Upgraded Brakes......no pedal pressure

Mark Howard · 09-06-2002, 10:43 AM

Hi guys. Been a while since I posted last.

My summer project has been to upgrade the suspension and brakes on my '75. I did everything to the brakes: ss lines, caliper rebuild, new pads, new spring clips, new rotors, 19mm MC, new feeder lines, everything but the reservior is new.

I finished last night and my wife and I bled the system well. No leaks and good clean Super blue fluid. Took her for a spin, but no pedal pressure, I mean none! I had to bottom out the pedal just barely stop at 5 mph!

What can it be? When I disassembled the system, I removed and cleaned all the lines, including the pressure regulator in the rear. Took forever to get the fluid through the system, but it all came through. I even double bled all nipples after the air was out.

I expect to have good pedal pressure, but not as good as my 911, but this thing is not even safe to drive down the street.

Opinions?

SummerSledSix · 09-06-2002, 12:00 PM

If you had a firm pedal when you were bleeding your brakes and now you don't, look for a puddle (or trail) of brake fluid somewhere. Could be you under / overtightened something and you have a leak. Has the level in your reservoir changed much since you filled it?

Next, I'd suggest checking your master cylinder pushrod adjustment. When I replaced my master cylinder (from a 19 to a 23), the pushrod was a different length because the M/C piston "bottom" was at a different position relative to the pedal cluster.

Also, are you sure you got all the air out of the proportioning valve? If you blew air through it, it may be clean, but they can be a bear to get filled again. At least one of the manuals / tech articles suggests bleeding the b@st@rd on the bench before you put it in.

So how did you bleed the brakes to begin with if your pedal goes to the floor? Bet your wife will think twice before she gets in the car for awhile

.

John Rogers · 09-06-2002, 12:01 PM

Air! You'll have to bleed them some more. If you are doing the 2 person bleed procedure, make sure the fluid level NEVER gets too low in the reseviour. Have you wife pump the pedal, then crack open the bleed screw till fluid runs out then close it while her foot is on the floor. If you are using Speed Bleeders you can crack them and then pump the air out. Make sure there is a short upward hump in the bleed line so air will not try to get back into the caliper. Make sure the m/c piston is returning fully and that there is the correct clearance between the rod and the piston. Since the system was empty it will have lots of moisture inside so after they get bleed properly, drive it a little then bleed the system some more. I imagine you have a bunch of air still in the prop valve at this time? Good luck.

philinjax · 09-06-2002, 03:08 PM

Mark,
Did you get a hard pedal when bleeding the brakes and before the test drive?
What was the caliper rebuild procedure?
Phil

jabb · 09-06-2002, 03:38 PM

Make sure the calipers have not been switched around.
Make sure the bleeders are on the top of the calipers.
The bleeder needs to be at the upper most part of the caliper.

Mark Howard · 09-08-2002, 08:29 PM

I have not had a chance to re-bleed yet to see if air is the problem. Pedal pressure was somewhat firm, so that does lead me to believe there is more air in the system.

Summer: no leaks, checked and double checked. all looks good. the 17 and 19 are identical in size when compared to each other, so I'm not sure about the pushrod length. Something to consider. Air is likely the cause.

Phil: I pulled the calipers and replaced the seals, did NOT split the calipers per the PP tech article recomendations. Cleaned the rust, used emory cloth on the pistons, bead blasted the calipers and reassembled.

Jabb: The calipers have two bleed nipples, upper and lower. I bled both. Switching the calipers around? Not sure on that one. Sent them off to be bead blasted and not sure which was which when the came back. I ASSUMED they were interchangeable.. Am I wrong?

philinjax · 09-09-2002, 05:28 AM

The pistons have to be oriented so that the heal of the raised face on the piston tops are "down stream" of the rotation of the rotor. These orientations are left-right sensitive so, if you interchage the left caliper with the right caliper after rebuilding, you are going to have squeal, chatter and uneven pad wear.

Phil

Jim Smolka · 09-09-2002, 05:41 AM

Try bleeding the system again, only loosen the top bleeders.

Is fluid comming out in a good stream when bleeding??

jabb · 09-09-2002, 06:02 AM

Since you have a lower and bottom bleeder you are OK ,
Like Jim mentioned I would just bleed the top bleeder

Mark Howard · 09-09-2002, 07:54 AM

Thanks, guys, understand. Will bleed again and again!

Phil: Wouldn't it almost be impossible to reverse the calipers due to the direction of the parking brake lever?

philinjax · 09-09-2002, 12:48 PM

Mark: Sorry, I was referring to the front calipers, not the rear.
Good luck at it.
Phil

scotty914 · 09-09-2002, 07:40 PM

i second and third the push rod lenth mine was not building pressure till the last 1 inch of pedal travel

adjusted it and wow !