Whining ML270 CDi - transmission, steering, something else?

[Bobby Dazzler]

This one has had me scratching my head for some time - probably four years!!

The car is a 2003 ML270 CDi automatic.

When pulling out of a T-junction or car park on to a main road - say a 90-degree corner - and accelerating more briskly than normal there is sometimes a loud whine that sounds like it's coming from the engine/transmission.

It's not every time, but over the course of the past four years or so it's probably become more frequent, but no more noticeable.

The best description I can muster is that the whine sounds a bit like postman pats van - like an old Austin A35 gunning it in reverse!! It's very noticeable and seems to increase in pitch as revs increase, with a corresponding drop upon a gearchange (auto).

If I stop, put it in neutral, and then rev the engine - the whine isn't there. If I then put it back in D and pull away then it's back.

It's never faded away on the same journey. If I stop the car, leave it for a while and come back, it's usually gone.

The first time it happened it was still under manufacturers warranty, so I called the dealer immediately. They asked me to take it in an hour or two later. Whilst it was sat on the drive it went away. They took it on an exhaustive shake down - with me - and found nothing.

Pretty much every other visit to two different workshops - I've mentioned it, and nothing has ever been found that could be causing it.

My first reaction was that it could be transmission - given that the pitch heightens as the revs rise and it stops making the noise when revving in neutral - but through time I now favour something to do with the power steering, given that it happens only following a 90-degree turn.

As it's been looked at so many times I've become less concerned. However over the weekend I noticed that after a whining session (no not me and Mrs D) - even when the whine had gone - there was "shimmy" in the feel of the steering when turning corners or tightly, lasting only a second or so.

I can't think of a better description than a shimmy - maybe light vibration, or murmor - hopefully you get my drift

Sorry for the long post but I tried to dump all of my thoughts.

Any thoughts?

 

[Mercedes cozy]

Have you checked the oil level for the power steering pump.
These ML's have a common problem to loose oil from a cooler pipe the connects to the radiator.

In order to check the oil you must take off the right side engine cover in silver.

Check it and see the level.

Also I changed the engine mounts on mine at 60K and it made the car run alot smoother.

Engine Mounting as are cheap to buy from the dealer. both for arount £45 approx

 

[Bobby Dazzler]

I hadn't checked the steering fluid level myself as the dealer supposedly looked at the steering.

I'll take a peek - I assume there's a marker on the reservoir?

 

[momomo]

The marker is usually on the dipstick, which is the lid.

 

[corned]

Forgive my ignorance Rob, but is yours a 4x4?

From your description, the power steering is a likely contender for guilty party, but if it is a 4x4 then there is a possibility it could relate to the diffs - particularly as it happens when they are also working their hardest.

 

[dokalj]

Mercedes Cozy, How much did it cost all in for replacing of the engine mounts? I don't think mine has been changed, would you suggest I change them anyway?

 

[dokalj]

Sorry to hear about your ML Bobby Dazzler, did you check the steering fluid level? Is the reservoir to the right of the engine, when looking in from the front under the covers?

 

[Bobby Dazzler]

Forgive my ignorance Rob, but is yours a 4x4?

From your description, the power steering is a likely contender for guilty party, but if it is a 4x4 then there is a possibility it could relate to the diffs - particularly as it happens when they are also working their hardest.

It is a 4x4. Will check PAS fluid - not sure I'll be able to tonight now though.

Good point re hard working diffs.

 

[corned]

Further on the diff subject:

How much differential (sorry for the pun) is there in your tyre tread depths?

An old mate of mine, many years ago now, had a 4x4 Cavalier (remember those?) and that made all kinds of odd noises if he didn't have all 4 tyres exactly the same tread depth. It couldn't cope with any one wheel rotating slightly faster or slower than the rest - in a straight line of course.

I wonder if you are possibly experiencing a similar phenomenon, accentuated/aggravated when negotiating a tight turn?

 

[jaymanek]

sounds like power steering pulley or fluid level.. or the pump.

