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**Wotname** · 11-04-2024, 18:32

I never thought of using a reground meat cleaver but it will soon be part of my toolbox now

.

To be honest, in my limited DIY experience, using compression has never worked for me but others have told me it has worked for them so I shared the info here.

I was once tempted to try using the live fire method but in the end, I wasn't courageous enough and went back and found a bigger hammer. Please please please tell me you only just backed off the head nuts (or bolts) a turn or so before hitting the starter! I like the theory but worry that if it goes wrong, it would go wrong in a big way. Good to hear that you were successful and lived to tell the tale.

**skipperpete** · 11-04-2024, 19:29

Yes Wottie, ⅓ of a turn, those 6-354’s with a monotorque gasket were a real challenge to unstick. I once saw a guy whack a screwdriver right through under the head taking a divot out of both sides of the liner lip protrusion. A simple valve grind instantly became an “engine out… full stripdown” to press out the old liner and squeeze in and hone to size the new one.

JustinT · 12-04-2024, 02:21

The YouTube link: https://youtube.com/shorts/-UBBC3CTQ...6JupdzoACqwESi
Working link now, can't work out how to embed on the forum.

Thanks for the info chaps!

I was being careful and looks like, from your advice, I was right. Was giving it little taps with the hammer but it seemed very stuck as I kept checking no bolts etc and since the video I too off the alternator bracket (wasn't fixed on the engine, just in the way) and the fuel feed pipes (again, were just in the way) but that didn't help. So, from you advice, it's about easing it off slowly. Thanks again.

I've got a head gasket coming in the post but I feel dubious about the quality of the new ones.

JustinT · 12-04-2024, 07:40

The head is off!
Now we know:

GrowleyMonster · 12-04-2024, 07:41

Quote:

Originally Posted by JustinT

Can't get the head off, am I missing something?
https://youtube.com/shorts/-UBBC3CTQ...AxDlDWJBzFi69i

I agree with Wot and Pete. First try tapping with a hammer and block of wood, then try a knife or some other thin and wide wedge shaped tool, and don't let it go in as far as the cylinder liner. You might have to do it in several places. Using engine compression can sometimes do the trick but try the other methods first, and make sure your head bolts are only loosened slightly, maybe a turn, and just bump the starter a few times.

BTW, here's a good book for you.
https://www.amazon.com/Marine-Diesel.../dp/0071475354

Great boat stuff author. All of his books should be regarded as required reading. And be sure to download the manual for your engine. You really do need it.

<EDIT> Oops I see you got it. Good show.You are making serious progress here. Hard to tell from pic, but is that a chip knocked out of the exhaust valve? Be sure you get all of the bits out of the cylinder and check your piston crown. A small dent may be okay but be sure it doesn't hide a crack. Me, I would pull the piston because you might have shavings riding on the rings and maybe ring damage, even if the piston is perfect. Check cylinder walls too. I am just betting your engine uses cylinder liners. If there is no detectable damage and you do a good job of cleaning up the cylinder then maybe you can just take care of your valve and stick the head back on with your new gasket. Don't do it hillbilly style, Use a torque wrench and follow the recommended tightening order in the manual.

JustinT · 12-04-2024, 08:56

Thanks all, cleaning the head up now. Maybe I need to pull all the valves out and clean?

Here is the partly clean head: https://youtu.be/b0gCmLiFTbs?si=VL5lvJjauEXP51DQ

GrowleyMonster · 12-04-2024, 10:12

Quote:

Originally Posted by JustinT

Thanks all, cleaning the head up now. Maybe I need to pull all the valves out and clean?

Here is the partly clean head: https://youtu.be/b0gCmLiFTbs?si=VL5lvJjauEXP51DQ

Yeah, I would. inspect, and lap them if indicated. Replace valve guides and inserts if needed. While you got it off is a great time to really give it a going over. If you have a mechanic who would be willing to do a quick visual and evaluate, all the better. OTOH if you are in a hurry to actually use the engine, chances are fairly good that simply replacing the bad valve and associated components and clapping everything back together would give you another 3000 hours of trouble free service. I say fairly good, not certain or even near certain. You got the head off, and it is in a comfortable and controlled working environment. What better time to get up close and personal with your diesel, and show it lots of love?

