Booster Install and Problems

[VDOG]

Ok lines ran Booster installed, MC bench blead, vacuum line installed on edelbrock 1406. When the brake pedal is applied, the truck rolls for a few more feet then the brakes grab. Its like there rolling untl a certain point then stopping the truck, as if I was slowing down the truck. But im slamming on them, in the back yard so not going far, just a few feet back and forth so at 5to 10 mph is should stop instantly, Am I correct? Isnt this why we get power brakes? It stop better with the metering valve and no booster, until the brakes locked up.

[clay68c10]

Is the round rod between the booster and master the right length? There are a couple of different sizes, maybe yours is too short??

[Dingfodgy]

You didn't mention that you adjusted your shoes and / or bled the entire brake system? When replacing a MC, Prop Valve, and Booster- you're gonna need to get the air out of the entire system. Before bleeding- adjust your shoes so that there is just the slightest bit of drag when free-wheeling, then back off the adjuster 1/4 turn. Now grab a buddy and bleed the entire system starting with the wheel cylinder furthest from the MC. (RR, LR, RF, LF is the correct order) If you do that and you still have mushy brakes- start looking for week hoses, bad shoes, etc...

[VDOG]

Originally Posted by Dingfodgy

You didn't mention that you adjusted your shoes and / or bled the entire brake system? . Now grab a buddy and bleed the entire system starting with the wheel cylinder furthest from the MC. (RR, LR, RF, LF is the correct order) If you do that and you still have mushy brakes- start looking for week hoses, bad shoes, etc...

Ok the disc brakes were installed last year. My only problem has been with the metering block not made for disc/ drum, so my wheels were locking up somedays. Rear brakes at as close to the drum as they can get without being appiled. I have bleed the system 3 times in the same order. I change the lines from the master and prop valve down to the frame.
The rod going to the master is fine, its the one that came with the booster.

[70rs/ss]

Get the correct proportioning valve and the rod coming with the booster doesn't mean it is correct for the truck. Does the rod sit firmly against the MC(is there any ply in the peddle before you feel resistance? Is the booster new?


Rereading this has raised a red flag or two, first is that MC from a non-power set-up? Is the Prop valve from the non-power manual brake set up? If yes to either or both, get Power brake components. A manual MC has a different sized bore to enable it to work without assist, but add assist and the components are mismatched.

[VDOG]

Originally Posted by 70rs/ss

Get the correct proportioning valve and the rod coming with the booster doesn't mean it is correct for the truck. Does the rod sit firmly against the MC(is there any ply in the peddle before you feel resistance? Is the booster new?

Booster is not new, came off a 4x4 truck. It might be a 1/4 to 1/2 of play before the booster. But I was thinking that was me on the adjustment when I hooked the pedel up to the booster. Again when pressure is applied it grabs then stops.

[70rs/ss]

OK, the booster is old and could be defective (not sure of that) but the peddle should be hard to push if booster is bad, next is the master cylinder the original one as in a manual MC? Then the prop valve is the drum drum, right it needs to be swapped for a disc, drum. Those are MUST DO's as mismatching manual parts with power assist and drum drum with disc drum isn't going to work. The play is the issue, the rod sits up against the piston in the MC and any push moves the cylinder, so the 1/4" is big since the piston only moves an inch or two through the whole stroke. I would buy a new rebuilt unit for a disc/drum power application, as a used brake component can fail and cause a whole lotts trouble. $130 from Autozone or the like.

[Longhorn Man]

actually, the master cylinders on these trucks are the same p/n for power or manual... it is literally just a booster intalled between the booster and firewall.
Also, a little freeplay is required on the pedal. I normally go for no more than 1/2 inch as measured at the pedal. If you don't have free travel, or not enough, the brakes will apply on there own as the system heats up. Any new master cylinder will (SHOULD) have a piece of paper in it that explains it. Ignore it liek I did, and your brakes will drag.
The distrabution valve from a 70 and older should not be used, the proportioning valve is prefered... HOWEVER, this step has been ignored by ppl on here and hardly any of them ever mentioned ill effects
You need to troubleshoot the problem.
With the engine shut off, pump the brake pedal, why holding pedal down, start the engine. The pedal should drop.
if it doesn't drop, the booster is bad.
Since this i a DAUL diaphram 3/4 ton booster, do this test to... with the brakes still applied, shut off the engine. If the pedal instantly goes hard, the booster is bad.
Unplug the hose from the carb. Suck on the hose (still hooked to the booster), you should be able to inhale a little bit. If it feels like an empty hose, replace the booster.
Now try blowing, you shouldn't be able to blow in it.
If it fails, then replace the elbow/check valve
With the hose still removed from the carb, cap off that fitting and fire up the truck. Move it at the 5 to 10 MPH you say you've already tested it at. Jab the pedal.
If it feels the same as when it's hooked up, then the booster is bad.

If it passes all this, then troubleshoot the hyd side of the system. Remember, if you installed a 3/4 ton/one ton master cylinder, it is plumbed backwards from the 1/2 ton set up. It is hard to screw it up since the fittings would be the wrong size, and I see no adapters there.

I strongly urge not getting used boosters. They can be blown and you not quite realize it... esp these daul diaphram units, and they can cause all kinds of problems.
i even lost an engine to a booster blowing out.

[VDOG]

Originally Posted by Longhorn Man

The distrabution valve from a 70 and older should not be used, the proportioning valve is prefered... HOWEVER, this step has been ignored by ppl on here and hardly any of them ever mentioned ill effects
You need to troubleshoot the problem.
With the engine shut off, pump the brake pedal, why holding pedal down, start the engine. The pedal should drop.
if it doesn't drop, the booster is bad.

