Brake Booster N/G?

Good friend comes over to use my shop for simple caliper and brake hose replacement. We install new front ATEs & hoses. 1979, really nice, manual 240D. We use the pressure bleeder to do the system including the clutch.

On the "test" drive the brake pedal will feel very hard to push after a couple of 'pumps" (he said this HAD been happening before) Sounds like the booster as the VP is making plenty of vacuum, 18 20 hg.

How can we make sure it is the brake booster? His locking system works and holds vacuum, maybe take everything off the "main"vacuum line except the booster?

Also.. the pedal will "fade", which I think may be cured by another bleeding, he said he replaced the M/S not long ago.
I mention this as the two problems could be related, but Im thinking they are not.

We replaced the calipers because the R/F one froze up.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Check the booster for being full of fluid from the bad previous master cylinder.
Robert

[QUOTE=LuckyEddie;2095906]Check the booster for being full of fluid from the bad previous master cylinder.
Robert[/QUOTE

Good idea, We are going to think about it over the week end and hit it again Monday.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

[quote=Stevo;2095946]
Take a good look at the O-ring between the Master Cylinder and the Booster as a source of a Vacuum Leak.

Last year I installed a rebuilt Master Cylinder (Kragens Auto Parts). After installation the pedal was kind of spongy and went down further than I would have liked before it started braking.

Over the last 1 1/2 year I have tried bleeding the system 3 times with no improvement. It was not good but dependable until last Monday when the pedal went almost to the floor. (Of course I so far cannot find the receipt to get an exchange under warranty.)

I decided to install a new Master Cylinder instead of a rebuilt. I now have an excellent pedal function an braking.
My problem all along was the poorly rebuilt Master Cylinder.
If bleeding the system 2 times does not cure the pedal "fade" I would suspect the Master Cylinder even if it had been recently replaced.

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84 300D, 82 Volvo 244Gl Diesel

[QUOTE=Diesel911;2096024]Yes, in regard to the "brake fading", thats what I suspected even thought the MS was recently installed, if another bleeding doesn't cure the fading, we'll try another MS.

As to the booster, we'll check for fluid inside, check the "O" ring and make sure we are not losing vacuum before it gets to the booster.

I was also thinking of pulling a good booster & MS from one of my parts cars then I'd have them for future needs if they verified our suspicions.

My friend is a plumber that has helped my out on several occasions over the years, a valuable relationship to cultivate. Every DYI home builder/owner needs to know a good plumber and an electrician

Thanks for the input

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"