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Sun Aug 27, 2017 8:48 am

jtauxe wrote: I've had two boosters ('73 and '75) rebuilt by Brake Materials and Parts in Fort Wayne, ID, and have been happy with the results:
http://www.brakematerialsandparts.com/

What was the turn around time and cost?

Mon Aug 28, 2017 1:38 pm

Power Brake Exchange in San Jose, CA. Good price, good work, the same part that came out goes back in.

Fri Oct 20, 2017 8:27 am

davebuckholts wrote: jtauxe wrote: I've had two boosters ('73 and '75) rebuilt by Brake Materials and Parts in Fort Wayne, ID, and have been happy with the results:
http://www.brakematerialsandparts.com/
What was the turn around time and cost?
Maybe 6-8 weeks and $200.

Looks like I may need to do another one on my '72 Sportsmobile.

I'll start that in a new post in this thread, since it is relevant.

Fri Oct 20, 2017 8:31 am

New brake booster issue:

In the 1972 Sportsmobile, I had a vacuum leak in the booster line, so I replaced the line. I also had to free up the check valve, and it all seems to hold vacuum, since the engine runs fine hooked up to the hose, which is connected to the booster servo.

Braided 12-mm vacuum hose from Bel-Metric:
https://www.belmetric.com/braided-metric-hose-oem-...p107f12u67
It's nice, but does not have the steel reinforcement coil.

But - still no boosting action. The brakes work, but there is no servo assist.

I figure that this means that the brakes, wheel cylinders, and master cylinder are all working. The bus does stop fine if I really stomp on the brakes. There are no identifiable leaks in the system.

Does this mean that the booster has failed in some way?

Fri Oct 20, 2017 8:45 am

It's not clear how you verified that vacuum was actually reaching (and staying in) the booster. Got a vac gauge and a tee?

Fri Oct 20, 2017 9:13 am

If it was me I'd adapt my mityvac to the vacuum port on the back side of the booster and pump it down. The mityvac has a gauge on it and a person can watch to see if it's leaking.

Fri Oct 20, 2017 11:27 am

Admittedly I am relying on indirect evidence. If there were a vacuum leak, like there was before I replaced the hose (and had to plug the ports on the dual carbs), then the engine would run like crap or not at all, really. Now with the new vacuum hose installed and connected to the ports on the carbs (well, connected to the splitter tube that penetrates the firewall, actually), the engine is running well. That tells me that the hose is holding vacuum. Since I verified that the check valve is working, does this not imply that I must have vacuum all the way to the booster?

Or is there a flaw in the logic...? :P

Fri Oct 20, 2017 11:46 am

Did you get the check valve in backwards?

Fri Oct 20, 2017 12:15 pm

aeromech wrote: Did you get the check valve in backwards?

Ha. No, I double-checked that one.

Fri Oct 20, 2017 1:49 pm

jtauxe wrote: Since I verified that the check valve is working, does this not imply that I must have vacuum all the way to the booster?

Well, that would depend on what you mean by "verified". Some guys would mean that they followed the directions in the Bentley manual, and if so they would be dead wrong,
because the Bentley manual has it ass-backwards. On the other hand, it's hard to argue with actual measurements made with a gauge. "Vacuum is as vacuum does", like the man sed.

Fri Oct 20, 2017 6:55 pm

kreemoweet wrote: jtauxe wrote: Since I verified that the check valve is working, does this not imply that I must have vacuum all the way to the booster?

Well, that would depend on what you mean by "verified". Some guys would mean that they followed the directions in the Bentley manual, and if so they would be dead wrong,
because the Bentley manual has it ass-backwards. On the other hand, it's hard to argue with actual measurements made with a gauge. "Vacuum is as vacuum does", like the man sed.
In the time it took me to replace my hose, mud wasps had moved in and filled my tube with mud. Engine ran fine but no vacuum was reaching the booster. Did you remove the hose at the booster and check there is indeed vacuum? Tube could also have collapsed somewhere.

Fri Oct 20, 2017 7:53 pm

jtauxe wrote:

Does this mean that the booster has failed in some way? Hi John,
Is this a rebuilt servo? Based on your description of the symptoms, I am going to say the booster isn't working properly. Did you check to make sure the pushrod on the servo engages the MC properly? Is your vent line on the front of the servo clear to pull free air? You've clearly done these before so I wouldn't think you'd overlook the simple stuff.

