So I bought a 99 Pontiac Montana (for $1200, too much considering the problems it apparently has). It had new tires, looked clean in the engine area, and seemed to run fine. So I bought it.
The low coolant light way on, but there was some, but little, in the reservoir, so I figured it was fine.
But as I took it on a 40 mile drive, I noticed that the gauge would run hot on slow traffic, but always short of the overheating area. Running it at highway speeds, the gauge would stay in the middle. Also, revving it in park would bring the gauge down.
Reading online, it sounded like it could be a low coolant problem.
So I peered into the radiator, and saw no fluid but lots of brown gunk. Looking under the oil cap, there was similar gunk. Although I don't think that was there when I first bought it (even though the oil wasn't new and had been driven at least 40 miles) and I changed it since then.
So now I'm pretty sure that either the intake manifold or head gaskets are bad. So I'm nervously going to attempt to replace them myself. I have some experience working on cars, but more experience working on my watercooled scooter, learning by doing maintenance as necessary.
Here'* the gasket set that I think I'm going with: 96 99 Pontiac Oldsmobile Chevrolet 3 4L High Performance Head Gasket Bolts Set | eBay
Is there a reasonable way to clear the gunk out of the radiator, or will I probably need a new one?
How likely is it that the engine was damaged by heat despite the gauge now being that high?