Too much brake pressure

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On the way to the repair shop to have the ball joints done on my 1979 surburban 1/2 ton the brake became really hard to push down. I'm wondering if the problem could be the power brake
booster?.. snipped-for-privacy@comcast.net
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A leaking booster and/or vacuum line are the most likely cause. Either way, very low vacuum makes the pedal get very hard. Unless you have hydra-boost, then it is connected to the power steering pump and it might be something as simple as low fluid level. There could be another cause, but these are the first ones that popped into my head.
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This happened on my suburban. Turned out the filter mounted on the vacuum line (from engine to booster) clogged and the booster stopped working. So I suggest you check this filter, costs ~$5 at any autoparts store.
mark
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"DIONYSUS" wrote

Easy to check.....turn off the engine, pump the brake pedal a few times, hold the pedal down while you start the engine, does the pedal sink down when the engine starts? If not, you have a vacuum/brake booster problem.
Ian
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Re: Too much brake pressure Group: alt.autos.4x4.chevy-trucks Date: Sun, Oct 19, 2003, 5:31pm (CDT+5) From: snipped-for-privacy@hotmail.com (shiden_kai) "DIONYSUS" wrote On the way to the repair shop to have the ball joints done on my 1979 surburban 1/2 ton the brake became really hard to push down. I'm wondering if the problem could be the power brake booster Easy to check.....turn off the engine, pump the brake pedal a few times, hold the pedal down while you start the engine, does the pedal sink down when the engine starts? If not, you have a vacuum/brake booster problem. Ian
Sound more like a vacuum problem than a booster problem .....To solve it just goto the nearest parts store. get a new hose and check valve..The ones that are on it are probly factory ...Which are like over 20yrs old to begin with....My motto is go with the cheapest solution first..which in this case is the vac line and check valve...Then you can buy yourself some beer, and tell your buddies how you fixed it all by yourself.
Steve C
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Well as of today Oct 22,2003 i've replaced the filter between the manifold and the check valve, and the check valve.However the problem remains way too much pressure needed to push brake pedal down, and not much brake when i can. Before i go for a new booster $(125.00 yikes) i'm gonna try bleeding the extra air if any out of the brake lines and /or adjusting the rear brakes . I have a service manual for a newer (1991) surburban and it mentions worn brake linings as a possible reason for exessive pedal pressure and my rear brake shoes could use some adjusting. I'm gettin desparate here ,and i don't want to spring for $125.00 for a new power booster especially if its not the snipped-for-privacy@comcast.net On Sun, 19 Oct 2003 14:57:21 -0500 (CDT), The_Gear snipped-for-privacy@webtv.net (Steve Cook) wrote:

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wrote:

Air will cause a SOFT pedal, not an excessively hard pedal. Same with worn linings, they'll cause you to have to push farther, but possibly not harder. I say you'll need to spring for a new booster...
On Sun, 19 Oct 2003 14:57:21 -0500

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Re: Too much brake pressure Group: alt.autos.4x4.chevy-trucks Date: Thu, newer Air will cause a SOFT pedal, not an excessively hard pedal. Same with worn linings, they'll cause you to have to push farther, but possibly not harder. I say you'll need to spring for a new booster...
Dude disconnect you check valve ....Then tell me you have a soft peddle....A Vacuum Brake booster is run off of what ???????Thats right Vacuum....So When the trucks running thats why my peddle softer than when its not..That right Petey the hose from your check valve goes to somewhere on your mantifold.. Which in return gives you booster the vacuum it needs....Worn pads will cause a soft peddle I give ya that....
Never heard a booster give a hard peddle...Not saying it wount....Everytime I ve had one go ..It would have a soft peddle ,and you would hear air when you pressed in the peddle...But if it somehow got restricted to where vacuum cannot be applyed....Then i can see it....
Steve C
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On Thu, 23 Oct 2003 20:53:50 -0500 (CDT), The_Gear snipped-for-privacy@webtv.net (Steve Cook) wrote:

If you read what I quoted, the guy was going to bleed the brakes in hopes of fixing the problem. I was telling him that it wouldn't help. If the booster fails, it's not working and can cause a hard pedal, that's how I see it, but I've not had one fail on me.
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I'm confused now how do i determine if the problem is the booster only? When i disconnect the vacuum line from the filter to the check valve (New) the truck just keeps running no change in idle shouldn't the idle get rough or the truck stall do to loss of so much vacuum? I can feel the suction strongly at the hose i've disconnected from the check valve when i do take it off the check valve. So how do i determine if the booster is gonzo?... snipped-for-privacy@comcast.net On Fri, 24
wrote:

