low vacuum = bad brakes - Page 2 - Third Generation F-Body Message Boards

Gumby · 10-30-2005, 12:30 PM

Ok so from your test I have a bad booster control valve. Which would seam to make sense. Its letting off the air/vacuum to fast quick / noisy woosh.

But I still need to change the whole brake booster???
Or is the booster control fixable???

Bristol · 10-30-2005, 03:26 PM

I just tried mine too. The first step it passed but the second the pedal returned immedietly. Tried it on my 97 Prelude with exactly the same results. I definetly dont have problems with the Preludes brakes

Gumby · 10-30-2005, 04:09 PM

What kind of noise you getting?

Booster in car sounds like when you open the 2-3in empty hole on a airbed, woosh. Where the used one is just a normal hiss. And that was pushing the rods in by hand.

I just hadn't had time to yank stuff apart to drop the coulmn yet. Or I would know 100% by now. The book doesn't mention the bolts being an impossiable reach.

MurcoRS · 10-30-2005, 04:54 PM

Quote:

Originally posted by Gumby
Ok so from your test I have a bad booster control valve. Which would seam to make sense. Its letting off the air/vacuum to fast quick / noisy woosh.

But I still need to change the whole brake booster???
Or is the booster control fixable???

The control valve is what allows positive air pressure into the back of the diaphragm when you apply your brakes, thereby letting the vacuum do it's work. When you release the pedal the control valve closes and the vacuum equals on both sides of the booster, at which point the return spring pushes the diaphragm back. When the engine is turned off, and you have your foot on the brake pedal, the air valve is still open and the vacuum should remain constant unless your check valve is leaking or you have a bad control valve. Try the 2nd test again, if your booster kicked-back after the engine was shut off that is a problem. I've done this test to literally hundreds of cars and only had 3 fail it - and they needed boosters. Those cars had locked-up brakes as the booster vacuum turned the brakes whenever vacuum from the engine was present.
The control valve is not repairable or replacable, and you would need to do all the labor to get the booster out anyway as it's built into the back of it.

Bristol · 10-31-2005, 06:10 PM

http://www.zippyvideos.com/1029113622006156/idle/

Just a clip of my vacuum gage at idle in park then in drive etc.

Gumby · 10-31-2005, 10:52 PM

Well Bristol I give up on the brakebooster. I'm never gonna be able to get at those bolts. maybe if I remove my seat and steering wheel, maybe. And since I can't get a firm 100% clue if its good or bad I am gonna throw money at an easier to replace solution first.

Gonna get a new $24 master cylinder and see what happens.

Then Ill change or rebuild the prop valve then if still nothing works. Ill have to hire a midget to do it for me. But its gonna hafta wait till last. Or maybe you will find a solution first.

Gumby · 10-31-2005, 11:12 PM

Wonder where you can find a prop valve rebuild or another car you can steal one from? They don't list it for sale at any auto stores.

Gumby · 11-03-2005, 02:31 PM

If I get a stroke of genius or some tips I should have the master cylinder changed today. If you end up getting one bristol use advanced auto if you have them around you. AZ $24 with no reservoir LLT warranty, AA $24 with plastic reservoir and LT warranty

Gumby · 11-03-2005, 05:14 PM

Well it ain't the master cylinder. Though it was probably time to change it anyways. The bottom of it had some grey nasty resuide on it. But brake feel hasn't changed 1 tiny little bit. Still have brakes to slow down but soon hit a pressure wall and it has no more stopping power. Can't even lock them up in stone. Bleed the piss out of them again. Used two big bottles of fliud to flush well.

Bristol · 11-03-2005, 06:03 PM

Thanks for the update. Mines coming into my shop on Sunday and am gonna have a tchnician help me hunt. Ill keep you informed

Bristol · 11-06-2005, 10:41 PM

Didnt get alot of time to go over the car but we were able to finish the final adjustment to the rockers ((wow...what a difference in how she runs...tires are a roasting)) and wereable to verify the master cylinder is good, the booster is good, the system is free of leaks, air pockets and the lines are good. The technician strongly suspects the porportioning valve is acting up and that there appears to be a small vacuum leak. Hopefully next weekend we will look into the valve and then hunt for this leak.

Toehead · 11-07-2005, 01:04 AM

To Gumby

That bolt is a bitch... Took me about an hour. you don't have to remove the column... unbolt it and let it sag. That lets you get to the bolt

Gumby · 11-07-2005, 06:06 AM

Quote:

Originally posted by Toehead
To Gumby

That bolt is a bitch... Took me about an hour. you don't have to remove the column... unbolt it and let it sag. That lets you get to the bolt

Well the problem is I just can't get down that low easy. The steering wheel is in the way to much for me to get my big butt down there to work right, it or the front seat needs to move.
----------------------------

Bristol, sitting on pins n needles to find out, what you find out.
Thinking of letting things be for a while myself. With a stick I can slow down just fine and with winter comin, it may not be so bad to have soft brakes that don't lock easy. 25-28 city keeps the V6 under the hood and on the road year round.

Gumby · 11-18-2005, 04:58 PM

You ain't had no luck yet, either?

