Komatsu PC60 head gasket question

[Dirkums]

Hi All,
I was hoping for some thoughts. I have a PC60 with a 4D94 motor. It has compression (or maybe exhaust) 'puffing' out between the head and block at the back right in the middle. You can feel it, but it's not very strong. Had a ticking since I bought it like a tappet noise, so guess that was it. Ran it 5 hours recently and it got louder and found it, so must have blown some extra material out. Head gasket I imagine, but apart from this, it has no issues. Runs fine, has no oil in water, or water in oil, and starts first pop. Can't figure out why it would blow like that. Intend to pull the head and replace gasket. (need to reuse the head bolts). this engine was fully rebuilt maybe 50 -100 hours ago a prior owner (although it's several years) and had the tick. Perhaps they misaligned or damaged on installation. Seriously tempted to ignore it but imagine it will get worse. Anyone had this on any engine and got an idea what I might find. Thanks for reading.

 

[Vetech63]

The cause could be one of multiple things.....they didn't retorque the bolts after its initial run, damaged the gasket, broken head bolt, etc.....

Running it like it is will just cause more expensive issues. If its losing compression then that cylinder is running rich causing the cylinder to wash down and burn up over time. Also super heated air blowing through there over time can burn out a path through your block or head deck. You would be better served to fix it now before it becomes a lot more expensive.

 

[Dirkums]

Thanks for that. I wondered about the damage on installation. No idea if re touque done. The motor was full rebuild and pump so possible the owner didn't bother with follow-up. Bore wash I knew of, the burning a path just makes sense now you say it. It's an old digger so if it does break again it's an 8-tonne pot plant so pull it down I will el pronto. Hopefully, it's still flat. cheers

 

[John C.]

I don't know of any requirements for re-torqueing of head bolts on any Komatsu engine. Vetech63 is correct on all the rest of the counts. I would not recommend using your hand to find a head gasket leak.

 

[heymccall]

I'd be more inclined to think exhaust manifold gasket leak.

 

[Vetech63]

I don't know of any requirements for re-torqueing of head bolts on any Komatsu engine.

There isn't for some engines. Its just something I do on all rebuilds regardless of manufacturer.

 

[Dirkums]

Hi Guys, great to read all the thought. It's definitely the head gasket. There is lots of room at the back of the motor so my hand was quite safe. I used a water spray as well to be sure of the leak. Today I spoke to a heavy diesel mechanic who worked on large excavators for years. he said, before I even asked, it's a retorque most likely. Had seen it many times with recent rebuilds. He also said, retorque it now. In a big majority of cases where it had no other issues or overheating you get away with that. Surprising. He said they would always retorque at 250 hours. No cost to try, so that's the first option.

p.s. another interesting point I forgot. I asked him about burning the block or deck, ie gouging from the escaping gases. He said, yes that's a real issue and had to fix a few of those, but seemed to take at least 700-800 hours to do it and at higher working revs, like 1800 for this kind of motor and with temperature. He would be very surprised if I would find any damage at all. I liked the sound of that. He also reckoned the tick isn't this. Most of them with the sound I described were in the timing gears. Oddly that's the only area I didn't put my stethoscope. Gotta check there next.

 

[Vetech63]

Seriously tempted to ignore it

This is why I pointed out the burned pathway in the block or head deck.

He would be very surprised if I would find any damage at all

I would agree if this engine hasn't been run a long time with the problem.

 

[Dirkums]

This is why I pointed out the burned pathway in the block or head deck.
Yep, that was good advice thanks. That really spooked me into questioning. The Mechanic was a totally random thing. He's in my class (I teach) - totally unrelated and talking about some mining work and he mentioned his experience and I relayed what you had said. He was also adamant about retorque being good practice for any engine. Just lots of experience. Cheers


I would agree if this engine hasn't been run a long time with the problem.

 

[Dirkums]

A long time since the last post but fixed it. Just a note for anyone with a similar problem as this was new to me and thought it was going to be a major.
The head bolts were all over the place in torque at 55-70 lb. I retorqued and it's all good. A diesel Mech with heaps of heavy equipment experience said he saw it frequently. So, also, I didn't slacken them off, I just started at 30, then went to 50 (got small movement), then 75, then 95. Many say slack off, but he said definitely don't. So far it's just sweet. This was most definitely head gasket and the puffs were very strong on my hand at the rear of the engine (heaps of room, quite safe) I didn't run it with the leak for long, but it takes 800 hrs to cut a hole he reckoned. Who knows if it will hold but so far perfect. This engine was rebuilt maybe 100 hrs ago, but several years as well (stuck in the swamp) so didn't take too small bites as need to get smooth movement for torque.