Head Gasket?

[mekelly]

I noticed that the coolant level was low in reservoir bottle on my 1994 explorer. I couldn't see any obvious leaks anywhere so I thought I'd start the engine and let it heat up and pressurize to see if I could find any leak points.

I started the engine (it was cold, hadn't been started that day yet) and noticed that coolant immediately started leaking between the upper radiator hose and the radiator (where they connect). It was coming out between the hose and radiator connection as if under pressure. I opened the radiator cap and coolant started bubbling out.

I shut the engine off, put the radiator cap back on and re tightened the upper radiator hose clamp.

This was about 2 weeks ago or so. It has not happened again although the fluid level has dropped some more in the reservoir bottle.

There's no coolant in the oil that I can tell and no oil in the coolant. The engine never gets hot, the temperature gauge is in the 'N' to 'O' range where it's always been. I don't really smell coolant burning in the exhaust, the exhaust isn't blowing white smoke.

I replaced the thermostat, water pump, radiator hoses, heater hoses, temperature sender and temperature sensor recently.

I am guessing a blown head gasket or cracked head but the engine temperature is spot on. That's with running the A/C for the first time this season and temps in the low 80's.

Is there any other plausible diagnosis? Any other tests I can run or things to check? Rent a coolant pressure tester, check plugs for coolant?

It's definitely loosing coolant but other than that one episode, I can't find any.

 

[natenkiki2004]

Bubbling when cold? That's very suspicious. I'd pull the plugs and see if any are different than the others.

 

[SuperKirby]

Are you going through coolant still, or did it just go down some after you filled it and hasn't more? If it's steadily going down, you're losing it somewhere. If after everything spilled out you refilled it, lost some, and now you're not I would say chances are there was air in your system and it's working it's way out. With my head gaskets, I had a steady stream of bubbles in the overflow tank when it was running. It looked like someone was blowing into it with a straw.

 

[mekelly]

It's still losing coolant. If I remove the radiator cap I can see very very small bubbles in the coolant. It only 'bubbled over' that one time on start up.

The upper radiator hose does pressurize after about 10 seconds with the radiator cap on when it's started cold.

Based on that, it seems like there's definitely combustion gases getting into the coolant.

Is it more likely to be a head gasket leak or a cracked head? I have the 1994 which is supposed to have the better heads.

I bought the car 6 months ago from a good family friend. They bought it new and kept it well maintained. He went over everything that was wrong with it (rear windows won't roll down, driver's door hard to close, etc.) when I bought it. Never mentioned it overheating so frankly I don't think it did (but you never know).

 

[FR-425]

I lose coolant from the reservoir just due to evaporation, their not air tight, about half gallon per week.

I used a combustion leak-test just to be sure.

Once the res is empty there's no more loss.

Test Kit:


http://www.sears.com/uview-combusti...a=00916147000P&kpid=00916147000&mktRedirect=y

 

[2stroke]

So I'm guessing you fixed the leak at the upper radiator hose. Even after bleeding the system good, does it still go through coolant constantly? A half gallon a week is a bit much, but I could see it in really hot areas. I would have the coolant tested.

 

[vq5speed]

You know the reservoir cold level fill line is near the bottom. So the level should not be full when the engine is cold. So if you keep topping it before you start it will boil out while driving. Then when you park it will suck it back to the radiator as the engine cools down leaving the level low where its suppose to be.

 

[natenkiki2004]

I lose coolant from the reservoir just due to evaporation, their not air tight, about half gallon per week.

I used a combustion leak-test just to be sure.

Once the res is empty there's no more loss.

Test Kit:


http://www.sears.com/uview-combusti...a=00916147000P&kpid=00916147000&mktRedirect=y

Don't take those tests as 100% accurate, especially that exact one you linked to...

https://www.youtube.com/watch?v=tMMm1XHUxQc