compression test and water

[Chuck Dyck]

I have been getting water in my oil all summer. I changed it 3 times and it looked good. Now I just changed the oil for winter lay up and there is water in the oil again. I just did a compression test and my results are 105-100-100-95 dry test and 120-110-110-100 wet test. Does this indicate I have a head gasket issue?
Chuck

[jcwright]

Hello Chuck.

You may already have this information from one of Moyer's answers to an FAQ about water intrusion, but just in case you don't, I've copied part of it below. I hope this helps some.

Jack.

"The most common way that water gets into the crankcase is from engine cooling water backing up within the exhaust system until it floods back through the exhaust manifold. It then passes into, and through, the combustion chambers, and down to the oil pan. This scenario can be caused by simply over-cranking a hard starting engine (with the raw water through-hull open) or from an internal failure of the water lift muffler.

Sometimes, problems within the exhaust system will only manifest after sailing. If water intrusion only occurs after sailing, try closing the raw water thru-hull fitting while sailing, and see if the problem goes away. If it does, you’ll have to troubleshoot the exhaust system, or keep your thru-hull closed whenever you’re sailing.

In a few cases, leaky head gaskets can result in a small amount of water getting into the oil. When head gaskets fail, there is usually evidence of poor running or hard starting caused by loss of compression and/or water fouling the spark plugs.

Exhaust system problems and head gasket failures have one important feature in common: It’s practically impossible for either exhausted cooling water or water from head gasket failures to enter the crankcase without first passing through the combustion chambers. Therefore, both of these sources of water intrusion would logically result in poor running, or some other obvious evidence of water being in the combustion chambers.

In rare cases, both Sherwood and Jabsco water pumps have the potential of passing a bit of water into the crankcase if their water seal leaks and the weep holes in their housings become plugged with grease or other crud. In this scenario, trapped water along the shaft of the pump can force past the second seal (the one preventing oil from coming out of the crankcase) and into the oil pan. Oberdorfer pumps have large weep holes in their housings and don’t really have this same potential.

If there is no indication of water getting in through the combustion chambers or any other way externally, a crack is usually indicated. If you do suspect a crack in one of your water jackets, you can pinch off the water discharge hose coming off the back of the manifold for several 10 second pressure checks. A flexible impeller pump in good condition can produce 20 PSI when deadheaded in this fashion. If there is a crack anywhere in the water-jacketed castings, this amount of pressure will force water into the oil pan at a rate that should be unmistakable.

If you can confirm that water is indeed entering your oil pan through a defective casting, you’ll have to remove the engine for disassembly and repair. Cracks in the floor of the cooling water jacket in the block are frequently repairable once the engine is disassembled for $200 to $400, depending on the length of the crack. – Updated: January 6, 2004"

[Dave Neptune]

If the engine is raw water cooled do a pressure check for "block" integrity. Check the manifold first they rust through long before the block.

Your compression numbers look OK. Doubt a leak there.

Dave Neptune

[Chuck Dyck]

Thank you

Thank you Jack and Dave.
I will check the exhaust manifold then do the water jacket test and take it from there.
Chuck

[Mo]

I'd focus on the pump if not having starting issues or water on plugs. That inner seal can fail after prolonged use. Dave mentioned pressure testing the block...do that after the pump, meaning, the pump is not included in the pressure test.

[Chuck Dyck]

Thanks Mo
I will check that out. I really hope that's it.

[Chuck Dyck]

My boat is now on the hard. I am going to take the water pump out this week.
How will I know if it is defective or not?
Chuck