Ed Scherer

Last weekend, I installed some Big Red brakes with cast hole rotors on the fronts. Did the bigger shields behind the rotors, too. Also took the opportunity to paint the rear calipers red. It wouldn't have been that big a job, except for two complications: a frozen bolt on one of the front calipers (had to drill it out and then wait a few days to get a replacement bolt), and the fact that my 17" wheels didn't quite fit over the calipers (1/4" wheel spacers took care of that).

Anyway, there's one problem left: spongy pedal . Bad enough that I can't take the car on the road yet. I thought I had gotten all the air out (I'm using pressure bleeding techniques, BTW), but there's still obviously some air in there *somewhere*. So my first question is: when putting in new calipers, where does the air tend to collect? I noticed that after I thought I had the air out, I tried hitting the calipers a little with a rubber mallet, and sure enough, it knocked a few more bubbles loose. Should I unbolt the calipers and shake them up a bit? Looking for some BTDT experiences...

Also, how much air am I looking for? Are a few tiny bubbles enough, or is there really a bigger pocket of air somewhere?

--
Ed Scherer
'90 928S4

Thom1

Hi Ed,

Sorry to here about your woes. As Rosanna Rosannadana said: "It's always somethin'."

See <a href="http://www.pelicanparts.com" target="_blank">www.pelicanparts.com</a> for brake bleeding procedures. I used a one man bleeding tool. It is just a check valve (one way) that slides over the bleeder. I pumped the pedal with the car running until I saw solid blue going through the tool's clear hose, added some more pumps, then closed the bleeder valve. (However, now I would start by using the check valve type of bleeder valve (speed bleeder) mentioned in earlier posts.) I kept filling the reservoir up to where I could see fluid so I would be sure no air was getting in. The problem with pressurizing the system from the reservoir is: You can run out of fluid in the reservoir, and let air in. However, pressurizers that keep adequate fluid in the reservoir should be fine. The Pelican site also lists a bleed sequence to follow: master cylinder, RR, LR, RF, LF. Use ATE Super Blue Racing brake fluid, alternate flushes with Gold. It is German with a high boiling point.
<img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

dr bob

Using the pressure bleeder is a Good Idea.

The Pelican sequence is right, but you might want to remember that you bleed the inner chanmber then the outer chamber on the four piston calipers.

If you still have air in the system after bleeding the calipers in place, you can rotate the caliper slightly so that the bleed screws are at the highest position on the caliper as you bleed.

There was a thread here in the last few weeks about the crossover pipe position on some replacement caliper kits. The calipers need to be installed with the arrows pointing in the normal wheel rotation direction, and the bleeders need to end up in the top positions when installed. Apparently some caliper packages were being installed without moving the pipes to the opposite ends.


/end of thought process.

dr bob

Another thought (after the end of the previous thought process...) is that you may have air in the ABS pump --if-- you ran the MC reservoir dry while pressure bleeding. I don't have a handy procedure for purging air from that part, maybe somebody will jump in with a hint or two. Wally?

Ed Scherer

Thom:

I'm using SpeedBleeders, as you suggested. The <a href="http://www.928gt.com/Brakes.htm" target="_blank">pressure bleeder I'm using</a> pumps fluid into the reservoir so I'm about 99% sure I didn't get any air in on that end.

I'm using ATE Super gold this time (there was blue in there before). I'm just about to run out of gold, so if I can't get the air out within about another 0.1 litre of fluid, I'll switch to blue again and replace all the gold. I've got 2 litres of blue.

Dr. Bob:

Hmmm... I did RR, LR, RF, LF order, but I did outer then inner.

I'll try unbolting the calipers and trying to get them more vertical. I'll probably tilt them back and forth and rubber mallet them a little more, in hopes of shaking a few more bubbles loose.

The thread a week or two ago about the crossover pipe / bleed screw swap thing was actually something I started, as my Big Red calipers came without the swap having been done. It's no big deal as long as you know you have to do it. There was at least one guy who, once I raised this issue, discovered that his calipers had been installed the wrong way around. Bummer.

Thank you both for your help. I'll be taking another hack at it tomorrow.

--
Ed

Jay Wellwood

Ed-

Soething else you can try is using the Mitivac pump for removing the air possibly in the calipers. Pretty easy to do and a 1 person job as well. Just be sure to check the brake fluid reservoir often.

hth-

Thom1

Hi Ed,

Sounds like you are just about there.

Dr Bob's inner first could be it.

Caliper reorientation and tapping could help too.

The ABS system... I sure hope not. But, he could have a point there too. I would look into that as a last resort due to the mystery of that component.

You did not mention bleeding the master cylinder. Do that before any other component.

I have not used a pressurizer. You can clean the brake fluid reservoir, and shine a bright light through it. You must be able to see fluid there at all times. Could a pressurizer put air into the system? Probably not, if you always see fluid in the reservoir. The old fashioned method of pumping the brake pedal with the engine running works great.

Even with speed bleeders (which I have not used yet either – they are supposed to be one way/check valves) could air leak into the caliper with the speed bleeders open too far?

Is the engine running during bleeding? With power assisted brakes, could the lack of power muck up the system? Perhaps someone could prove me wrong on this point?

HTH,
<img src="graemlins/roflmao.gif" border="0" alt="[hiha]" />

Joe R

YA know the spongy feel could just be that the pads are not bedded in and are touching on an edge first. This can give the symptom of long pedal travel and spongy feel.

Ed Scherer

For those of you who might have been curious, I did manage to get the brakes bled successfully (a couple of weekends ago or so).

I unbolted the front calipers and rotated them and twisted them, rapped on them a bit with a rubber mallet, and then bled them. Sure enough, got a few more bubbles. Seems to have made a big difference.

Anyway, I'm really happy with the installation now.

(Photos of the finished job as well as the some photos of the installation procedure)

--
Ed

Jerry 87 928S4

Ed, sure looks nice! Thanks for the pictures.

bad S4

Ed, You are an inspiration,especially to me with a Black S4.
It is time for new brakes on Bad S4 and I may go
with your set-up
Thanks
Olonzo Roberts
Bad S4
87 S4
Blk/Blk
5-Speed.
27K Miles
New York City

bad S4

Also Ed,
Where did you purchase the Big kit and rear drilled Zimmermans and caliper paint
Thanx
Bad S4

Ed Scherer

I got the Big Reds and all rotors from 928 Specialists.

--
Ed

Ed Scherer

Oh... and the caliper paint was from G2 USA.



I'm not sure I'd recommend the brush-on caliper paint that I used over the spray-on paint that I think people usually use. The G2 is a perfect color match for the Big Reds, but I was a little slow and was having some problems with it getting a little thick by the time I was done with both calipers. It didn't help that I painted them in a warm room with a fan blowing (heat plus lots of air movement certainly contributed to the paint drying pretty quickly). You'd never notice from a distance, but it wound up not being quite as smooth as I would have liked.

If you look at the above photo (click to get a big, high-res version), you can see that the caliper I painted (small caliper on top) has an identical color to the Big Red (big caliper on bottom). The little imperfections I mentioned in the previous paragraph probably aren't discernable in this photo; the digitial photo just doesn't capture it.

tdelarm

Ed,

How's the new brake set-up feel to your old ones?
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />