Brake Booster Opinions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

rusty71 · 06-04-2016, 01:12 PM

I converted my 71 to have power brakes, I'm certain I have all the pedal rods adjusted correctly, because the pedal travel and play in the pedal feel pretty good. My problem is my brake pedal is still hard. I had a new 7" single diaphragm booster on the shelf so I just used it. Do you all think it could be too small for the truck? My engine is a stock 350 and makes plenty of vacuum. With the engine off and pumping up the brake pedal, I can't hear or feel the vacuum leaking the booster. When I start the engine with the pedal pushed I didn't notice the pedal drop either. This makes me think the booster is bad rather than the rod not pushing the master cylinder piston all the way in, I didn't seem to have any trouble bleeding the brakes when I did that. Any opinions would be appreciated.

**Rickysnickers** · 06-04-2016, 02:16 PM

Take the vacuum line off the booster and see if the pedal is still the same. If it is, it could be the booster is bad. You could use a vacuum pump to see if the booster holds vacuum as well.

davepl · 06-04-2016, 02:35 PM

Cycle the pedal several times when the engine is off to make sure any residual vacuum is gone first.

Then do exactly like you did - start the truck with your foot off the brake. If it doesn't suck the pedal down ANY, then you've clearly got a bad booster or bad connection or check valve or something, but most likely the booster.

After running it pull the hose, see if there was any vacuum being held in the reserve - there should be. You'd hear/feel it when you pull out the big check valve fitting.

Andy4639 · 06-04-2016, 07:54 PM

I just went through this with a 8" booster and I hated it. I swapped a good 11" booster for the whole setup in 8" chrome booster and master cylinder. I hated it. The brakes felt terrible so I went back to the factory 11" and all is well now.

rusty71 · 06-05-2016, 03:33 PM

Quote:

Originally Posted by davepl

Cycle the pedal several times when the engine is off to make sure any residual vacuum is gone first.

Then do exactly like you did - start the truck with your foot off the brake. If it doesn't suck the pedal down ANY, then you've clearly got a bad booster or bad connection or check valve or something, but most likely the booster.

After running it pull the hose, see if there was any vacuum being held in the reserve - there should be. You'd hear/feel it when you pull out the big check valve fitting.

I tried those to diagnose it and the pedal feels exactly the same, still a hard pedal. I can drive the truck down the road and get it to stop its just really difficult. I want that good solid throw you through the windshield pedal. lol Even thought the booster is new I'm starting to think its bad or too small, and isn't giving me enough line pressure.

rusty71 · 06-05-2016, 03:35 PM

Quote:

Originally Posted by Andy4639

I just went through this with a 8" booster and I hated it. I swapped a good 11" booster for the whole setup in 8" chrome booster and master cylinder. I hated it. The brakes felt terrible so I went back to the factory 11" and all is well now.

That's good to know! Was it just a regular single 8" diaphragm booster? Or was it the 8" dual diaphragm booster? I was considering the 8" dual diaphragm for my truck, because I like the cleaner look of the small booster, but if it doesn't work very well I won't bother buying one.

**Already Gone** · 06-05-2016, 04:37 PM

I just ordered this one in black.

http://67-72chevytrucks.com/vboard/s...d.php?t=691791

**A1971Blazer** · 06-05-2016, 04:41 PM

I just got an 8" dual diaphragm set-up for my K5..........I haven't installed it yet because I had to make up a new rear brake line from the front coupling all the back to the rear hose and two new lines across the rear axle.

The PO had someone replace the lines and apparently they just bought two ready-flared lines that were too long. It was a twisted up, cobbled up mess with a leaky compression fitting in the mix as well.....after I got it all back together and bled out..........the brakes are working fine....

I should have the 8" set up on soon....I'll update as soon as I git 'r done....

Dan Wales · 06-05-2016, 06:29 PM

Just went through this with a 8" booster on friends 66. He went through 2 boosters before getting a good one on the third try.

Dan

rusty71 · 06-09-2016, 04:08 AM

Quote:

Originally Posted by A1971Blazer

I just got an 8" dual diaphragm set-up for my K5..........I haven't installed it yet because I had to make up a new rear brake line from the front coupling all the back to the rear hose and two new lines across the rear axle.

The PO had someone replace the lines and apparently they just bought two ready-flared lines that were too long. It was a twisted up, cobbled up mess with a leaky compression fitting in the mix as well.....after I got it all back together and bled out..........the brakes are working fine....

I should have the 8" set up on soon....I'll update as soon as I git 'r done....

Definitely post your results with the new booster. Sounds like I may have brand new booster that's bad from everything that's been posted. I may just switch back to a full 11" booster and see what happens.

Andy4639 · 06-09-2016, 07:55 AM

Quote:

Originally Posted by rusty71

That's good to know! Was it just a regular single 8" diaphragm booster? Or was it the 8" dual diaphragm booster? I was considering the 8" dual diaphragm for my truck, because I like the cleaner look of the small booster, but if it doesn't work very well I won't bother buying one.

It was the dual one and I'm telling you you want be happy until you go with a 11". GM used them for a reason on the 1/2 ton trucks!

