W124 300D noisy idle

[BOILING POINT]

Hello all,

I have just purchased a w124 300d auto, the car has many issues. The ones that concern me the most are as follows...

The engine sounds like a bag of spanners while on idle, this goes away as soon as the throttle is pressed.

The serpentine belt tensioner is goosed, it has collapsed internally.

Maybe rear subframe bushes need replacing, bangs when it changes gear under load.

Wiper does not self park and this drives me totally bonkers!

Anyway, I would like to address the idle issue please.
I have done some searching on the forum search engine but to no avail.
The noise made on idle is like a metallic clatter and is not diesel knock.
If the revs are raised even slightly the noise goes away.
I was thinking it maybe related to the tensioner, but that is making a squealing because it is twisted due to collapse.

Does anyone have any ideas?

many thanks in advance BP

 

[jonnyboy]

You need to do the things you definitely know about first in order that they are eliminated.
Do the tensioner and put a new belt on, then see where you are at.
Have you looked at the servicing/oil quality/quantity ?
Those diesels are usually bulletproof if looked after. Don't expect one to be as quiet as a modern diesel though.
Google the wiper - I suspect it's a relay or suchlike, or possibly a faulty combination switch (the indicator stalk) . If you need a mechanism give me a shout as I think I have one.

Welcome, by the way.

Good luck.

John

 

[SilverSaloon]

Ensure that the shock absorber on the belt tensioner is working. Press down on the top bolt of the shock when idling to see if the noise goes away. its about £45 to replace IIRC and relatively easy to fit yourself, if a little fiddly. i've posted instructions below on how to replace it.

the wiper; probably a relay.

for the gearchange bang, check that the vaccum connection on the crossover bar on the manifold is connected. if it falls off, it causes bangs when gear changes. this is the big silver thing that runs across the top of the engine - under here is a vaccum pipe.

here is the how-to on the shock:

- slacken the belt and take off the pully(s)
- loosen the fan shround and pull it out the way a bit to gain access
- get a spanner down to the 5(?) small bolts that hold the pully on
- VERY carefully start to undo these bolts (probably using a spanner or similar to stop the pully from turning). ONLY undo a bit on each - DO NOT REMOVE or it will spoil your day!!!
- once all 5 are loose - the pully should be able to be moved a few mm.
- you now should * JUST * be able to undo the lower bolt enough to allow the old shock absorber to slide out of its bolt. the bolt still wont fit fully out though!!

- then fit the new shock and tighten up the bolt.
- tighten up the 5 pully bolts again, ensuring everything is still aligned and the pully is nice and flat in position.

you can see the bolts i loosened here:

JUST MAKE SURE YOU DONT UNDO THEM TOO MUCH! if you do, they will fall out and it will be a nightmare to refit without removing the radiator!!!!

hope it helps!!!

Derek

 

[Gawdi]

The engine sounds like a bag of spanners while on idle, this goes away as soon as the throttle is pressed......

The noise made on idle is like a metallic clatter and is not diesel knock.
If the revs are raised even slightly the noise goes away.

Does anyone have any ideas?

many thanks in advance BP

BP - Welcome to the wonderful world of the W124 300D.

The sound of spanners banging in a bag, is a wonderful sound.... especially v early on a cold morning when your trying not disturb the neighbours as you start up the car...

In the days when the engine was new, car reviewers commented on how loud it was on start up, compared to other diesels, but equally praised the engine for its refinement and smoothness when underway.. Well most of the other diesels of that era have gone to the great motorway in the sky, where as the 300Ds are running on as strong as ever...

Give it a little love and care, and it will see you alright..

When I got mine 3 years ago, I too had a new tensioner fitted and a new V belt... that didn't make any differnce to the idle noise levels, but gave better peace of mind... Apart from regular oil changes and now needing 1 or more glow plugs changing, that been it.. Not bad for a 19 year old engine in daily use...

Hope you get the other things sorted, but if your mechanically minded, you'll find the W124 a very easy car to work on...

Welcome!

 

[BOILING POINT]

Hello again folks,

I changed the tensioner today, thanks for the write up but it was the tensioner that had failed, not the damper.
The squealing has stopped but the idle is still very loud, it now sounds just like a tractor. Maybe this is normal, it is very smooth and quiet when its +1200rpm.
Will stick some engine flush in tomorrow and change the oil + filter on monday.

Many thanks for the input people.
BP

 

[a111r]

Useful 'how to' advice from Silver Saloon (a fellow veg / bio freak!)

You may have a nailing injector(s), caused by nozzles past their sell by date.
V. Cheap to recon.... by a factor of 'lots', compared to CDIs. Old tech.
Try Helptoday for good prices, or Stanley R. Harris.

 

[3 phase]

I agree a good how to by Silver Saloon, I tried Derek's method this afternoon but unfortunately the 10mm head bolts on the water pump pulley would not budge behind the fan, and one had started to round off.
So, what to do?
I had already removed the tensioner pulley and the spring and I noted that the tensioner pivot had a plastic cover on it which reveals a 17mm allen bolt. Yikes nothing that big in my tool box!!, so after some head scratching a friend suggested whipping a wheel bolt off. Then we slid a 17mm ring on the bolt before sliding the rest of the bolt head into the allen socket. Protecting the radiator core with a piece of plywood I put a tube on the open ended part of the spanner and wound the pivot bolt back a few turns. This enabled the tensioner assembly to move just enough to slide the bottom bolt of the shock out so the old one could come away and the new one be fitted.
Fantastic smooth and quiet idling now!!

 

[Dave Richardson]

Anyone have any thoughts on the noise being the alternator pulley ?
Dave

 

[3 phase]

Well it certainly wasn't the alternator on mine although now it idles so quietly it is easy to check where any other extraneous noises are coming from:bannana:. The noise coming from both mounts of the tensioner shock was extreme at idle , so it would have been impossible to point a finger anywhere else til that was fixed.
I suppose the old wooden broom handle trick on the alternator and your ear might give an indication of noise?