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Another Texan with a pesky truck

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Hey y'all,

Another Texas guy here. I've been looking around and am getting mixed answers on what I should do with my 1999 Silverado w/4.8 v8. About a month ago I had the heater core and radiator replaced, they were both completely clogged and getting zero flow through them. Through either luck or genius engineering my truck wasn't overheating, but I decided to do both anyways. When I drained the cooling system it was black like oil had been getting in there. This brings me to my issue. My truck which has 235K miles doesn't burn oil, and it doesn't leak oil, but somehow it loses oil at the rate of about a quart a week. I am constantly adding oil. It is going into my cooling system. Now I haven't done a test on the oil to see if it has coolant in it, but I can tell you that when I change my oil it is pretty black, not milky, so there wouldn't be much coolant in there.


The other symptom I have is that it sounds like i'm getting a little piston slap when I first start to drive the truck. Not necessarily when I start the truck, that usually sounds fine, it's when I start to drive the truck. And it only does it for 2-3 minutes, then she calms down and runs normal (other then a little lifter knock..235k remember).


I'm hesitant to say it is a head gasket. I don't have oil and coolant mixing both ways. just oil into the coolant. And it doesn't have piston slap all the time, just when I first start to drive it. I thought about trying some bar's stop leak with carbon fiber, but common sense leads me to believe this may not be a good idea for the motor or my new radiator/heatercore.


Any advice would be greatly appreciated. Any thoughts on what I should check or have checked first.


Thanks guys,




PS. Far North Dallas area

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Hey guys, thanks for the replies.

The old radiator had oil in the coolant, I replaced the radiator and it is still happening. Correct me if i'm wrong, but this would mean that it's likely not an oil cooler leaking inside the radiator. (unless the oil cooler part is taken off the old radiator and put on the new one, I didn't do the work and have never looked that closely at the components of a radiator). Are there any other places this could happen? Oil pump, water pump? would a compression test tell me if its a gasket?


Thanks y'all

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