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  #1  
Old 11-09-2001, 01:24 PM
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Front Main OIl Seal Trouble

Hey guys, here's a good one: Have noticed a small oil leak at the front of my 85' 300D engine. Has 205k mi. and runs well. Changed the oil pan gasket before and did not help so I presume it's the front main seal. The oil is splattered over some of the accessories (like the AC, luckily not the belts) so I think that the oil seal is leaking onto the balancer and being spread by the speed of its rotation. Oil accumulates on the underside of the oil pan, so I guess that is why I tought it was the pan gasket.

Any ideas or comments and you agree with my assesment? I hate to see oil on my driveway. I guess it's time for an new front seal, or is there another option?

Also, is replacing the seal a DIYer job or should I contract this one to my trusty mechanics (any ideas on what it would cost)? What specialized tools would I need and what's the procedure (as I have learned not to trust Haynes blindly)?

Thanking you all in advance, oh gods of the diesel Mercedes!

Adam

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  #2  
Old 11-09-2001, 02:02 PM
LarryBible
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Wash it thoroughly with hot soapy water at the car wash including underneath, then drive it home raise the car and look for the leak. I will be surprised if the source is the front seal.

If it is, you will need to remove the radiator, belts and harmonic balancer. Be very careful putting the balancer back on. There are two pins instead of a keyway. Crankshafts have been rendered useless by people just sticking the pins roughly in place and then draw everything down with the bolt. Instead, put the balancer in place slightly counterclockwise of the alignment position, then pull it down with the bolt WITHOUT the pins in place. If they line up, put the pins in, if not pull the balancer and try again. If it takes fifty tries, so be it, it's worth it to keep from destroying the crankshaft.

Good luck,
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  #3  
Old 11-09-2001, 04:11 PM
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I agree with Larry, as I have had similar problem on my 1982 240D and it turned out to be a bolt on either the power steering pump or airconditioning compressor bracket that came loose. Unless you run a seal like the one on the front dry, it is unlikely to fail in service. Frequent oil changes and keeping the level within the range on the dipstick will keep the seal lubricated and cooled during normal operation. Run it dry and it will overheat and get scratches and grooves, ultimately leading to failure. Jim

Edit Note: The bolt went into the block and penetrates one of the oil passages. I do not know if this is a tolerance stack up issue or if it is on all the 240D and 300D engines. Jim
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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Last edited by JimSmith; 11-09-2001 at 04:35 PM.
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  #4  
Old 11-09-2001, 04:25 PM
LarryBible
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The only oil leak I've ever had on the front of an engine in a 123 has been the power steering pump.

Good luck,
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  #5  
Old 11-09-2001, 07:19 PM
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There are several things that can leak on the front of the 617 engines:

Large bolt with aluminum washer seal next to the timing pointer (covers a bolt pin for the slide rails, I think).

Several bolts that hold the power steering pump in place -- they go into the oil space and must be sealed with Permatex when installed, or they leak.

Vacuum pump housing at the bottom -- hard to get to this bolt on W115s, easier on W123s.

Font seal.

If the front seal is leaking, it will throw oil up the side of the motor in the direction of rotation. Makes a huge mess.

Larry's directions are excellent -- I will only add that the seal actually runs on a spacer, about 6 mm thick -- if the seal is leaking, pull this and reverse it, and if it has a worn spot on both sides, replace it.

Unfortunately, a special puller is required most times to get the spacer out -- it gets rather stuck with time, and there isn't much room. It's fairly important to have a fresh seal surface, as the old rough one will eat another seal in short order.

There is also an installation tool that is very handy for getting the seal over the spacer without cutting the sealing lip. Probably not worth purchase, but if you can borrow one, it will make the job easier.

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #6  
Old 11-10-2001, 01:37 PM
LarryBible
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Peter,

Now you have me worried. I don't specifically remember a spacer. I just oiled the sealin surfaced and slipped on the end of the crank, layed the crank, then carefully put on the pan, ensuring that the seal was in proper position. Maybe there was a ring on the crankshaft when I slipped on the seal, I just don't remember.

At least the good news is that it's not leaking yet.

Have a great day,
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  #7  
Old 11-10-2001, 04:37 PM
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Larry:

It goes in front of the chain sproket. Usually stuck tight enough you think it is part of the crank unless you take the sproket off and the spacer falls off.

It was missing on the short block my brother bought, so he didn't put a new one in. The Haynes 123 series manual doesn't show it (it does show a Chevy piston, though!). Chilton shows it in the exploded diagrams, but doesn't label it (and has pictures of a Chevy 350 head!)

