Compression test results

[pgarland]

OK, here is a little bit of background on the problem;

Car overheated the other day. It was in my driveway, I had just come out and started it because I hadn't driven it in a couple of days. I let it run for a few minutes while I was doing something else, I came back to it and it was overheating. I immediately shut it down, and let it cool off (let the water in the overflow tank stop boiling). First things first, I checked the coolant in the overflow reservoir...there were little brown chunks floating in it, and it had a bit of a sewage smell to it (not sweet at all). I went ahead and topped it back up with water (to replace what had boiled off earlier), and started the car back up, to see how long it went before it started getting hot again (trying to see if maybe the radiator was blocked I guess...the faster it overheats, the more likely that something is blocking the free flow of the coolant). Well, it didn't take long at all to get hot again.

In the beginning I was thinking the brown chunks had something to do with the heater core or were a sign of something else (it didn't look like oil to me at first for some reason, maybe in my mind I was just trying to block out the possibility of it being the head gasket...), but as the small puddle that spilled out of the overflow tank dried, it turned a light brown in color, and I couldn't justify the smell that was coming from it as anything other than burnt oil. The radiator on the car is less than a year old, and about 6 or 7 months ago I replaced the heater hoses on the car, and did a full coolant system flush then. I have also replaced the thermostat about the same time I did the heater hoses, and the car has been running fine for months now until the other day. So, pretty sure it is the head gasket, I went out today to do a compression check. Below are my results:

Cylinder 1: 198 PSI
Cylinder 2: 151 PSI
Cylinder 3: 153 PSI
Cylinder 4: 201 PSI

Now, this seems to me that I have a blown head gasket, and that it's leaking oil into the coolant from between cylinders 2 and 3. But according to the Haynes manual, these numbers are within the 25% difference tolerance (although they are right there at the 25% mark). Should I be looking at something else as the culprit here maybe? The car has about 137,000 miles on it, and was definitely abused in a former life (I bought it from a dealer who bought it at auction...no way of knowing the real history on it, but from everything I've seen, I don't think it was very well cared for by it's first owner), so I'm sure the motor is a bit tired (which could explain the lower compression numbers on the middle cylinders). Just wanted to get some outside opinions before I decided to go ahead with a head gasket replacement, especially as it's 93 degrees (heat index of 104) here today, and is supposed to be just as hot tomorrow, and I can think of much better ways to spend my weekend .

Many thanks in advance for the help guys.

 

[BLINKY619]

ok when you have the radiator cap off and let the car run... do you see little bubbles comming out? if so im pretty sure its your head gasket.... also have you checked your thermostat?

 

[pgarland]

I went back and checked the thermostat again, just to rule it out as a possible culprit. I boiled it on the stove, it opened like it was supposed to. I didn't think it would be the problem though, because it is relatively new (only a few months old), and my upper radiator hose was getting hot (which means the thermostat was opening properly, letting the coolant through). But, it never hurts to be sure.

As far as the bubbling, I haven't had the chance to check for that with the car running yet. I will definitely give it a go in the morning though. I'll update as soon as I get more information.