Wiring harness, head gasket

[KermitF]

Hey Guys,

Two questions:

1. Does a '96 C280 suffer from the bad wiring harness syndrome? (and if so, what mileage/yearly age should I expect it to first make itself a problem?)

2. If the head gasket is leaking on a '90 300E (w/no oil in coolant reservoir at this time), will engine run slightly hot?

[Kestas]

I'm pretty sure the bad engine wiring harness problem is limited to the 93-95 model years.

Head gaskets can fail so the engine runs hot and introduce no oil in the coolant. This leak path would allow exhaust gases to enter the cooling system, although I would expect some overpressure symptoms in the cooling system.

[KermitF]

Thx Kestas.

Follow-up questions - I am only running marginally hot at moment (@95-100 - car typically runs right at 90C). Is this slight increase the sort of thing that points to bad head gasket?

Also, w/181K mi. and no symptoms indicating any valve problems, if it does turn out that I need head gasket, does it make sense to do complete valve job at this time?

[Kestas]

If you're observing a slight increase in running temps, it could be many things besides a head gasket leak. It could be as simple as a tired thermostat, or deposits could have built up inside the radiator. If you need to rule out the head gasket, radiator shops have a way of detecting exhaust gases in the cooling system.

Your cheapest "first step" approach to diagnosing this problem may be to replace the thermostat and see if that solves the problem. The radiator itself can be boiled to remove deposits at the radiator shop, or treated at home with a citric acid flush treatment.

With those miles, if you do remove the head, it's prudent to have the head professionally reconditioned, even if it's healthy. It's one of those "while it's apart" things to do.

[KermitF]

Thx for advice Kestas - thermostat next.