vt brake upgrade front and rear

[peter1]

Vr v6 abs with vt front and rear brake with vs booster with vt master cyclinder the problem i am having is the brake pedal good but when driving the brake pedal is getting harder and biulding up pressure and it starts and then lock up the rear brakes unless once you slow the pressure drops.If not i have to release the pressure by undoing the brake bleeder nipples.

[Brett_jjj]

Sounds like a problem with the master cylinder not relieving the fluid pressure properly and its building up pressure and holding the rear brakes on.Id check out the booster pushrod etc and if its all ok,then get either another master cylinder or a rebuild kit for it.Also is the brake pedal returning fully to the pedal stop?If not check the pedal return spring,and is the ABS light showing at all.It might be an error in the ABS system.You can check the ABS system for error codes just like you can flash up the error codes for the ECU.You just bridge terminals 5 and 12 on the 16 pin ALDL diagnostic plug under the steering column to flash the ABS codes up on the ABS dashlight..The ALDL connector terminal numbers go from right to left,top to bottom,so terminal 1 is the first top right one.And terminal 16 is the last left bottom one.
(I also remember reading somewhere that someone had trouble like you with the rear brakes holding pressure and they had done the VT conversion too on a VS.It ended up being something to do with the VS booster pushrod length or something along them lines.So might also be worth looking at if you dont find anything else wrong.Im pretty sure he also had a low spoongy pedal sometimes too)

[RX25SE]

As above, the pushrod on the VS booster is too long for the VT master.
I spaced my master away from the booster.
Do not pull the pushrod out of the booster as the reaction disc inside the booster may drop out.

[peter1]

Hi thank you for your advice and help and my brake pedal goes back to normal and I'm going to try to putting spacer between the booster and master cylinder after i check my abs codes once i try this i'll let you know how it goes thanks for your help.

[Cheap6]

The ABS solenoids have one way valves in them that prevent fluid pressure from being trapped between the wheel cylinders and the solenoid. The only way the ABS can be involved is if one of those was blocked i.e. it will almost certainly be the length of the pushrod as above.

[RX25SE]

The ABS solenoids have one way valves in them that prevent fluid pressure from being trapped between the wheel cylinders and the solenoid. The only way the ABS can be involved is if one of those was blocked i.e. it will almost certainly be the length of the pushrod as above.

To add to this,
If it was a blockage, no ABS code would be logged.

[edals]

Question, If you just simply put on VT/VX Brake callipers onto a Standard VR, Do you need to upgrade the brake master cylinder or will it still be fine even though your going from single pot to twin pots.

[RX25SE]

Question, If you just simply put on VT/VX Brake callipers onto a Standard VR, Do you need to upgrade the brake master cylinder or will it still be fine even though your going from single pot to twin pots.

Depends on the bore size.

Try a search as there is a very good chance all your questions have been answered.

[peter1]

thank you the problem was the pushrod once i put spacer all good thank you for all your help much appreciated.