Overheating 99 Ford Explorer

Looking for some ideas. Recently my Ford Explorer started overheating. It's a 99 4.0L SOHC with 120,000 miles. Once it cooled down I checked the coolant and it looks a nice green although the overflow tank was blackish. I started the cold vehicle up without the radiator cap on. Once the temperature gauge made it about to the middle I started to get a good geyser which make me think that the thermostat opened and the water pump is working. When it gets hot turning on the heater drops the temp for a while. Am I missing something?

Reply to
ace3d.tm
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Geyser? Overheating can blow the head gaskets, which then causes exhaust gases to get into the coolant, which leads to further overheating. The exhaust gases make big bubbles which cause the coolant to be forced out, and bubbles to come out if you have the radiator cap off.

A good test (be careful, use common sense when doing this) is to warm it up with the radiator cap off, put it in gear with the brakes on and rev it a little- 1200 rpm is good. Slip the clutch if it's a stick. Have someone watch the radiator outlet. If bubbles are coming out and the coolant level is heaving up and down, you have a blown head gasket. If it's good, coolant will be circulating, but it won't be heaving up and down and blowing bubbles.

-Paul

Reply to
Paul G.

exhaust gases make big bubbles which cause the

Paul,

Thanks for the tips. Once the engine hits operating temperature the coolant comes out of the uncapped radiator. The temperature normally is half way but with this problem it has been getting to 80% of the way to "H". Before that I didn't see any bubbles but the coolant was dribbling out. I have not noted in oil in the coolant or coolant in the oil. There hasn't been any consumption of coolant so I'm hoping it is not a blown head gasket. I think likely I'll flush the coolant system and if it is still getting hot take it in for them to see if the head gasket has gone.

Reply to
ace3d.tm

The exhaust gases make big bubbles which cause the

Plugged radiator?

Reply to
Big Shoe

The exhaust gases make big bubbles which cause the

Thanks for the help folks. I let it get to the 80% of hot and then shut it down and there was an oil film in the overflow so it must be the head gasket. My guess is the the first couple of times in got hot there was very little coolant loss, i.e. only small leakage, and now that it's got hot around 5 or 6 times the problem is much worse.

Reply to
ace3d.tm

furtheroverheating. The exhaust gases make big bubbles which cause the

I had a clogged heater core that was causing some overheating problems but this one sure sounds like a blown head gasket.

You can supposedly (never tried it) buy test strips from an auto parts store that will detect exhaust gases in the coolant. But of course a cylinder compression test would be more conslusive.

Reply to
Ulysses

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