Blowby on komatsu pc50 with Yanmar 4d84

[Spadman]

Lot of blowby and overheating. No water in oil. I've got 420 lbs compression on 1 and 4 and only 110 lbs on 2 and 3. Suspect head gasket but have been trying for days to get counterweight bolts broke loose to pull engine and do complete job. Should I just pull head and hope that's as far as I have to go?

(Bent a Harbor Freight 3/4 drive ratchet with 3 ft cheater. 1000 lb torque IR impact would not budge bolts. Could not move it with better ratchet and 4th bar. I put penetrating oil on but assume bolts go all the way through counterweight to get to threads.)

All ideas appreciated.

 

[Spadman]

Does anybody know if there is an opening to the crankcase in the block between the center two cylinders on the 4cyl Yanmar in this Komatsu excavator? That's the only way I can see a warped head and blown gasket causing blowby as well as overheat with no water in oil.

 

[xcmark]

Dont keep running it , pull the head off your going to find the gasket is breached in the middle of the two jugs. Check to see if the head is still flat clean it up really good and put it back togeather. I dont think these motors have a history of head gasket problems but it can happen with any motor. Run it to get it on a trailer and into the shop where you can keep it dry and work with good light , power ,compressed air and tools. This isnt a field job unless its absolutly a last resort.

 

[John C.]

Counterweight bolts are usually torqued with a multiplier. What is the size of the bolt head?

You will have to pull the head. I don't believe this engine has liners. Overheating usually causes warped and/or cracked heads.

Good Luck!

 

[Spadman]

:bashThanks xcmark and John C. For your comments. I do have the machine in the dry and positioned under a chain hoist to lift the counterweight. I pulled the head and unfortunately I have to go farther. The gasket was not breached as expected. I have signs of galling and blowby on the cylinder walls of the two middle cylinders, both on the side toward the front of the engine and in line with the pin.

I got a friend to come by and lend some more weight to break the counterweight bolts loose. The biggest had 36mm heads with 24mm threads.

 

[Spadman]

Question about damper connecting main pump to flywheel

I'm just beginning the teardown of my 4D84 Yanmar. When I took the damper off the flywheel that connects the main pump, I noticed three cracks in the rubber part of the doughnut shaped damper, seemingly all the way through. Is this normal? Should the damper be replaced?

 

[gbock1000]

Spadman, how did your rebuilt go? I'll have to rebuild mine soon too, it has some blow by going on. Does this engine have cylinder sleeves? I see some rebuild kits on Amazon that have the sleeves. Right now my issues is that it's making allot of oil. I have already rebuilt the injectors, but its still leaking diesel in the oil. I'm suspecting the fuel pump now since it does seem to have a pathway that diesel could leak into the motor. The previous owner put on a jockey pump because it kept loosing the prime and would take a long time to start. I have removed the jockey pump after I fix a fuel line leak that seemed to be causing the problem. Do you have any ideas that I could explore?

 

[Spadman]

Sorry I just saw this. I had to tear it completely down to find the problem which was wear in the middle of three cam journals. The bearing surface was cast in the block but same size as front cam bearing. I bought a second front bearing and had the block bored to fit. Completed the overhaul with new pistons, etc and it performed fine. The block does use liners but I didn’t need them.