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Oil and Coolant Mixing

Discussion in '1992-Present Chevy & GMC models' started by k5kowboy, Dec 26, 2002.

  1. k5kowboy

    k5kowboy Newbie

    Dec 25, 2002
    Likes Received:
    Norfolk, VA
    I have a question that I am hoping someone can answer. I have a 1995 GMC Yukon 4WD with a 5.7L Engine. It has a little over 65K miles. While checking the oil a few days ago, I found it to be about 2 Qts low and there was coolant on the dipstick. I then checked my coolant overflow container and low and behold, found oil in it. I immediately figured it was one of the head gaskets and was making plans on digging into it this weekend. However, I was told through the grapevine that one of my relatives had the same problem with 2 of his Burbs that are about that same year model and both had about 65K miles on them. Apparently, there is a plastic piece somewhere on the intake where the coolant and oil run really close together and it is a "known" problem of it cracking allowing the mixture of the two liqueds. However, I have looked online and can't find anything about it. So, before I go digging into this thing too much, I was curious if any of you have heard or experienced anything along these lines?



    I did some crawling around the beast this morning and found a couple of interesting things. First, there was very little water on the dipstick this morning, in fact, I could barely find any at all. I checked the coolant overflow and it has a dark color to it, but when I dipped a stick in it, I didn't find any oil. I popped the top of the radiator, and there is no oil there..just pure ole antifreeze. So, I pulled one of the valve covers to see if I could find any traces of water in there and there isn't any. Second, I have a small coolant leak where the line connects to the water pump. Can't see any reason for oil to mix with it there tho. But, when I crawled under the monster, I found oil covering two lines that run from the radiator to the oil filter (I'm assuming it is a oil coolant system). The oil is right where the line changes from a solid line to a flex type line. My question is...could the point where the coolant does it's thing at the oil filter be the point where I could be getting the water into the oil?

    Ross /forums/images/graemlins/k5.gif

    1978 K-5
    1995 GMC Yukon
  2. 95 Silverado

    95 Silverado 1/2 ton status

    Nov 9, 2001
    Likes Received:
    Central PA
    Your Yukon, like my '95 pick-up, has an engine oil cooler in the radiator, those two lines run to the the cooler in the left side radiator end tank. If parked, the oil and water would separate and be harder to see. If the oil cooler would develop a leak it would provide a place for the oil and water to mix. The right side radiator tank has a cooler for the transmission fluid, if it develops a leak it can contaminate the transmission fluid and you can end up with transmission fluid in the coolant. The two metal/rubber lines running from the oil filter carry oil to the radiator, not anti-freeze to the filter. I think the intake leak problem is more prevalent in the vortech engines, yours being a '95, it should still be TBI, the intake gasket could be leaking, but it will usually leak coolant to the outside of the engine, the oil won't leak into the coolant system.

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