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Old 22-11-2013, 17:45   #61
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Re: Can you get pressure in oil tank?

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Originally Posted by gjordan View Post
My thoughts on a completely dead cylinder, are to remove the valve cover and rotate the engine, and see if the valves are all moving properly.
My thoughts exactly. zero compression can come from a few different places. This quick & easy test helps to eliminate or confirm a few possibilities.
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Old 04-12-2013, 11:55   #62
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Re: Can you get pressure in oil tank?

We pulled the valve cover. One of the connecting rods that controlled the valve came was off track or out of its guide, so it was not closing the exhaust valve. That was the reason that there was zero compression in that cylinder. That seems like a weird thing to happen (maybe running at really high RPMs could do that??). Would that (or the previously bad injectors) explain diesel getting into the oil sump?

So, that is fixed, we have rebuilt injectors, etc. and now we will see if that fixes everything up. Now, all I need is for spring to get here so we can finally use our new boat! Thanks for all the advice and help y'all.
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Old 04-12-2013, 14:14   #63
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Re: Can you get pressure in oil tank?

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Originally Posted by cheslr View Post
We pulled the valve cover. One of the connecting rods that controlled the valve came was off track or out of its guide, so it was not closing the exhaust valve. That was the reason that there was zero compression in that cylinder. That seems like a weird thing to happen (maybe running at really high RPMs could do that??). Would that (or the previously bad injectors) explain diesel getting into the oil sump?

So, that is fixed, we have rebuilt injectors, etc. and now we will see if that fixes everything up. Now, all I need is for spring to get here so we can finally use our new boat! Thanks for all the advice and help y'all.
Just as I suspected. Part of a maintenance schedule is a valve adjustment. Too much slop can bend or even brake push rods, or other parts of the valve train. But having so little Hrs on the motor, the rebuilder must have not tighten down the lock nut enough on the adjustment.
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Old 04-12-2013, 21:46   #64
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Re: Can you get pressure in oil tank?

Now before you put it back together, you should check to see if the problem was a stuck valve. Take a heavy mallet and see if the valve in question moves freely. I have had a few bent pushrods in my past and they were always from a stuck valve. I recently had a stuck valve in a 75 year old tractor, that not only bent the pushrod, but bent the rocker also. Take a good comparison of the rocker on the other cylinder to see if yours might be bent. I am glad it is not something deeper (ie. more expensive) in the engine. Good Luck. _____Grant.
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Old 04-12-2013, 23:07   #65
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Re: Can you get pressure in oil tank?

The push rods (not connecting rods) don't close the valves, they open them. The valve springs do the closing. The zero compression reading suggests a stuck or bent valve which is not closing. When a valve stays open it leaves a lot of free play for the push rod and rocker arm to rattle around in and the push rod eventually gets stuck somewhere. Then the cam pushes it up and bends it. Your bent push rod was caused by the failure of the valve to close, not the other way around. In any case, your problem won't be solved by a new push rod. By the way you can test for bent push rods by rolling them across a flat surface. If it is bent it won't want to roll.
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Old 05-12-2013, 20:45   #66
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Re: Can you get pressure in oil tank?

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We pulled the valve cover. One of the connecting rods that controlled the valve came was off track or out of its guide, so it was not closing the exhaust valve. That was the reason that there was zero compression in that cylinder. That seems like a weird thing to happen
When I lived in Canada, I threw a push rod from under a rocker arm in the 258 straight 6 that was in my jeep CJ. I drove it like that for about 2 days, with terrible gas mileage. The local mechanic blamed the problem on the "insanely heavy maple syrup" that I was using for motor oil (10W40). He popped the push rod back into place, put 5-30 oil in the motor & off I went. I never had a problem again. I went back to 10-40 at the next oil change & drove that thing for years after that. I never really did positively identify the root cause of that little one-time mishap.
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Old 05-12-2013, 20:50   #67
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Re: Can you get pressure in oil tank?

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The push rods (not connecting rods) don't close the valves, they open them. The valve springs do the closing. The zero compression reading suggests a stuck or bent valve which is not closing.
In my little episode, the push rod popped out of the little dimple in the rocker arm where it belonged & ended up off to the side a little, in an area that caused to valve to be held open all the time. Apparently, that can happen.

Your scenario of a stuck valve stem is probably more common. This would be especially true on a low-hours motor where the stem to guide clearances are still very close. The likelihood would increase further on a motor that sits a lot in a moist environment without being run for long periods of time. In that case, the possibility of rust on a valve stem would increase.
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Old 06-12-2013, 10:20   #68
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Re: Can you get pressure in oil tank?

