[martureo]

Are most of you using the Febi 08972? I had for the last 20 years, and recently used the LiquiMoly equivalent to modern CHF11s (synthetic green fluid), as Kent in one of his videos recommends doing so for 1986 cars onward.

I did the flush six months ago since the engine rebuild, and now the box is leaking from the input area, and there is seepage from the high-pressure hose between the clamped end and fitting. One of the shop mechanics said it could be because modern PS synthetic oils have smaller molecules, and they could seep past seals that are used to the older, thicker mineral oil-based fluids. Also, I checked my records, and the box was last resealed almost 20 years ago--probably better life than average, so who knows if the leak would have happened either way (could it take six months for smaller molecules to get through? Given the hose issue at the same time, maybe so).

The guys at the shop really want me to go back to the 08972, particularly since we're going to most likely reseal a lower-mileage box from the donor sedan.

Honestly, it doesn't really matter what fluid you're using as long as its approved by MB for the system and that it doesn't contain stop leak additives. If your box is 20 years since the last service then you're going to start getting more and more leaks as you continue to use it.

My side hustle is reconditioning these boxes and I can tell you that if you have ANY leaks right now from age then the clock has already started, you will get more and more fluid leaking out. If one of the seals starts leaking then its a good indication of the age of the rest of the seals. I wouldn't suggest anyone try to replace just one.


For my service I usually use modern power steering fluid as its clear. I've had a few customers who wanted to run hydraulic fluid instead and didn't want the ATF dye staining their new fluids.

 

[martureo]

Have you had anyone using the green CHF 11s in these late '80s-early '90s boxes?

The master mechanic/one of the shop owners suggested we first swap it out with the one from the lower mileage donor car before opening either up. He said in the past at the dealership, he probably resealed 60-70 of these boxes and they were often problematic and leaking again even less than a year later. (My reseal job almost 20 years ago was after it had already been resealed a year and a half earlier, interestingly enough. It may have still had a small leak, as the shop I went to back then gave me a Febi 08972 bottle to top off with.) The other shop owner (current place) has a 124 wagon with about 300,000 miles and the box has never leaked.

Only a handful of customers have told me what they were planning on using. Most end up using ATF or generic PS fluid. Yes, some have expressed that they'll use the CHF fluid.

The only real concern you should have is if the fluid is incompatible with the seal materials. Unless you're using something that will degrade/swell the seals, or you have a fuel/oil leak which exposes the seals to a different fluid, you shouldn't need a reseal for at least a decade.