Power steering pump

[balimatharu]

I have gone through the forums about power steering pump problems.
My story is a bit different.
I am restoring my 250sl California. Now after one and a half year have managed to put every together.  Reconditioned engine, front and back axles , prop shaft, bodywork  the whole lot.
Surprisingly everything works except the power steering pump.
The power steering system was working very well. All I did was to cosmetically clean and sprayed black.
Now the pump doesn’t seem to power up. There is no leak or any noises.
I have bled it at least 6 times as per instructions.  I even retro filled the pump from the bleeding nipple.
I wonder what went wrong with it while it was sitting on the shelf on a loose plastic bag.
Is there a simple way to test it in situ.
Any help would be appreciated.

Bali

[Pawel66]

And you did not lose the woodruf key while putting it together?

[balimatharu]

Yea I put the key. The pulley goes around and the nut too rotates. You can see the fluid rumble in the reservoir no bubbles or frothing. When I was bleeding the fluid was pouring nicely into the reservoir. Quicker as the revs. go up. I am using a clear tube.

[MikeSimon]

There are ways to test the pump. Unfortunately, they are not that simple without the right equipment. You would need a T-connection with a pressure /flow gauge in the outlet line. The MB dealer should have that. Or any good hydraulic shop.
The first step for yourself to diagnose is, take the outlet hose off and see if the pump puts fluid out. Beware of a lot of splash, potentially. Prepare accordingly.
You may have a stuck flow control valve.
In rare occasions, the vanes are stuck in the rotor from sitting and don't come out of the slots, thus not creating any flow (or pressure)

[balimatharu]

Thanks.
I will let the fluid soak and  keep trying. If I gently tap on the pump body while it is going around. This can’t do any harm ?
There must be some activity inside, as there is flow of the fluid from the nipple and increase quite a bit when the engine is revved up.
Bali

[balimatharu]

MikeSimon
Not having any luck. As you mentioned that I could remove the outlet pipe and you did say it is messy.
What about if I just slightly loosen the pipe and see what happens. If there is pressure the fluid should spurt out.
In my city it is not easy to find hydraulic shop.
I just read from one of the members having trouble finding a right used pump.

[balimatharu]

Today I just did that. Removed the battery bracket and loosened the output pipe. Started the car and revved the engine. The fluid poured out but not with a pressure. Opened the nut further still no big pressure.
So it is established that the pump is not producing enough pressure. As I said earlier that the pump was fully working before I took it out.
The pump is very quiet and no leaks whatsoever.
There seem to be no easy fix except to reconditioned the pump.
Is that what I should do.
Please advise.
Bali

[balimatharu]

One more question on this.
Is there an inlet valve in the steering gear box?

[Pawel66]

Sorry cannot be of much help as I am not a mechanic, but maybe a couple of stupid ideas (other than the key on the shaft) will help: something got into inlet of the fluid? Piece of masking tape? Something dropped to the reservoir and blocks the supply hose? Fluid filter got clogged as it was sitting on the shelf and you did not replace it?

[MikeSimon]

Bali: Hydraulics 101....The pump does not "produce" pressure. It only "produces" flow. Pressure is created when the flow runs against a restriction, i.e.: the piston in the steering gear/box.
If the flow increases when you increase the rpm from idle (600-700 rpm) to around 1200 rpm, everything should be fine. The flow control valve then limits the flow at that level and the excess flow is recirculated inside the pump.
If a pressure gauge would be connected in the outlet hose, the tester would throttle the output behind the gauge and the pressure between pump output and throttle valve would go up, showing the pressure in the gauge. Up to a maximum of 65 or 82 bar, whatever pump you have, and then the pressure relief would kick in.
Let's go back to the original symptoms.
Once everything is connected, you have no power steering support? You may still have air in the system, which prevents pressure to build up.

[WRe]

Hi,
maybe you should check the flow control valve with its valve pressure release valve inside.
Attached some pictures of our pumps and a documentation of a Vickers VT27 pump which should be very narrow to our pumps maybe the same.
...WRe

[balimatharu]

Hi WRe
Thank you very much.
Is this valve situated inside the pump or is accessible from outside.
The photo is not clear
Bali

[WRe]

Hi Bali,
Sorry I don't know but look for this locking pin (13), maybe it's accessible from outside.
Afaik the 82 +/- 5 bar pumps are only used in V8 heavy cars, so ours should have the 65 +/- 5 bar pumps.
.. WRe

[MikeSimon]

Several answers:

- There is no "inlet valve" in the steering box.
- The power steering pump is indeed based on the Vickers VT27 unit, which was the most common steering pump in the U.S. in the late 50s/early 60s
- The control valve is accessible from the outside, without taking the pump apart. It sits at a 90° angle to the shaft. You have to remove the pump from the engine as the bore points toward the
   engine side. See picture 6 in WRe's post

[balimatharu]

MikeSimon and WRe.
Thanks for your valuable help.
Tomorrow I am going to remove the pump.
When I reassembled the car, I put the pump first then the pulley, the radiator and lastly the bonnet. 
From your experience does the radiator has to be removed.
BTW today there was about 20 % power on the steering but only at 2000 revs.
Thank you all for the time being.
Let me see what I find in the pump.
 
