If you are feeling vibrations in the seat and not in the steering wheel, it could be back tires out of balance.

Take the car to Silver Star Motors in Monterey Park, Ca. Speak to the owner Robert Wong - very honest and fair.

I've read some of the driveshaft DIY threads and if the u-joint is the problem, that looks to be the most pain in the ass part. Since I'll be taking the car to another mechanic for a second opinion, I might as well see what they say, then request it's put on a lift and then see for myself.

If oil cooler lines are becoming harder and hard to find, and the available ones are ****-tier quality, I'll definitely be going the mod route (modding the the oil cooler to accept custom fittings, mod the metal part of the lines to accept my custom tubes, etc.). I mean, unless I'm mistaken, the oil cooler lines just take the oil from point a to point b under known pressures. Given today's material science and available hardware I'm sure I can fabricate a long term solution. This sort of thing is fun for me - had to do it a lot with computer water cooling solutions.

Will check all mounts for premature wear; something seems up if one only lasts for 2 years or so.

As for suspensions symptoms... Front tires seem to be worn more than the rear, car has an alignment issue where it pulls to the right slightly, something is noisy in the back over bumps like something is loose... Sometimes turning left produces some resonance (no vibration, just an odd, dull sound)... That's about it. Otherwise it feels great, very smooth and solid.

The steering wheel is totally solid. No vibration whatsoever. The current tires on the car look a bit old and likely need to be rotated, if not replaced. I've been meaning to have them rotated and balanced. I don't think it's the tires however since switching into neutral kills all vibration. Feels like driveline vibration since the neutral thing, and it being speed / throttle dependent. The driveshaft being fiddled with previously and improperly reassembled / installed seems probable, maybe something with the tranny yoke or something.

Thank you for the recommendation! I have a small laundry list of things to do / check out myself, I'll then take it to another local specialist for a second opinion, and depending on how that goes will take it to silver star motors. Hell, Robert Wong is great, it'd be fun to take it to him anyway to see what he says.

You have to be careful on the oil cooler lines, the heat of the oil is 275F.....Not many hoses are capable of handling that heat

I haven't researched any of this yet, but why not just use full-metal tubing the entire way? The only part of my oil cooler that is leaking oil is hose-on-metal... All metal-on-metal contact points are bone dry. It's not like the hoses need to move around or be flexible for any reason, and the pneumatic pressure can't be a factor.

Or if that can't be done for some reason, at least engineering the POS to make the rubber hoses more user serviceable. Perhaps id have to venture into the industrial market to find some hoses capable of handling ~300f fluid. Maybe I'm just overly optimistic, but if existing hoses fail at around 2 years, that seems easy to outperform. If you drive 2 hrs a day avg for 2 years, that's roughly 1500 hrs operating time. Someone can slap me if there aren't industrial hoses capable of withstanding 300f for 1500 hrs before significantly degrading.

The hose have to flex with the engine.....an all metal to metal fittings won't work....I just used hose and clamps on mine..

Oil Cooler Line Rubber Replacement..... - Mercedes-Benz Forum

Here's a howto for a proven solution using standard aircraft quality components that are surprisingly cost effective - http://www.peachparts.com/shopforum/diesel-discussion/354554-converting-oil-cooler-lines-stainless-braided-hose.html

If flexibility is needed, self-pivoting nozzles could solve that.

There are also flexible metal hoses that handle well over 300f.

But all that gets a bit complicated and perhaps a somewhat large initial investment... From the looks of it you could just replace the hoses without removing anything else.

Ah, mach4, I read a post of yours earlier regarding this stuff. It's what got me started on this idea in the first place.

What's that old phrase... An ounce of prevention is worth a pound of the cure!

I like the idea of reusable fittings, but when it comes to servicing the spent hoses, it doesn't look all too more convenient that doing it like cooljay's method of hoses and clamps - either unclamp and replace hoses, or unscrew and replace hoses. Unless I'm missing something it's more or less the same.

Well, aside from hose servicing convenience, there's one big question... Does the stainless steel braided hose significantly outlast traditional hoses?

Also wanted to say thank you for everyone's responses - they've all been very helpful.

My originals lasted 27 years. The replacements are holding after four. I'd tell you what brand I used, but I don't remember.

Which re-enforces my thought that if ~30 years ago they could produce quality hoses, there's no reason today replacement hoses can't be had (unless those original hoses use now-illegal materials/chemicals).

Diesel purge is mostly naphtha (zippo lighter fluid).

Do a complete purge, (as opposed to just adding to the tank) I use the set up in the screenshot. You burn the stuff straight, two cans. Afterward, replace the two under hood filters.

Not sure why your mechanic frowns on testing the injectors, how else will you know if they are doing their job? If you get a bad spray pattern, new nozzles will fix that. These cars are 30 years old. Items wear out.

Yeah, have a look yourself at the driveshaft, inspect the flex discs too.

Numerous items have been replaced, good.

Your list of parts replaced do seem to be redundant, perhaps throwing money at an unknown problem. Or perhaps, as you speculate, garbage parts.

Injector lines, I'm going to assume the jumper lines.

I have to wonder about the machined rotors, were they warped, do you know? Otherwise, there is a wear limit.

I bought my first MB from a flipper that was used to BMWs, he said this is his first and last Mercedes. The left front wheel bearing was too tight, I believe, a month and $1100.00 later I figured that out.

That work was done by an inde MB mechanic. Probably saw me coming. Not gonna happen again.

I hear ya, but part producers (MB [or anyone else, for that matter] can't make enough profit producing high quality parts for 30+ year old cars) today save money by using lean manufacturing technics. Not a large enough market. The Chinese buy (steal?) then make the parts from blue prints from sub par materials.

I doubt the materials are the issue.

Just had driveshaft (240D) rebuilt- ujoint repalced, center support bearing replaced ( I supplied), DS balanced, and shortened 4 inches- under $200.00

I had my DL redone about 27 months and 33K miles ago. Cost was $300.
They replaced the 2 end Bushings< center Support and Bearing, and the U-Joint with a grease able one.

I was having a rumble in the drive train that had me stumped, checked everything front to rear. Ended up being the rubber tore in the Center Support big time. The original German one had been on there for 332K miles. I guess they used a lesser quality off shore Support.

Not all drive Line shops can or will do the MB and BMW staked in U-Joints.
The notchy feel in the joint is common on every DL I have taken out at PNP and my own. I had mine replaced because of loosness in the joint.

Ordered a new Febi, and hand a made in China sticker along with the Trans mount I replaced. Interesting to see how long this one lasts. Next time it will be from the dealer.

The IP should last the life of the engine. I see all too many time the IP is the first thing to zero in on and replace when there is a problem.

The Injectors should be checked every 100k miles and the nozzel`s replaced if need be.

The original Oil Cooler lines seem to have been on the majority of these cars 25 - 30+ years. that doesn`t mean the rubber hoses are as plyable as the were when they left the factory, and probably should have been replaced much sooner. They should have been made as MACH4 linked to in his thread from the factory. Then it would have been much easier and quicker to replace. I had the one`s on our 85 made the similar way.

If you see a weaping of oil around the fittings, and seem it is the lower lose on the cooler that weaps, replace it before you loose your engine oil.
It does seem the older hoses were made with a better grade of rubber than what is available today.

The price that mechanic is charging in crazy, he saw you coming.


Charlie