Quote:
Originally Posted by cheslr View Post
We pulled the valve cover. One of the connecting rods that controlled the valve came was off track or out of its guide, so it was not closing the exhaust valve. That was the reason that there was zero compression in that cylinder. That seems like a weird thing to happen (maybe running at really high RPMs could do that??). Would that (or the previously bad injectors) explain diesel getting into the oil sump?

So, that is fixed, we have rebuilt injectors, etc. and now we will see if that fixes everything up. Now, all I need is for spring to get here so we can finally use our new boat! Thanks for all the advice and help y'all.
Yep... that's exactly what happend on my 4-236 perkins. Check that the push rod is perfectly stright now (probably not) and ask yourself; is there is any way you could have had water in that cylinder? is it the aft most cylinder?
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Old 06-12-2013, 16:55   #69
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Re: Can you get pressure in oil tank?

Not sure if there cold have been watering that cylinder at one time or another in the past since we just bought the boat and the engine was acting up. It was the forward most cylinder where this happened - is water more common in the aft cylinder if that happens?

I will get with mechanic to see if they checked if rod was straight or not. Thanks for the advice. If not, is this something that I could "relatively" easily check myself?
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Old 06-12-2013, 17:30   #70
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Re: Can you get pressure in oil tank?

The engine usually has a little tilt at or forward (Vdrive), usually the lowest cylinder is the first to get water if the boat gets water in the exhaust from outside. Just roll the rod on a very flat plate (rollling only the straight center portion on the surface) you can tell if it humps up when rolling. If it back in and running fine... I assume he set the valves clearances? Probably OK... although hard to imagine it coming out without bending....
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Old 06-12-2013, 19:06   #71
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Re: Can you get pressure in oil tank?

I just looked at a diagram of the engine and connecting rod is the wrong term I used above. It has to be push rod mechanic was talking about (I got message through boatyard). It looks like the only way this would cause zero compression would be if it was off to the side of where it connected to the rocker arm instead of seated in it not allowing valve to close all the way. Not sure how that would happen and not bend that push rod. The stuck valve first could have caused rod to get off as well too. Looks like I have more questions to ask mechanic next week. They said it was running fine with no smoke, no fuel in exhaust anymore, etc. They said only smoke from exhaust was at full throttle tied up to the dock (engine probably being overloaded) so my first thought was that it was OK. Any other questions I should ask other than if rod was straight, valve stem ok, valve adjustment ok? Or, if the thing is running fine and not smoking now should I just enjoy the darn thing and stop worrying?
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Old 06-12-2013, 19:08   #72
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Re: Can you get pressure in oil tank?

Cheechako, why do you ask about water in the cylinder? Does this cause Alvie's to be stuck open?
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Old 06-12-2013, 19:17   #73
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Re: Can you get pressure in oil tank?

Water in the cylinder can really make your day a bad one. It can bend con-rods and generally ruin your engine. If it doesn't do that nasty thing it can rust the rings to the cylinder wall and seize the engine. It also causes all kinds of corrosion in the exhaust valve/manifold areas. Sea water in your engine is not a good thing at all. (not that any water in the cylinder is a good thing) I think that you would see different symptoms if you had water in a cylinder.

To answer your other questions, yes, ask your mechanic. If you know/trust him relax knowing that the engine is running fine. If you don't really know him, verify that the engine is working well, then relax.
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Old 06-12-2013, 22:12   #74
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Re: Can you get pressure in oil tank?

Water in a cylinder, or even water in the exhaust system near an open valve can cause a stuck valve (rusted valve guide), more typically an exhaust valve but can be both. The valve that is stuck open, even the slightest can give you the zero compression, and the bent pushrod. What I dont understand is how the mechanic didnt isolate the bad cylinder in the first place, Typically you run the engine and crack(loosen) the injector line to each cylinder one at a time to find the faulty cylinder. Sending out the injectors for a rebuild before figuring out which cylinder was bad, sounds like very poor (very expensive) trouble shooting to me. You might ask the mechanic about that, but be prepared for a song and dance. ___I am glad it is working now. ______Grant.
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Old 08-12-2013, 02:40   #75
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Re: Can you get Pressure in Oil Tank?

It makes perfect sense to me that a motor that sat for a long time (possibly with a valve open) would get some rust on a valve stem & then when the motor was started, that valve would hang open & cause a lack of tension on the rocker arm that would cause the push rod to fall out of place, which would then continue to cause zero compression even after the valve stem loosened back up again from running the motor. I can see where putting the push rod back in place would get that cylinder to run again.

I am wondering, however, if you are still "making" oil in your crank case or not. You may have had 2 separate problems in that engine & putting the pushrod back in place may have only solved one of them. I don't see how a valve being held open, giving zero compression, would cause your crank case oil to rise.

I would continue to monitor the oil level closely for a while if I were you.
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