Brake Bias Valve Question
04-04-2008, 09:15 PM
#1
Rennlist Member
Thread Starter
Brake Bias Valve Question
Has anyone put the 5/33 Brake Bias Valve from the 928 on their 968? Part number is 928.355.305.02. Anyway, do you have to completely bleed the brakes prior to removal? I suspect yes, but wanted to ask the experts. I searched the forum and could not find a definitive answer...
Thanks in advance.
Rob T.
Thanks in advance.
Rob T.
Last edited by rob76turbo; 04-04-2008 at 09:16 PM. Reason: Fix part number error
04-05-2008, 01:16 AM
#2
Rennlist Member
It's fun to get to and takes small hands / patience... but you do not need to bleed or empty the brakes prior to replacement of the valve. The process will leak a bit of fluid, but it's not too bad. Protect painted surfaces, etc. You do need to bleed the system afterwards.
Now, whenever you "open up" the brake system, you want to bleed the appropriate part(s) of the system. The valve is a little special. It attaches to the ABS pump in the fender, which has its own little internal brake fluid reservoir, separate from the main (plastic) reservoir. For this reason, bleeding the ABS becomes a function of actually cycling the ABS.
By this I mean, you've got to engage it pretty actively so that it forces any air out of the pump and pump plumbing. My method included a good power bleed of the system (that's a litre of fluid). Take the car out on wet roads and light up the ABS like there's no tomorrow for a while (general disclaimer here, make sure you obey all laws, drive safely, be alert to any changes in braking performance, etc.). Then, power bleed the whole system again with another litre.
Each one litre bleed, if spaced pretty evenly across the four corners (and clutch if you're ambitious), is pretty much a complete replacement of the brake fluid in the system. My rationale was:
- Push all captured air out of system in general
- Release any air in ABS pump or it's reservoir (the ABS cycling exercise)
- Now push any of that captured air out
I hope this helps.
Now, whenever you "open up" the brake system, you want to bleed the appropriate part(s) of the system. The valve is a little special. It attaches to the ABS pump in the fender, which has its own little internal brake fluid reservoir, separate from the main (plastic) reservoir. For this reason, bleeding the ABS becomes a function of actually cycling the ABS.
By this I mean, you've got to engage it pretty actively so that it forces any air out of the pump and pump plumbing. My method included a good power bleed of the system (that's a litre of fluid). Take the car out on wet roads and light up the ABS like there's no tomorrow for a while (general disclaimer here, make sure you obey all laws, drive safely, be alert to any changes in braking performance, etc.). Then, power bleed the whole system again with another litre.
Each one litre bleed, if spaced pretty evenly across the four corners (and clutch if you're ambitious), is pretty much a complete replacement of the brake fluid in the system. My rationale was:
- Push all captured air out of system in general
- Release any air in ABS pump or it's reservoir (the ABS cycling exercise)
- Now push any of that captured air out
I hope this helps.
04-06-2008, 08:25 AM
#4
Three Wheelin'
I used a set of vice grips and a rag (so as not to damage the valve itself) and just took it slow. It's not that bad, you just need some stubby wrenches and like I said, a set of vicegrips really helps!
Steve
Steve
04-06-2008, 12:37 PM
#5
Rennlist Member
Ditto what Steve said. I hate being able to turn something only a few degrees at a time, so patience was the ticket for me. I do not recall any other specific magic pointers.
