99 Venture - Coolant in Oil Question

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May 18, 2003
My wife drives a 99 Venture (3.4L) which had the intake manifold gaskets replaced this past December. The van was purchased used at 19k and has run Mobil 1 5W30 & GM oil filters since that point. I usually average 7500 miles between changes, but have gone to 10K a recently. The van does not use any oil. The van had the intake work done at 56K and it now has 65K on it. Prior to intake work, I noticed the coolant level dropping a little over a few months timeframe and probably added 1/2 gallon total. When I realized the intake was leaking, the oil had about 4k on it and the filler cap was "foamed" up. I changed the oil and took it to the dealer where they replaced the gaskets, etc. I then changed the oil again and ran it for about 1k and changed the oil again. Currently the oil has almost 7k on it and there are no other signs of coolant in the oil.

I realize the engine was probably damaged by the coolant in the oil. Did running the Mobil 1 synthetic help this situation at all? I plan to do an analysis at the next change, but that will be several months away. I asked GM for an extended warranty on the engine, but they would not budge. I did get them to pay for 1/2 of the cost of the repair, even though we were way of of warr.


I wouldn't say for sure the engine is damaged - which I assume you are asking specifically about the clasical pitted, damaged bearing journals. I would pull a sample now and see where you are - 7K miles. You can learn a LOT from a UOA.
Sample AND change oil again, right now, pronto, but up the oil viscosity to 10W30 or 5W40 until you see what shape the engine is in.
I defenitely agree with Molakule.

Gee-what a surprise another 3.4 intake manifold leak. In my very humble opinion GM has not owned up to this total disaster in the 3.1 AND 3.4 ENGINE. I am the last person in the world to file a lawsuit-but if there was ever a class action suit-this would be it. It took GM years to live down their auto transmission boondoggle in the 80's. They never learn.
I also want to add that an Auto-Rx treatment and a short run of Chevron Delo 400 15W-40 may be in order. From what I read (no personal experience) Auto-Rx does a good job of cleaning bearing surfaces of coolant scunge.
I replaced the oil & filter last night with Mobil 1 10W30. I ordered two kits from Blackstone, but haven't received them yet. To collect oil, I filled up a "freezer" ziplock bag from mid-drain. Have I contaminated the oil by putting it in this bag? The oil was very hot when it came out, but the bag held it...

Will an oil analysis show damage made to bearings, if the damage was not made on the current oil? The oil was changed during the gasket replacement with dealer oil, again 100 miles later with dino 10W30, again 800 miles later with M15W30, and now again with about 5000 miles on it. The oil "looked" good coming out and it hasn't used any oil or coolant since the gasket replacements. There are now about 65k on the engine.
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