Blow by problem on 730D

[MBdeere]

I found my blow by problem. 3 broken piston rings on one piston. and sloppy rings on the other piston. Funny the engine always started easy. and did not smoke much at all. Now if I could just figure out the oil pressure problem .

 

[Wayn_h]

Regarding the oil pressure problem, have you checked the main bearing clearances? Drop the pan and put some plastigauge in there. Excessive worn bearings will give you low oil pressure. If you had those ring problems, that tells me other parts are worn also.

Wayne

 

[F-I-T]

...tough to drop a pan on a 730D....

 

[skip33652]

your oil pressure problem is probably half blow-by and half loose bearing clearances. when you have a lot of blow-by the oil can be heated which makes it thinner plus it will dilute the oil with diesel due to improper combustion. it is kind of like a snowball rolling downhill. Heated oil loose bearings oil pump works harder which heats the oil thinner hotter and finally less pressure. check your camshaft bearings as well . main bearings on those can be up to .013" I think. 820 book says max clearance .015".

I always chuckle when someone says an old 2 cylinder diesel must be in good shape as it starts good and runs great. Almost all are way beyond wore out. I overhauled an 80 one time that had been stuck and then pulled to break it loose . the skirt of one piston was laying in the bottom along with the lower ring and both top compression rings were brken as well as two others . and 4 bent pony rods. Both engines ran pretty well considering.If you overhaul it now correctly it will last several life times.Paul

 

[Mike M]

I have had several 720's that had varying oil pressure. At an idle hot would be around low ? but when cold at fast idle would be high or peg the gauge.

My own 720 which has been rebuilt,including reground crank and new mains and rods with clearance on the low end of range,and I even put in all new relief and bypass springs still pegs the gauge cold fast idle and drops to medium at warm idle. I suspect worn gear to body clearance in the oil pump ?

 

[730d se]

Not if you turn them upside down and side ways, that pan will drop right out of the way. LOL

 

[Wayn_h]

LOL on drooping the pan, my bad!

But you know what I mean!

Wayne