Crankshaft installation - rear seal tightness - PeachParts Mercedes-Benz Forum

mplafleur · #1 10-04-2008, 10:49 PM

I'm rebuilding a 240D. In fact it's my old 240D that my son bought from a friend of mine. He had the block machined 1st over and bought all the parts to rebuild the engine and lost interest. My son bought the project and I'm helping hime get it together.

While putting the crank in I noticed a few things. The thrust washers are too thick. I guess the machinist didn't widen the shoulders 1st over for the thrust washers. Unfortunately, we are missing one of the original washer halves so we will have to order anther set of original size (2.15mm). However, I decided to continue the installation and I can install the thrust washers later by removing the bearing cap and inserting them next weekend.

On to the question for this post. After installing the bearing caps, I could hardly turn the crank. I have to hold onto two crank throws and hall up on it to turn the crank. Wondering if the problem was the 1st over machining/bearing or the rear fiber seal, I took it all apart and removed the seal and torqued it all up again. Now it spins nicely. So it's only a seal issue.

This time I removed some of the seal where the needle sticks up so the bottom of the seal will seat lower. I lubricated it well and put the crank back in. It spins a little better, but not much.

Should I worry about this? The bearing are fine, it's just a tight seal.

barry123400 · #2 10-04-2008, 11:52 PM

Gotta be reasonably tight to seal. I believe on installation you trim the seal a mm higher than the saddle on each side. Thats about it if the right seal is installed. It will compress with time and use.

You may want to check the archives for the exact protusion allowance after trimming. The only concern I can think of is if the seal was not trimmed properly during initial installation.

mplafleur · #3 10-05-2008, 12:05 AM

I haven't put the upper pan on yet, so the two halves of the seal aren't together yet. And yes, you do trim them to 1 mm proud.

mplafleur · #4 10-05-2008, 12:36 PM

I'm surprised no one has an answer for this yet.

I'm going to assume the tight seal is ok and continue building up the block.

jt20 · #5 10-05-2008, 01:38 PM

your crank should not bind upon installation. It is possible that you may see leaks in the future is the seal is not set all the way before install.

follow the fsm properly.

it requires a well-lubed wooden handle of a round profile to massgae the seal into place.

from experience: you do not want to set the entire span of the seal all at once, it will not slide in the holding groove. Instead, begin at the center once you have determined where the center of the seal will meet the prick.

force is required to ge the seal in there, push hard, use body weight, work your way up the seal from the center. A lump where the prick is will be noticeable.

p.s. 1 mm may be less than you imagine.

jt20 · #6 10-05-2008, 03:36 PM

forgot to mention that oiling all sides of the seal facilitates installation

and as I recall, I used gentle blows from a hammer against the short face of a 2x4 to really set that seal.

mplafleur · #7 10-05-2008, 09:46 PM

I didn't oil all sides and it was higher where the prick is located. Being higher at that point is why I think I have more resistance. I inserted the seal and pressed it in with the the handle of a hammer. It went in easily enough and I could see at the ends it was seated completely.

I've inserted the pistons today and snugged up the con-rod caps.

The question is, should I get another seal and try again? (before it gets harder)

Caesium · #8 10-05-2008, 09:48 PM

Quote:

Originally Posted by jt20

forgot to mention that oiling all sides of the seal facilitates installation

and as I recall, I used gentle blows from a hammer against the short face of a 2x4 to really set that seal.

Dang! My seal better not leak... Or you'all here my curse all the way from AZ!

jt20 · #9 10-05-2008, 10:11 PM

^^ your seal-setting skills are far superior to ours, and you mentioned nothing about a binding crank.

jt20 · #10 10-05-2008, 10:16 PM

Quote:

Originally Posted by mplafleur

I didn't oil all sides and it was higher where the prick is located. Being higher at that point is why I think I have more resistance. I inserted the seal and pressed it in with the the handle of a hammer. It went in easily enough and I could see at the ends it was seated completely.

I've inserted the pistons today and snugged up the con-rod caps.

The question is, should I get another seal and try again? (before it gets harder)

The best I can say to support you is that as long as there was a constant reveal of the new seal inside the radius of the holding groove, you should be set.

the binding is what worries me. Perhaps, if it is the lump you assume, you could remove / gouge / drill a very fine pilot hole for the prick.??

like a 1/32 drill bit and go 2/3 the way through the seal.??

ps engine looks real nice.. new pistons?

mplafleur · #11 10-06-2008, 07:11 AM

Quote:

Originally Posted by jt20

Perhaps, if it is the lump you assume, you could remove / gouge / drill a very fine pilot hole for the prick.??

like a 1/32 drill bit and go 2/3 the way through the seal.??

I actually tried that. After the first time I set the seal and found the crank hard to turn. I removed the seal. The crank turned fine. I tried to dril a hole where the prick is. It's not easy. Ever tried to drill a hole in rope? It's not actually rope, but the analogy works.

Quote:

Originally Posted by jt20

ps engine looks real nice.. new pistons?

Yup. New pistons. Thanks.