OM603 Front Crankshaft Seal leaking

I replaced the front crankshaft radial seal on the mighty '87 300SDL, and it leaks much worse than when I started.

The car started out with a slight to moderate oil leak coming from the front of the engine. The way the oil got thrown around the various parts behind the serpentine belt, it looked like it was coming from one of the sealing points on the front of the timing chain cover, rather than from the cover itself. A small leak looked like it was coming from the bottom of the Vacuum pump cover, so I replaced the Vacuum pump cover gasket.

I couldn't identify any other leaks, so I replaced the front crank seal. The manual called for a hub puller, but the hub pulled off in my hand with no problem. The mating surfaces of the hub and crankshaft were smooth, with the exception of a slight groove in the inside of hub, towards the front. It looked like it was designed that way, so I didn't think it was damage, so I didn't think of replacing the hub.

I cleaned the timing chain cover where the seal went, and pushed the seal into place, but didn't use any special tool, other than a large socket which I used to gently tap the seal flush with the timing chain cover. Was this a fatal error?

I coated the seal and hub surfaces with a little white moly assembly lube. The hub slipped over the woodruff key and started on the crankshaft. Since the bolt and washers securing the hub seemed to exert an even pressure on the hub, I pressed it in by tightening the bolt until the hub was set. Wrong?

I didn't have a torque wrench, so I applied about as much pressure tightening the Crank end bolt as it took to get it off, which amounted to pulling with most of my body weight on the end of a 4 foot pipe slid over a large 1/2" drive breaker bar with a 27mm socket on the crank end bolt.

Upon reassembly, there was a severe oil leak from the bottom of the front of the engine, that seems it could only come from the seal. It's bad enough to coat the bottom on the oil pan and leave a tablespoon or two on the floor.

Does anyone have experience with this? Could not using the proper hub installer or over-tightening the Crank end bolt cause this?

many thanks
Bruce S

I did not have a problem with mine at all...in fact it seemed like it could not have been done incorrectly other than having the washers facing the proper way.

How many miles are on the engine? I wound up replacing my hub as well since I had a friend replace the crankshaft seal only a couple years prior.

603 Front Crankshaft Hub and Seal Job - Pics!

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1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000

Thanks much for the reply and the cool pics and description. Unfortunately, I seem to have done exactly what you did, except for replacing the hub. I'm thinking that an old hub and a new seal might be worse than the old hub and the old seal? Like a bearing and its race? Anyway, I faced the washers with the concave side facing the engine. Was that wrong? I remember as I was tightening down the bolt and seating the hub, that near the end I felt something "give" slightly, as though something were slipping or moving into place. Then I torqued the bolt and put everything back together.

thanks
Bruce S

Hi. The groove is probably your problem, the seal won't seal against the groove. You can sleeve the hub; sleeves are available at any industrial supply house, one brand is the Parker Quick Sleeve. They come in various sizesand you buy one for the size you need; they slip over the hub. Good way to go if you can't get a new hub.

Yup. A new hub is less than $100...I did research to find a sleeve but I did not find anything and wound up just getting a new hub.

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1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000

Does this engine benefit from using an installation sleeve like on the 617s to protect the seal?

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1981 300TD 310k miles
1970 280sel 172k miles
1966 230 Fintail 162k miles

"Where are we going? And why am I in this hand basket?"

Thanks, I can't think of anything but the hub either, but the little groove I saw was on the interior of the hub where it contacts the crankshaft. I can't see how any appreciable oil is going to come between the interior of the hub and the crankshaft, so do you mean the groove on the interior is a sign that the outer surface that contacts the seal must be worn as well?

thanks
Bruce S

No, the groove would be where the old seal contacted the hub and wore into it. If the hub is smooth and nick free in the area where the seal contacts, it is most likely OK.

Anytime there is an established wear groove from the seal. At least a surface replacing speed sleeve item should be utilized. Most larger truck service centres will have a atock of them on hand.

Also when changing seals also compare the part numbers on the original and the replacement. I have seen just one small change in the end of a part number like an X added make a problamatic situation.

Mercedes makes an alternative part numbered seal that is designed to ride on a different area in the event that the hub is worn. I looked into this but decided just to get the latest part number hub and seal and be done with it. No leak since!

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1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000

Yes, I heard about that seal, but my local Mercedes dealer hasn't, and the seal they sell looks just like the one I put in, with no offset as described in the manual. I like the idea of sleeving the hub where it contacts the seal, but no matter how thin the seal is, it's still larger than the seal expects, so it would be an experiment.

thanks

I've heard good results with the hub sleeve...

But I too once replaced the vacuum pump seal & I continued to have an oil leak which only got worse. Based on a new vacuum pump seal and oil spray like yours I was certain I needed a new crank seal...well until I actually replaced the old Vacuum Pump (using a steel vs paper gasket) a year later... which cured my theoretical "crank seal leak". I was shocked. Even a MB shop said it was a front main seal leak. I actually had the new seal in hand for the "while I'm there repair" work but ran out of time.

I'd make damn sure your V. Pump Gasket is sealing for certain before tearing into the front seal again. 'Cause it will fool many with the amount of oil and spray pattern that also drips right down through the crank area.

For the second Vacuum Pump seal job I used tacky gasket spray on both sides of the V. Pump gasket & let it dry over night. Cleaned the heck out of all mating surfaces, and very carefully torqued it in a cross pattern sceme.

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1986 300SDL 440,xxx

Good point, I'll recheck. Did use the metal gasket this time. Will report.

thanks
Bruce

86-300sdl.

Turned out to be the Vacuum pump. After I got the radiator, etc. off and could see everything, the new crank seal was just fine, and the bottom two bolts on the Vacuum Pump cover had sheared off. Obviously, I way over-torqued them. "Well, gee, George, there's oil in there, better make them tight, huh?" But no, they only wanted 9- ft-lbs, which felt like WAY too little. But I pulled the protruding bolt shafts out with vice-grips, and reinstalled the cover using the same (new) gasket plus some gasket seal for good measure, and at 10 fit-lbs, it's holding and working perfectly with no leak. Apparently over-tightening the cover bolts didn't ruin the gasket, which was a metal affair with a ridge running down the middle all the way around.

Of course, now I have a nice new untouched Elring front crank seal, if anybody needs one.

SOLVED!

thanks everyone.

Thanks for checking back in! Great to hear.

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1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000