Bleeding Spongy Brakes, Proportioning Valve Questions Options

[Cjllong]

I did a rear brake pad replacement. After putting everything back together and bleeding the brakes, I still had spongy brakes. I inspected the old rubber lines and found a leak. I bought 4 steel braided brake lines and intalled them all today. I re-bled the brakes, using the family member method mentioned on Pelican Parts, and STILL have spongy brakes! (IMG:style_emoticons/default/headbang.gif) I have double checked everything and nothing leaks. The Pel. Parts article mentions bleeding the proportioning valve, but it's not very clear to me as to how it's done. Does anybody have any pics of this valve and how to bleed it correctly? I believe I still have the 17mm master cylinder and I think I'm going to have to buy the 19mm. I just have to do it secrectly, so my wife doesn't find out!! Thanks!

[LowGT]

did you set the venting clearance on the rear pads before bleeding?

[race914]

At one time I developed a persistent spongy pedal. After going through all of the standard procedures (several times), I finally received a tip to have a helper lightly tap on the proportioning valve while bleeding the rear brakes. Sure enough, even though I had just bled the back brakes (several times) with no air bubbles. With the tapping I got a couple big bubbles. That fixed the problem and the spongy pedal was gone..

I can't say you are experiencing the same problem, or if this will fix your spongy pedal, just sharing my experience.

Probably worth a try though!

[TravisNeff]

The procedure on the prop valve is to slowly unscrew the inlet (the line that comes from the shift tunnel in the cabin) with a rag around the fitting, crack and have someone pump the pedal (once will probably do), then tighten. Go to the outlet side and do the same.

Your spongy pedal may also be due to swollen pedal bushings in your pedal cluster.

I finally went and got some speed bleeders, flushed the fluid until clean then used a quart of fluid (recycling the fluid) and spent a hour or two bleeding - its all good now!

[McMark]

Check this thread out...

[davep]

There are a few other tricks.
Most important, do not let the fluid level in the reservoir get too low such that air gets into the master cylinder. If you have to replace the MC and or brake lines this can be impossible. However it can be minimized.
Be sure to set the rear pad venting clearance to 0.004" before bleeding, and be sure the front pads lock the rotors when you do them.
Original rubber lines are preferred over all other lines.
Old rubber lines need to be replaced at least every 10 to 15 years.
The time honoured method of pumping the brake pedal to bleed the brakes has the advantage of compressing air bubbles and helping them move through the system.
Rapping with a hammer (dead blow preferred) while pumping has the best chance of dislodging bubbles. This works for both the proportioning valve and the calipers.

[Cap'n Krusty]

Still no answer to the question "did you set the venting clearance?" Did you? The correct setting is .004", and you'll NEVER get a good pedal until it's set correctly. In close to 35 years of 914 service, I've never had to mess with the proportioning valve. Ever. Oh, and scrap those SS lines ............. The Cap'n

[Cjllong]

I did set the venting clearance, but the tech article on PP said .008". I guess I can try .004", but that's the first I've heard of that. What's wrong with the steel braided lines? Thanks for all the other responses!

[TravisNeff]

.008 is a misprint from the factory and it got it's way into various manuals for the car. .004 is the spec to use.

[Cjllong]

I'm suprised Pelican Parts hasn't changed that in thier tech article. I checked my Haynes manual and it also said .008".

[davep]

Make the correction in your Haynes manual in ink. The Cap'n is a dealer trained mechanic, and got the info direct from the factory instructors. This is one bit of false info that got out and was never properly corrected.