Help identifying brake booster

[1stchevy]

PO installed the booster on my truck and I'm pretty sure it isn't working. I have a new master cylinder and prop valve and the pedal is hard as heck to push down. I checked vacuum from the engine and it's pulling pretty good. Any help is greatly appreciated.

Chris

[425HP409]

To test a vacuum booster,
First: with the engine off, depress the pedal three or four times to remove any residual vacuum in the booster.
Second: hold pressure on the brake pedal and while holding it down, start the engine
Third: If the booster is operating correctly, the pedal will go down when the engine started while you are still holding pressure on the brake pedal.

[1stchevy]

I've tried that also, the pedal drops very slow and I feel like I have to stand on the brakes to get them to stop.
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[68gmsee]

I have one similar to yours that I used on my 69 Chevy. It's been many years ago but I recall taking it the booster off a 77 Chevy Impala.

Has the truck always had this problem?

It does sound like the booster is bad. After you check as mentioned above and before you condemn it to the scrap pile, check the linkages real careful. Make sure the problem is not the adjustment on the pushrod link between the booster and master cylinder. It has to be correct and they do make two styles of master cylinders. One with the recessed piston area being shallow and another that's deeper. The pushrod has to match.

Also, there's a possibility the proportioning valve is malfuntioning and/or the brakes/pads have become glazed over.

[1stchevy]

Yes the truck was like that when I bought it. I purchased the truck about a year ago and installed front disc and 5 lug swap and 4/6 ECE drop and I've only driven the truck around the block a few times because the brakes are so hard to get to stop.
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[Sport/Truck]

This is probably a good question to ask here as it could be your problem.
I was told that if your running a cam, it may not have enough vacuum to properly run the booster.

Thats what I was told by a local custom shop here in Albuquerque when I inquired about a brake booster.

Can anyone confirm this?

Chirs, have you measured your vacuum or just used your thumb to feel it?

[1stchevy]

It has got a bit of a lope to it and I've only checked vacuum by feel.
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[68gmsee]

I would just go get a vacuum gauge at local auto parts and check the engine vacuum at idle. These gauges are fairly cheap and a good tool to have to adjust idle/air and carb settings.

[1stchevy]

Thanks 68gmsee I'll pick one up and check the vacuum on it. If it is a bad booster would I be able to just get either the Delco or Bendix booster and bolt it on.
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[68gmsee]

Originally Posted by 1stchevy

Thanks 68gmsee I'll pick one up and check the vacuum on it. If it is a bad booster would I be able to just get either the Delco or Bendix booster and bolt it on.
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Yes. The better ones will cost you some dollars. I prefer buying local myself since I can always return them if it's not what I want or if defective but be aware that they're usually a cheap rebuild.

[PanelDeland]

Also check the check valve.It should have a directional arrow on it.The arrow should point away from the booster.

[1stchevy]

I'll check it also thanks Panel!
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[1stchevy]

Originally Posted by 68gmsee

Yes. The better ones will cost you some dollars. I prefer buying local myself since I can always return them if it's not what I want or if defective but be aware that they're usually a cheap rebuild.

When you say better ones I guess your referring to a brand new booster not a remanufactured one.
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[1stchevy]

So does anyone have any clue as to what kind of booster I currently have installed on my truck? And do any supporting vendors have new boosters for sale?

[1stchevy]

ttt
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[red69ss]

it looks similar to the one on my truck, which I was told came off an 84 c10.

If it were me I would go to a stock booster for one of these trucks, thats what I plan to do if something happens to mine. The reman. ones are less than $100, you may have to use a stock bracket and rod if you went that route.

Here's a pic of the one on my truck, I got this booster with the truck and I pulled the master cylinder off the firewall and installed it . it works great.

[1stchevy]

Thanks for the info red69ss!

[red69ss]

Originally Posted by 1stchevy

Thanks for the info red69ss!

no problem , after going back and reading your post I think 68gmsee is pointing you in the right direction. I would check the vaccum with a gauge ,if you have a lot of cam you may need a vaccum canister. I've never dealt with this but the guys here can help you through it.

The last truck I had the brakes were not great on , I always blamed it on the fact it had a small seven inch aftermarket booster on it . The truck had a pretty big cam in it and it could have been the vaccum instead. good luck

[1stchevy]

Checked vacuum from the engine it's good and when I pull the check valve out of the booster I also get the burst of air. I'm thinking the booster on my truck might be a 3/4 ton booster and the master cylinder is for a 1/2 ton. Can anybody tell by looking at my pics?

[68gmsee]

Originally Posted by 1stchevy

Checked vacuum from the engine it's good and when I pull the check valve out of the booster I also get the burst of air. I'm thinking the booster on my truck might be a 3/4 ton booster and the master cylinder is for a 1/2 ton. Can anybody tell by looking at my pics?

Possibly, yes. It should work though. I have the same booster I used on my 69 1/2 ton. Can't tell from the pic what m.c. you have. Maybe if you post a pic of the master cylinder itself.

Also, give us a little more info on your truck. Year, 1/2 ton or 3/4 ton? I'm assuming disc/drum but additional conversion to all disk?

One other thing to be aware of is that in some instances the rear and the front lines were reversed and on disc/drum it does make a difference.

[1stchevy]

The truck is 69 1/2 ton with a front disc conversion, 1/2 ton master cylinder and prop valve rear is drum. I know that a 3/4 ton booster and a 1/2 ton master cylinder will not work together. All of the 1/2 ton boosters I've seen have a recessed area that the master cylinder bolts to and the booster on my truck is flat.

[68gmsee]

Originally Posted by 1stchevy

The truck is 69 1/2 ton with a front disc conversion, 1/2 ton master cylinder and prop valve rear is drum. I know that a 3/4 ton booster and a 1/2 ton master cylinder will not work together. All of the 1/2 ton boosters I've seen have a recessed area that the master cylinder bolts to and the booster on my truck is flat.

Booster face is flat? I don't think I've ever seen one. All I've ever seen also have a recessed center.

Any chance you can get a number of it?

[68gmsee]

Here's a site to do a comparison.

http://www.getdiscbrakes.com/disc-br...-brackets.aspx

[1stchevy]

Yes booster face is flat. I'll try to get a number later.
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