Can you rebuild hyd pump on TD

[rickjordan]

I am suspecting that my self leveling hyd. pump is drawing in motor oil. Actuall I am fairly certain of it. The fluid in the res. is real dark. Last year I replaced the nitro. cylinders and put in new Febi/Bilstein hyd. fluid, which was clear. Can this pump be rebuilt, if so, where can I order the rebuild kit? If I can't rebuild it, I know it's big bucks, but how hard is it to replace it?

[BIGRED]

It is a seperate sealed unit and has nothing to do with motor oil. The darkness is most likely coming from the parts that are rubber. Mine has the same issue and I plan to replace all the rubber hoses which I am sure is the source.

I think the best way to know if the pump works is, does it raise and lower as it should?

Good luck
Don

[dmorrison]

I just changed my hydraulic fluid. It does get dark.
Have you changed the filter in the supply tank?
Take off the return line of the tank. Unbolt the metal return line using 2 wrenches then unscrew the plastic top on the tank. Pull the unit out and you will see the filter for the system. Get a new one from Mercedes or fastlane and replace it.
Cosider replacing the filter with a new one and then 1 month later it the hydraulic fluid is that dirty.
If you think it is oil it should show as a film.
Take out a little hydraulic fluid and add a few drops of oil and look at it. Does it look the same in the tank or is the hydraulic fluid in the tank just dark? If just dark then try the fliter.
To take the filter off the top unit. push on the spring holding the filter against the top unit. The spring goes through the filter and hooks on a plastic tab that has a hole it it. The spring end is turned in a U shape so you push on the spring and move the spring sideways to unhook it. Try it a couple of different ways and you'll figure out which way you have to move it to get it to release.

Dave

[leathermang]

I don't know if they were just trying to sell me THEIR hydraulic fluid ( at $16 a liter) .... but every MB mechanic I ever talked to said to only use the MB hydraulic fluid for that system ... I had a 1981 wagon....
Have you checked to see if the Febi/Bilstein hyd. fluid is compatible with the system seals, etc... ?

[jassz]

Our self levelling strut leaks like crazy on one side. Right now the car lifts up, then immediately drops down again (a little embarrassing!). It is the main reason we bought a parts car. We were told they were about $700Canadian to purchase one new. Twitch twitch.

It's a little intimidating though, because the Haynes manual, (which covers all other types of complicated repairs) says NOT to attempt to replace the strut yourself, have a professional do it.

So, how about you do it first, then tell me how you did it?

[leathermang]

I have used that ploy several times... so far it has not worked...

[BIGRED]

I did some reading in my manual. The pump gets it's lubrication from the hydro fluid in the system. I can see an o-ring in the pictures and my logic tells me that with the pressure of the hydro pump, vs the engine oil pump, the battle would be lost to the hydro pump. Meaning that if it had a leak and it could go anywhere inside the engine (if being a keyword) thats what would take place and it would empty into the engine. It must be impossible for that to happen from an design standpoint (?) So if the pump has pressure and it had a leak, I would say it can't suck engine oil in, but rather would blow hydo oil out.

[engatwork]

Replacing the rear struts is diyer type work. It is like replacing a shock but you have to remove and reinstall the fluid like to the strut. Nothing to it really.

[rickjordan]

There is one thing I failed to mention, that makes me believe the sys is drawing in oil. The level in the res. has risen slowly, but surely. When I changed the rear nitro. cylinders, I filled the fluid up to the full mark. The level is now up to the MB Star, for those who have this sys.. I replaced the rear nitro. cylinders in Dec. of 2001. So, maybe it is the rubber hoses that is causing the darkness, but where is the extra fluid coming from? The prescribed fluid change for this this sys. is every 2 years.

[jassz]

The level in the res. has risen slowly, but surely.

I gathered that the system works by pumping the fluid out of the reservoir when the car is running, then sending it back when it is not. Are you sure the fluid level didn't just rise and fall as part of that cycle? Were you comparing the level with the car running at one time, then shut off the next? I think the fluid level would be higher in the reservoir when the car is shut off.

Just seems odd it could be filling up with something else...

[engatwork]

Rick - to answer your original question the manual I have shows it as being rebuildable.

[peterhardie]

Rick:

I have the same problem; My fluid level goes up, is definitely soot-soaked motor oil. The part is tres expensivo, so I have been holding off. No problems, just check my fluid levels often. I drained the fluid out of the hydro reservoir once, and didn't refill; it filled itself!

Two mechanics I have talked to about it say that when the pump goes, you start trading fluid between the engine and the pump. They say the pump is not rebuildable, but all mechanics say that. The question is can you get the parts, and are there metal components that wear. Waterpumps come to mind as similar.


Peter

[rickjordan]

I have always made a point to check fluids at the same time, ie; with the eng. off. So, whenever I check the motor oil, I make a point to give the hyd. fluid a quick check. This is how I noticed the leel rising over time. I know for absolute fact that the level was dead on with the arrow on the hyd. res. the day I changed the fluid, and the days and weeks following. Today, 1 year and 4 months later, the level is at the Star on the hyd. res.
I have the W123 CD manual, and it infers that the pump can be rebuilt. If indeed the pump is drawing in oil, it would be through the o-ring that seperates the pump from the drive gear in the eng.'s head. I don't know if that o-ring is available. What I think I will do is draw out some fluid, to the full mark (arrow) and watch it more closely. The color and consistency of my motor oil hasn't changed, so I a presuming the hyd. fluid isn't getting into the engine. My real concern here is that the suspected mixing of hyd. fluid and oil will harm the rest of the system $$$$$$$.

[JimSmith]

Guys,

To draw engine oil into the self levelling system, engine oil must be present at the suction port of the pump, and it must be available at a higher suction pressure than the normal system oil from the reservoir. These conditions exist when the dynamic seal at the pump interface with the drive hardware (the exhaust camshaft on my 190E 2.3-16) begins to deteriorate, and they can be made worse when the suction line or filter is clogged.

The pump itself is relatively simple and robust, and not likely to need rebuilding to the pump parts. The seal to the drive mechanism may well need to be replaced and that is not likely to be expensive.

My fluid gets changed every 4 years or so, because it does get dark (it is constantly running even when the system demands for fluid are zero), and it is relatively easy to replace. I normally unscrew the reservoir bottle cap, turn the car on, and let the stream of discharge fluid run into an old oil bottle. I do this until the fluid gets low enough that I can get the filter out and clean the rest of the reservoir. Then I install a new filter and pour new stuff in to near the top of the reservoir (and yes, it is expensive but I have never used more than two liters at a time) and restart the engine. I "feed and bleed" the system until the stuff coming out the discharge tube into my old oil bottle is nice and clear. Then realign the discharge flow to run back into the reservoir, top the reservoir off to the full mark with the car running, and put the cap assembly back on the reservoir.

Hope this helps, Jim

[peterhardie]

If you do find a kit and rebuild the pump, let us know the where and how. fastlane here lists them at $473 or so.