General motor question

[77 Ford]

My son's ranger is slowly over heating. He took it somewhere and they told him they thought it had a blown head gasket. I just took a look at it last night and ran a compression check and I'm getting 120 to 130 on all 4 cylinders. There is no white foam/froth on the dipstick or the underside of the filler cap. I just don't see how this can be a blown head gasket.

My question to you is , is it possible to have a blown head gasket and good compression, I just do not think it is.

[Lavoy]

Any bubbles in the radiator when it is running?
Lavoy

[gus]

You didn't say age, year or??? Kind of hard starting point, but.... My 93 was starting to heat up some in it's old age. Just needed the radiator cleaned. Not the inside, the bugs had plugged it pretty well. A high pressure washer ended the problem. Also had the same on a Bronco II, same cure.

[Stan Disbrow]

Hi,

Yes, one can have a tiny leak from the head gasket that puts only a little combustion gas in to the water jacket. Remember, the pressure in the cylinders is many times higher than what you see on a compression gauge due to the small bomb set off when it fires.

The tell-tale is gas bubbles in the top of the radiator when running. You will only see water vapor in the hot exhaust with a gross leak from the water jacket into the cylinder. But, the leak will start off minor most of the time.

Another thing to look at is the temperature of the water at the top of the radiator vs. the temperature of the water in the engine jacket. It is also possible that the thermostat is not opening, or opening enough. This will show as high temp in the engine jacket and low temp at the top of the radiator.

I have an F150 farm truck with a 302 which shows too hot early on, then drops off rapidly once the thermostat finally opens. I am too lazy to pull the intake manifold off and change the fool thing. So, I just put the heater in high for the few minutes where the temp is too high until the thermostat finally opens. That works out to be just enough cooling to avoid a real problem. One day, the thermostat will stay stuck closed, and I will finally have to do something about it....

Stan

[scampr]

Napa sells a kit that sniffs for exhaust gas in the cooling system.. I have used them for years and never had one lie to me... just another thought

[Tigerhaze]

My son's ranger is slowly over heating. He took it somewhere and they told him they thought it had a blown head gasket. I just took a look at it last night and ran a compression check and I'm getting 120 to 130 on all 4 cylinders. There is no white foam/froth on the dipstick or the underside of the filler cap. I just don't see how this can be a blown head gasket.

My question to you is , is it possible to have a blown head gasket and good compression, I just do not think it is.

A blown head gasket will show on compression if the break is between the combustion cylinder and the water passage- however it may not show a compression loss if the break is between a water and oil passage.

There is also such a thing as a "seeping" head gasket- this is common to Hondas and Acuras. The head gasket in that case is "blown" slightly between the combustion chamber and water passage- usually the rear cylinder which causes overheating. Due to the design the water doesn't enter the combustion chamber and the car will still run great (just overheat) but a compression test would detect leak down.

BTW, is your son's Ranger a late 80s/early 90s with the 2.9L 6-cylinder engine? If so there is a design flaw that can cause overheating. I can send you a web link to a good webpage that describes the issue- it has to do with the design of the cylinder heads. I only know about this because I thought about buying one recently and decided to pass after reading about the design flaw- the truck I was looking at had the tell-tale symptoms (overheating/white vapor from tailpipe but good compression).

[77 Ford]

Thanks everyone for the information, to answer a few questions. It's a 4 cyl ranger, I think it's an 89. It has the little engine with 2 plugs per cylinder.

I will check it for bubble when running next time I look at it. I'm really leaning towards a stuck open thermostat. The upper house warms up so I don't think it's stuck closed although i suppose it could be partial like someone else suggested.

It looks pretty easy to change the thermostat and it's not really out of the way towards doing a head job anyways.

Thanks!

Phillip

[77 Ford]

Follow up:

It was a stuck closed thermostat. I pulled the thermostat and it would not open in pot at full boil. I asked my son how he did the upper hose was hot test (which normally checks for a closed thermostat) and he replied he check it after he had drove it for 45 minutes. I explained that test is really something you should do in just a few minutes of running that at 45 minutes it could of heated up thru under hood temperatures.

There was some oil in the water so it's possible there is still a head gasket issue but it's running good and we're only 15 bucks deep at this point so we're going to keep an eye on it for now.

[gus]

If there's oil in the water, plan ahead for a good time to do it and fix it now. The "fix" will only get more expensive if you wait.

[Ray III]

Glad you did not let them "fix" the head gasket. Very common mis-diagnosis in cars. Why people don't check the simple stuff with an IR temp gun is beyond me.

Does it have an automatic transmission? Leaking cooler in the radiator can be a source of oil in the water.

I had a 2.3 once (single plug), that motor was bombproof.