Front seal replacement 617 engine
 

I need to replace the front crankshaft seal on my '82 300D. Any insights? Is it usually necessary to replace the seal spacer? I would not think so, but I don't want to cut any corners. Too much work involved to be frugal with a $10 part. But it looks like pullling the spacer (engine in vehicle) could be the toughest part of the job.

Well, it certainly helps to have one in there, as we left it out on the 300D and it blew oil everywhere!

I'd replace the spacer -- it may be difficult to get out, but the usual cause of leakage is that there is a slot in the spacer and the lip of the seal will not retain the oil any more -- a new seal will still leak.

If it's the originaly, you can just reverse it and go again (the wear spot is at the front of the spacer), but you won't be able to tell until you get it apart.

Front hub is a problem -- it's located by two steel pins, and they CANNOT be driven in after the hub is in place, they are harder than either crank or hub, and will ruin both if not properly aligned. Larry Bible has a very good description of how to do this, do a search. Been a while since the subject has come up, though!

Make sure all three washers are in place under the bolt going back in, and in correct orientation (they are Belville spherical washers).

Peter

Peter, thank you for your response. As is frequently my experience, the more I "search" the more questions I have.

I thought I understood the process of reinstalling the harmonic balancer, but your statement that the alignment pins "CANNOT be driven in after the hub is in place" leads me to suspect that there is a gap in my understanding. Other sources seem to suggest that the pins are to be seated once the balancer is installed on the crankshaft and properly aligned.

The process will likely be obvious once the job is undertaken. But given the consequences of not getting the balancer aligned properly, any additional amplification would be most appreciated. Thanks.

The holes for the 2 pins are 1/2 in the crankshaft and 1/2 in the hub (an arrangement also known as a "Dutchman"). When you put the hub back in, the pins should already be in the half-holes in the crankshaft. Make certain you mark the hub and the crank BEFORE you take them apart. If you start the hub without the pins, you won't be able to get them in, it's a tight enough fit doing it the right way :eek:

So the pins are installed in the crankshaft first, and then the balancer is pulled onto the pins and the crank simultaneously?

yep, pushed to be more exact, by that big, hawking bolt that gets lubricated and torqued to 270-300 Nm IIRC. I used a M8 bolt with some washers and an aluminum spacer on the front of the block to keep the hub from rotating. Worked great, and no danger of cracking the upper pan

Pete, thanks so much. That brings the picture into focus. Other sources left me with the impression that the pins should be installed in the balancer before the balancer was installed on the crank. Thanks for clearing things up.

I've been able to work the spacer out with 2 opposed screwdrivers. It should slide out if even pressure is applied. There is an MB tool for this operation but the price of it is wacky...

Be sure to mark the crank and the hub before removing the hub. The crank hub is balanced to the crank shaft.

LarryBible and TCane have plenty to say about the harmonic balancer installation here, here, and here. Enjoy.

If you attempt to drive the pins in and the holes aren't perfectly aligned, you will score both crank and balancer, making it impossible to remove the blancer, etc. Both are MUCH softer than the pins.

Larry Bible's explanations are MUCH better than mine. Basically you must get the balancer and crank properly aligned with the pins without applying any great pressure to the bits, else the pins dig into the crank. Sometimes you can draw them down easily, sometimes not, and it's also important not to pull the balancer on with the pins half way in!

The spacer can stick on a high milage engine, but they do come out. Don't bugger up the seat for the seal, though -- if the flange doesn't seat all the way round, it can leak a little. Not near as much as the seal does with no spacer in there, though. Don't ask how I know....

Peter

1983 300td front crankseal job
 

i've got everything off but the spacer. it looks and feels scored and i want to replace it but it won't come off with pliers, tapping, or wishing. should i give it some heat? when i pulled the balancer the dowel pins came with it. i get the impression from the posts i read that i should tap them out and reinstall them after the balancer is almost all the way back on and lined up perfectly. is that correct? my new front crankseal has a half shoulder on the outside edge. does that face up or down when it's installed

Try prying simultaneously with two small screwdrivers 180 degrees apart.

Have you checked the instructions in the FSM ?

front crankseal
 

new to the list .....what is the FSM?

Factory Service Manual