Przemo91

Hello. I've had a problem for almost a year. The noise of the ABC tandem pump is as shown in the link below. The Pentosin CHF fluid and the ABC filter were replaced, the system was flushed, and a rodeo test was performed. Unfortunately, the symptoms did not subside. The mechanic's verdict was the ABC pump. was replaced, but still the same, then we replaced the pulsation dumper but the pump makes noise. The ABC pump pressure is correct, there are no errors, the suspension works properly, it raises and lowers. There is no loss of fluids, no leaks. I have no more ideas where to look for the cause. Do you have any ideas where else I can look for the problem? The noise is more intense when turning the steering wheel. This does not occur when lowering and raising the suspension.

Link for video:

JohnLane

Foaming fluid usually indicates a nitrogen bomb is leaking nitrogen into the fluid.

Replace all the accumulators. Perform another rodeo. See how it behaves.

Jaap

But the accumulators and pulsation dampers are all in the ABC circuit and not the power steering circuit, right?
In the 2nd video you can see that the power steering reservoir is filled with white foam.

(Just to make sure) is the power steering circuit also filled with CHF11S, Przemo91?

Przemo91

I guess so. Doesn't the power steering use the same fluid as ABC? Is the fluid changed separately?

Jaap

The pump is a tandem ABC/power-steering pump with 2 completely separate circuits.
Both need to be filled with CHF11S ONLY.

Przemo91

I was convinced that it was the same system, do you know the fluid replacement procedure or do you have a manual on how to replace the fluid in the power steering system? I know ABC fluid replacment

Jaap

All i found is this AR46.30-P-0010SX: Fill power steering pump and bleed
It's not specifically for ABC equipped cars though

Przemo91

Thanks a lot for your time and manual pdf. This is for the Airmatic version. This makes me wonder why I can't find the ABC version? I can't find information anywhere whether the tandem pump has the same fluid? Although why would there be two tanks with an oil level gauge?

Przemo91

Below is a video of how the fluid behaves when turning the steering wheel with the ignition off.

JohnLane

It is power steering making noise and foaming fluid. I may suffer from reading comprehension issues. Stranger has happened.

Airmatic cars will not have the duo-pump.

Power steering foaming fluid will have to be air getting in via the return circuit or via the front seal on the pump. Any leaks in the return line to the pump?

I always used ZHM in power steering and ABC until the 222 car which uses a different fluid for MBC and electric power steering. :-(

Przemo91

There are no fluid leaks, the ABC pump has been regenerated, the only place it can discharge fluid is the power steering tank. I changed the cap as well

Jaap

In this case you're not looking for fluid leaks, you'll want to check if air can enter the low-pressure power steering lines(s) somewhere.
Like JohnLane said: "Power steering foaming fluid will have to be air getting in via the return circuit or via the front seal on the pump."

Przemo91

Foam in the liquid theoretically indicates this, and the sound of the pump indicates air in the system. I will look again because I have already inspected the hydraulic connections at the ABC pump. The return circuit to the power steering reservoir is the larger hole or the smaller one?

Jaap

Low pressure (return line) is usually larger hole.

Przemo91

johnnyrocket52

Has this power steering pump ever had the steering wheel turned all the way right/left when turning the car around in a parking lot?
Steering to the limits can blow the seals out of most hydraulic power steering pumps. You will hear the pump make high pitch noise when in that zone of destruction. When I get into that over pressure zone, I immediately steer out enough to hear normal operation of pump. Seals internal could be damaged and sucking air internally into system causing the sudsing you describe.

Electric steering is immune to over pressure when steering the wheel full left/right. No hydraulics.

If the car is being driven like that, it will never be healed.

Johnny

Przemo91

Sometimes the steering wheel was turned to the limit but immediately went back, I don't think it destroys the pump every time. Which external seals exactly do you mean? I would like to point out that the pump sometimes stops making sounds for a while, after driving e.g. 50 km in an urban cycle, after turning off the ignition several times.

johnnyrocket52

Operating it to the extreme motion and over pressuring the P/S pump damage is cumulative. The pumps typically run at 1100-1300 psi. Add in dirty, low fluid, and the pump along with external components can meet an early grave. The internal and external seals get compromised and it will lose ability to make enough pressure to operate as designed and can leak to the outside world where we live. When certain seals leak, air could be Venturi into the system and foaming occurs, and minimal outside leaks will not be observed.

Example, inside the reservoir, above the P/S pump fluid, is air head space at atmospheric pressure, accounting for thermal expansion of fluid. Somehow a component venting back to the head space is sucking air from there?

Is the correct P/S fluid, not contaminated with moisture being used?

Make sure it’s not Aunt Mildred’s sewing machine oil…


Best
Johnny