350sd loud knock/ping, lots of clattering poor vacuum
 

Its a 1991 MB 350sd turbo diesel. Has around 160K miles. Ever since the car was bought, there has been a loud ticking noise, and the spring/tensioner spring always jumped.


Recently on a highway cruise, problems slowly progressed. First it started making louder than usual ticking noise. The brakes seemed like there wasnt much vacuum on them. It was also surging. This was a week ago.

Now sitting in the driveway, usually when you turn the key on, the glow plug light will shine a few moments later go off then you know its ready to start, well now the glow plug light wont shine and I believe they dont heat up either. Once you start its louder than expected. Loud ticking or clanking sound from the injection pump area. When idling, it surges. To kinda describe it, its like mmmmmmm *clack(motor jumps)* mmmmmmm *clack(motor jumps) etc etc... happens when you try to rev it also... To scared to let it run long enough to entirely warm up. The brakes were weird feeling also.

Any suggestions?

Loud knock? Hmmm, what's your oil consumption rate?

it sounds like your serpentine belt tensioner bearing is going bad. i just replaced the one on my 90 350sdl. i also had to replace the tensioner shock prematurely because it was going bad and i didnt realize it.

i dont see any reason for the brakes to be affected though.

nor the glow plugs.

good luck

tom w

Already replaced the tensioner and shock spring thing pulley and all. Less than 2000 miles ago. Oil consumption is pretty high. The stop lever leaks, but much thanks to the write up, it will be fixed once its running correctly.

The brakes dont change when the car is on or off. Like there is no vacuum to the booster.

When you turn the ignition switch off, it still "diesels". It still runs.

The motor has one cylinder that seems to ping real hard every 4 rotations, im assuming.

Any help?

Thanks, Drew.

Loud noise, no booster function, UM, vaccume pump?
 

I don't know your vehicle really, but, the VP can do what you describe, and FWIU, it can take down a motor.
anybody wanna chime in with me?
John

The early style vac pumps (no rivets on the cover) like to fall apart and toss bearings into the motor. I caught mine just before it happened, it was knocking badly! My car sat for around three months until I scored an updated pump.

That 350SD has the lovely 3.5L that usually takes a poop, it's about at the mileage too when they fall apart. :(

Not sure when the updated vac pump came out, hopefully this isn't the issue with your motor. I've seen plenty of high mile 603s with the original vac pump... 300K or more.

The Dieseling (is it called gasoline-ing in a Diesel?) is probably caused by insufficient vacuum to engage the stop mechanism in the IP. It should shut off promptly if you give the stop lever a good firm push. Probably worth confirming to discount IP problems.

When you get comfortable to have it idle, loosen each injector line one at a time to isolate the noisy cylinder. You can move injectors around to see if it's the injector or the cylinder. If it's the cylinder then I'd start with the delivery valve seals.

Sixto

I would vote for the vacuum pump, the loss of power brakes, loss of vacuum shut-off, and the noise are too much of a coincidence. Can you tell if the noise is coming from the vacuum pump?

I'd pull and inspect the vac pump before starting that car again. If it is the vac pump you are playing with fire!:eek:

ditto craig, ditto hattie.

tom w

If it's the old style pump, don't put it back on the engine.

If it looks like the bearing has come apart, pull the oil pan side cover and sweep with a magnet to get the bits and pieces out. Someone I know in this area just lost a 603 to a diligent oil pump that sucked a vacuum pump ball through the oil pump mesh. Can't figure it out but that's the evidence.

Sixto