Overheating Issues

[anto]

Mom's had this car for a while (95 LE, 5FSE), I recently did a tune up on it. It consisted of:

New plugs, wires, cap and rotor.
New coolant temp sensor, oxygen sensor, PCV valve and gasket (those things get so brittle)

I replaced her radiator & cap a while back due to the top portion cracking. Recently, the lower half of the rad cracked open somehow and the car overheated. I replaced the radiator, thermostat & gasket, and filled it with 60/40 Water/Zerex G-05.
HERE IS THE PROBLEM:

When I heat up the car, everything is fine. Upper & lower hoses are hot.
After the car has been driven for a bit, the overflow tube starts shooting bubbles into the overflow tank. Eventually the coolant is so offset by the bubbles that a bit overflows out of the tank. When the car cools again, the coolant is sucked back into the radiator like normal.


At first I thought it was a headgasket, but there seems to be no coolant in the oil, and no oil in the coolant. A compression test yielded ~200 psi on all the cylinders (a tad high). I am seeing some milky light brown goo underneath the oil cap, but I'm thinking that's from the massive sludge in the engine.

WHAT is going on?! I'm super confused.

[BlueFusion6851]

The milky crap under the oil cap is coolant. Sorry to say, but, your headgasket is gone.

[Kep]

Occasionally, a head gasket will blow and allow exhaust into the coolant and then bubbles into the overflow reservoir. Often that will also cause overheating (exhaust rases the coolant temp dramatically). A mechanic (or you if you get the tool) can check the coolant for exhaust gasses with Block Tester Fluid. The blue fluid turns yellow if the exhaust is escaping into the coolant. (They may have an electronic test these days as well.) You might also get results from a radiator pressure test.

Kep

[Mike Gerber]

Originally Posted by BlueFusion6851

The milky crap under the oil cap is coolant. Sorry to say, but, your headgasket is gone.

That light brown crap can also be condensation from short trip driving. I along with many other people that do a lot of short trip driving have noticed that from time to time. Don't panic just yet. Do the test that Kep suggested to determine if it really is a blown head gasket. How long was the car driven while it was overheating?

Mike

[anto]

The car was apparently driven until "smoke and steam started to rise out of the engine bay, and the temp needle was in the red"

I was thinking it might have been bubbles that didn't work itself out of the system, but I'm almost sure it's the headgasket.. I radiator pressure tested it, but the tester was weird and didn't fit the radiator correctly.. I fiddled with it and got it to hold 20 psi and discovered a small leak, but pressure started to drop due to a poor cap seal..

I'm going to take it to a mechanic to see if there are traces of exhaust gas in the coolant. Do the exhaust gases stay in the coolant after it's been driven?

[Kep]

The Block Tester Fluid is put in a tube that is hooked onto the radiator fill. The car is started and when it is hot a vacuum is put on the tube and it pulls any exhaust fumes through the fluid. If there is exhaust the fluid changes color.

Kep