Replaced Booster - Kung Foo Grip Brakes

Moderators: Sluggo, Amskeptic

Post Reply
User avatar
type2sam
I'm New!
Location: Boston
Status: Offline

Replaced Booster - Kung Foo Grip Brakes

Post by type2sam » Fri Apr 30, 2010 1:55 pm

Happy Friday all...

After 2 years of driving with a leaky booster, I had it rebuilt by the fine folks at H&R and installed it in my '73 Bus last weekend. Took it for a drive this afternoon and right away noticed the AWESOME braking power.

Also noticed some interesting squeaking as I drifted up to the first traffic light. Drove about 1 mile and looped back for home.

All the while, the performance of the normally peppy Boston Bob 2.0 seemed somewhat subdued..

About a quarter mile from home, going downhill I noticed the bus did NOT want to coast freely...and increasingly was slowing down....more gas....barely...barely...able...to...accelerate...straining.....CHT jumping up over 400..spock...help me....spock..

Got it into the driveway and shut her down and was hit with the fine aroma of really hot brakes.

So, my thoughts are:

The calipers or brake cylinders, upon seeing forces they've never seen (from the new booster) have gotten stuck in the full on position.

I screwed up the distance that I screwed the brake pedal actuating shaft into the nose of the booster. I will revisit the Bentley spec, but the pedal did seem to be higher than before....

I am putting my money on the second item above. Won't have the opportunity to look at it until Sunday..so any thoughts you all have would be helpful.

Thanks,

Scott

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: Replaced Booster - Kung Foo Grip Brakes

Post by Amskeptic » Fri Apr 30, 2010 3:41 pm

type2sam wrote:Happy Friday all...

After 2 years of driving with a leaky booster, I had it rebuilt by the fine folks at H&R and installed it in my '73 Bus last weekend. Took it for a drive this afternoon and right away noticed the AWESOME braking power.

Also noticed some interesting squeaking as I drifted up to the first traffic light. Drove about 1 mile and looped back for home.

All the while, the performance of the normally peppy Boston Bob 2.0 seemed somewhat subdued..

About a quarter mile from home, going downhill I noticed the bus did NOT want to coast freely...and increasingly was slowing down....more gas....barely...barely...able...to...accelerate...straining.....CHT jumping up over 400..spock...help me....spock..

Got it into the driveway and shut her down and was hit with the fine aroma of really hot brakes.

So, my thoughts are:

The calipers or brake cylinders, upon seeing forces they've never seen (from the new booster) have gotten stuck in the full on position.

I screwed up the distance that I screwed the brake pedal actuating shaft into the nose of the booster. I will revisit the Bentley spec, but the pedal did seem to be higher than before....

I am putting my money on the second item above. Won't have the opportunity to look at it until Sunday..so any thoughts you all have would be helpful.

Thanks,

Scott
Your pedal should have a minor 1mm click followed by another click of play being taken up. The first click is the pin at the pushrod clevis, important, the next click is the pushrod tapping into the booster control valve cup, critical proof that the booster and master cylinder are playing nicely. Remove belly pan and loosen 17mm locknut at the 15?mm deal, and rotate the 15mm as necessary so the pushrod gets shorter.
If the master cylinder does not get a chance to extend to its circlip, the brake lines are not opened to the reservoir, then residual heat expands the fluid in a closed system and it applies the brakes without your consent.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

User avatar
type2sam
I'm New!
Location: Boston
Status: Offline

Post by type2sam » Fri Apr 30, 2010 7:11 pm

Thanks Colin - the situation you describe mirrors what I experienced. I let her sit for a few hours then drove her into the garage - no kung foo grip.

User avatar
type2sam
I'm New!
Location: Boston
Status: Offline

Post by type2sam » Sun May 02, 2010 4:40 pm

Success!

Reducing the length of the pushrod did the trick. Drove around town with brakes working normally and basked in the delight of not having to suffer a choppy high idle (lean) when stopped at a light.

Thanks Colin!

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Post by Amskeptic » Sun May 02, 2010 4:55 pm

type2sam wrote:Success!

Reducing the length of the pushrod did the trick. Drove around town with brakes working normally and basked in the delight of not having to suffer a choppy high idle (lean) when stopped at a light.

Thanks Colin!
You are WELcmmm.
ColinInNorthCarolinaThunderstorms
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

Post Reply