no compression from two cylinders

[heinz]

I have been reluctant to take my boat out since the engine overheated during a storm I was caught in. It had collapsed the exhaust pipe and melted the top of the spark plug wires. I replaced the pipe and finally got around to check the compression. It turned out that the two inner cylinders showed no compression what so ever. The front and back showed 95-100. I also did a wet test on those cylinders and still no compression.
Some comments in the forum mention stuck valves. But that appears to be with low compression. No one had mentioned no compression at all! I am wondering though if this can be caused by a combination of a poor head gasket and sticky valves?
Any comments are greatly appreciated.
Heinz

[Mo]

Hello Heinz,

Sorry to hear that happened. It doesn't sound good to me. Have a look in the oil and see if there's water in it. You can also remove the side plate and check to see if valves are moving. You might try removing plugs and look at valve movement with light as someone turns over the engine with a hand crank.

I really don't want to sound pessimistic here but I think it prudent to be realistic. I know of two perfectly good A4's that sustained a cracked block between the cylinders from overheating. Your's overheated pretty good to start melting components, especially if you were pushing her in a storm. One the intake blocked and the other was T-stat problem. Both went unnoticed until alarms went off and both were not salvageable.

I'll send you a PM

[Mo]

Sent you an email.

[Hymodyne]

lifters stuck

I recently had 0 compression on two cylinders, 1 & 4. It was sticking lifters, not valves. I had to remove them, polish them and their bores.

James

[romantic comedy]

sounds like a blown head gasket. There could be a breach between the 2 cylinders, or just around them.

[Nicholasmiller]

I agree - I overheated my engine and blew the head gasket. I would check for sticking valves first as Mo suggests by taking the side plate off. If the valves are stuck you can squirt Marvel Mystery oil in the cylinders and let it soak in overnight - if they do not unstick you can gently tap them down with an Allen key through the spark plug hole. If the valves are not stuck, take the head off and take a look to see if the head gasket is blown. Changing the head gasket is fairly easy (you will need to order a new one from Moyer in any event as they should not be reused) but you will probably need a small chisel tapping all around the head at the gasket to get the head off. Good luck!

[joe_db]

This would seem to make the overtemp alarm fairly useless.

Hello Heinz,

Sorry to hear that happened. It doesn't sound good to me. Have a look in the oil and see if there's water in it. You can also remove the side plate and check to see if valves are moving. You might try removing plugs and look at valve movement with light as someone turns over the engine with a hand crank.

I really don't want to sound pessimistic here but I think it prudent to be realistic. I know of two perfectly good A4's that sustained a cracked block between the cylinders from overheating. Your's overheated pretty good to start melting components, especially if you were pushing her in a storm. One the intake blocked and the other was T-stat problem. Both went unnoticed until alarms went off and both were not salvageable.

I'll send you a PM

[Mo]

Little bit of a hijack but it can be easy to miss stuff.

This would seem to make the overtemp alarm fairly useless.

Not always. These both happened in heavy weather where the engine was working hard. Both boats were in the 35 foot range as well. One of them we spent a few days trouble shooting it thinking it was head gasket...changed that and still couldn't get it to fire up. The engine was removed and sent out and that's when the crack was found. I had a pic of that block somewhere but can't find it in my files now. At one point I posted it in a thread somewhere.

In all seriousness, lots of other incidents where alarms worked just fine. In chop it's easy to be distracted from glancing at guages, and in all fairness, it takes just moments to heat up an engine once something goes wrong.

Just 2 weeks ago I was out in 3-4 meter seas, three boats got caught in a blow that wasn't supposed to happen. The other 2 boats are fairly new to sailing so I kept under motor just to stay back with them...so I was holding 4 knts or so but the tossing was wicked. On the beam and she'd roll so much her stick would almost touch another wave. The engine ran perfect, however I got sea sick and spent 4 hours barfing in the cockpit...then had to turn around and put myself between one that was falling back (diesels LOL)...anyway, SICK AS AN ANIMAL...it would have been easy under those conditions to miss a rising temp gauge...so easy. Can't make this stuff up....wind in the gusting 30 kt range, building seas, heavy rain, throwing up and the puke blowing back over my wet weather gear.

Wet, dehydrated, cold (on a warm day) I'm the last to dock. Layed the boat on the dock perfect and was putting my lines on when George came over. He noticed me moving pretty slow and helped me secure the boat...then he came with the hose and I stood arms out as he hosed me off. Cleaned up the boat and went home. The other boats didn't know I was sick until they saw it on facebook....one thought it strange George was hosing me off (thought it was some weird sailor thing). LOL

As for the engine...all I did was listen for the wet exhaust...I was very worried about the others, both had their kids with them as well...I was alone. The newbies were queasy but kept there cookies down.

Now one would ask why we didn't go back because this wind and rain blew in just miles from out overnight spot....Couldn't turn around and go back because we'd come out over a shoal with just 1.5 feet to clear on a dropping tide...so it was what it was....but the A4 held her own. The seas were wild because of all the shoals around the area as well. Waves coming in form 300-500 ft depth then into 60-80 foot depth...up she comes! There was a graphic post on my Facebook re: can't make this shT up...would have been so much more comfortable with sails up but then Odyssey would have taken off and left the other behind...not in me.