W124 e300d power steering/self levelling pump

[stigsblade]

I am on a bit of a roll now so want to get my car right up to scratch! I am havinig an occasional problem with the hydraulic fluid level for the power steering/self levelling pump in that it occasionally overflows. is there some kind of valve which prevents this happening or is it as has been previously suggested a faulty pump. If the latter can the pump be serviced or repaired and if so is it DIY or pro job.

Thanks guys

 

[219]

Which part is overflowing ?

The six cylinder cars have a tandem pump with two separate chambers - one reservoir for PAS on top of the pump and another for SLS in a bottle to the side , marked ZHM .

It is normal for the hydraulic oil in the SLS system to fluctuate in level according to the load in the back f the car and how much fluid is pumped into the spheres to compensate : remove load from the back of the car and fluid is returned to the reservoir - there are maximum/minimum marks on the side of the reservoir above/below which the levels should not stray - if someone has 'topped up' when a load in the back has caused fluid to be pumped into the accumulators , then there will be too much fluid in the system and the reservoir could indeed overflow when the car is unloaded .

PAS can fluctuate slightly in level , but it is unusual for this to 'overflow' - more usually it will run low due to leaks in the steering box seals .

Having said the above , the tandem pumps are known to wear out after high mileages . Rarely , you can get away with rebuilding with the seal kit which is about £30-ish from MB , but usually by the time a loss of fluid is evident it is too late and a new pump at £400+ is required : when the seals go , the bearings run dry and the shaft wears out the pump housing - been there , got the T shirt ! The pump in my 300TE went at just shy of 200K ( my pump ran dry because of a rotten hydraulic pipe underneath the back of the car caused all the ZHM fluid to leak out , once the pump bearings ran , I then lost PAS - this happened in the space of less than a week since i had last looked under the bonnet ! ) , luckily I sourced a secondhand one for £100 from a low mileage car in a breakers .

 

[krimat2005]

I've got one from 260E with 100k, let me know if you interested PM.

 

[Number_Cruncher]

I am on a bit of a roll now so want to get my car right up to scratch! I am havinig an occasional problem with the hydraulic fluid level for the power steering/self levelling pump in that it occasionally overflows. is there some kind of valve which prevents this happening or is it as has been previously suggested a faulty pump. If the latter can the pump be serviced or repaired and if so is it DIY or pro job.

Thanks guys

Have you fitted a new filter?

 

[stigsblade]

If you mean in the hydraulic system, no. Where would I find it?

 

[Number_Cruncher]

The power steering has a filter in the base of the reservoir on top of the pump - you can release it by undoing the M6 nut under the cap and removing the spring and plastic fluid level indicator.

In the self levelling system, there's a strainer under the plastic reservoir cap.

 

[stigsblade]

Have now changed ps filter but sl filter was out of stock. can this just be cleaned? the reservoir appears to gradually reach overflow point over a couple of days standing, with the car way down on its springs as a result. firing the engine up resolves the problem but by this time there is a big oilsplill on the drive.

 

[Number_Cruncher]

>>reach overflow point over a couple of days standing, with the car way down on its springs as a result

That sounds odd.

I wonder if someone has previously misadjusted the height control valve to make the car sit up at the back?

If you measure the vertical distance between the centre of the wheel and the lip of the wheelarch in both the sagged and running conditions, and I'll cross check with mine and post back for comparison.

Measuring between the wheel centre and the wheelarch lip means the measurement isn't affected by whatever size of wheel and tyres you or I have got fitted.

Yes, as the self levelling has a strainer rather than a filter, it can be cleaned out.

 

[stigsblade]

will measure as you suggest. Had rear springs fitted last year, potential for mis adjustment there perhaps? am away next week, will report when I get back.