OM617 N/A main bearing problem- I'm baffled - Page 3 - PeachParts Mercedes-Benz Forum

Stretch · #31 06-17-2015, 01:07 AM

Off on a tangent?

How about this?

I think we have ascertained that the crank being tight after fitting of plain bearings was due to incorrect bearing sizes right?

How about this bomb shell - there is no rod knock! This is a normally aspirated engine isn't it? Have you checked the oil pump drive coming off of the intermediate shaft - those buggers knock and might be thought to be rod knock...

ROLLGUY · #32 06-17-2015, 10:30 AM

Quote:

Originally Posted by Stretch

Off on a tangent?

How about this?

I think we have ascertained that the crank being tight after fitting of plain bearings was due to incorrect bearing sizes right?

How about this bomb shell - there is no rod knock! This is a normally aspirated engine isn't it? Have you checked the oil pump drive coming off of the intermediate shaft - those buggers knock and might be thought to be rod knock...

Well since it was ran low on oil, the rod bearings were a little worn, I only assumed that the knock was coming from a rod and nowhere else. It very well could be from somewhere else (I hope it is now that it is back together). I tried to get it running yesterday, but my battery went dead twice. It has been charging all night, and I will try again this afternoon. It sure takes a long time to prime the fuel system! I have been pushing the primer pump constantly while cranking the engine, and there is still no fuel coming out of the injector lines. I had the same problem before, so I am used to it now. It eventually started to want to fire, and finally did. I have been using WD40 as priming fuel, squirting it down the intake runners. I will update this afternoon, so say a prayer for the engine and I (mostly for the engine

)

Stretch · #33 06-17-2015, 10:32 AM

Well if it runs stick a mechanic's stephoscope on the cap at the top of the oil pump drive and have a listen for me will you?

t walgamuth · #34 06-17-2015, 01:54 PM

A rod will twist if there is a small hydrolock. It could be detected probably by looking at piston position at the top of the stroke. If the rod is twisted a little it also will sit low.

ROLLGUY · #35 06-17-2015, 03:56 PM

Quote:

Originally Posted by t walgamuth

A rod will twist if there is a small hydrolock. It could be detected probably by looking at piston position at the top of the stroke. If the rod is twisted a little it also will sit low.

I probably won't be able to see this, as the head is still (and always has been) on.

ROLLGUY · #36 06-17-2015, 08:24 PM

I have killed my battery three times today trying to start it. For the longest time I had all 5 injector lines loose, and finally #5 started dripping out fuel. I have cranked and cranked, and no fuel comes out of the other four. I finally decided to tighten the four, and try to start it. It then wanted to start, but then the battery died again. I am not sure what is going on, as it should have started by now knowing how much cranking of it I have done.
Here is a photo of the crankcase before the pan went on (I was going to post it days ago, but did not get a chance):

Notice how clean everything is. It looks like a new engine inside (photo does not do it justice).

Here is the engine ready to start. The exhaust system fits perfectly just laying on the ground, and seals tight enough to not need bolts:

Tomorrow I will try again after the battery charges.....Rich

Dan Stokes · #37 06-17-2015, 09:07 PM

Fingers crossed.

My first start-up required a touch of starting fluid. I know it's bad stuff but nothing else worked. Now I glow it for a few seconds and it fires right up.

Dan

ROLLGUY · #38 06-18-2015, 05:10 PM

I finally got it running, and the knock is still there. On a positive note, I have isolated it to #2. There is hope though, as I have not ruled out a bad injector. I am going to switch a couple around later on, and see if it follows the switch. If so, then I will be relieved.....Rich

ROLLGUY · #39 06-24-2015, 01:45 PM

I have taken the advice of my engine builder to try the following procedure. Since #2 is the noisy one, I was able to get the rod cap off without removing the upper pan:

The procedure is as follows:
1) remove rod cap and wipe off as much oil as possible
2) put plastiguage on journal, and install and torque rod cap bolts
3) remove rod cap and view results
4) if still on the high side of the allowable tolerance, "dress" the surface of the rod cap on sandpaper on a flat surface (glass or granite)
5) clean rod cap and start at #2 again, and continue the procedure until the clearance is in the allowable range.

