I've got the brake booster pulled out of my '59 Mercury so I can clean the schmoo out of it and fix a stuck linkage. I got the casing apart and it dumped a good quan***y of oil down my leg. This is an 8 screw booster, I want to say it's a Bendix Master-Vac. It has a leather seal around an aluminum piston, it's not a diaphragm type. The oil that was in it seemed like a light mineral oil. Does anyone have a recommendation for the type and amount of oil that I need to put back in it? I was reading up on on early hydro-vacs and it seems like they use the same type of leather seal, so I ***ume I can use their recommended mineral oil or corn-based hydraulic fluid? Thanks!
A vacuum brake booster should be dry inside. Only Hydrovacs that are powered by the power steering pump have fluid in them. I'd have to saythat Egads is correct in that the master cylinder had been leaking fluid into the booster for a long time.
I think you meant to say Hydroboost? The hydrovac doesn't have any oil in the booster side of it, but does have brake fluid in the hydraulic side
I agree, the master has been leaking into the booster. I found the same thing on my 54 Mercury. I'm not sure what to use on the leather seal, but I seem to remember Neat's Foot Oil being used. I just pulled a 59 Edsel Service Manual and it says to use vacuum cylinder oil, whatever that is.
I should mention that the oil is just being used to lubricate the seals during ***embly. The booster should be dry inside.
The stuff that came out was nothing like brake fluid. I'd just put it back in but half of it went down my leg LOL. The early hydrovacs with the leather seals used a couple ounces of oil in them even after oiling the seals during ***embly. Some have a fill plug, others say to squirt 1-2oz through the vacuum port. The later boosters and hydrovacs with rubber seals are supposed to be dry. This booster has a big leather seal around the piston so it needs oil, just don't know for sure what kind won't eat the leather. Like the service manual says, need "vacuum cylinder oil". I'll see it I can find Neats Foot Oil.
Found from a Chilton's manual, every 6 months you're supposed to inject 1oz of Neats Foot Oil into the booster if the original Bendix vacuum cylinder oil cannot be found. Off to the leather store...
I lubed the seal on the piston with Neatsfoot oil, and dumped about a half cup of it on either side of the piston in the housing before re***embly. Brakes work great now. The old oil has certainly done it's job, the seals are still in really good shape 60 years later. If anyone is following this in the future, Cal-Ranch or Tractor Supply Co has Neatsfoot oil in the horse tack section. It looks pretty close to what was in it originally.
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