Hello,
Thank you all for your help, this forum is a godsend. I recently purchased an 85' 300TD wagon with 285k on the clock. I had to make a hasty decision to buy the car because the guy was leaving the next day. After test driving, I was sure it was an injector nailing beacuse the car had great power, blows no smoke, and had great oil pressure. I was surely wrong! After removing the fuel lines one by one (no change) I removed the injectors and glow plugs (prechambers intact) Next I removed the vacuum pump. I did notice a small scarring on the ramp the piston rides on (see pic) but all the bearings in the pump are intact. I did notice a random part hanging out under the hood and I kept it just in case(I didn't even know if it was a car part) turns out it was one of those valve things in the vacuum pump but it's not missing any. This would lead me to believe the pump had previously failed. The car had good vacuum no issues that I know of. How hard is the spring supposed to be on the VP? I cant budge that damn thing. I brought the car to a Mercedes specialist and he thought it was something(a nut or bolt) lodged in the #3 cylinder and the only way to find out would be to pull the head. $1500 to maybe, maybe NOT find the problem! Needless to say, that didn't happen. I pulled off the bottom oil pan and it was suprisingly clean just 2 tiny metal shavings and a rubber grommet or O-ring (any idea where the rubber came from??) the screen was clean but the rubber pickup boot had a tear(see pic) I'm assuming the oil level goes above this right? So that's where I'm at now, stuck with no "smoking gun". I have read Konstans thread and believe we have a very similar problem but I don't have a garage unfortunately, or the time to pulll my engine. Any suggestions are hugely appreciated. Thanks-Art

Video of the sound with air cleaner removed. FYI-The noise does not change whether it's hot or cold / idle or high rpm's.
http://www.youtube.com/watch?v=GDE9QITjteg

Attached Thumbnails

     

Welcome to mercedesshop.....

'Rubber' is the oil pump pick up bumper. Goes on the end of the pick-up tube bell and should rest against the bottom of the oil pan.

Without it, the oil level needs to be higher to prevent air being sucked into the pump on cornering or braking.

The VP ramp is worn and will take out the ball bearing roller on the VP arm.
The roller already looks brinnelled.(?)

The return spring is strong and will need a lot of pressure applied to push it in.
Vac' signal should read 21 to 23 inches after a minute or two running.

Did you release each injector line one by one while the engine was running to see if the knock stopped?

Listening to your Video it sounds like valve train..very tinny. Remove the valve cover yet ?

I put many, many miles on a motor that was sounding similar to that. I would guestimate the noise is either a rob bearing or a main bearing. Go ahead and adjust your valves, do a diesel purge, etc. www.dieselgiant.com is a great resource.

__________________
Regards,
Ian White

1995 E300 Diesel w124 OM606
2014 E550 w212 M278 biturbo

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)

Thanks guys,
I did indeed pull the fuel lined one by one and there was no change. As far as the pickup boot, I was referring to the o-ring or grommet in the oil pan. The pickup boot is torn but is not missing any rubber. I noticed on the return tube it's just a straight piece of metal no rubber on it(is there supposed to be?) I finally got the vac pump to budge, just needed more leverage.
As far as the VP ramp, anyone know where I can get one? Or can I file this one down? As far as the brinnelled roller (thanks for adding to my vocabulary) I think it was just my fingerprints, looks pretty smooth.

I have taken the valve cover off but have since put it back on because everything seemed ok.? What should I be looking for? Camshaft looked smooth, no wear. According to the bill from his mechanic, a valve adjustment was done a few months ago.

I'm debating putting it all back together, changing the fluids, filters and doing a diesel purge and hoping for the best. If the noise didn't stop from removing the fuel lines, I'm doubting this is fuel related.....however the jacka$$ I bought the car from had it on empty(reserve) when I picked it up but have since filled it up and driven it 20 miles or so. I have found a car 3 hours away with a good engine just in case, I just need to sell my Harley to fund it(tear). Thanks-Art

The 'O' ring is probably the lower half of the grommet for the turbo return tube into the upper side of the oil pan....or part of an old one.


BTW FYI....Make sure the screen for the oil pump pick-up has no holes or gaps. Had a 1987 300SDL here with totaled engine because a steel ball had entered the oil pump at 70 mph and stopped the oil pump dead...the engine seized about two miles later. All because the pick-up screen had a gap big enough to let it in.


Push down on each valve to look for weak/broken valve spring.
The noise does sound like it is half engine speed which indicates valve train....and it does continue as the motor is shut off.

If you rev it to 3000 and shut it off...does the noise still continue as the motor dies ? This test eliminates fuel system related noise.

"The 'O' ring is probably the lower half of the grommet for the turbo return tube into the upper side of the oil pan....or part of an old one."

-Uhh, is that bad?

This noise is definitely mechanical, i'll check the valves but I'm looking at a receipt for a valve adjustment 2 months ago. If the mechanic didn't notice a busted valve doing this....well lets just say he will get a call from me.

Any word on where I can get a Vac pump ramp? I cant find it anywhere.

I'm thinking of buying an 81 300TD, can I just drop the engine in an 85 300TD??
Thanks-Art

I'm thinking of buying an 81 300TD, can I just drop the engine in an 85 300TD??
Thanks-Art

'O' ring MAY be the lower half of the grommet. It seals the return steel line to the oil pan. The end of the oil return line has a non return valve built into it.

VP ? Keep looking, you'll find one.

Does you engine have the Hydraulic Pump on the front of the cylinder head ?
If so, so must the replacement engine.

The '85 will have a sensor in the bell housing...(.iirc that's the only difference ) instead of the crank pulley end to run the later instrument tach..so if installing an '85 where an '83 used to sit you need to change out the bell housing plate. It will all be pretty obvious when you see it.

The pre '85's use the front mounted sensor by the crank damper and a tach Amp on the inner fender.

That's what was done with my 84 TD. You can install the tachometer and tach amp from the 81 into the 85 and add a wire between the tach amp and the tacometer. It's a pretty straight-forward modification.

__________________
1984 300TD

x2. In fact, when I swapped the 84 300D motor into my 81 SD, it had two tach pickups, one on the bellhousing, and the other up near the crank pulley.
OP: Try and find a w123 617 to drop in if you must. There are a couple annoying differences between the w123 and w126 617's of the era.

__________________
Regards,
Ian White

1995 E300 Diesel w124 OM606
2014 E550 w212 M278 biturbo

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)