yotawalt

My 93 pickup (22r-E) has 207,000 miles and a coolant leak. It was a very slow leak until a couple of weeks ago. Now much more pronounced, about a quart of coolant every hundred miles.
Coolant has leaked onto the top of the bell housing. I pressurized the cooling system, and could not find any leaks, but did see that the area in back of the head appears wet. I could not see any leaks near the water pump
Compression readings are 178, 180, 180, 163. The plug in the low-compression cylinder looked damp when I pulled it out.
I can see a little foam on the inside of the oil filler cap (a new thing for this truck).
In the last couple of weeks, it seems like the engine runs rough for a minute or so at startup, and I wonder if that is because I'm getting coolant in that fourth cylinder.
So, is this enough evidence that my problem is a head gasket? I would have thought that my compression would be worse than this with a head gasket problem. If it is head gasket, what else should I do for my wonderful yota when I have the head off? I think I'll replace the timing chain, sprockets and guides.

XtraSlow_XtraCab

Sounds like a bad headgasket. I lost coolant at almost that same rate and borrowed a pressure tester. It turns out I lose it at the head/block surface right behind the alternator and behind the exh manifold.

A bad headgasket does not always mean worse compression. In my case, coolant leaks at the gasket and down the side of the block, NOT into the combustion chamber. So, I'm waiting til warmer weather and just topping off the radiator every week.

163 is a bit of a drop off from your other numbers. As this problem persists, you should have white smoke coming off the tailpipe and the truck will run rough more and more upon first start-up of the day. With the engine cold, you can remove the radiator cap and start the motor. If coolant leaks into your cylinder, than conversely cylinder compression can push air into the coolant system... making for over-pressurization of your coolant system.

Looking under the oil cap was a smart move. Give it a week of driving and it will actually look like milk under there if there is a gasket leak between oil and coolant passages (which majority of the time there is).

yotawalt

Thanks, XtraSlow. Sounds like head gasket time is coming.

samf

I had a coolant leak on my 87 22R. It was under the exhaust manifold. I found out that because of the iron block and aluminum head and coolant passing over both it creates electrolysis an actually puts a charge in the coolant. I guess it's call "going toxic". The current eats the head gasket through the metal. GM has a problem with the same thing on their older V6 motors. I was told to changed the coolant regularly. ??