Mon Oct 30, 2017 8:09 am

TomWesty wrote: jtauxe wrote: Does this mean that the booster has failed in some way?
Hi John,
Is this a rebuilt servo? Based on your description of the symptoms, I am going to say the booster isn't working properly. Did you check to make sure the pushrod on the servo engages the MC properly? Is your vent line on the front of the servo clear to pull free air? You've clearly done these before so I wouldn't think you'd overlook the simple stuff.
I guess I should get the engine running, climb under there, and see what happens as a partner presses the brake pedal (while parked of course).

And while I could check for vacuum at the front of the hose (I will anyway) this is new hose, and the check valve was cheded both to make sure it is pointing the right way ("<-MOTOR" in the correct direction) and I tested it by sucking on it at the bench. It did need freeing up.

I will do these tests, though I am suspecting dysfunction of the original 1972 servo. I watched the bus sit and go nowhere for 20 years, and that is never good for it.

Perhaps I should not be surprised that this would be my third servo rebuild in a row.

Mon Nov 20, 2023 2:03 pm

I recently got my 71 westy (EJ2.5) running and driving. When I had it in for the inspection I found the check valve was in backwards as per the bentley, once we swapped that around the brakes have more stopping power.

But from the descriptions of proper working brakes it still seems like they could be better? it's been a long time since we've had a bus.

the brake booster is definitely pulling a vacuum, the idle goes up when you press the pedal, you can hear the booster pulling air into it and the idle goes back down. The pedal is firm when you are braking.
everything is new or rebuilt except the booster, it came with the bus, and he said it was a known good booster, the one on the bus was crusty rusty

How much vacuum should it be holding?
how much added stopping power should you get from the booster?

Mon Nov 20, 2023 2:16 pm

to test the vacuum.

Start the bus with the parking brake on and your feet off the brake. Let it idle a minute. Turn the engine off. Do not step on the brakes yet. Wait 5 minutes and step on the brakes. The first step should feel normal, the second time you step on it, it will feel normal, the 3rd time it will get hard to push because the vacuum has been used up. If it is hard from the beginning and does not change then your booster, line or check valve is leaking. The check valve holds the vacuum in the booster.

Test 2. With the vacuum used up in the test above, hold the brake down and start the engine. You should feel the brake pedal move down a little more when the vacuum from the engine hits it.

It helps a little to have the hand brake off during these tests but you will have to chock the wheels if you do this. I usually have the hand brake on. I do these tests every few months just to be sure the booster is working right. You can almost do it by habit - meaning you stop the car, put the emergency brake on, turn the engine off and after 20 -30 seconds step on the brakes a couple times. You'll feel them get hard as the vacuum gets used up. FWIW my bus sat in a field for about six months before I bought it. The booster still had vacuum in it. They are not supposed to leak at all, but if they can hold vacuum for 5 - 15 minutes then you will be good to go. If the vacuum is gone in a minute or two then something is leaking - e.g. booster, line or checkvalve.

Mon Nov 20, 2023 3:55 pm

Engine speeding up when brake is pressed means the booster valves are leaking. It is when you let UP on the pedal that a little bit of air gets sucked into the engine, and it is not really enough to speed up the engine. I have to pump the pedal like a madman to have any effect on engine speed. The booster should hold 100% of whatever the vacuum in the intake manifold is.

Mon Nov 20, 2023 4:39 pm

Booster out and sitting on my toolbox. Made a rubber plug for where the master cylinder goes. Used my mityvac hooked up to the vacuum port. Had to pump about 100 times but finally pulled a vacuum of about 15 inches of hg. It held for 15 minutes so I’m calling that a good booster

Mon Nov 20, 2023 6:17 pm

kreemoweet wrote: Engine speeding up when brake is pressed means the booster valves are leaking. It is when you let UP on the pedal that a little bit of air gets sucked into the engine, and it is not really enough to speed up the engine. I have to pump the pedal like a madman to have any effect on engine speed. The booster should hold 100% of whatever the vacuum in the intake manifold is.

Went out and tested it out again, it’s definitely sucking air as soon as I press on the pedal. It’s enough to try to stall the engine when it’s cold
I will have to get a new one, or one of the two I have rebuilt

Thanks for the help guys

Thu Nov 23, 2023 6:52 am

Okay , now I see how it should stop :D

I bought the Wolfsburg west booster, installed it last night and it stops like a new car.

Thu Nov 23, 2023 9:55 am

Good to hear that you got it sorted.