Tiger Joe · 06-09-2016, 08:45 AM

FWIW I have no issues with my dual 7" booster on my truck and it works just fine

Custom 68 · 06-09-2016, 02:45 PM

I'm sure different brands and quality will work differently.

rusty71 · 06-10-2016, 02:50 AM

Quote:

Originally Posted by Custom 68

I'm sure different brands and quality will work differently.

I have no doubt about that, the trial and error part sure sucks though.

rusty71 · 06-10-2016, 02:56 AM

Okay, so I just read in another thread on the forum that the brake pedal needs another hole drilled in it about an inch lower, to give the correct pedal ratio when converting a truck that didn't originally have power brakes. I have NOT done that to my truck. Has anyone else done this? Maybe this is my problem and I'm not pushing the piston in the master cylinder in all the way.

06-04-2016, 01:12 PM	#1
rusty71 Registered User Join Date: Oct 2013 Location: Western, Ky Posts: 26	Brake Booster Opinions I converted my 71 to have power brakes, I'm certain I have all the pedal rods adjusted correctly, because the pedal travel and play in the pedal feel pretty good. My problem is my brake pedal is still hard. I had a new 7" single diaphragm booster on the shelf so I just used it. Do you all think it could be too small for the truck? My engine is a stock 350 and makes plenty of vacuum. With the engine off and pumping up the brake pedal, I can't hear or feel the vacuum leaking the booster. When I start the engine with the pedal pushed I didn't notice the pedal drop either. This makes me think the booster is bad rather than the rod not pushing the master cylinder piston all the way in, I didn't seem to have any trouble bleeding the brakes when I did that. Any opinions would be appreciated.

06-04-2016, 02:16 PM	#2
Rickysnickers Senior Member Join Date: Oct 2014 Location: Eagle, ID Posts: 2,984	Re: Brake Booster Opinions Take the vacuum line off the booster and see if the pedal is still the same. If it is, it could be the booster is bad. You could use a vacuum pump to see if the booster holds vacuum as well.

06-04-2016, 02:35 PM	#3
davepl Registered User Join Date: Aug 2006 Location: Redmond, WA Posts: 6,332	Re: Brake Booster Opinions Cycle the pedal several times when the engine is off to make sure any residual vacuum is gone first. Then do exactly like you did - start the truck with your foot off the brake. If it doesn't suck the pedal down ANY, then you've clearly got a bad booster or bad connection or check valve or something, but most likely the booster. After running it pull the hose, see if there was any vacuum being held in the reserve - there should be. You'd hear/feel it when you pull out the big check valve fitting. __________________ 1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible

06-04-2016, 07:54 PM	#4
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: Brake Booster Opinions I just went through this with a 8" booster and I hated it. I swapped a good 11" booster for the whole setup in 8" chrome booster and master cylinder. I hated it. The brakes felt terrible so I went back to the factory 11" and all is well now. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

06-05-2016, 04:37 PM	#7
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,105	Re: Brake Booster Opinions I just ordered this one in black. http://67-72chevytrucks.com/vboard/s...d.php?t=691791 __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021

06-05-2016, 04:41 PM	#8
A1971Blazer Senior Member Join Date: Nov 2013 Location: East Tennessee Posts: 2,128	Re: Brake Booster Opinions I just got an 8" dual diaphragm set-up for my K5..........I haven't installed it yet because I had to make up a new rear brake line from the front coupling all the back to the rear hose and two new lines across the rear axle. The PO had someone replace the lines and apparently they just bought two ready-flared lines that were too long. It was a twisted up, cobbled up mess with a leaky compression fitting in the mix as well.....after I got it all back together and bled out..........the brakes are working fine.... I should have the 8" set up on soon....I'll update as soon as I git 'r done.... __________________ 1967 C10 Step side 1968 C10 Step side 1970 Chevrolet K/5 Blazer 1972 Chevrolet K/5 Blazer .............

06-05-2016, 06:29 PM	#9
Dan Wales Registered User Join Date: Aug 2013 Location: Lake Wales Florida Posts: 50	Re: Brake Booster Opinions Just went through this with a 8" booster on friends 66. He went through 2 boosters before getting a good one on the third try. Dan

06-09-2016, 08:45 AM	#12
Tiger Joe Registered User Join Date: Mar 2015 Location: South of Pittsburgh Posts: 428	Re: Brake Booster Opinions FWIW I have no issues with my dual 7" booster on my truck and it works just fine

06-09-2016, 02:45 PM	#13
Custom 68 Registered User Join Date: Nov 2001 Location: Springfield, MO Posts: 2,928	Re: Brake Booster Opinions I'm sure different brands and quality will work differently. __________________ Dave 1968 Custom Chevy with turbo charged 5.3 gen III 4l80e swap 1967-71 GMC 3/4 ton long step 4x4 (not sure what year exactly?) "A good friend will bail you out of jail...but a true friend will be sitting next to you saying "that was frekin awesome". "If it doesn't fit force it...If it breaks then it needed to be replaced anyway!"

06-10-2016, 02:56 AM	#15
rusty71 Registered User Join Date: Oct 2013 Location: Western, Ky Posts: 26	Re: Brake Booster Opinions Okay, so I just read in another thread on the forum that the brake pedal needs another hole drilled in it about an inch lower, to give the correct pedal ratio when converting a truck that didn't originally have power brakes. I have NOT done that to my truck. Has anyone else done this? Maybe this is my problem and I'm not pushing the piston in the master cylinder in all the way.



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