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Old 02-04-2016, 10:27   #1
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Blown head gasket?

Just cleared the harbor when I hear a clicking sound from engine so I check below and get lots of exhaust but no water leaks. Limped back to slip, temperature ok but more exhaust and louder sharp clicks close inspection shows all looks normal externally . This is a 1983 Perkins. Im getting ready to grab my wrenches and remove head but is my diagnosis correct?
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Old 02-04-2016, 10:46   #2
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Re: Blown head gasket?

Sounds like it could be an exhaust leak between the manifold and the head to me.

How does the oil and coolant look?
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Old 02-04-2016, 11:06   #3
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Re: Blown head gasket?

Check oil, check coolant. Check for exhaust leaks. Also, when you remove the rocker cover, check that a push rod hasn't come off the rocker.
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Old 02-04-2016, 13:29   #4
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Re: Blown head gasket?

Thanks for the suggestions, yeah I should check the manifold to head gaskets and everything under rocker cover before the hard work of removing the head. On other hand we are cruising to Mexico in Nov and this would be a reason to have the head serviced anyway.
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Old 02-04-2016, 23:35   #5
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Re: Blown head gasket?

Forgot to mention, no oil in coolant and no noticeable coolant in the oil. Almost got the heat exchange removed today so we'll check those exhaust port gaskets soon.
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Old 02-04-2016, 23:41   #6
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Re: Blown head gasket?

Had this myself it was a sticky valve on a 1978 6354 .. Worth checking first
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Old 03-04-2016, 01:53   #7
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Re: Blown head gasket?

My father taught me to fix engines, and his good advice was always to work on the cheapest possible problem first. He would NEVER take a head off first if the engine made a bit of noise.

Why are you taking the heat exchanger off?? The first thing to do is to tighten up the exhaust manifold bolts and see if that makes a difference. It solved a similar problem on my 4108.
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Old 05-04-2016, 23:40   #8
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Re: Blown head gasket?

All great points, thanks! I decided to remove the heat exchanger since the bolts that hold it on, are those at the exhaust ports, and I'm still thinking one of those 4 gaskets would be leaking. Not quite done yet.

The bigger plan is that since we have 4000 hours on the engine and going cruising in a few months, I hoped to machine the valve seats.

A sticking valve was suggested, and would certainly cause the kind of noise I heard, but could a sticking exhaust valve be able to fill the boat with exhaust fumes? Maybe exhaust coming back out the air intake? So, if valve is sticking, probably need to redo the head anyway.
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Old 06-04-2016, 00:13   #9
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Re: Blown head gasket?

While running at operational temp, pull the cap on your expansion tank and watch for bubbles, if present then it would indicate a head problem.
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Old 01-05-2016, 22:31   #10
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Re: Blown head gasket?

Update to my previous posts: Removed exhaust manifold and replaced gaskets, re-assembled, tried to start engine, exact same problem. Tries to start, runs roughly like on 3 cylinders, for a few seconds then dies. Tons of oily smoke in the boat. I can't tell if this is oil smoke or diesel smoke. It is definitely not water vapor.

Cleared out the smoke, put a gas mask type breathing filter, then cranked the engine while looking closely. There is a pulsing gust of high pressure leaking out in one area of the valve cover. This appears to be the source of the oily smoke, and the clicking popping sound seems to be the high pressure releasing from under the edge of the valve cover.

I tried several on-line searches but none seemed to cover the exact same situation. Everything under the valve cover: push rods, rocker arms, springs, valve stems as far as I can see, the clearances, etc. seems normal. I'm thinking it may be a cracked or badly damaged valve allowing the compression stroke of one cylinder to escape past the valve guide into the valve cover. I next will crank the engine without starting it, with valve cover removed, to see if this theory holds.

In any event, it looks like the head must come off.
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Old 01-05-2016, 23:17   #11
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Re: Blown head gasket?

With combustion gases pulsing past the valve cover seal, I'm a little surprised the valve train components appear OK. Did you rotate each cylinder to TDC for a quick look(feel) at the clearance? Might be worth the time before disassembly starts.

Also, sometimes it's hard to spot a broken valve spring without a careful, well lit inspection.

Maybe a cracked head? Around a valve guide boss or seat, not in a water passage.

Best of luck.
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Old 02-05-2016, 01:37   #12
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Re: Blown head gasket?

If you have high pressure gasses escaping from the valve cover gasket, you are pressurizing the crankcase. If so, you should have air coming out of the dip stick tube and oil filler cap, too.
Usually a head gasket failure bleeds air between cylinders or between a cylinder and water or oil passage. But your oil and water looks ok. If the engine didn't get hot, I wouldn't think the head gasket failed. Cylinder to cylinder leak in a 4 cylinder engine probably would keep the engine from running and may not pressurize the crankcase.
If a valve sticks in the guide the engine makes a loud tapping sound, almost like a metallic snap. If a valve did stick it could have cracked or put a hole in the piston, broken rings or cracked the valve guide. All of these would cause high pressure in the crankcase and valve cover. Diesels have very tight clearances between the valves and piston top. You could have a bent or broken valve. By removing the valve cover you could see if all looks normal. A compression or leak down test would tell a lot. If you take the rocker shaft and rockers off, you can wiggle the springs and see if one moves or lifts out.
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Old 06-05-2016, 12:28   #13
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Re: Blown head gasket?

OK, figured it out, after doing a ton of completely unnecessary work. Turns out I had two loose fuel injectors. I didn't discover this until I had everything disassembled, head bolts out, just getting ready to crack the seal. As I was starting to remove the first injector I noticed the nut was very easy to remove, in fact I could have almost turned it without a wrench.

Right away I re-torqued all the injector nuts to the specified value and cranked the engine - no more pops of escaping gas from the cylinders. Put it all back together, filled up the coolant and it runs perfectly now. If I had been able to detect exactly where the loud pop of escaping gas was coming from in the beginning (I tried) then the fix would have taken 5 minutes.

I'm not sure why, but all the injector nuts were quite loose. I do torque the cylinder head bolts yearly, but never checked the injectors. I'll definitely be checking these and other connections on the engine more often.
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