M110 Front Main Seal Pushed Slightly Out

[mmiller]

1978 W123 280CE/ M110.984

Getting ready to replace the Front Main Seal. Wish me luck on that. I was underneath the Benz snooping around today with a flashlight, and inspecting the crud beneath the seal. I noticed that the front of the seal was protruding about 1.5mm from the front of the block. (Gee, no wonder oil was leaking!) It wasn't completely out, but it sure wasn't seated where it should be. Not even leaking enough to drip or puddle.

Now, before I replace the seal, I want to insure that nothing has caused the seal to push itself outward. Since I am the 4th owner (vehicle has 115,000 miles), I don't know if the seal was ever replaced before. I did see in the FSM that the outer edge does require sealant when installed. So it's either possible that the seal has just lived its useful life, it was replaced and no sealant used, OR, something has caused if to pop forward. I'm not noticing any other telltale signs. When I recently replaced my ring gear and had the flywheel removed, only minor signs of the rear main seal seeping were observed. I also just adjusted the valves. It had been a couple of years.

So now the questions for the engine gurus, could a clogged blocked Vent Valve (between the Valve Cover and the wall of the Head) cause enough pressure to unseat a seal? Could improperly adjusted valves cause excessive crankcase pressures causing a seal to push out? Car runs fine, no pressure noticed with dipstick or oil fill cap removed and engine running.

Help is sure appreciated.
MM

[Stretch]

I can't tell from my armchair for sure but it sounds to me like the seal wasn't fitted properly in the first place.

One thing that happens on OM61X engines (I know not the same as yours but of same vintage so...) is that the seal wears a lip into a ring that slides over the nose of the crankshaft. If you don't replace this ring along with the seal then you can get leaking with a new seal. If your M110 has a ring like this and it has a lip / ridge then it is possible a clever mechanic purposefully left the seal poking out so the seal runs on another bit.

Just a guess.

(Though more likely it was a bugger to fit and was left in a "good enough" position)

See what it is like when you take it to bits.

######

As for crankcase pressure pushing out a seal - I'd expect the rubber part of the seal to fail not for the whole seal to be pushed out as you describe. For that to happen I'd expect to see oil seeping from the outer edge and for it to be a silly loose fit. I don't think it is very likely.

Again - go see.

[mmiller]

Hi S,


Once again, thanks for your thoughts. I'm still amassing parts, supplies, and fortitude. As you may have spotted in the 'wanted parts' forum", I'm still in search of the elusive proper flywheel lock. That may determine when the whole operation commences. Already ordered is the Spacer Ring you referred to. I've managed to locate a used special tool (on the cheap) to pull the old one off, so I won't have to perform the dual opposing screwdriver dance. I tend to agree with you that the existing seal was not deeply enough seated, and or without sealant to 'secure' it in place.


I'm not familiar with what a 'blown' seal would look like, so just tossed that out to cover all possibilities.



Have a Blue Moon on me!
MM

[97 SL320]

Leaving the seal out 1.5 mm or so isn't an issue in most applications. This might have been done during a prior repair to overcome a groove on the hub / shaft. In some industrial engine applications, the seal can be in a stock location , forward a bit and rearward a bit.

There is such a repair called " Redi Sleeve " This is a thin sleeve that presses over the shaft.

[Stretch]

Here's a link for making a special tool to help with fitment of the seal =>

PeachPartsWiki: Replacing Front Crankshaft Seal with "Special Tool"

The flywheel lock is indeed an important part of the job - with the engine removed (yeah I know!) "standard" flywheel locks like BGS 1771 can be used but I've not reached the stage where I've tried to use one of these locks with the engine in the vehicle before.

When I fitted the front seal to my OM617 when it was fitted in the car I ended up using a block up against the front balancer to stop the crank from turning - it wasn't pretty. I guess there's a mega torque requirement for that front crankshaft bolt on the M110 just like there is for the OM617 and M102 (two engine types where I've done this job) - a big effing torque wrench is required.

[mmiller]

It almost sounds like the 'Spacer Ring' which I am replacing. A sleeve which fits over the nose of the crank. The OD of the spacer ring rides against the ID of the seal. The sleeve can be difficult to remove, but as mentioned, I do have the MB removal tool. I only want to perform this surgery once!

Originally Posted by 97 SL320

Leaving the seal out 1.5 mm or so isn't an issue in most applications. This might have been done during a prior repair to overcome a groove on the hub / shaft. In some industrial engine applications, the seal can be in a stock location , forward a bit and rearward a bit.

There is such a repair called " Redi Sleeve " This is a thin sleeve that presses over the shaft.

[mmiller]

Right you are regarding 400 Nm. I found a link which will help calculate all that. You need to know the actual Tightening Torque of the bolt/nut, how many pounds of Force You can deliver, and how long your lever (extension on the end of the torque wrench) needs to be.