So I have a distrabution valve not a proportion valve (see pictures)?
I just thought it was an older version of the prop valve. Ok you did not say how many times to pump the brakes. When I pumped the brakes up about4 to 5 times and turned the enigine on the pedel did not go to the floor. When I pumped once or nomore then twice and started the engine, the pedel when to the floor. Not sure what that means

[norwegianc10]

What kind of cam are you using, got enaugh vacuum to run powerbrakes?

[Longhorn Man]

that looks more like a proportioning vaalve to me than a distribution valve... do you know exactly what it came off of?
As far as your pump the pedal and start the engine.... that's just wierd what you are getting for results.

[BLACK AND BLUE 67-72]

You have a proportioning valve. First off how big is your cam it may not create enough vac for the booster, get a guage and check it and to check your booster do as longhornman said get in your truck don't touch your brake pedal start your motor let it run for a few seconds then turn it off, push your brake pedal a couple of times it should get harder to push and come up farther from the floor(this removes residual vacuum) then push down on the brake pedal and hold it down while you start the engine, the pedal shoud drop if the booster is working. If it does not then your booster is faulty. Also your master cyl, where did it come from? There is a possibility that the master cyl coud be bypassing, causing you some grief.....

[VDOG]

Originally Posted by norwegianc10

What kind of cam are you using, got enaugh vacuum to run powerbrakes?

Im going to get a vacuum gauge today. The guy who built this engine installed a large cam (dont knw the specs) because he was using a manual transmission, told me it would lose some power with my automatic trans.
So yes my cam could be an issue.

[70rs/ss]

I guess my thoughts were a miss match of parts could be causing some of this and a new unit with MC and booster would eliminate any issue. I was thinking the rod was the issue, but not sure? I am curious, as I haven't had an issue quite like this, keep us updated.

[VDOG]

Originally Posted by 70rs/ss

I guess my thoughts were a miss match of parts could be causing some of this and a new unit with MC and booster would eliminate any issue. I was thinking the rod was the issue, but not sure? I am curious, as I haven't had an issue quite like this, keep us updated.

The parts are used, but not miss match. Came as a unit. Unless it was mixed before I got it. Again, pumping up the pedal about 4 or 5 times, then the pedal does not go down, if I pump it once or twice, turn the ignition on, it goes to the floor. I was told it still could be air, or my cam is too big.

[Boog]

Even if the booster is bad the pedal should not go plum to the floor unless there is still air in the system. A thorough system bleed is in order.

[milled]

I'm betting mc is bad.

[VDOG]

Ok guys here are the numbers I get with the vacuum Gauge.
At startup, 8 to 10 inchHG, or 200 mmhg the needle was fluxuating.

Then after a few minutes at idle it went between 13 and 15 inchHG and actually stayed on 300mmHG which was about the 13 or 14 inchHG mark.

So its safe to say I have vacuum.

[dwcsr]

You need a minimum of 18 for the booster to work correctly

[mahanian]

You have air in the lines and/or master cylinder, no doubt in my mind. The reason the brakes get firm when you pump it is because you are compressing the air in the lines and backfilling with brake fluid. The booster is working fine, that's why your foot goes to the floor when you start the truck. I had a very similar problem years ago when I replaced the master cylinder on my 67 Camaro. It's tough to get all the air out of the master cylinder. I had to bleed my brakes several times.

No matter if you have disc/disc, disc/drum, or drum/drum you will always have a proportioning valve. The front brakes should always take more load to prevent the rear from locking up.

My 2 cents...

One more thing...be sure to bleed the proportioning valve as well if it has a bleeder valve. Bleed till no bubbles are present

[VDOG]

Originally Posted by mahanian

You have air in the lines and/or master cylinder, no doubt in my mind.
No matter if you have disc/disc, disc/drum, or drum/drum you will always have a proportioning valve. The front brakes should always take more load to prevent the rear from locking up.
My 2 cents...
One more thing...be sure to bleed the proportioning valve as well if it has a bleeder valve. Bleed till no bubbles are present

I purchased a Vacuum Bleeder so I will try that today. Also where do you bleed the prop valve?

[sandking]

VDOG, if these are the same parts you got from me, they should work good. My brakes worked really good in the Blazer before I removed the parts. I do see the firewall booster bracket is different, its alot closer to the firewall. Check to make sure the shaft in the plunger is set correct. Try bleeding with the vacuum bleeder. Also, you may want to get a vacuum booster if your vac is too low, less then $60 from Summit Racing.

If you find any of the parts that I sold you bad, let me know, and I will refund your money.

[VDOG]

Originally Posted by sandking

VDOG, if these are the same parts you got from me, they should work good. My brakes worked really good in the Blazer before I removed the parts. I do see the firewall booster bracket is different, its alot closer to the firewall. Check to make sure the shaft in the plunger is set correct. Try bleeding with the vacuum bleeder. Also, you may want to get a vacuum booster if your vac is too low, less then $60 from Summit Racing.
If you find any of the parts that I sold you bad, let me know, and I will refund your money.

Hey Bro:
Everything is fine I have a better pedel since I used a vacuum bleeder.
The booster is different because I found this one with the brackets and arm so instead of transfering the brackets I just used the booster and your master. Guess I had a lot of air, the brakes are much better now. Just could not give up $75.00 for brackets new so when I saw the booster, I jump on it.

[mahanian]

I would suggest bleeding them again after 100 miles or so.

[Longhorn Man]

No matter if you have disc/disc, disc/drum, or drum/drum you will always have a proportioning valve. The front brakes should always take more load to prevent the rear from locking up.

GM says otherwise.
The drum/drum trucks have a distribution valve, not a proportioning valve.