Welcome to Just Commodores, a site specifically designed for all people who share the same passion as yourself.

New Posts Contact us

Just Commodores Forum Community

It takes just a moment to join our fantastic community

Register

Weird brake problem

Brett_jjj

Well-Known Member
Joined
Oct 16, 2009
Messages
6,805
Reaction score
94
Points
48
Location
Tamworth NSW
Members Ride
vs commodore
Yesterday I replaced the front and back brake pads,I removed the calipers to clean up and grease the slide pins, and to generally make sure the caliper seals etc were all ok...I completely drained the old brake fluid and bled the system.The pedal feel was nice and firm like it should be,I drove the car to bed the new pads in,and they bedded in perfectly...Then last night whilst driving into town,the brake fail dashligh came on, and the brake pedal was just about going to the floor when the pedal was pressed.I thought I must have left a bleeder screw a bit loose and she'd sucked in a bit of air,so I thought Id just check them and rebleed it this morning.Now this morning the brakes are back to normal again,they are exactly like they should be with new pads and a bled system.I checked the bleeder screws and brake hose connections, everything is sealed tight and not leaking at all.Ive never seen this happen before in all the years Ive been doing my own brake services.Has anyone ever had this happen, or heard of it happening, or maybe have an idea of what might have caused it.Ive since driven all over town this morning and they are working excellent again.
Its a VS with no ABS.
 
Last edited:

88GreenVN

Next Exit Left
Joined
Jun 12, 2006
Messages
6,795
Reaction score
135
Points
63
Age
57
Location
Surprise, Arizona
Members Ride
Dodge Ram Van 1500 5.2 V8
Sounds like it had 1 small amount of air left in the lines. The second bleed did the trick hey.
 

Brett_jjj

Well-Known Member
Joined
Oct 16, 2009
Messages
6,805
Reaction score
94
Points
48
Location
Tamworth NSW
Members Ride
vs commodore
I didnt end up re bleeding them this morning though,because they are back to normal again,the pedal is firm with normal travel like it should be,and it was just as firm first up yesterday when I bedded the pads in,this is what I cant work out,the brakes were excellent first up yesterday,then last night they went to the floor and the brake fail light was on,then this morning they are back to normal again with no light showing..
 

88GreenVN

Next Exit Left
Joined
Jun 12, 2006
Messages
6,795
Reaction score
135
Points
63
Age
57
Location
Surprise, Arizona
Members Ride
Dodge Ram Van 1500 5.2 V8
Strange indeed. Even if the booster fails you still have a firm pedal. The only way the pedal can go to the floor is if there is air in the line some place.
 

Brett_jjj

Well-Known Member
Joined
Oct 16, 2009
Messages
6,805
Reaction score
94
Points
48
Location
Tamworth NSW
Members Ride
vs commodore
Strange alright,I cant work out what could have caused it. Theres definitely no air in the system as the pedal is heaps firm like it should be and has the proper travel,the booster is working fine,when the brake pedal is held in and the engine is started,the pedal sinks in a bit like it should..Its got me stuffed why its happened.And I dont feel safe driving it knowing that it went to the floor just out of the blue, but now is back to "normal" again.Ive found from past experiences that if a bit of air is still in the system,it usually just makes the pedal a bit spongy with a bit longer travel,but last night it was nearly to the floor.
 

immortality

Can't live without smoky bacon!
Staff member
Joined
Apr 15, 2006
Messages
17,259
Reaction score
6,609
Points
113
Location
Sth Auck, NZ
Members Ride
HSV VS Senator, VX s2 Calais S/C
possibly a master cylinder that is on it's way out.

was there a lot of pedal travel with the old pads or generally more travel then you have now?
 

Brett_jjj

Well-Known Member
Joined
Oct 16, 2009
Messages
6,805
Reaction score
94
Points
48
Location
Tamworth NSW
Members Ride
vs commodore
Yeah,there was a bit more travel there before I replaced the pads and fluid,but there usually is,the pedal always seems to get a little bit longer when the pads are near the end of their life.The travel was not excessive though,but you could tell the difference between how they were before and after the pad change,less travel and a good firm pedal.It "feels" just like it always has when Ive put new pads and fluid in,theres no difference there from any other time ive done it..I agree,I think its something up with the master cylinder.Theres nothing else that I can see,that would cause the pedal to just go to the floor just out of the blue and cause the brake fail light to come on.Ive been checking out the VT front brake conversion anyway,the VS is way underbraked at the best of times for a car that size and weight so I might kill 2 birds with 1 stone.Thanks for your time and input guys.cheers.
 

88GreenVN

Next Exit Left
Joined
Jun 12, 2006
Messages
6,795
Reaction score
135
Points
63
Age
57
Location
Surprise, Arizona
Members Ride
Dodge Ram Van 1500 5.2 V8
The VT M/C booster upgrade is very much worth the effort. All 3 of my VN's have now had this upgrade and I'm very happy with the brakes on all 3. None had the calipers or rotos changed so still stock in that area. I figure we are not racing anyone so if we have to stop big time once we can give the brakes a while to cool while we change undies :) so no need for 1,000 worth of rotors/calipers.
 

immortality

Can't live without smoky bacon!
Staff member
Joined
Apr 15, 2006
Messages
17,259
Reaction score
6,609
Points
113
Location
Sth Auck, NZ
Members Ride
HSV VS Senator, VX s2 Calais S/C
so whats happened most likely is that where the pistons was in the master cylinder it has worn into the alloy a little with the old pads, when you fitted the new pads the piston has moved back some in the master cylinder pack past the wear point. there may be a small ridge/lip in the master cylinder where it has let fluid past the piston allowing it to travel a lot further.

the VT style MC is a straight bolt on (to your existing booster) but you need a small spacer to go between the MC and booster to get the spacing correct. or you could adjust the rod as it has a threaded section on the end but i'm not sure what length it would need to be adjusted to
 

immortality

Can't live without smoky bacon!
Staff member
Joined
Apr 15, 2006
Messages
17,259
Reaction score
6,609
Points
113
Location
Sth Auck, NZ
Members Ride
HSV VS Senator, VX s2 Calais S/C
The VT M/C booster upgrade is very much worth the effort. All 3 of my VN's have now had this upgrade and I'm very happy with the brakes on all 3. None had the calipers or rotos changed so still stock in that area. I figure we are not racing anyone so if we have to stop big time once we can give the brakes a while to cool while we change undies :) so no need for 1,000 worth of rotors/calipers.
i'll 2nd that. makes a huge difference to the brakes.
 
Top