Of course, you could take that to extremes and pull the engine altogether, and get jiggy widdit. Crappy old oil years unchanged probably caused or contributed to your valve failure. The same could possibly have taken a toll on your bearings, rings, cyl liners, and so on. Not saying you must do a full overhaul or rebuild, no, but this is a good time for it if you think you want to. Check peripherals like heat exchanger, wet exhaust system, coolant pipes and hoses, etc and definitely you got zincs that could use replacement. Or maybe you no longer have any! At the very least, flush your cooling system. Replace coolant to spec. Belts. Hoses. All of that. You will learn a LOT about diesels if you read Nigel Calder's book as you proceed with a full or even partial teardown and refurb. Some stuff might require some work by a machine shop, but most of it is within your capability at home or aboard.

You have a simple, reliable engine, as long as everything is like new or close to it. It will probably outlive the hull, and be pushing another boat around 100 years from now, if you go nuts with it now. Myself, I don't care what, if anything, my diesel will be doing 100 years from now, or even 50. I just want mine to keep going for as long as I can keep going.

JustinT · 12-04-2024, 10:22

Thanks for the tips, yes, it's also very addictive making this beast all clean and working properly.

After the engine is fixed I need to take the yacht around Ardnamurchan Point:
https://maps.app.goo.gl/j7CeM5dEh78Uu2oZ6
One doesn't want any chance of engine failure out there!

deblen · 12-04-2024, 11:39

Good work!!!

/ L

JustinT · 12-04-2024, 12:44

Quote:

Originally Posted by deblen

Good work!!!

/ L

Thanks

If I'd followed your advice 2 years ago

Actually, now that I have the head in bits I can see a lot of carbon and muck on the working valves and exhaust.

Clearly the engine was compromised on the stuck side long before I got the yacht. Now I'm all excited to have it all working again on two cylinders!

JustinT · 12-04-2024, 12:54

Quote:

Originally Posted by GrowleyMonster

At the very least, flush your cooling system. Replace coolant to spec.

Oh, by the way, the boat has raw water cooling, saltwater no less.

**skipperpete** · 12-04-2024, 14:05

While the head is off, you need to inspect the cylinders for imperfections. Make sure that the shiny bit is the same height on both cylinders and also compare the piston heights with a straight edge and feeler gauges. If the rings are broken they leave signs on the liner walls and if the engine ever had a hydrolock or valve/piston collision there’ll be crown damage or different piston heights. While you’re doing this quick inspection its always worthwhile to bring the pistons up to TDC and then go a 1/2” past TDC on the down stroke and physically push on the piston crown…. The amount of movement ( and occasionally an audible click) gives you an idea of how much wear is on the conrod bearings.
It ain’t quite “Miller time” but you’re getting closer.

JustinT · 12-04-2024, 15:25

Quote:

Originally Posted by skipperpete

While the head is off, you need to inspect the cylinders for imperfections. Make sure that the shiny bit is the same height on both cylinders and also compare the piston heights with a straight edge and feeler gauges. If the rings are broken they leave signs on the liner walls and if the engine ever had a hydrolock or valve/piston collision there’ll be crown damage or different piston heights. While you’re doing this quick inspection its always worthwhile to bring the pistons up to TDC and then go a 1/2” past TDC on the down stroke and physically push on the piston crown…. The amount of movement ( and occasionally an audible click) gives you an idea of how much wear is on the conrod bearings.
It ain’t quite “Miller time” but you’re getting closer.

Thanks, yes, tomorrow I intend to give the cylinders a good going over and make sure of TDC for when I go back to fix it all back. I assume the cam will be TBC when the cylinders are at the top? (Sorry, that's lazy of me, I'll look at the DV20 manual) I'm going to make a mark on the flywheel for TDC.

**skipperpete** · 12-04-2024, 17:35

Quote:

Originally Posted by JustinT

Thanks, yes, tomorrow I intend to give the cylinders a good going over and make sure of TDC for when I go back to fix it all back. I assume the cam will be TBC when the cylinders are at the top? (Sorry, that's lazy of me, I'll look at the DV20 manual) I'm going to make a mark on the flywheel for TDC.

Other than doing a visual inspection of the cam lobes/followers you can pretty much ignore the camshaft and followers and you can easily see top dead centre as each piston approaches it. You do need to deal with the pushrod though, its usual to roll em on a flat surface to check for straight, and its not unheard of to straighten a solid pushrod…. Tubular …. not so much.