c5mtl

iTrader: (3)

My car has been suffering from a case of incredibly weak brakes ..the pedal seems hard with absolutely no initial bite and will not engage the abs unless excessive force is applied. At slow speeds you have to plan your stops and factor in an extra few feet. Pedal has to go as far down as possible before you get any real stopping power . Brake booster passes all classic tests and holds vacuum for a good 15min after car is shut down. Weird thing is disconnecting the booster vacuum line did not change anything in the feel of the brakes. Almost like the booster is not doing anything . Car has a decent size cam in it 239/251 64? and makes about 7-8 inches vacuum at idle. Problem was still there with a smaller cam in my previous setup. Pads are new hawk hps rear rotors are new fronts are 1 year old. System has been bled 3 times and I don't think I have any air in there.
Maybe try a vacuum canister?? Also Brakes don't seem to get better as vacuum builds in the system. Abs system is tested works perfect with no codes
Comment please
Thx
99 a4 c5 408 1015rwhp 1000rwt

ULTIMATEORANGESS

iTrader: (4)

master cylinder?

c5mtl

iTrader: (3)

Passes the classic tests

ULTIMATEORANGESS

iTrader: (4)

ill go with something obvious. calipers?

c5mtl

iTrader: (3)

Thx for the suggestions but I don't think calipers are a problem ...car is capable of stoping from 150mph after a 1/4 run

Paul Bell

iTrader: (9)

This is the external ENGINE section.

You should be asking brake questions in the suspension & brake section OR the Corvette/C5 section.

LLLosingit

iTrader: (4)

You answered you own question " disconnecting the booster vacuum line did not change anything in the feel of the brakes"

If there was no change at all when it was disconnected then it's not working.

This also made think the booster isn't working "pedal seems hard with absolutely no initial bite"

LLLosingit

iTrader: (4)

You can also try these tests http://www.roadkillcustoms.com/hot-r...#axzz3CgeT6w82

c5mtl

iTrader: (3)

totally agree...but it open up another question....the fact the booster holds vacuum does it make it defective?? or is it just lack of overall vacuum

LLLosingit

iTrader: (4)

It should hold vacuum when it's not running as long as the diaphragm is good and the one way check valve is working. Inside the booster is a diaphragm and if I remember correctly one valve. If the diaphragm leaks you would most likely hear it.

I'm not a brake specialist by any means and have never had to replace a brake booster for any reason other than it leaking but since it does have other moving parts then it's possible that it could go bad for other reasons.

c5mtl

iTrader: (3)

problem seems to be totally related to low vacuum...ill cruise up to 40mph put the car in neutral bring the revs up to 2000rpm which now gives me 15in vacuum instead of 8 and brakes are flawless.....added a vacuum canister but it didn't seem to help....need a vacuum pump...any suggestions or experiences on model? Another thing ...why is it the all these high end snapon and auteil scanners cant do an automated abs bleed procedure on 97-03 c5's but have no problem with other gm cars of thoses years?? am I stuck going to the stealership?

ULTIMATEORANGESS

iTrader: (4)

is there a competent performance shop near you that can perform that service?

c5mtl

iTrader: (3)

Lots of shops and ever some good ones but nobody has a tech2

LLLosingit

iTrader: (4)

You could also look into a hydro boost setup, It's been done with junk yard parts. I don't know if it would be cheaper than a vacuum pump but it might be worth looking into. https://ls1tech.com/forums/conversio...ydroboost.html