Bali

[Berggreen]

Tomorrow I am going to remove the pump.
When I reassembled the car, I put the pump first then the pulley, the radiator and lastly the bonnet. 
From your experience does the radiator has to be removed.

Hi Bali

My mechanic has just removed and installed the power steering pump in my 280SL several times without removing the radiator - but all done from under the car on the lift. But I think this is proof it can be done!

Good luck!

Christian

[Berggreen]

Afaik the 82 +/- 5 bar pumps are only used in V8 heavy cars, so ours should have the 65 +/- 5 bar pumps.

This is very interesting and makes sense!!

Can you confirm that both the 230, 250 and 280SL all were originally delivered with the Vickers VT27 (TYPE 01) 65 bar power steering pump?

If so, can we then conclude that if we have the 82 bar pump (TYPE 08) mounted in our cars, they have been installed later and sourced from later heavier cars like the r107?

Thanks,

Christian

Ps: Would be great, if we could document this in the manual, which currently is very empty when it comes to the power steering pump.

[Pawel66]

MikeSimon and WRe.
Thanks for your valuable help.
Tomorrow I am going to remove the pump.
When I reassembled the car, I put the pump first then the pulley, the radiator and lastly the bonnet. 
From your experience does the radiator has to be removed.
BTW today there was about 20 % power on the steering but only at 2000 revs.
Thank you all for the time being.
Let me see what I find in the pump.
 
Bali

Yes, it can be done from underneath. You may want to cover radiator with a piece of cardboard not to damage it with a spanner or pulley while being removed. The pulley should come off since you tightened it only recently, hopefully not too strongly. As per, I think, ja17 or Benz Dr  instructions, I applied pressure on one side of the pulley and jiggled it out of the shaft from the other side with a large screwdriver. Repeated it while turning the pulley a bit each time.

While you are there, there is this bolt there with its orifice protruding inside the block - if you have not sealed it during assembly, it is time to do it now to prevent future oil leaks.

There is my thread on this topic on the Forum. Difficult for me to find it now on the phone.

[WRe]

Hi,
here you find Pawel's thread: https://www.sl113.org/forums/index.php?topic=30276.msg219254#msg219254.
Remember that there are two different types of threads: metric and inch screw thread.
...WRe

[WRe]

This is very interesting and makes sense!!
Can you confirm that both the 230, 250 and 280SL all were originally delivered with the Vickers VT27 (TYPE 01) 65 bar power steering pump?
If so, can we then conclude that if we have the 82 bar pump (TYPE 08) mounted in our cars, they have been installed later and sourced from later heavier cars like the r107?
Thanks,
Christian

Ps: Would be great, if we could document this in the manual, which currently is very empty when it comes to the power steering pump.

Hi Christian,
Sorry but I can't confirm this. It was MY conclusion of the data in attached document (Workshop Manual W123) but I believe that it makes sense.
...Wolfgang

[Berggreen]

Hi Christian,
Sorry but I can't confirm this. It was MY conclusion of the data in attached document (Workshop Manual W123) but I believe that it makes sense.
...Wolfgang

Thanks Wolfgang...it does make sense.

But would be great, if someone has a similar overview for the w110/w111/w112/w113, to fully confirm our assumption that our cars were originally delivered with the VT27 TYPE 01 pump with 65 bar pressure - and not the 82 bar TYPE 08 or later models from heavier V8-cars.

If so, we could put this overview into the manual to clear this up once and for all, and maybe also add some of the installation/de-installation as well as venting tricks and details, which have circulated in the forum over many years.

Cheers,
Christian

[MikeSimon]

Wolfgang's overview shows the 82 bar relief only for the VT49 (the ZL49 is the equivalent ZF pump) This unit is a completely different pump. It has an aluminum housing and an integral reservoir. It was the generation that replaced the VT27.

[Berggreen]

Wolfgang's overview shows the 82 bar relief only for the VT49 (the ZL49 is the equivalent ZF pump) This unit is a completely different pump. It has an aluminum housing and an integral reservoir. It was the generation that replaced the VT27.

Thanks Mike,

Yes that exact VT49 82 bar pump I have in my 350SE (w116) from 1977.

However, the VT27 also exists in a 82 bar version, see pictures and model plate below, and I even have one on the shelf - but unfortunately it does not work even though it was renovated. :-(

So the question is if and when MB installed this version in the w113, because I see many VT27 82 bar pumps for sale online, where the sellers state that it fits the w113.

To attack the question from a different angle: Does the power steering house differ between the w113 models (230/250/280), and would a new model of the power steering house, eg. in the 280SL, require a higher operating pressure, thus a 82 bar pump?

Cheers,
Christian

[balimatharu]

Hi all.
I am still on about my non working PAS. I managed to remove the pump. it was easier than it looked. It was fitted about 2 months ago so every opened up without much struggle. Most of the work was done from underneath. I managed to move the radiator about an inch by removing the lower mounting bolts and pushed the lower end forward.
Now what I found on the pump. Next to the inlet tube there is was a shallow hole full of dried muck. Cleaned out the hole actually it is about 13mm deep and threaded 6mm hole. There is no sign of any fluid leak.
As I said before I never played around with the pump. It was fitted as I found it. 
Will this solve the mystery of the pump not working now.
Please help.

[balimatharu]

Here is the photo after I cleaned it out.

Bali