Hey guys,
I'm a newbie. Bought my first Mercedes 300D diesel yesterday. It's a 1992 2.5 turbo with a few issues but I think the price was right.
The car tossed its old serpentine belt and the old owner cracked the tensioner off right where the pulley bolt attaches. I am attempting to remove the old tensioner to grab a part number and replace it but the thing does not want to come off. I removed everything from it including the big retaining circlip but it still doesn't budge.
Am I missing something here? I tried a couple of pry bars to pop it loose but I don't want to create any new problems (like a cracked timing chain cover) so I'm tentative about applying any real pressure. Is it common for these bearings to get rusted on the shaft that they sit on? Is a special tool or puller required normally for removal?
Any info is appreciated.

There is a bolt through the tensioner arm into the front cover. The bolt takes a 12mm hex bit. It's torqued to about 70Nm or the same as an injector.

Sixto
87 300D

Thank you sixto,
I did look at the bolt holding the tensioner but it didn't look like an allen bolt. It might be filled with some grime giving it a circular look so I will get the 12mm allen tomorrow (mine stop at 10mm...grrr). I see alot of people asking if sealant is necessary when replacing this bolt...why would it need sealant? Isn't it just connected to a timing chain cover?



I noticed another strange thing today. It looks as if the power steering pump was recently replaced with a used one...a slightly different one at that. I'm putting 2 and 2 together and coming up with the conclusion that possibly the old w124 PS pump seized and broke the serpentine belt and tensioner. When I bought the car, the PS lines were just hanging loose. Today I realized that the lines do not thread into the pump because the pipe thread nuts are too big. I'm wondering if the last owner stuck a used pump from an older w123. Anyone know if they used a smaller thread size on the older MB power steering pumps?



The last owner spoke very poor english so I was pretty much on my own to figure out what's going on.

I know it doesn't really answer your question, but I don't believe that the 123 PS pump would work, they all ran V-belts and I don't think the whole assembly would line up.

Possibly from a 201 or other, but if the lines don't thread in, how do they hold (significant) pressure?

__________________

Gone to the dark side

- Jeff

How do they hold pressure? They don't...lol. They don't even connect. Sorry, I guess I wasn't clear on that. It never even dawned on me to attempt to thread them on as I was buying the car. I just assumed it was the same power steering pump that had always been in the car and that the seller only disconnected the lines in his attempt to change the tensioner and or serpentine belt.


Like I mentioned earlier, there was a huge communication barrier between me and the seller. We all know what it's like when a foreigner sells a car with issues, all of a sudden they no speaka da english. I towed it home. Today was the first time I attempted to connect the PS lines so that water wouldn't get in there while degreasing the motor. The pulley is in the trunk so I'll check if it lines up with the other pulleys tomorrow. If so, I guess I'll just change out the connector end nuts on the PS lines. Probably alot cheaper than replacing the PS pump. My bet is that it came off a w123 because he had a parts car in his driveway.

If you saw a circlip there must not be a cap over the bolt. There's a cap over the bolt through the pulley also.

The hole for the bolt goes through to the timing chain cavity. That's why you need sealant.

Sixto
87 300D

I've just recently spent a week or so trying to replace the PS pump on my W124 (euro) car. It would appear that W124 cars were fitted with one of two pumps. One has a part number starting with 124 and the other 210. The 124 pump is rated at 110 bar and has slightly smaller connectors than the 210 pump that is rated at 90 bar. I'm guessing the 210 pump was fitted to later cars.

Here in the UK the 124 pump my car was fitted with is very hard to find. In the end I got a 210 pump from a scrapyard and also picked up the high pressure hose and the return connector. The return connector is attached to a rubber hose with a clamp, so can be swapped easily. The high pressure hose connectors to some hard lines under the block, and the can be unscrewed and changed there. Steering is a little bit more difficult now with the lower pressure but I dont care.

If the pump on there now has a ribbed pulley, it is probably the 'other' W124 pump, so you will need either the correct one or the different lines. If it has a V-belt pulley its probably from the W123.

I think you are correct Tombance. I just got off the phone with a guy selling Mercedes parts on craigslist and he was confused that my car was a 5 cyl diesel. He claims that they were all 6cyl diesels in the US and said that I had a "bastard" euro motor (his words) that was not even worth diagnosing my engine smoking issue. Can anyone confirm this difference in a euro and US model 2.5 tubo diesel? I did notice that the emissions sticker said "non catalyst".

I guess this might also explain the difference in the power steering pumps. I had thought about doing exactly what you said...changing the high pressure hose and the fitting on the return hose to make it fit. The ribbed pulley does line up well. When you say it is "harder to steer", is it very noticeable? What type of car did you take the PS pressure line from? By chance would you have that PS pump part number starting with 124? I have no old original pump to get it from because he didn't include it with the car.

sixto...my plastic caps were missing when I bought the car but I did see and remove the c-clip thinking that the tensioner was going to pop right off afterward. Now I know better thanks to you guys.

Blan:

The 124 300D in the US had the 6cylinder in 1987, and the 5cylinder in '90-'93.

Whomever you talked to is an idiot.

__________________

Gone to the dark side

- Jeff

I took it and the lines from a 1992 Euro 300D (N/A OM603) and my car is a 1991 250D (N/A OM602). I'm not sure if there was a date threshold for the swapover or not. As far as I know none of the 1986-1993 diesel W124 cars here had any emissions equipment. Mine doesnt have EGR or a catalyst, just a straight manifold. I cant see how that makes our cars 'bastards', seems like they would be far easier to diagnose to me.

The pump I took off is numbered 124 460 02 80 and I replaced it with part number A210 466 26 01. Here are some pictures, the new pump first and then the old one with the parts attached that I had to swap:









Steering difference was only noticeable when I first started it up after the swap, but I'm used to it now and its not hard at all, still a lot of assist there. I'm guessing this is the way it came from the factory with this pump as the steering boxes werent different.

Thanks for the guidance guys!

I am here as I am a fool that replaced tensioner arm without sealant. There is a slight oil leak from the center bolt now. However as I checked while changing the hole for the bolt doesnt seem to go through anything.

Would loctite 243 works instead of omnifit 100M as specified in the manual? I could not find omnifit100

I've never used sealant on this bolt, and never had a leakage problem. I suppose you could wrap some plumbers tape around it. Thread locker? Absolutely not. You'll be doing this job again if you hold onto the car, and it will need to come off.

You realize this thread is 12 years old? With that said no sealant is needed on the bolt.

You torqued it’s to 70Nm or whatever spec is and oil leaked out?

IIRC there the FSM calls for sealant like you said.

Sixto
98 E320 wagon 197K miles