Believe me, if you left yours out, you will know -- the seal will just touch the end of the crank where the spacer fits -- you will lose about a quart per hundred miles and there will be oil EVERYWHERE. If the seal is actually sitting on something, the spacer is in there. The pulleys will be about a quarter inch off, too.

If not, I'd get one and put it in -- I hate oil leaks....!

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #8  
Old 11-10-2001, 07:34 PM
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As a side note, after the engine installation in my SD last week, I had a very small oil leak somewhere in the front. I traced it down today and after spraying with brake clean and careful watching, traced it to the front seal. I pulled it off and I am embarrased to say it looks like I did not install it properly. When I did the rebuild, I assembled everything including the pan, then hammered the seal in place. Looks like the seal did not fully go over the spacer and torn a bit. Looks like an installation tool would be helpful, I envision a long thin piece of cylindrical metal or plastic that the seal can slip over. Of course I cannot locate a seal this late in the day and now have a dead car for the next three days taking up a slot in my garage. Other than that the rebuild was very successful. Please note I screwed this up with the engine out of the car, so it might be very possible to have trouble getting it right while the engine is installed...just go slow and careful. If the seal does not go tight to block it isn't right.
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  #9  
Old 11-10-2001, 08:01 PM
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Buy another spacer and you can use that as an assembly tool. Slip the new seal on the new spacer then slide the new spacer with seal onto the end of the crankshaft. Now push the new spacer tight against the original spacer and just slide the seal onto the original spacer and press in place. If you replaced the original spacer you can use it as the second spacer and follow directions above. ~~~~~~~~~~~~~~~~~~PEH~~~~~~~~~~~~~~~~~
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  #10  
Old 11-11-2001, 01:17 PM
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THANKS

I guess this sounds like a job for the pros. I will have my motor steam washed and then try to observe the leak (though I should note that the engine is pretty soiled at the moment, all over; especially in the front). I sincerely hope it isn't the main seal, because the engine had never been run dry, or overheated. The leak just seemed to develop over the last year or so. Also, it will only leak a few drops, and only after it's been driven for a while (so I guess it's leaking from the pressurised end). Anyway, the motor could use a good cleaning, and then I let you know.

Otherwise, replacing the seal sounds like a job I should leave to my trusty MB garage friends to handle. I sounds like you need all sorts of special tools, and a warranty would also be nice. I hate to screw up and have to do it again (as it's my daily) considering everything I'd have to remove and replace. But thanks for the advice, as you all know how very much help you are to me and others.

Thank you.
Adam
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  #11  
Old 11-11-2001, 06:57 PM
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ATLD: The belts on that engine are hard to replace so if they are worn, you might change them when the front seal is being done because there won't be any extra labor. ~~~~~~PEH~~~~~~
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  #12  
Old 11-11-2001, 10:12 PM
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ALTD:

Sounds exactly like a front main seal -- when it gets old and hard, grit gets under the seal, wears a groove in the spacer, and suddenly there is oil on everything. Usually only an annoyance, unlike a Chevy 350, where the chain cuts through the sheetmetal front cover when the timing gears (nylon!) wear -- can run the engine out of oil unexpectedly in short order.

Good luck!

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #13  
Old 11-12-2001, 10:48 AM
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Belts are new (1 year old) and did them myself. No sweat, but I will probably take the car to my mechanic and have them replace the seal for me (as I have none of the specialty tools required, and don't plan on having to do this again). What should it cost; so I know if I'm being cheated, I will supply the parts for the shop(don't trust them, even if I specify OE) so I would like to know the approx hours (ave.) for the job.

But first the engine will be steam washed, just so I'm sure that it's not something simple. Also, should the "spacer" be replaced with the oil seal, and does the oil pan have to be removed for this procedure?

Adam
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  #14  
Old 11-12-2001, 11:19 AM
LarryBible
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Make SURE you are using a Tech who is familiar with the pinned, rather than keyed harmonic balancer. If they are not familiar with the proper way to install it, they can DESTROY the front of your crankshaft.

Good luck,
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  #15  
Old 11-12-2001, 11:46 AM
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Oil Leak

Where would this type of leak be located. I have a leak around my oil pan, but it seems to be above it. I can look down over the engine and see no oil, but underneath it is around the oil pan area.

Is that where this seal is located, or should I just change the oil pan gasket?

Blair

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