Compression test results

[q240z]

I bought a '97 OBW that was running rough a week ago. The previous owner said it had been diagnosed by an indie mechanic and the dealer as having a "blown cylinder." I found a broken spark plug on the #2 cylinder and figured that the mechanics were just lazy. The car doesn't overheat (yet), even with the AC cranked up in steamy hot Washington, DC. After replacing the spark plugs, checking the wires, and resetting the CEL, I thought I might have fixed it. It certainly ran better, but there was still a persistent ticking sound that seemed to come from the right side of the engine. And then the blasted CEL came on again after about 2 miles of driving.

 

I went out and picked up a compression tester yesterday and found #2 had 180, #4 had 172, #1 had 175 (I was getting really excited by this point), then #3 came in with 28! HA!

 

Houston, I may have found the problem! It looks like "blown cylinder" means blown cylinder head gasket.

 

The oil is as clean as can be. I pulled the valve cover yesterday and it looks like new inside--it looks like the original owner was religious about oil changes. When I checked the coolant originally, I didn't let the car fully warm up before looking for bubbles, which lead to my misdiagnosis. I'm pretty sure that the thermostat hadn't opened and was holding the air back. When I let it fully heat up yesterday there were obvious bubbles in the coolant. Here's the wierd part--there's no steam out the tail pipe.

 

The thing is, I don't want to replace the HGs and then find out that the ticking sound is coming from something else deep in the engine. I found a thread on the early Subi forum where the guy's overheating and ticking problem went away when he replaced the head gaskets.

 

I have two questions:

A) If combustion gases are going past the gasket and entering the coolant passages, why isn't coolant showing up as steam at the tailpipe?

2) How in the world could a blown head gasket be related to a ticking sound?

 

As always, thanks for your thoughts and opinions in advance.

[frag]

Just an opinion on "A".

Its the exhaust gases that are entering the coolant system not the reverse cause exhaust pressure is much higher than coolant system pressure. So no coolant in the cylinders.

These leaks are often very small and the coolant pressure at engine shut off is probably not high enough to force it's way past the gasket and to the cylinders.

If you let things go and the leak becomes bigger, you might begin to see some white vapout at the tailpipe.

From the top of my head...

[Midwst]

The next test to do is called a cylinder leak down test. It does require a special tool. This checks if it is indeed a head gasket, or maybe a mechanical problem, like rings, valves,etc. Might even be able to detect a cracked block. The fact that the insulation was broken on the spark plug causes me to think twice about the head gasket diagnosis. Head gaskets don't normally break spark plugs. I would have this test done first just to make sure, because otherwise you could do the whole head gasket job, put it back together and find...still not okay. Of course, chances of it being a mecahnical problem are pretty low...but personally I'd have that checked first. Its not a test you can easily do yourself, unless you are very mechanically inclined and experienced in what to look for. Best to take it to a shop that specializes in engine work. Cost is about $65-$75 i think. Also the fact that only one cylinder is bad and not 2...plus no coolant in oil or oil in coolant....plus ticking sound. It is possible you broke a piston ring.

[frag]

The broken plug is in cyl no 2 and the faulty cyl is no 3. Maybe there is no relation between the two.

[q240z]

The external insulator was the one that was cracked on the plug. There wasn't any mechanical damage to the combustion chamber end of the plugs.

 

The lousy thing about doing this work is that I have every tool I need to do leak down, compression testing, an engine crane and stand...all in Portland, Oregon, while I'm now living in DC. I'm just an impatient bastard, so I end up buying new tools because I don't want to wait for shipping. As it stands, I've got a compressor on both coasts, so I'll just set the regulator at 100psi and then use the quick disconnect hose from my new, east coast compression tester to hook each cylinder up. If the line pressure drops to 90psi, I'll know my leakdown is 10%. I'll be able to confirm the blown HG this way by looking for bubbles in the coolant, too.

[Midwst]

Take a listen to the oil filler tube for air escaping past rings. If coolant bubbles, Could be a head gasket blown on the outside edge...but more often the head gasket blows between cylinders.

[Meeky Moose]

well headgaskets on early 2.5's blow internally and leak compression into the cooling system.. they usually loose compresion on one cylinder when this happens.. (mine lost #2)

 

anyways.. do yourself a favor and find a 2.2L engine out of a 95" subaru and drop it in.. you'll need the complete motor.. it bolts right up, you use the 2.5 flex plate and torque converter the rest is plug and play..

 

you'll have a small loss in power (not really noticeable) but gain the reliability of a 2.2L (they run 300k with proper maintenance just fine)

 

been there done it

[q240z]

I've got the compressor running in the garage right now, getting ready for the big leakdown test.

 

 

Meeky, what sort of compression did you have on that dead hole in your car? Did you also have any sort of ticking sounds going on? I've got something that doesn't sound metallic, it's more like a pinhole exhaust leak (but without any exhaust leaks apparent). Also, what happened to your fuel economy when you swapped out motors? Anything noticeable?

 

I hear what you're saying about swapping out the engine, but I'd really like to avoid that if I can. Are there other issues besides the head gaskets that make these 2.5s anchor material?

[q240z]

freakin' double post