LINK: https://www.sensorsone.com/force-and-length-to-torque-calculator/#torque

Using my Tightening Torque of 400 Nm as a target reference, and assuming I can deliver 74 Pounds of Tightening Force (shouldn't bust my b*lls at all), I need a four (4) foot Long Extension. The Length of the extension was what I wanted to know when I went shopping for tools and supplies. If I used the 3 foot handle from my floor jack, the Tightening Force would be 100 Pounds. I'm opting to let the extra 1 foot of extension do the work.

Originally Posted by Stretch

Here's a link for making a special tool to help with fitment of the seal =>

PeachPartsWiki: Replacing Front Crankshaft Seal with "Special Tool"

The flywheel lock is indeed an important part of the job - with the engine removed (yeah I know!) "standard" flywheel locks like BGS 1771 can be used but I've not reached the stage where I've tried to use one of these locks with the engine in the vehicle before.

When I fitted the front seal to my OM617 when it was fitted in the car I ended up using a block up against the front balancer to stop the crank from turning - it wasn't pretty. I guess there's a mega torque requirement for that front crankshaft bolt on the M110 just like there is for the OM617 and M102 (two engine types where I've done this job) - a big effing torque wrench is required.

[97 SL320]

Originally Posted by mmiller

It almost sounds like the 'Spacer Ring' which I am replacing. A sleeve which fits over the nose of the crank. The OD of the spacer ring rides against the ID of the seal. The sleeve can be difficult to remove, but as mentioned, I do have the MB removal tool. I only want to perform this surgery once!

For this type of setup in general, a bit of Permatex Aviation Sealer ( Not Gasket Shellac ) anywhere there is a metal to metal joint that leads from oil to the outside is a good idea. Just be sure to use it sparingly as we don't want it on the sealing lip area. I don't know what the manual suggests.

[mmiller]

Good tip to know, thanks. The FSM says very little about reinstalling the Spacer Ring. It does mention 2 types of MB sealer to use on the outside lip of the Seal. They are probably nothing exotic. I think I read somewhere that Blue RTV is a good substitute.


While we are at it, what would you recommend using on the Water Pump Gasket, to be used sparingly. Permatex Aviation Form-A-Gasket #3?

Originally Posted by 97 SL320

For this type of setup in general, a bit of Permatex Aviation Sealer ( Not Gasket Shellac ) anywhere there is a metal to metal joint that leads from oil to the outside is a good idea. Just be sure to use it sparingly as we don't want it on the sealing lip area. I don't know what the manual suggests.

[Stretch]

The spacer ring can be a right pain in the arse to remove - which is why it usually gets left on.

It ain't cheap either considering it is just a really wide (machined) washer (!)

[mmiller]

$96 List. My cost is $61. It's just money .

Originally Posted by Stretch

The spacer ring can be a right pain in the arse to remove - which is why it usually gets left on.

It ain't cheap either considering it is just a really wide (machined) washer (!)

[Stretch]

Originally Posted by mmiller

$96 List. My cost is $61. It's just money .

If it is just money - send me some.


I probably haven't mentioned it before: But I is just a poor Nigerian orphan prince who's down on his luck...

[mmiller]

Not a problem. I just received an email from the Price of Siam. He will send me 3 million dollars U.S. via Western Union, once I send him my bank information, social security number, driver's license number, and $90.


How much do you need?

Originally Posted by Stretch

If it is just money - send me some.


I probably haven't mentioned it before: But I is just a poor Nigerian orphan prince who's down on his luck...

[97 SL320]

Originally Posted by mmiller

Good tip to know, thanks. The FSM says very little about reinstalling the Spacer Ring. It does mention 2 types of MB sealer to use on the outside lip of the Seal. They are probably nothing exotic. I think I read somewhere that Blue RTV is a good substitute.

You are welcome.

I only use RTV in corners of valve covers / oil pans and not on seals.

If the seal you are installing has a rubber OD, I use a bit of oil as lube since in effect you are installing a o ring. However, MB might be more or less gluing the seal in place to prevent it from vibrating out.

Also when installing, be aware that some parts don't have a bottom lip on the seal bore allowing the seal to be pushed all the way through.

Originally Posted by mmiller

While we are at it, what would you recommend using on the Water Pump Gasket, to be used sparingly. Permatex Aviation Form-A-Gasket #3?

Yep, this is the stuff. It stays somewhat pliable after drying. The gasket shellac in a small brown bottle drys kind of brittle so I tend not to use it. There are also some similar Permatex sealants in a tube that I tend not to use either because they are too thick.

When using the #3 , just a thin coat works fine. Too much acts like grease and the gasket can split / push out. The goal with the sealer is to take care of small seepy leaks as used surfaces tend to get corroded. The gasket is there to take care of large leaks. Many times the factory does not use anything.

[97 SL320]

Originally Posted by mmiller

I just received an email from the Price of Siam.

I just received an e mail from Sam I Am. Apparently he is using an Apple Newton. Egg Freckles?