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Brake Booster Trouble

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fleshy1

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I am not getting any assist from my brake booster on my RB MGB. The line from the manifold to the servo is completely crushed under a vacuum. Would this be a check valve (on the booster) problem or is the booster itself messed up?

Thanks for the help.
 
If I understand you correctly; the vacuum hose has collapsed. This is a common problem where a cheap grade of hose has been installed. Try replacing that hose with modern Fuel Injection Hose. -Hope that's all it is.---Keoke
 
With engine off I pulled the vacuum hose and it made a sucking noise then reformed to it's normal shape. I guess I'll stop by the local chain store to see if they have a hose that would work.
 
yup-yup. Re-enforced hose to handle vacuum loads. Your check valve & booster are apparently working fine, BTW.
 
OK Replaced that hose. Still didn't help.... Any more suggestions?
 
Check valve is in the bottom of the booster where the hose attaches to it...you should have 15 inch pounds of vacuum to properly operate the booster...too much would collapse the hose.
 
Ok, pulled the check valve and blew through it, shot it with a little cleaner, seems to be working....maybe I should just get a whole new one....
 
Does it only work in one direction? How much vacuum you putting to it?
 
It is only working in the direction of the manifold which would make sense since I want to pull vacuum for the assist. I know that my nominal idle vacuum is around 16 to 17 in lbs. The system seems to be fuctioning now, but I'd like to not have to clean that valve every week since the grommit is starting to look a little tattered.
 
maybe time for a rebuild of the booster? I know there are kits available...
 
It's possible that you may have some trash in the booster housing and when calling for vacuum it's sucking some rust and or dirt through the valve. I think the booster housing can be taken apart and cleaned. I don't know if it will damage the diaphram in the process though. PJ
 
I just rebuilt one - its almost a 2-man job...only because of the spring inside...is yours a "crimp" or "twist" type?
 
Gotta LOVE that big-arse spring!! Like tryin' to shove a snake thru a keyhole... BACKWARDS. /ubbthreads/images/graemlins/devilgrin.gif
 
I have the twist type. I checked out the proceedure and it looks like I'll need a vise and a face mask /ubbthreads/images/graemlins/laugh.gif

This seems to be a case of fixing one problem only to amplify another. A few weeks ago I replaced a defective MC. I also dicovered that the servo and MC had a vacuum leak where they join. My MC did not have a rubber gasket and I did not see one on the servo so I used some RTV to make a seal. The seal was finally good enough to allow the booster to function which probably resulted in trash getting sucked into the check valve.
 
Good luck - don't stand directly in front or behind it! & move your cars out of range....or get a budy to open it whil you hold the parts.
 
....this'll be interesting....
 
I rebuilt a booster once. Notice I said once. I'd classify it in the windshield catagory. Only with a windshield, you don't have to duck or run if you make a mistake! /ubbthreads/images/graemlins/rolleyes.gif PJ
 
Yeah... all ya get is a funny "snick" noise... "Awww, <EXPLETIVE DELETED>."
 
A little follow up here...

I had the booster stop working, again. I pulled out the check valve and blew through it. I noticed some light brown liquid dripped out when I did this. I put a finger in the booster and it came out wet!

Then I recalled that the old MC didn't show any outward signs of failure. Turns out it was leaking into the booster. I stuck a shop towel in there and let it wick out the fluid. Took about 5 reps to get the towel to come out dry, but I think this may have got to the heart of the trouble.
 
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