Oil in coolant, 4.5
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HT4100 4.1, 4.5, 4.9 Discussion, Oil in coolant, 4.5 in Cadillac Engine Technical Discussion; I recently bought a 1988 Eldorado 4.5.The car has 102000 and the body is in mint condition. The water pump ...
  1. #1
    8eldorado8 is offline Cadillac Owners Member
    Automobile(s): 1988 Eldorado
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    Oil in coolant, 4.5

    I recently bought a 1988 Eldorado 4.5.The car has 102000 and the body is in mint condition. The water pump recently went and I replaced it. A lot of the coolant was drained and replaced. After running a few errands I checked the overflow resivoir and it was black. I stuck a screw driver to the bottom and there was a crud that looked like wet brown sugar on it when I pulled it out.

    After closely examining the engine I saw that both valve covers had brand new gaskets meaning there was some kind of recent work done on the engine. My question is, is this because recent engine work was done and the cooling system was maybe never flushed could this have stirred up because of replacing the water pump? If there is an actual problem what do I need to look into intake leak, head gasket?

    The car runs perfectly fine as in temperature, idling, driving, heater works. Any help is greatly appreciated.

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  3. #2
    HUF's Avatar
    HUF
    HUF is offline Cadillac Owners Connoisseur
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    Re: Oil in coolant, 4.5

    How thick was the layer of crud? It could be GM-recommended old coolant additive (Bar's Leaks Gold powder). Head gasket failures are very rare on 4.* engines. If you do not know when the coolant was replaced, you might want to do that. Put Bar's Leaks Golden powder stuff into the radiator neck. You can buy it in tubes at Wal-Mart for a less than two dollars. One tube will be enough.

  4. #3
    drewsdeville is offline Cadillac Owners Master
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    Re: Oil in coolant, 4.5

    Quote Originally Posted by HUF View Post
    Head gasket failures are very rare on 4.* engines.
    Er, I respectfully disagree. I myself have done 3 4.X headgasket jobs. Aluminum block under cast iron heads makes for some abnormal thermal expansion and contraction that tears up the headgaskets, just like the intake gaskets.

  5. #4
    creeker is offline Cadillac Owners Connoisseur
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    Re: Oil in coolant, 4.5

    If it was my car I would clean out the overflow tank, maybe some one put the bars leak into it instead of the radiator, you probably dont even need to add more bars leak,
    especially if you dont drain cooling system.

  6. #5
    creeker is offline Cadillac Owners Connoisseur
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    Re: Oil in coolant, 4.5

    Quote Originally Posted by creeker View Post
    If it was my car I would clean out the overflow tank, maybe some one put the bars leak into it instead of the radiator, you probably dont even need to add more bars leak,
    especially if you dont drain cooling system.
    I just thought, if it was oil in overflow tank, it would be floating on top of water, not laying in bottom of tank, so it's good news that it's probably bars leak.

  7. #6
    the recluse is offline Cadillac Owners Connoisseur
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    Re: Oil in coolant, 4.5

    ^^^^Agreed. It could be sediment from the cooling system itself (little to no coolant equals rusty water and sediment). Either way, sediment on the BOTTOM is better than oil on the TOP.

    Flush the system vigorously, back, forth, front, to back. If there is that much sediment in the reservoir, than the radiator must be a mess...

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