Need help with weak brakes
Thread Starter
Drifting
Joined: Feb 2005
Posts: 1,869
Likes: 61
From: montreal quebec
Need help with weak brakes
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 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 ear 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
Thx
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
Thx
Last edited by c5mtl; Sep 7, 2014 at 02:31 PM.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Try a vacuum canister.
During deceleration, you build higher vacuum and will charge the canister. Use the stored vacuum to actuate your vacuum booster. 7-8 inches of vacuum isn't going to adequately apply vacuum to the brake booster.
Bill
During deceleration, you build higher vacuum and will charge the canister. Use the stored vacuum to actuate your vacuum booster. 7-8 inches of vacuum isn't going to adequately apply vacuum to the brake booster.
Bill
Thread Starter
Drifting
Joined: Feb 2005
Posts: 1,869
Likes: 61
From: montreal quebec
As always Bill is the man to help and suggest fixes....thx for the comments
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
After you plumb in your vacuum canister, and IF, you find out that it just isnt enough, you can add in a simple 12 VDC electric vacuum pump that will pull and keep a vacuum on the canister. There are several different sizes and systems. it wouldnt take too much to keep the resivour at the correct vacuum. They also sell limit switches that will shut the pump off at a specific vacuum.
http://www.amazon.com/s/?ie=UTF8&key...l_3svdb63ihc_b
Heres a vacuum control switch that you could easily add in to have an automatic system
http://www.amazon.com/s/?ie=UTF8&key...l_3svdb63ihc_b
Heres a vacuum control switch that you could easily add in to have an automatic system
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
do you have a huge cam? i've never seen 7-8' unless the car has broken ringlands. of course i know it can be from a large cam but that's extremely low vacuum.
completely agree with bill about the canister by the way
completely agree with bill about the canister by the way
Thread Starter
Drifting
Joined: Feb 2005
Posts: 1,869
Likes: 61
From: montreal quebec
defiantly not broken ring lands ...motor is new and strong made 1014rwhp
cam is 240/250 range 650 lift ...even my 230.242 cam only made about 9inchs....i have unplugged everything looking for vacuum leaks and found none...boost tested system and everything on the boost side was sealed tight.... Let me ask this does running breather on valley cover and both valve covers hurt vacuum production?
cam is 240/250 range 650 lift ...even my 230.242 cam only made about 9inchs....i have unplugged everything looking for vacuum leaks and found none...boost tested system and everything on the boost side was sealed tight.... Let me ask this does running breather on valley cover and both valve covers hurt vacuum production?
Safety Car
Joined: Aug 2011
Posts: 4,442
Likes: 407
From: Portland OR
Have you bled it while activating the the abs pump. I had to pay the dealer to do that with the tech2. It helped. I had gotten air in there.
Also, any chance you have glazed the pads? It might be worthwhile to have a look.
Some things to consider.
I had the same issues.
Ron
Also, any chance you have glazed the pads? It might be worthwhile to have a look.
Some things to consider.
I had the same issues.
Ron
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Crankcase pressure doesnt effect manifold vacuum. On your boosted engine a vented crank case is the way to go.
That being said, you could possibly benifit HP wise from a crankcase vacuum pump to keep the crancase in a very slight vacuum.
That being said, you could possibly benifit HP wise from a crankcase vacuum pump to keep the crancase in a very slight vacuum.
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Thread Starter
Drifting
Joined: Feb 2005
Posts: 1,869
Likes: 61
From: montreal quebec
After driving for 15 min the pedal is not hard anymore but still needs to go to floor before any real stopping power happen...almost like air in the system....gonna bleed and install canister...see what happens
Thread Starter
Drifting
Joined: Feb 2005
Posts: 1,869
Likes: 61
From: montreal quebec
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?