GM 3800 Series II- Coolant In Oil, not head gasket?
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June 4, 2007
GM used the 3800 V6 Series II in their full sized cars from 1995-on. The engine can be distinguished by a large plastic cover that says Series II on it on top of the motor. It was first used in 1995 Pontiac Bonneville, 1995 Buick Park Avenue, and 1996 Olds 88/98, Buick LeSabre models. From 1995-1999 this motor has a tendancy to develop coolant in the oil. Many people assume a blown head gasket or a cracked head or block. However this is not usually the case. GM made the upper half of the intake manifold out of plastic on these cars. Early models had a tendancy to warp and deteriorate the plastic where the EGR tube admits hot gas into the engine to reburn for emissions control, and this causes a leak to develop where engine coolant goes in and out of the manifold around the throttle body. Coolant leaks from the hole eroded in the platic, and runs down into the lifter valley, or is sucked into the engine and burned. In extreme cases the cylinders will fill up with coolant and hydro-lock the motor. Usually this is seen as a symptom, by white sludge that looks like soft-serve ice cream built up in the top of the oil cap or in the PCV system, and the engine is going through a lot of coolant, and you can smell hot coolant especially in the exhaust. The fix for this is to replace the upper intake manifold with an improved design that is on the market. It is available at most parts stores or through the dealership. Cost of the parts is about $150 plus it is advised to flush the oil system and change the oil, and repalce the spark plugs if they are fouled out due to the coolant in the cylinders. Total labor is about two hours. Compare this to the cost of new head gaskets, which often are not the problem, and you can see why so many people often sell or junk their Series II 3800 cars cheaply. If you know what you are doing this can be fixed easily. In some cases there may really be a bad head gasket, but since the upper intake must be removed to service the ehad gasket, it is easy to inspect before you go any deeper into the engine. Good luck, and if this helped you, please indicate it below.
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