Is It Possible - So Much Change With So Little Done?

[Pawel66]

Is it possible that just fluid change (to one with MB specs) and hoses change made so much difference (light, smooth, silent) in how the PS is working?

I had the power steering working ok in my car. Bled it some time ago to make sure there is no air and I have never seen any bubbles in the reservoir. I was going to replace the fluid with MB specs fluid, but I was not in a hurry with it.

Then I noticed my flexible hoses started leaking and started appearing spongy - probably wrong material was used. I bought original hoses from MB, and I replaced them. I also poured the MB fluid. I had the pump out, but I did not do anything with is as it was dry. I went through bleeding procedure as described here.

The PS is now working so much better, I was surprised how light and smooth and silent it can be. What did I do? I would never think just fluid and just hoses would make so much difference.

[MikeSimon]

The fluid as such is not a big contributor. Unless it went through a severe 'burning" cycle, it actually lasts almost forever (provided no air, moisture and contamination is induced) In later years, when systems were vacuum filled at the factory and reservoirs had good working closures, it was recommended NOT to change or service p/s fluid at all.
Contamination can be a problem. Dirt can clog up small passages and can obstruct components in the pump and gear from moving.
From what you are saying, I think the most effect you experienced was from changing the hose. These pressure compensation hoses in the p/s system are important for the system working properly. If they are too rigid and do not give, you will experience noise and if they are too soft and give too much, they compensate too much for pressure build up and you lose p/s support.

[Pawel66]

I see, makes sense, thank you!

The hoses started leaking through the walls, actually, not from the connecting points from under clamps, they looked really bad.

[Aaron h]

As of late, I've been very shocked at how many so called "Mercedes Shops", and even Dealerships, unknowingly install coolant/heater hose on the power steering system, or use heater hose for fuel lines.  To me this is as alarming as seeing someone pour brake fluid into the power steering system or antifreeze into the transmission.  It's very apparent that most modern day technicians have no idea that different hoses are used to transport different fluids.  Please please please check that your car has the correct hose for each particular system, ask your mechanics if they know the differences, and if they don't then they must educate themselves before someone dies or before someone's Pagoda wrecks or catches fire. 

[MikeSimon]

Totally agree, Aaron. This is a growing problem in the "industry". Good mechanics are hard to come by for the service dealers and even harder to retain. Proper factory training is becoming more and more expensive and mechanics are not being sent to these classes. Maybe one or two individuals have a "certificate" and the others are general "wrenchers". Hourly pay for good mechanics is rising and putting a big burden on dealerships. Hourly rates of $120.- for service work are becoming the norm.
In Germany, way back, it used to be, a shop was only allowed to perform safety-related work (brakes,steering, etc) when they had a "master mechanic" (KFZ- Mechanikermeister) on the premises.

[Aaron h]

Mike, last fall Brad Currie, a fellow forum member, brought his W108 280se to me for various repairs.  During the time it was with me the power steering all of a sudden quit working.  Naturally, I thought that maybe a sudden leak occurred having caused the total loss of power assist.  That wasn't the case.  It turns out that the previous mechanic had installed coolant hose on the supply line from the reservoir to the pump intake, as well as on the return line from the gear box to the reservoir.  The hose literally swelled shut and caused oil starvation to the pump.  I suppose I took it for granted that all mechanics knew that coolant hose can't be used to transport ATF.  As you and I have seen, that's not the case.  Just last week I saw a 560sel on Bring-a-Trailer that has red heater/coolant hose going from the fuel tank to the fuel pump.  That' just outright dangerous.  I called the seller out on it, but I don't know what became of the listing.  That particular hose/fitting combo is still available from Cohline for around $25-$30.  I don't understand why people are so damned cheap when it comes to something as important as a fuel hose. 

[Pawel66]

Aaron h - that exactly was my case.

[Aaron h]

Maybe we should make up a spec sheet denoting which Cohline products cater to which substance each type of hose will transport, and make it available to the forum members. 

[stickandrudderman]

I once made the mistake of installing silicone hose to replace the bent hose that connects the reservoir to the pump, thinking that silicone hose was resistant to everything.
I was wrong!

[RAY]

Now there's an honest man !

Hope your keeping safe Colin.

Best

Ray

[Benz Dr.]

Everyone makes mistakes. I just blame all of mine on someone else and then the problem goes away.

[MikeSimon]

Hey Dan...Didn't know your first name was Donald....

[wwheeler]

Material compatibility to fluids is not an intuitive thing. The higher priced material doesn't mean it will resist more than a less expensive material. Most think Viton (FKM) resists everything when in fact it is very poor in brake fluid. The best thing you can do is google material compatibility for the fluid you are trying to seal. There are countless charts which show my example above. Here is one:
https://mykin.com/rubber-chemical-resistance-chart

[MikeSimon]

I agree, Wallace. It seems like Viton has become that "universal wonder material" for hoses and O-rings. All it basically is, is a high-temp NBR. Brake fluid is one nasty medium for almost anything out there. And to top it off, brake fluid is not brake fluid. You have glycol based and silicone based. And they aren't even compatible with each other.