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+--- Thread: Knock, Knock... (/showthread.php?tid=4843)
Knock, Knock... - Cadin - 08-25-2013
Hey Gang,
I have a OM617 that is knocking pretty well. I took it to the local Mercedes guys for a listen, and they think it is in the top end somewhere. They doubt that it would be the block.
It sounds to me like it is coming from around #1. I loosened each injector to see if the sound disappeared but to no avail. I have done the diesel purge, and added some Lubro High-Test.
It is more noticeable at idle when warm, and when revved with no load, quiets a bit. Revved with load is VERY noticeable.
Does this data help, or shall I post a vid?
Later,
Nater
RE: Knock, Knock... - raysorenson - 08-25-2013
Other: piston
RE: Knock, Knock... - Duncansport - 08-25-2013
(08-25-2013, 07:35 AM)raysorenson Other: piston
+1
Piston slap is my guess
RE: Knock, Knock... - Simpler=Better - 08-25-2013
Adjust your valve lash, see if that helps. If you have a huge gap you might be hearing the lobe slap a loose adjuster nut. Piston slap is bad but I've seen SBCs run with piston slap for a long time.
How does it run otherwise?
RE: Knock, Knock... - Cadin - 08-25-2013
Where does piston slap fall in the level of worry scale? e.g. Engine failure eminent <---> timing adjustment and no big deal
RE: Knock, Knock... - Duncansport - 08-25-2013
(08-25-2013, 06:22 PM)Cadin Where does piston slap fall in the level of worry scale? e.g. Engine failure eminent <---> timing adjustment and no big deal
I've been driving my V6 Saab with an awfull piston slap for 50,000 miles. It'll blow up some day I'm sure....
RE: Knock, Knock... - Simpler=Better - 08-25-2013
My Dad's Silverado had it for like 30k, and didn't hurt anything (truck blew up 30k later when a hired hand ran it with a dry cooling system & popped radiator). Just let it warm up before you put a load on it.
My DD has piston slap (or terrible shot bearings or loose valvetrain or a box of bolts in the crankcase). Just let it warm up and you ought to be fine for a while.
Rebuilding is big money, and big time. If you already have slap you might as well run it until it pops then think about rebuilding.
RE: Knock, Knock... - Austincarnut - 08-25-2013
your prechambers fell out and shotgunned your piston because of poorly executed wvo install.
RE: Knock, Knock... - raysorenson - 08-25-2013
(08-25-2013, 06:22 PM)Cadin Where does piston slap fall in the level of worry scale? e.g. Engine failure eminent <---> timing adjustment and no big deal
There's a curve. It typically starts quietly enough and flies under the radar for a long time. As the piston develops more clearance in the bore, the wear accelerates.
I've got a very nice '85 300td in the driveway that's had a piston noise for as long as I've had it in the herd. Something let go a little while ago suddenly. Probably broke a skirt. It will stay in the driveway until a good deal on a motor comes along.
RE: Knock, Knock... - Cadin - 08-26-2013
Right on, thank you guys. It certainly sounds interesting pushing a FJ80 at 65mph! (~3000rpm)
Simpler=Better: I checked the #1 In/Ex last night and it was too tight. I will check the rest of the valves, I need to cut the wrenches to adjust. I can only hope! She runs excellent otherwise. Oil Pressure is a 1.3-1.5 bar at 90C at idle, raising to 3.0 bar by 2000rpm.
The current consensus seems to be: There is no reason to F' around with anything but a full rebuild so run 'er til she stops or starts drinking oil.
Basically, I should have an engine on hand for The Day.
(Thank you again for all the prompt responses!)
RE: Knock, Knock... - Simpler=Better - 08-26-2013
Sounds good. 3,000rpm is fine (if loud) it will run all day at that speed.
RE: Knock, Knock... - willbhere4u - 08-26-2013
Piston slap wont usually blow up the engine but it will oval out the cylinder bore over time and slowly loose compression on that cylinder. some time the piston will come apart but not always that usually happen after its already lost compression.
My girl friends forester has piston slap until the engine warms up for a few minuets until the heat expands the piston in the bores It sounds horrible like a rod knock especially on cold days but it has over 300k on it its been like that as long as we have had it. We have put over a 100k on it! it uses a little oil but I'm not to worried about it.
I would still do a valve adjustment and rebuilt injectors with heat shields. Injectors can be transferred over to a new a engine. Try some Lucus oil stabilizer to lube up the cylinder bores remember the turbo engines have piston squirters so thick heavy oil will stick better to the bore and lube the bottom of the pistons and rings better
RE: Knock, Knock... - Cadin - 08-26-2013
That puts my mind a little more at ease, now I will try to get a good compression baseline and keep an eye on her.
Man is it loud! Guess I can just tell folks that it's a detroit diesel!
RE: Knock, Knock... - Grecy - 08-28-2013
Hey man,
What mileage are you getting with the OM617 in the FJ80?
Do you have a build thread somewhere?
Thanks,
-Dan
RE: Knock, Knock... - Cadin - 08-29-2013
(08-28-2013, 05:49 PM)Grecy Hey man,
What mileage are you getting with the OM617 in the FJ80?
Do you have a build thread somewhere?
Thanks,
-Dan
Hey Dan,
I don't know on mileage yet, as it has been many short trips, but I have done a 40-mile round trip with no issues apart from the knocking. I have a build thread over at ih8mud,com in the fj80 section, same username.
Most folks I talked to before beginning (that have swapped this motor into other rigs), thought I may get 23-25mpg, but I don't realistically expect much more than 20mpg; so we shall see, but it is still a far cry better than the 11.9mpg I was seeing before...
I put a vid up of the knock and of the blowby...
Knock
http://www.youtube.com/watch?v=9BzmsirF9Xs
Blowby
http://www.youtube.com/watch?v=WKqZsPTGAs0
RE: Knock, Knock... - Cadin - 12-03-2013
3k on swap... still truckin'...
RE: Knock, Knock... - willbhere4u - 12-03-2013
Good to here. If it was a bearing issue you would have bad oil pressure