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Re: Too much brake pressure Group: alt.autos.4x4.chevy-trucks Date: Fri, Oct 24, 2003, 12:35am (CDT+1) From: snipped-for-privacy@comcast.net (DIONYSUS) I'm confused now how do i determine if the problem is the booster only? When i disconnect the vacuum line from the filter to the check valve (New) the truck just keeps running no change in idle shouldn't the idle get rough or the truck stall do to loss of so much vacuum? I can feel the suction strongly at the hose i've disconnected from the check valve when i do take it off the check valve. So how do i determine if the booster is gonzo?... snipped-for-privacy@comcast.net On Fri, 24 Oct
Take your check valve out of your booster ...With it still on the hose now do you have vacuum through the valve? you said you disconnect the valve from the hose to check it but the valve needs to be on....If you have vacuum through the valve to the booster then replace the booster... Steve C
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Ian already told you how to check the power booster. With the engine OFF, pump the pedal up until you have good pressure. Holding the pedal DOWN, start the truck. The pedal <should> drop to the floor like a stone. If it doesn't budge, you have a bad power booster. Read replies more carefully; you could have diagnosed this and fixed it a week ago.
Doc

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Re: Too much brake pressure Group: alt.autos.4x4.chevy-trucks Date: Fri, Oct 24, 2003, 3:44am (CDT+5) From: snipped-for-privacy@levyclan.nospam.us (MikeLevy) On Thu, 23 Oct 2003 20:53:50 -0500 (CDT), The_Gear snipped-for-privacy@webtv.net (Steve Cook) wrote: Re: Too much brake pressure Group: alt.autos.4x4.chevy-trucks Date: Thu, newer Air will cause a SOFT pedal, not an excessively hard pedal. Same with worn linings, they'll cause you to have to push farther, but possibly not harder. I say you'll need to spring for a new booster.
. If you read what I quoted, the guy was going to bleed the brakes in hopes of fixing the problem. I was telling him that it wouldn't help. If the booster fails, it's not working and can cause a hard pedal, that's how I see it, but I've not had one fail on me.
Ok maybe you should be more clearer in your posts.....Air in the braking system (LINES)will cause a soft peddle. So no need to bleed ..If your vacuum line has a hole in it and sucking AIR you will have a hard peddle.....Yes you should feel vacuum in the line to your check valve....If you dont follow it to the intake to see if its hookes up or if your hose is bad.....Just saying air when talking about a booster is like saying its over there without pointing... Steve C
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. . . .
. Group: alt.autos.4x4.chevy-trucks Date: Thu, Oct 23, 2003, 2:22am (CDT+1) From: snipped-for-privacy@comcast.net (DIONYSUS)
Well as of today Oct 22,2003 i've replaced the filter between the manifold and the check valve, and the check valve.However the problem remains way too much pressure needed to push brake pedal down, and not much brake when i can.
<edit>
I'm gettin desparate here ,and i don't want to spring for $125.00 for a new power booster especially if its not the problem... ///////////////////////////////////////////////////////////////// simmer down.......
Is the vacume routed by itself, or do you have it tied in to something else...??
Have you been working on the brakes?
Try this....
make sure that the pedal linkage under the dash isn't binding for some weird reason.
make sure you don't have the brake fluid filled all the way to the very top.
unbolt the master cylinder enough to wiggle it around a little....see if you hear a vacume leak.
have a buddy loosen one line at the master cylinder JUST ENOUGH TO LEAK ... WHILE YOU PRESS THE PEDAL..... tell him to close it before you get to the floor.. no air...no prob.
they are all quick easy tests....
if that doesn't give you any results, or if you want to give some answers to the 2 questions at the top.....do a repost and we'll try again to save that electric bill money for you.
MarshMonster ~:~
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When my booster went out (96) The brakes worked ok if I braked easily, if I hit the brakes quickly the were hard. I also heard a noise (vacuum) when they were applied. Also I had my foot on the brake with the engine running and turned off the engine, the pedal pushed my foot up.
(shiden_kai)

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People got along with non-power brakes for decades... I have them in my 72' Malibu. Just stop harder if your pockets are deep.
(shiden_kai)

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"KJ" wrote

72'
I don't know if you are aware of this or not, but there is a substantial difference between standard brakes (non-power assisted) and power assisted brakes that no longer have the assist.
I had non assisted brakes in my 71 Road Runner. They weren't great, but they weren't that bad either. But try driving around in a modern car or truck with the assist disabled......you won't like it.
Ian
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True, and I have done that. But no one likes spending money they don't have. Use two feet if that's what it takes - as long as the truck will still stop.
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"KJ" wrote

have.
stop.
Right, and be a danger to everyone on the road around you. You often have more stopping power with one of the hydraulic circuits completely emptied of fluid...then you do with non-assisted power brakes. Like anything else, if you don't have the money to keep the vehicle in operating trim....then you might just as well walk, or take the bus.
Ian
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Re: Too much brake pressure Group: alt.autos.4x4.chevy-trucks Date: Sat, Oct 25, 2003, 3:21am (CDT+5) From: snipped-for-privacy@hotmail.com (shiden_kai) "KJ" wrote True, and I have done that. But no one likes spending money they don't have. Use two feet if that's what it takes - as long as the truck will still stop. Right, and be a danger to everyone on the road around you. You often have more stopping power with one of the hydraulic circuits completely emptied of fluid...then you do with non-assisted power brakes. Like anything else, if you don't have the money to keep the vehicle in operating trim....then you might just as well walk, or take the bus. Ian
I'm with Ian on this one..... Steve C
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