While driving my recently purchased minivan (a 1999 Pontiac Montana) for about 40 miles, I noticed the temperature gauge was reading high when I wasn’t moving very fast, though short of what appears to be the overheating zone. Opening up the radiator revealed no coolant that I could see, but plenty of brown sludge. Looking under the oil cap revealed more brown pudding-type stuff (that wasn’t there when I did an oil change when I first got it).
The lack of coolant makes me nervous that the engine might have overheating without the temperature gauge reading it properly. Is that possible? The heater was working, which searches seem to suggest means there must have been some in there.
I figure that either the intake or head gasket must be bad, so I’m nervously setting out to replace both using a gasket set like this: http://tinyurl.com/h244422
What I’m more worried about though, is clearing the cooling system out of all the gunk. It sounds like oxalic acid and washing soda and backflushing might work? But I’m anticipating a large quantity of sludge, oily, rusty coolant water. How am I going to dispose of it all?