300sd rolled bearing (I think) - PeachParts Mercedes-Benz Forum

Biotour · #1 06-11-2009, 09:26 PM

Well let me start off by giving a brief history of the car. I bought it about 3 months ago and it was running fine, I didn't notice any major oil leaks and was able to drive it around with no problems. Then I decided to do a valve job to improve performance, and inadvertently introduced air into the fuel lines. I thought I had made the valves too loose so I tightened them back up and realized it was just air. Oops. Well I went for a 400 mile drive and ended up not tightening the valve cover enough so it leaked some oil. I got that fixed but I still had to redo the valve job so I did it when I reached my destination. After the valve job was finally done I started it up, drove about 100 yards, and a loud distinct rod knock appeared. I had topped off the oil before the valve job, and just let the engine idle for about 20 min after which the knock went away. Then I had it happen again a couple weeks later, the dipstick was totally dry. And it was knocking much louder than before. Did an oil change and filter, this time I just drove it around town for about an hour before the knock went away. And I've been checking the oil level every 20 miles or so since. So last weekend I was driving 10 miles back to my house when it started knocking really loud on the freeway. Pulled over, oil level was at the low mark. Pressure was bouncing between .5 and 1 at idle. Drove to a buddy's house really slow who just happened to live nearby. Topped off the oil, let it idle, it sounded much worse and ended up stalling. I haven't started it since. It definitely sounded like grinding metal. I want to pull the pan and check for bearing pieces, is it possible without removing the engine? Is it worth rebuilding or do I look for new engines? Or just another car? I live in long beach ca so if anyone wants to help me out that'd be awesome. It's an 81 300sd, 263k

video here:
http://www.youtube.com/watch?v=G2UXqc3aofM

kerry · #2 06-11-2009, 10:18 PM

It's a goner.

pawoSD · #3 06-11-2009, 10:20 PM

Yikes....that doesn't sound good at all! The lower pan is easily removed on the 617, just remove the allen bolts all the way around the pan....there's a bunch of them.

kerry · #4 06-11-2009, 10:24 PM

What are you going to learn by dropping the pan? It's got a bad rod bearing. The fact that it was run low on oil means that other parts of the engine were probably harmed also. Yank that engine and replace it.

Biotour · #5 06-12-2009, 12:26 PM

i found an 85 300D turbo (not SD) for $500 with bad rear axles and the body isnt in the best shape. will i be able to swap this engine and transmission in? id rather do them both since they come out together. i'm just not sure of the differences between the years, i wish there was a chart somewhere that had all the differences.

lietuviai · #6 06-12-2009, 12:52 PM

The 85 could be a trap oxidizider model and since it's a 300D the oil pressure sender and speedometer are mechanical. Those items are electric on the SD. Not a big deal. The mods needed to adapt the intake and exhaust are a little more involved but not a big deal.
You might have all the parts you need for the swap.

bigblockchev · #7 06-12-2009, 01:24 PM

I have seen 617s run out of oil and not screw up the crank. Pull the pan check the rod and main bearings and then proceed on the basis of what you have found. The engine I have experience with lost it's oil pump drive shaft when the drive gear moved up due to a loose thrust bolt. We replaced several bearings cleaned up the pan and the engine was still running 10 years later. Dont jump to conclusions before you have seen what is inside. Cheers Dan

kerry · #8 06-12-2009, 01:42 PM

Quote:

Originally Posted by bigblockchev

I have seen 617s run out of oil and not screw up the crank. Pull the pan check the rod and main bearings and then proceed on the basis of what you have found. The engine I have experience with lost it's oil pump drive shaft when the drive gear moved up due to a loose thrust bolt. We replaced several bearings cleaned up the pan and the engine was still running 10 years later. Dont jump to conclusions before you have seen what is inside. Cheers Dan

Have you listened to the YouTube video?

moon161 · #9 06-12-2009, 01:54 PM

|8-||

rrgrassi · #10 06-12-2009, 03:03 PM

With the oil pressure fluctuating at idle indicates bad main bearings as well.

I say do a R&R and swap out the engines. Pull the rear diff on the '85 as well and install on the SD. You will need the axle shims from the '85.

Biotour · #11 06-12-2009, 06:55 PM

what improvement would i get from the 85 rear diff?

Biotour · #12 06-13-2009, 03:58 AM

And will the transmssion swap over or will I need to make some modifications?I'm leaning a little towards just keeping the 85 and fixing the bad cv joint, and dealing with the ratty interior.. And just selling the 81 sd. What do you guys think? How difficult is this swap going to be? I don't have a garage and will probably attempt to do it in a parking lot somewhere this weekend.

Biotour · #13 06-13-2009, 07:17 PM

Tell you what.. If one of you guys wants to do the work for me you can have the parts car and the old engine for free. I just have no time to do this work myself.

pawoSD · #14 06-14-2009, 12:06 AM

Quote:

Originally Posted by Biotour

And will the transmssion swap over or will I need to make some modifications?I'm leaning a little towards just keeping the 85 and fixing the bad cv joint, and dealing with the ratty interior.. And just selling the 81 sd. What do you guys think? How difficult is this swap going to be? I don't have a garage and will probably attempt to do it in a parking lot somewhere this weekend.

Fixing up the interior and swapping the axles would be a LOT less work than a full swap.....but then you'd still only have a W123....and not an awesome W126.

pawoSD · #15 06-14-2009, 12:08 AM

Quote:

Originally Posted by Biotour

what improvement would i get from the 85 rear diff?

They are 2.88:1 ratio vs the 3.07:1 found on the pre-85's....physically the same, internally different. Overall its a minor change, it reduces freeway RPM's by about 200 (lower) or so....so a bit better mileage and a little quieter.