I recently got the 70D motor grader home (saved from the fire wrench) and started looking into a possible wrist pin knock, pulled the valve covers off and found both push rods are bent on #6 cyl. there are no broken valve springs any where, either something got in on top of #6 piston or possibly could have that piston came apart ???? any ideas??? I will be tearing into it further this week.
Thanks
Vernier

Are you able to work the valves by hand. I use a large rubber deadblow or a sledge and piece of wood to push them down and see if they snap back.

May have gotten water in it and had a hydraulic lock.


Matt

Matt- Yes I am able to push the valves down and they will return, I can turn the engine over by hand seems like there is a hard spot when that piston comes up to TDC This machine has been sitting for a while and has a good rain cover over the exhaust, I don't suspect water anywhere.I plan on putting on direct start. so will have a spare pony later.
Vernier

Looks like this could be another case of CAT's two piece pistons that could come apart. I had this happen on my D47u. The top aluminum portion of one piston came unscrewed and was sent out the exhaust in a million pieces. It bent a conecting rod, destroyed one push rod and the rod guide. The engine never stopped running. We dropped the oil pan and found all the broken goodies in it. It might be worthwhile to take a peek in yours. Good luck. I had a 70D for years and now I have a 71D.

I ,m sure the 70-D is new enough to not have that old style screw together pistons in it but I agree that it seems like something got in the way of the valves when they tried to open & they were restricted by something.

Maybe if there installed, the tip off the “Glow Plug”

Kelly

Took the head off this afternoon and found a broken piston on #6cylinder, also bent the rod, I will be checking on parts prices tomorrow. May be looking for a good running 318 engine.
Vernier

I ,d think if your engine has ran well so far that it would pay to get a rod & piston & liner & do a valve job on it would fix you up well rather than buy a used engine that you don,t know anything about. Also just a D318 engine would need lots of changing around of parts & assemblies to make up the grader engine setup unless it was out of a grader like yours.Just my opinion.

Could someone tell me where to get a parts book for this machine, I have one but the first 18 pages are gone!!! and it looks like some of the engine part numbers are in that section. No. 12 motor graderSer # 70D 3311
Thanks
Vernier

Manual source is either ebay or here:
www.cat.com/cda/layout?m=90800&x=7