engine apart you better have a couple thousand ready.

    try the stop leak as I recommended this is a quick way to determine if its a leak that requires engine break down.

    I use this product on the old high mileage engines and it works so long as the system is clean .
    #8
  9. Conlan Rose

    Conlan Rose Super Moderator

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    It may be the frost plugs....
    #9
  10. rdoty

    rdoty New Member

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    Since the leak is from the rear of the engine I think the expansion plugs probably aren't the problem. Correct me if I'm wrong but I think there's two in the back of the engine and they're inside the bellhousing so if that's the case the coolant would be dripping from the drain hole at the bottom of the bellhousing. Can't find any photos that show them but from an internet search that's what I think.
    #10
  11. Conlan Rose

    Conlan Rose Super Moderator

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    You are correct. It may be an intake gasket or one the cooler lines(ones that go to the cab) leaking on to the firewall and driping where you are seeing the drip.
    #11
  12. rdoty

    rdoty New Member

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    Wanted to follow up on this....it was a manifold gasket leak. Replaced the manifold gaskets and no more leak.
    #12
  13. JohnnyMac-Tahoe

    JohnnyMac-Tahoe New Member

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    Liquid travels in strange ways. I had same issue a while back. Never found the source... until it completely blew out.
    Turns out it was a plastic connector at the firewall where the feed and return lines go through for the heater core. (Why the plastic pieces are even there I have no idea)
    I ended up busting all the plastic **** off and connecting the hose directly onto the steel nipple with a hose clamp. Works great now!
    #13
  14. rdoty

    rdoty New Member

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    FINAL FOLLOWUP WITH A MAJOR CORRECTION! A day after my last post there was a pool of coolant under the engine. Took it back and the mechanic called me to say that it was from the radiator and he could replace it. BIG RED FLAG since I'd checked it under pressure previously. After I told him that couldn't be the problem he called again to say that he replaced some fitting at the back of the manifold and the problem was now fixed. Next day...another pool of coolant (scratch that mechanic). Then I took it to another guy who specializes in re-building Chevy 350's. By this time I was really desperate....either fix the problem or trash the truck. He crawled around the engine and said he was sure it was the freeze plugs, the ones underneath the motor mounts. It would cost $500 to pull the engine to replace OR $1600 to pull it and rebuild it. What convinced me was that he's rebuilt over a thousand engines and he gives a 12MO 12,000 warranty. I swallowed hard and took the plunge. When I went in to pick up my truck he showed me the intake manifold which had a major erroded spot at the rear where it had obviouslly leaked previously. He replaced it with one that he had on the shelf at no additional charge. Then he showed me three freeze plugs....all rusted through! "I'm surprised it even held coolant at all" was his comment. On top of that he replaced the water pump with new at no charge, replaced a broken sensor PLUS repaired some wires going to the 4WD unit. Final bill was $1580 and the truck runs like new....with NO LEAKS! Although I spent a lot more than I expected to plug a coolant leak I'm a lot happier. (I'd been quoted $1200 to replace head gaskets and $3500 for rebuild at other places). BTW for anybody in the Denver area it's Engines by Don (Don Nyborg) 303-718-7449. Not a fancy place (pretty grody actually) but it's the result that counts.:party:
    #14
  15. j cat

    j cat Active Member

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    I knew this was gonna cost a couple thousand . I guess you sure don't like stop leak !

    once they start breakin down this old engine my guess of 2 thousand really not a guess .
    #15

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