 

[Bobby Dazzler]

Further on the diff subject:

How much differential (sorry for the pun) is there in your tyre tread depths?

An old mate of mine, many years ago now, had a 4x4 Cavalier (remember those?) and that made all kinds of odd noises if he didn't have all 4 tyres exactly the same tread depth. It couldn't cope with any one wheel rotating slightly faster or slower than the rest - in a straight line of course.

I wonder if you are possibly experiencing a similar phenomenon, accentuated/aggravated when negotiating a tight turn?

I only ever replace all four at the same time, and all pretty much identical.

I read some years ago - when looking at Shoguns - that on a 4x4 it's best replace all at the same time to avoid damage to the diffs.

 

[Bobby Dazzler]

sounds like power steering pulley or fluid level.. or the pump.

Thanks Jay. I assume replacing the pump is the most costly of the possible PAS problems - should I take a seat before getting prices?

 

[skemball]

If the ML uses a viscous coupling differential between the front and rear drive it might be the cause of the noise - when turning there will be a wheel speed difference with the two front wheels relative to the rears

 

[bramleyestate]

Same noise/problem

Hi, I am having exactly the same noise/symptoms on my ml 270cdi '02. Again it commences during hard acceleration and whilst turning, doesn't need to be as much as 90 degrees even 30-40 degrees and like yours it doesn't go away once its started until i have switched off the engine and returned to it later. I am thinking of changing the gearbox oil and have been reading that it is essential to use the mercedes oil??
Did you manage to find a cure for this noise? I have thought about it being connected to the steering, but the oil is in between the high and low marks, so I wouldn't have thought this could effect it. Of note my resevoir is on the rear left whilst facing the vehicle, so just in front of the steering wheel.
Thanks Jules

 

[momomo]

I think it is essential to use mercedes oil and filter. It may be a bit expensive i agree, but that gearbox will be a lot more expensive to fix or replace if it does go wrong. So use mercedes oil, filter and replace the sump gasket as well when the oil is changed.

Are you sure you are looking at the steering fluid reservoir? I think that is the brake fluid reservoir you are referring to.

 

[Bobby Dazzler]

Hi, I am having exactly the same noise/symptoms on my ml 270cdi '02. Again it commences during hard acceleration and whilst turning, doesn't need to be as much as 90 degrees even 30-40 degrees and like yours it doesn't go away once its started until i have switched off the engine and returned to it later. I am thinking of changing the gearbox oil and have been reading that it is essential to use the mercedes oil??
Did you manage to find a cure for this noise? I have thought about it being connected to the steering, but the oil is in between the high and low marks, so I wouldn't have thought this could effect it. Of note my resevoir is on the rear left whilst facing the vehicle, so just in front of the steering wheel.
Thanks Jules

Jules, no I've not looked into it further, but when I have chance to take a look I'll post back. It's not happened since I posted - it's occasional.

 

[panason1c]

Is it a sort of 'hydraulic' sounding whine?, if so,the whine could be caused by low gearbox oil level or, more likely, a partially restricted gearbox oil filter causing starvation of the atf when asked to work hard. Changing the transmission oil and filter is part of routine maintenance anyway so you've nothing to lose by doing it.

 

[bramleyestate]

Thanks momomo, you are quite correct, not sure why i confused it with the steering resevoir! The steering res is located under the right plastic engine cover and the dipstick is showing that it is low, but I don't think it will take that much to fill it up. I have been quoted £about £158 to change to gear oil, from x2 local gearbox garages, they appeared to know the vehicle well! Was going to do it myself, but not sure? The oil alone is about £60 from ebay.

 

[Bobby Dazzler]

Hmm. Not had chance to look at my manual yet but there are two scales that look like this.


---Max

80degC

---Min


---Max

20degC

---Min


Checked when engine cold and it's showing the level to be just within min for 20degC.

I assume the upper range is for when the vehicle is at normal operating temperature, and the lower range is for cold.

If so I could do with topping up.

 

[Bobby Dazzler]

Topped up a while back, no noises since.