Bristol · 11-18-2005, 07:35 PM

Not yet. Im gonna work on it hopefully on Sunday again. Think Im gonna measure line pressure at each caliper.

JesasaurusRex · 11-18-2005, 08:13 PM

Quote:

Originally posted by CaptPicardsZ28
Here you go but I am moving it to a spot next to the brake booster where my MSD box is currently because I think my hoses are too long from the booster to the canister and i want to shorten them up.

Just put mine on today, curious, does it matter which line goes from the intake to the vac can (gold or black fitting) or is it irrelevant?

Bristol · 11-18-2005, 08:16 PM

Yes it does matter. The plastic connection is a 1 way check valve just like the one in the booster. I believe that the brass fitting line goes to the booster while the plastic fitting line runs to the intake.

JesasaurusRex · 11-18-2005, 08:20 PM

Quote:

Originally posted by Bristol
Yes it does matter. The plastic connection is a 1 way check valve just like the one in the booster. I believe that the brass fitting line goes to the booster while the plastic fitting line runs to the intake.

Thank u

757MANNY · 11-20-2005, 08:42 AM

HEY I OWN AN 86 IROC I PUT IN AN OVERSIZED CAM AND HAD THE SAME PROBLEM I HAD NO BRAKES THE ONLY THING I CAN RECCOMEND IS BUY AN OVERSIZED VACUUM CANISTER OR RUN 2 CANISTERS THATS WHAT I DID AND I CAN GET AT LEAST 3 GOOD PUMPS TO STOP BEFORE MY PEDAL GETS HARD. AFTER SPEAKING TO VETERAN HOT RODERS THEY TOLD ME THATS THE DISADVANTAGE TO A BIGGER CAM. IF YOU WANT A GOOD VACUUM CANISTER GET A CRANE CAM CANISTER.

Bristol · 11-20-2005, 12:15 PM

My technician at work thinks there may be a mechanical problem but if its just vacuum Ill buy an electric pump

Gumby · 11-25-2005, 09:37 PM

N E Word?

Gumby · 01-08-2006, 05:10 PM

Well I don't know if you got anywhere Bristol but I am gonna get a new prop valve ordered. Found them for $48 shipped, comes with new fittings.

the way it works and the way my back brakes acted leads me to it. They didn't want to bleed until pedal was pushed, n a few times for no reason as low speed, just lightly tapin the brake my left rear wheel locked for a sec.

plus geting the price to uder $50 was nice. [also rebuildable]
plus I won $175 in vegas off two bets and didn't even go. Told my Mom to bet 17 black and 36 red for me, well it ended up being a machine and had no colors, 17 didn't hit but 36 did. She said people on her trip won more at the money machines.

Bristol · 01-08-2006, 06:10 PM

Im probably gonna be doing a master but am considering doing the comination valve as well. Anyone have GM part numbers for a 91 Z28 1LE??

CaptPicardsZ28 · 01-08-2006, 07:31 PM

Quote:

Originally posted by 757MANNY
HEY IF YOU WANT A GOOD VACUUM CANISTER GET A CRANE CAM CANISTER.

And a crane cam canister is better because??? All canisters regardless of brand simply hold air. They are nothing but empty cans...

25thannivZ28 · 01-10-2006, 10:30 AM

Hey, im glad I ran into this subject. Just yesterday, I had called TPiS and bought their ZZ-X cam .050 239/239 .558/.558 112 deg. In addition, got the Mini-ram and 58mm TB. Do you foresee vacuum being an issue with this? Anyone running this type of Cam/intake? Thanks.

CaptPicardsZ28 · 01-10-2006, 01:13 PM

Quote:

Originally posted by 25thannivZ28
Hey, im glad I ran into this subject. Just yesterday, I had called TPiS and bought their ZZ-X cam .050 239/239 .558/.558 112 deg. In addition, got the Mini-ram and 58mm TB. Do you foresee vacuum being an issue with this? Anyone running this type of Cam/intake? Thanks.

If I recall correctly, a normal cam for tpi is 114 deg, so your 112 deg cam shouldn't be a problem I don't think. If it is it would be a small one and a canister would be more than enough to help with brakes.

Gumby · 02-06-2006, 08:16 AM

N E Word Bristol?

Bristol · 03-05-2006, 11:04 AM

Sorry to leave you hanging Gumby. Heres the latest. I had the car out ((day permit)) to attend a local care cruise/meet. I tried a few things. I came down a slight hill and let the engine do the braking. I hit the brakes hard and well they grabbed hard for the first time in months.I played around with the car a little and yesterday for whatever reaseon ((no vacuum leaks)) she ran really good considering the mods and stock tune but the idle was like 750rpm and the brakes felt really good....not great but easily well enough. Im currently doing the whole prom tuning so Ill let you know what comes of it.

Gumby · 03-05-2006, 05:45 PM

what all did ya do?

did ya change the prop valve or just tune?

Bristol · 03-05-2006, 06:39 PM

I just set everything back to factory spec. an reset some sensore and kick down cable. and tried dropping to drive at a good clip going down a hill. As the engine began to wind down hit the brakes and they fely good. Im currently having help getting a tune done and as soon as its done Ill let you know