Do I need to Lubricate hydrovac brake boosters?

[Old Man Powell]

I got my two rebuilt hydrovac boosters. The paper work that came with them says some hydrovac boosters need to be lubed. Mine are from a 1974 Chieftain. I did some searching and I have seen talk about lubing the boosters they were talking about much older styles... like from teh 50's and 60's. Still not sure If I need to lube mine. If so, how much and with what? My chasis is a 74 RM400/500. Can't find anything from themanuals about the boosters needing to be lubed.

[gacato74]

This site here shows some info on adding oil. I came across the same thing, and this has some good in-site. It is another forum site.


http://www.binderplanet.com/forums/showthread.php?t=77210

Ok the truck brake specialist who i have been getting my parts from returned after our Australia day holiday so i called them about this and was put on to the fella who runs the hydraulic overhaul department and who knows Hydrovacs inside out. His advice is:* Early Hydrovacs with internal leather cups need ligt mineral oil to keep the leather supple and sealing correctly. These Hydrovacs either have the fill plug on the rear cover to enable filling to overflow, or dont and require 1-2 liquid Oz oil injected into the top air line of the booster.* Later Hydrovacs which have a rubber diaphragm (like a black rubber ice-cream container) should NEVER have any oil in them at all. The oil can and will cause th rubber to swell, become soft and eventually tear. This will lose all vacuum assist and so is very dangerous.Mine is the later with the rubber diaphragm, all rubber seals, no fill port nad a V-Band clamp between both booster covers. I kept mine dry and just used some rubber grease on all seals and diaphragm outer rim where it seals to help it bed in and seal as we do at work. He said what i did was absolutely correct.Hope this helps others!

THis is what I found ...

george