I did this procedure at least five times, getting closer each time. Four of the results:

I was satisfied that the tolerance was good, and put it back together.
It started right up without the glow plugs, but the knock is still there. I am convinced that it is not a rod bearing that is causing the knock, as it is well within (even a little on the tight side) the range of specified oil clearance. The knock is nowhere near as bad as it was originally, but still there nonetheless. I don't want to pull the head, but it seems that that might be the next step. If so, I will pull #2 piston and have the rod re-sized and check the wrist pin again. Again, I am at a loss as to what the exact problem is....Rich

DeliveryValve · #40 06-24-2015, 02:58 PM

Hey Rich,

Couple of questions..

The rod bolts are Torque to Yield type of bolts. Did you reused the bolts and if you did, did you measure the stretch? When you re-torqued them, you need an initial value of around 35 ft lbs. Then you stretch the bolt with an additional 100° turn. If the bolts are not in spec, then you can't get the desired torque.

Second, did you check the end of the oil pump shaft? If you are not certain the knocking was coming from #2, the oil pump shaft along with the helical shaft could be very worn and possibly make the knocking noise.

See pics of an oil pump shaft beginning to wear. Still serviceable for a lot of miles though.

ROLLGUY · #41 06-24-2015, 03:15 PM

Quote:

Originally Posted by DeliveryValve

Hey Rich,

Couple of questions..

The rod bolts are Torque to Yield type of bolts. Did you reused the bolts and if you did, did you measure the stretch? When you re-torqued them, you need an initial value of around 35 ft lbs. Then you stretch the bolt with an additional 100° turn. If the bolts are not in spec, then you can get the desired torque.

Second, did you check the end of the oil pump shaft? If you are not certain the knocking was coming from #2, the oil pump shaft along with the helical shaft could be very worn and possibly make the knocking noise.

See pics of an oil pump shaft beginning to wear. Still serviceable for a lot of miles though.

This engine had less than 100,000 on it, and was run low on oil. I am sure it is #2 and only #2 that is the problem, as the knock goes away when the injection line is loosened. I can't imagine that the oil pump shaft would go bad that soon, or cause a knock.
Also, I have not checked the stretch on the bolts. I have been using the proper torque (35 ft lbs + 90-100 degrees additional rotation).

DeliveryValve · #42 06-24-2015, 03:34 PM

Quote:

Originally Posted by ROLLGUY

This engine had less than 100,000 on it, and was run low on oil. I am sure it is #2 and only #2 that is the problem, as the knock goes away when the injection line is loosened. I can't imagine that the oil pump shaft would go bad that soon, or cause a knock.
Also, I have not checked the stretch on the bolts. I have been using the proper torque (35 ft lbs + 90-100 degrees additional rotation).

Just saying, Those need to be checked so you can rule them out. I think Mercedes has had a reliability issue with those types of pumps, hence they went to a chain driven unit on the later turbo models. That pic of the pump was from a factory low mileage reman motor.

ROLLGUY · #43 06-24-2015, 04:38 PM

Quote:

Originally Posted by DeliveryValve

Just saying, Those need to be checked so you can rule them out. I think Mercedes has had a reliability issue with those types of pumps, hence they went to a chain driven unit on the later turbo models. That pic of the pump was from a factory low mileage reman motor.

Well since the knock goes away on #2 when the fuel is cut, I can only assume it is a rod or wrist pin causing the noise. However, the pump shaft is very easy to check, so I will have a look. I believe my next job will be to pull the head and have #2 piston/rod checked and re-sized.

Maxbumpo · #44 06-24-2015, 05:02 PM

Priming the injection pump: the manual pump ONLY puts fuel through the pump, NOT out the injection lines. When the feel of the pump and the noise it makes change, which can take 50 - 75 strokes of the pump, then you've primed it. After that you must crank the engine over with the starter to get fuel pushed out to the injectors.

ROLLGUY · #45 06-24-2015, 06:52 PM

Quote:

Originally Posted by Maxbumpo

Priming the injection pump: the manual pump ONLY puts fuel through the pump, NOT out the injection lines. When the feel of the pump and the noise it makes change, which can take 50 - 75 strokes of the pump, then you've primed it. After that you must crank the engine over with the starter to get fuel pushed out to the injectors.

Yes I am aware of that, and it took a loooooooooooooooooooooooooong time to get the air out of this one. I have installed IP's before that took no more than a couple rounds of 30 second cranking sessions to get the air out. Even after I got this engine sort-of running, it still had some air in the lines and took a minute or so to smooth out. Fortunately, the couple times I put it on the stand, worked on the rod cap, put it back on the floor and started it up, it fired and ran perfectly on the second crank. This last time, it started with the first crank without the glow system hooked up.