Fitting rear crankshaft seal on an OM617 - PeachParts Mercedes-Benz Forum

Stretch · #1 11-18-2010, 07:49 AM

G'day All,

I thought I'd just check with people who have done the job before.

I've just fitted the rear crankshaft seal in my OM617 motor block and I want to know if it looks like it is as far in there as it should be.

I have been told by an engine builder that this can be a tricky little *&^&^#XX$#%# as if it is done incorrectly it can cause localised heating which in turn can cause failure of the last (rearwards) main bearing.

(Full discussion on this is in posts 20, 21 and 22 of this thread:-
OM617 Front crankshaft seal nightmare - should I re-align the upper oil pan?
)

I've made a photograph of the seal - thanks in advance for your help tips and advice.

Alastair · #2 11-18-2010, 07:59 AM

Yup, That doesnt look too bad....

When I fitted mine, I used a large diameter hammer-handle and my full weight to 'roll' the thing into the groove--Its a lot stronger than it looks....

Note, Dont 'rub' it, Roll the weight over the seal to force it into the groove.

Leave 1mm standing proud when trimming off....

When rear bearing is assembled, the engine will appear quite tight to turn until this seal beds to the shaft, Use LOTS of oil over it when fitting crank and bearing cap.....

The bedding in happens after the first few seconds of running...

layback40 · #3 11-18-2010, 07:01 PM

X2 with Alastair. I cant see any assembly oil there !

Stretch · #4 01-16-2011, 12:44 PM

Here are some pictures of the seal going into the upper oil pan just to make the set complete.

Note the new knife blade to try and get a clean cut...

kerry · #5 01-16-2011, 12:51 PM

Is there a reason for a knife as opposed to a razor blade?

vstech · #6 01-16-2011, 12:53 PM

I don't like the mashed look of the seal ends.
does everybody who has done this think trimming around the end to keep extra material from sandwitching between the halves would be a good idea?
I have never done this job so don't take my word for it!

Stretch · #7 01-16-2011, 01:11 PM

I didn't have a razor blade - I guess I should have tried to get one - but it cuts quite well with a new knife blade.

You are meant to cut the seal about 1mm above the mating surface according to the FSM (chapter 03-327). The making of a special tool that fits over the seal and guides you during cutting is also recommended <= I skipped that bit.

kerry · #8 01-16-2011, 01:30 PM

What would that tool be like? Would laying a 1mm thick piece of metal next to the seal at least get is started at the correct height?

Doktor Bert · #9 01-16-2011, 01:55 PM

The most important factor is there be NO portion of seal material between the block and upper oil pan, as previously pointed out.

Previous advice about rolling/forming the seal with a hammer handle/wooden dowel/rolling pin is also wise. A section of PVC pipe works well too. When I was working on these 617's every day, I had a rear section of an old crankshaft, cut from a junk core, that only consisted of the two rear main journals. I would install and use as a fitting guide.

I cut the seal flush on one end and leave a slight amount sticking up on the other. Use a one-edged razor blade to trim off any 'threads' of fibers left that could get between the two case halves.

In my opinion, the seal is properly installed when the crank must be 'broken free' from rest with a slight amount of effort before it will turn and should stop abruptly when released. You should NOT have to use a prybar to turn the crankshaft.

The old Pontiac V8's with a rope seal were properly installed when it took 10-15 lbs/ft to break the crank loose from rest.

Stretch · #10 01-18-2011, 08:10 AM

Quote:

Originally Posted by kerry

What would that tool be like? Would laying a 1mm thick piece of metal next to the seal at least get is started at the correct height?

Yeah indeed that is effectively it - a 1mm thick piece of metal with a rectangular hole cut in it - it is also shown in chapter 3-210

Stretch · #11 01-18-2011, 08:27 AM

Quote:

Originally Posted by Doktor Bert

The most important factor is there be NO portion of seal material between the block and upper oil pan, as previously pointed out.

Previous advice about rolling/forming the seal with a hammer handle/wooden dowel/rolling pin is also wise. A section of PVC pipe works well too. When I was working on these 617's every day, I had a rear section of an old crankshaft, cut from a junk core, that only consisted of the two rear main journals. I would install and use as a fitting guide.

