123 brake fluid reservoir question-puzzled - PeachParts Mercedes-Benz Forum

Boston Benz · #1 06-12-2005, 12:42 AM

RE: a 1984 123 sedan. I attempted to pressure bleed the brakes on this car with a Snap-on hand pump style bleeder. The device attaches to a common "screw-on" metal cap with a male adapter which screws onto the plastic reservoir neck. For some reason, the black metal cap isn't screwing on to the plastic neck correctly. It only turns two or three rotations (consistent with a wrong thread pitch match). I know that 1981 and prior model years had a different thread pitch. I thought that anything post 1982 was all the same universal thread. I believe it's a M45 x 3.50, standard for ATE brake reservoirs (even up to model year 1992!). After applying 15 p.s.i. of fluid pressure, the fluid began to hiss out the side. I rescrewed the cap onto the neck four times, still the same. Does anyone know if the reservoirs are different in 1982/1983/1984/1985 model years???

dieseldiehard · #2 06-12-2005, 12:54 AM

All the same as far as I have ever seen, is the rubber gasket there?
I have seen replacement caps FS. The one on PowerBleeder fits fine.
WHOA just a minute . . . . 15 psi? I never went over about 5 psi. Maybe you have it pumped up too high?

dieseldiehard · #3 06-12-2005, 01:02 AM

45 mm cap Adapter fits most Euro cars
http://www.motiveproducts.com/03adapters.html

#4 06-12-2005, 01:32 AM

the bleeder we use at our shop runs at about 20-25 psi

dieseldiehard · #5 06-12-2005, 01:44 AM

I worry about the brake reservoir level sensing switches, you know the two black buttons atop the reservoir. I saw fluid blow out of one of them once with pressure up 10 or 15 psi since then I have kept the pressure under 6 or 8 psi. There can be quite a head of air above the fluid in the Power booster, that is what is compressed.

#6 06-12-2005, 01:56 AM

Quote:

Originally Posted by dieseldiehard

I worry about the brake reservoir level sensing switches, you know the two black buttons atop the reservoir. I saw fluid blow out of one of them once with pressure up 10 or 15 psi since then I have kept the pressure under 6 or 8 psi. There can be quite a head of air above the fluid in the Power booster, that is what is compressed.

we usually replace the rubber caps and the rubber grommets where the reservoir attaches, i personally never had one leak or blow off the master cly.
for alot of the newer cars to bleed correctly sometimes you need at least 25psi

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