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  1. #1

    Default Anti-Freeze In oil? What may be causing this?

    I have a 1999 Silverado with the 4.8L and this past December it seemed to start getting worse gas mileage(or so I think), and previously it had slowly been loosing coolant. I figured the coolant loss was due to the water pump going bad, but when I finally looked at it the water pump seemed to be fine. I had my oil changed yesterday morning and they said that there was coolant in my oil. I checked today, and there was condensation in the oil cap, I did taste it and it is antifreeze. This sort of explained where my coolant had been slowly leaking to over the past few months. The truck has has a ticking noise for a while now, not a knocking but ticking noise whenever the engine is on and it ticks faster as the rpm increases. I believe that its something to do with the lifters. I haven't noticed any smoke coming out of the exhaust, nor does the oil on the dipstick look milky. There hasn't been any performance issues that I have noticed since the start of the coolant leaking, the only thing I have noticed or felt is happening, is my gas mileage decreasing. The last thing is, my oil pressure runs at about 60 at 2000rpm but 40 when idling. I'm not sure if this is normal for my truck, I don't remember it being that way but maybe it was and I just noticed now because I'm more paranoid about a major issue.
    What could this be from? Blown head gasket? I feel like I would really notice something performance wise if the head gasket was blown.
    Cracked engine block? How would I figure out if this was the case?
    Bad intake manifold gasket?
    I'm on a budget and pretty handy, I've replaced the intake manifold gasket before along with the knock sensors I believe I could replace the head gaskets, which I would replace the lifters at the same time if that was the case. I just don't know what the problem is here.
    I'm just trying to get an idea of what the problem might be. Thanks
    1999 Silverado 4.8L V8 2WD
    6" suspension lift by Fabtech
    3" body lift
    Toyo Mud Terrain 35" tires, 16" Weld Racing Rims
    Magnaflow cat-back exhaust
    K&N cold air intake
    Hypertech Performance Programmer
    Viper Security w/remote start
    Kenwood Speakers, 2 12" Kicker Comps
    Valor 7" flip out head unit

  2. #2


    either your intake gasket has blown out and is running antifreeze into the lifter valley. Or your head gasket is blown. best thing to do is go get a coolant tester and see if combustion gases are getting into the antifreeze. if u are you could be getting some in the cylinder and some in the oil. if its the gaskets just do your research on everylil thing. plan it out and just do it. ive been in your shoes before. but im gonna give you a tip if you have a coolant leak. everybody says coolant sealers are snake oil. THEY ARE NOT. get a bottle of CRC copper seal bout 10 bucks. or if u want the better go with blue devil the big bottle. oreilly carries it. follow the directions very closesly do exactly what the directions say. do not just pour it in or itl be a waste of 50 bucks. blue devil worked on my old school malibu a year ago and just recently my 90 k1500 that i sold had a blown head gasket and crc copper seal, sealed it up and the pourous white smoke stopped. depending on the person u are u will either replace gaskets or do the liquid seal. the liquid seal works and in winter time noone wants a HG job in the cold.

  3. #3


    Hi, SilveradoKid:

    The most likely culprit is a head gasket that has started to leak for one reason or other. First confirm that it is the head gasket, then you need to determine what caused it, if possible. Sometimes they just fail.

    Take off the water neck from your engine where the return hose takes water back to the radiator, assuming you have a V-8 and the neck is on top. When the engine is cold of course. Take out the thermostat. Start the truck and have someone race the engine up and down while you watch the water in the port where you removed the thermostat. Do not try to warm up the truck! If you see bubbles, you have a head gasket leak or a crack in the head.
    1994 Chevy K2500 Silverado, 454 (modified), original owner.
    And other vehicles and toys.

    "...If you can meet with triumph and disaster
    And treat those two imposters just the same;'ll be a Man, my son!" Rudyard Kipling

  4. #4


    I tend to lean to the side of a blown head gasket also. I am not a fan of stop leak type products as a long term cure. Like was mentioned before if it failed there may be a reason for it.

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