Scott Turnbull

OK, I am stumped. When I pulled my car into the garage to do the auto to manual conversion 8 months ago the brake pedal was solid as a rock. After conversion, both the brakes and the new clutch system were spongy.

I removed the clutch slave and did the "push the rod all the way in" thing and also bled the clutch master from inside the car. Worked great! Clutch is solid and I have now driven the car around the block 4 times (much to the dismay of my neighbors....the Yeti does howl!). Clutch and drive train are working great!

However, even after bleeding 3 full quarts ($30) of Super Blue through the system using both a power bleeder and the wife pumping the pedal methods (no, not at the same time) and doing both the "start at the farthest wheel method" and the "new Wally, start at the brake master, then the fronts, then the rears" methods, the pedal is still spongy! Obviously, no leaks anywhere

The only variables/changes to the brakes system during this process were done in the last couple days of the conversion. They are:

* Cut the end of the "nipple" off the brake fluid reservoir where the "Blue Hose" attaches, and attached Blue Hose to supply the clutch system.
* Changed all four stock brake lines to new braided steel lines.
* Then bled, bled, bled......

Trying to get her on the track in a couple weeks to sort out the conversion and need to get this figured out by then. I am out of ideas. Any help/ideas are greatly appreciated.

Scott Turnbull

**BUMP**

Bill Ball

Well, none of the experts are jumping in, so me, who has never seen the workings of the brake and clutch hydaulics on a 928 up close, is going to wade in...

Is there a loop or high spot in the new hosing that could be trapping air? Most likely you still have air trapped somewhere in the new plumbing.

Scott Turnbull

Thanks for the reply Bill. That seems logical, but the only item moved or replaced was the new SS brake lines. Additionally the new lines were installed incorrectly on the front at first in a big "U" shape with the bottom of the U facing down. This should have been conducive to bleeding. I changed the lines around the proper "S" shape and bled them again. Still no difference. Everything else on the system was untouched and was sealed the whole time I did the conversion until the final couple of days. The lines were change quickly and not left open for more than a few seconds while they were being replaced.

Robert_H

Scott,

When I did my brakes, I was also getting a very spongy feel at the pedal. It turned out to be the seals to the pistons in the calipers. Both fronts had very small leaks which allowed the spongy feeling, but not enough to see a leak of any kind.

Rob

GlenL

If the car is street legal I'd drive it around for a few days then bleed it again.

TeufelHei

I don't think the Marana PD would like that too much.

Scott: "But officer I was only going 15 MPH"
5-Oh: "Be that as it may, your son was not wearing a helmet or his harness, and this is a school zone!"

Scott Turnbull

Ron,
Thanks for the tip. I am not seeing any leaking, but didn't know there could be that small of a leak to cause this kind of a problem. I will check that out. How did you test/find this issue?

Glen,
Good suggestion, but definitely NOT street legal. And with my exhaust I can't exactly be sneaky.

Tim,
You're a nut!

Bill Ball

Did you read this thread?....

https://rennlist.com/forums/showthre...ft+brake+pedal

Rod Underwood

This will probably expose my ignorance, but I once had a truck with the same problem, not with both, but with the brakes alone after installing a new master cylinder, new calipers and pads, and bleeding it all to death.

Ultimately I found that the brake actuator rod - between the pedal and the master cylinder - was ever so slightly out of adjustment, even though I had not touched it. The new master cylinder had slightly different clearances and a simple adjustment of that rod made the brakes hard as a rock. I guess it wasn't allowing the piston to move far enough forward or return far enough to allow fluid in and out correctly.

Having never gotten into my new 928 which I don't even have home yet, I have no idea if this is relevant.

Don't throw tomatoes if I'm totally off base.

Rod

GlenL

Did you bleed the master?

Rubber or braided SS lines?

algie928s4

Hands on experience after same experience was tapping the calipers whilst bleeding for any trapped air and a new bleed nipple on master cylinder- don't know which one did the trick but A okay now.(S4), a friend with an S2 found a small nick in his blue pipe- okay now.
And if your racing, don't you go faster all the time without brakes?

TeufelHei

Yeah Scott, brakes are over rated anyhow.

v-tach

i had the same problem with my 86.5. changed the brake master cylinder, fluids -still spongy. then i got high performance brake pads - what i difference...
v-tach

Scott Turnbull

Bill,
Thanks for the link. Gave me some ideas to check. The Brakes feel spongy with the car off or running. They will not "pump up" by pumping them several times and then holding the pedal.

Rod,
That is interesting. I will play with the adjustment on the brake actuator rod. Wouldn't have thought of that.

Glen,
Bled the master three times. SS Lines.

algie928s4,
I will try tapping, shaking the calipers and re-bleeding. Bleed nipples should be ok, but will consider this if other options fail. Used a brand new Blue Hose for the conversion. I am not quite the racer as many of the others on this site. I still need brakes!

Tim,
Quit posting on my threads. People will start thinking I know/like you.

v-tach,
Brake master is only a couple of years old and I have race compound brake pads installed already. Brakes were fine when I pulled it in the garage.

Thanks all for your ideas. I will do a little more work this weekend and see where we get.