I cut the seal flush on one end and leave a slight amount sticking up on the other. Use a one-edged razor blade to trim off any 'threads' of fibers left that could get between the two case halves.

In my opinion, the seal is properly installed when the crank must be 'broken free' from rest with a slight amount of effort before it will turn and should stop abruptly when released. You should NOT have to use a prybar to turn the crankshaft.

The old Pontiac V8's with a rope seal were properly installed when it took 10-15 lbs/ft to break the crank loose from rest.

Thanks for the input Doktor Bert.

With your comments in mind I decided to measure the stiction of the crankshaft during the installation of the upper oil pan.

Here's what I did:-

1) I applied the heat resistant sealant around the edge of the upper oil pan and fitted it in place - I then let it cure as directed on the packet.

2) After the curing before the final tightening of the bolts (as per the instructions on the sealant packet) I measured the torque required to turn the crankshaft. This turned out to be about 21 ft-lbs / 29 Nm.

I measured this in two ways - with a torque wrench - slowly adjusting the torque until the break in the wrench coincided with the movement of the crank. The second way (used to confirm the first) was to calculate the torque needed by using a spring balance (scales) pulling at a known distance.

3) I then tightened down the upper oil pan and re-measured the torque of the crankshaft. It was about the same - 30 Nm (though still 29 Nm in places)

Note that this is just a measurement of the torque for spinning the crankshaft with the pistons fitted - the timing chain / oil pump / camshaft weren't connected.

So barely a noticeable difference in crankshaft stiction with the seal in place or (more or less) not in place.

vstech · #12 01-18-2011, 09:42 AM

I think DB is talking about JUST the crank installed with NO pistons on it yet.

Stretch · #13 01-18-2011, 01:21 PM

Quote:

Originally Posted by vstech

I think DB is talking about JUST the crank installed with NO pistons on it yet.

Thanks John,

I think that that is probably what he meant too - I had been advised to go through a process of fitting the crank and seal and then taking it all apart again (see the link to another thread in post #1) by an engine builder here in Holland. However, in that thread the idea was somewhat belittled as it isn't in the FSM...

I've ended up doing a sort of halfway house assembly - I haven't measured the stiction of the crank without pistons and seal fitted - and then fitted the upper half of the seal in the crank and measured the stiction and then fitted the lower part of the seal in the upper oil pan and then measured the stiction - which I guess would be the best way if it were not for one thing:-

The effect of sealant at the upper oil pan / engine block mating surface - which must have a slight influence on the tightness of the rear crankshaft seal too. (I guess it should make it looser)

I've ended up just installing it and then seeing if the addition of the upper oil pan pinches the rear crankshaft seal - which as far as I can measure it does not by much if anything at all.

From my recollection 20 ft-lbs of torque feels about right - I hope I'm correct - and I hope the upper oil pan doesn't leak! It's all nail biting stuff here...

SirNik84 · #14 01-18-2011, 01:58 PM

Quote:

Originally Posted by Army

The making of a special tool that fits over the seal and guides you during cutting is also recommended <= I skipped that bit.

I wish I had access to the factory service manual for the 48 GMC I'm rebuilding with a co-worker. The rear seal is exactly like the seal on the 617, but when they talk about trimming the seal they tell you to use "a sharp blade. See Figure (whatever)"

Well in the picture they have a guy holding a picket knife that looks some thing like this.

General Motors Specialty Tool!

Stretch · #15 01-18-2011, 02:07 PM

Quote:

Originally Posted by SirNik84

I wish I had access to the factory service manual for the 48 GMC I'm rebuilding with a co-worker. The rear seal is exactly like the seal on the 617, but when they talk about trimming the seal they tell you to use "a sharp blade. See Figure (whatever)"

Well in the picture they have a guy holding a picket knife that looks some thing like this.

General Motors Specialty Tool!

Nice one - but you can see that it is just a lock knife - not a flick knife - it could be worse!

If you get the chance to measure the stiction of your GMC crankshaft once it is fitted I'd be interested to hear what it is... all ball park figures are interesting - with enough information we could even set advisory limits for future builders.