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Old 10-27-2005, 11:30 PM
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dmorrison dmorrison is offline
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Join Date: Dec 2002
Location: Colleyville, Texas
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Replacing the 300TD front crankshaft seal and other front of block oil leaks

Well I've been busy and did not take pictures for this job, but here are my thoughts on it.

I replaced all the following on the 82 300TD due to an oil leak from the front of the engine. I assume it was the front crank seal. But while I was there I replace all the potential oil leak gaskets and seals on the front of the block.
and some other items recommended by the mechanic at the dealer, who I trust.

1. Front crank seal and centering bushing.
2. Front crank support sealant.
3. Vacuum pump gasket
4. Hydraulic pump gasket.
5. Water pump, only because it was leaking.
6. Timing chain rail support crush washer
7. Sealant on bolt holding the TDC sensor bracket, which is actually an access for a oil check valve.

1. Front crank seal. I bought the Sir tool seal press, M0061, to press in the seal. I would not want to press in the seal any other way. It could probably be done but if it is not perfectly straight you could have a leak soon. The seal I got online was different, in looks, then the one I removed. But it is sealing fine. The centering bushing may need a tool to remove if it is "difficult". It is Sir Tool M0033. At 183$ I figured I would wait to see if I needed it. I did not. The spacer spun freely and I was able to just pull it out with my fingers. Installing it does not require a tool. The large bolt presses it into position.
After doing all of this you need to change the oil. Cleaning the seal area caused cleaner and debris to fall into the crankcase.

2. Front crank seal support. The turbo ( and maybe non-turbo) engines have a support on top of the crank that is bolted to the block. Mercedes uses a sealant on this ( a Mercedes sealant that was $12 a tube. I used it but the service adviser I use said I could use RTV blue) Once unbolted it just lifts off. BUT it requires an aligning tool to install. Sir tool does not make this (maybe you can get extremely close and be OK ) the shop Foreman was kind enough to loan me the tool over the evening to do the installation. Its easy to install. apply sealant and then bolt in. allow the Mercedes sealant to dry 24 hours prior to running the engine.

3. Vacuum pump gasket. Removing the pump. You don't know where the cam is so you may have pressure on the unit while unbolting it. This may lead to a stripped bolt Allen insert section, due to the pressure on it. I did this. My recommendations, remove all bolts, but two bolts that are opposite to each other. Then hold pressure on the front of the vacuum pump while pushing the pump against the block. Unscrew the two remaining bolts and then release the pump. Also make sure the Allen bolt heads are very clean.
Clean the surfaces and I used High Tack to install the gasket and then bolt in the vacuum pump.

4. Hydraulic pump. Unbolt the 4 Allen bolts and clean the mating surfaces. Leave the hoses connected and just place it aside. New gasket, again used High Tack and installed it. Be careful not to lose the attachment ring that guides to drive shaft to the engine shaft.

5. Water pump. It is not necessary to remove this for the oil leaks. But a couple of notes. DON'T buy it a Oreilly's. It was brand new. I installed it and the front hub shaft is larger Than the original Mercedes unit, so the pulley would not fit. The Mercedes unit comes with the proper mounting bolts WITH sealant, and a gasket.

6 & 7. Between the vacuum pump and crankshaft seal is a TDC sensor. The bracket holding the sensor is held on by a large bolt that is actually an access hole to knock out oil check valves. This large bolt has sealant on it. I use the Mercedes sealant. Under the bracket is the chain rail holding bolt. This bolt uses a crush washer. The crush washer is like a oil pan drain plug washer, but much larger. It can leak. Also the bolts can get loose with age. Install new sealant on the one and a new crush washer on the other. NOTE- nowhere are the torques for these bolts listed. I looked everywhere and asked at the dealer. Just snug them down, there pretty big.

Wait 24 hours for the sealant to cure, change the oil and your set.

A couple of other notes.

The radiator must come out to use a puller on the vibration damper. Fan and clutch must be removed. Power steering pump unbolted and set aside. All belts removed which means loosening the alternator, power steering pump and AC compressor. All pulleys removed.
When removing the vibration damper make sure you mark the damper position in relationship to the crank shaft. This does not require tremendous precision. the vibration damper goes on one way OR 180 Degrees out. The damper has two round positioning units, called "fitted pins" in the manual, to prevent it from rotating. So it only goes in either one way or 180 degrees out. To install the vibration damper I removed the 2 small fitted pins and placed the damper on the shaft as accurately as I could. Use a rubber dead blow hammer to install it. Then drove the cylinders into position with a hammer. The cylinders may flake off some material while doing this. I was informed that this is OK and normal.
Torquing the crankshaft front bolt. It calls for 270-330 Nm (200-243 Ft Lb)for the torque. I use the method recommended in the manual. Place a large (1 inch by 12 inch ) brass punch, that's what I used, between the damper cut out and the upper oil pan section. My wife was able to hold it while I torqued the bolt. Where do you find such women

So far no leaks.

The front seal is probably the actual leak source, but its hard to see. I was searching for a leak for a while. I have replace the following

The Turbo drain seals,

617 Turbo oil return line. Replacing seals

And the oil separator seals and check valve.

617 engine, replacing the oil separator check valve in the upper oil pan.

Hope the rear seal holds on for a while.

1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car

Last edited by dmorrison; 07-12-2006 at 04:34 AM.
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