Why would a 240D buzz?

[pj67coll]

So, I test drove a 240D today which was quite good in some respects but one thing I noticed was that it seemed to have quite a "buzz" to it. The engine seemed to be vibrating quit a bit particularly at idle. Even when I turned the idle speed down. Not easy to describe except in relation to my previous 240D manual (this is auto) which was so smooth at idle there were times you would swear the motor wasn't even running except for begin able to hear it. Do any other owners have a clue what I'm talking about? I assume the mounts on this car are all original, or at the very least over a decade old and could stand replacing, but surely they would not cause a high frequency buzz like vibration would they? I'd expect more of a kind of heavier duty shake of the whole vehicle. Only other thing that might have a bearing on it was that the oil pressure seemed quite high to me. By that I mean even when warmed up after a freeway run it was above the 50 percent mark when idling. Maybe like it was idling too fast. Thought I detected a bit of nailing too. Might that have something to do with it? I know these seem like some rather vague questions but I've only direct experience withe one 240D so I have no data set to compare it with.

- Peter.

[uberwasser]

Could be motor mounts. Bad mounts can provide all sorts of interesting vibrations, depending on what state of failure they're in. If the car is vibrating when stopped, that's definitely one of the key items. Now, the vibration could also be made worse by valves out of adjustment, or other similar deferred maintenance items. You'll have some items to address should you purchase this car, in any case, as that vibration is not supposed to be there.

Oil pressure sounds normal to me. Good oil pressure in a warmed up engine will be 2bar/30psi. That's above the half-way mark on the gauge. Should peg the gauge full at anything above idle when warm.

[Skid Row Joe]

Originally Posted by pj67coll

So, I test drove a 240D today which was quite good in some respects but one thing I noticed was that it seemed to have quite a "buzz" to it. The engine seemed to be vibrating quit a bit particularly at idle. Even when I turned the idle speed down. Not easy to describe except in relation to my previous 240D manual (this is auto) which was so smooth at idle there were times you would swear the motor wasn't even running except for begin able to hear it. Do any other owners have a clue what I'm talking about? I assume the mounts on this car are all original, or at the very least over a decade old and could stand replacing, but surely they would not cause a high frequency buzz like vibration would they? I'd expect more of a kind of heavier duty shake of the whole vehicle. Only other thing that might have a bearing on it was that the oil pressure seemed quite high to me. By that I mean even when warmed up after a freeway run it was above the 50 percent mark when idling. Maybe like it was idling too fast. Thought I detected a bit of nailing too. Might that have something to do with it? I know these seem like some rather vague questions but I've only direct experience withe one 240D so I have no data set to compare it with.

- Peter.

No. Never heard of it.

Put up a YouTube of this buzzing you speak of.....

[pj67coll]

Originally Posted by Skid Row Joe

No. Never heard of it.

Put up a YouTube of this buzzing you speak of.....

Have to buy it first... Tomorrow is D day for a decision. It's between this and two other cars. This is the first time I've seen a W123 with working A/C. And not just working but working well. Trying not to let that influence me over more serious matters.

- Peter.

[Zacharias]

Basically seconding what uberwasser said.

Bad motor mounts can cause buzzing through the chassis.

The oil pressure is excellent. Nothing wrong with that. Maybe just confirm what weight of oil the person who has it now is using.

I would not expect a motor that runs as nicely as you say this one does, to be nailing. Possibly the injectors have just been rebuilt? That would account for the smooth idle and newly rebuilt injectors can make more noise for a while.

[t walgamuth]

Sounds like a good car. If the idle is smooth and the blowby is minimal I'd expect the buzz to be something relatively minor.

[pmckechnie]

Check the power steering fluid. If it is low, you will get a buzzing sound.

Paul

[pj67coll]

The idle is not smoothe. It was my original 240D that had the unbelievably smooth idle which is perhaps why I'm being so harsh on this. There is blowby. Enough to wobble the metal filler cap but not blow it off. My one I used to have would blow the cap right off the engine. The fluid levels were all good except the oil was just under a half on the dipstick. He was using 50 weight oil in it he said. It's a nice car but probabably just too much for me if he wont come down in price at all.

Going to look at a 300E now

- Peter.

[t walgamuth]

Uneven idle is a bad sign on a diesel. Unless you can verify it is a bad injector it indicates low compression in one cylinder.

[pj67coll]

It's not that the idle is uneven as such, just that it seems to be a kind of buzz vibration. Really hard to describe. There's at least 240K miles on the engine so there may be a low compression issue but I don't have the time to get it checked out. I may just take a gamble because I have to get a car today and it's come down to a choice between this and a 1991 Buick Regal 3.1 liter. $500.00 price differential. 240D is 3 grand, Buick is 2.5. Both cars are in good overall shape and all ancilliaries work on both. Cruise, windows, air con etc. But all things considered I'd prefer the Mercedes.

- Peter.

[sleepstar]

is the buzz part of the vibration or separate? as someone mentioned the power steering can buzz... i've encountered this on my car

[pj67coll]

Originally Posted by sleepstar

is the buzz part of the vibration or separate? as someone mentioned the power steering can buzz... i've encountered this on my car

It's not so much an audible buzz, as a buzzy vibration. I know that makes no sense. I'm going back to see the car again in a few minutes and if I feel confident enough I'll play Russian Roulette with it. If not, it's the Buick...

- Peter.

[jab0028]

Check your air filter housing mounts. Mine wore out and make a buzzing sound which progressed into a helicopter sound. Replaced them with new and the sound went away.

[sleepstar]

if the exhaust mount at the transmission is worn that can cause a buzzy vibration

[pj67coll]

Oh well. It doesn't matter now. I had to get a car this weekend and eventually bought an old Buick. Piece of crap but at least it runs and seems to be fairly decent. Just keep on saving and hopefully get something decent down the road.

- Peter.