air in brakes

johnboy914 · 09-02-2003, 07:40 PM

I have bled my brakes 5 times now, each time I bleed them I end up with a very firm pedal and super responsive braking. The next day, there is squish in the pedal and my eBrake warning light is on. If I bleed the brakes again, the blinker goes off and I have a firm pedal again. I dont understand how I can be getting air in the system. My brake system is 19mm MC, front calipers and rotors from a 73T and stock rear with Pvalve in place.

Any thoughts??

John Rogers · 09-02-2003, 07:55 PM

If it were me I'd get rid of the p-valve and use a tee, make sure you have the correct clearance between the piston and rod in the m/c and then use the two person bleeding method. You never mentioned if these were new calipers as that will affect the way the pedal acts and you never mentioned how you bled them??? Good luck

johnboy914 · 09-03-2003, 03:31 AM

The fronts are not new. As for bleeding, I am using the one guy method, hose on the bleed screw into a container of brake fluid so when I stop pumping no air should be sucked into the caliper, only fluid.

John Rogers · 09-03-2003, 06:38 AM

Well I've tried that method and it never seemed to work for me. I use the two person method even with Speed Bleeders and so far I've never had a problem with air. Good luck.

914GT · 09-03-2003, 08:34 AM

If the pedal is firm after bleeding but goes back down the next day, that sounds like a master cylinder problem to me. If you don't have the Speed Bleeders you can get one of these H.F. one-man bleeders (http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=37201) for $3.99. You can remove the plastic bottle and attach tubing from the check valve to a larger container for those big bleeding jobs. They are cheap and you can use them on more than one car.

Bleyseng · Bleyseng's Garage

Check your brake lines as there might be a crack in them too. If they are old replace them quick!

Geoff

johnboy914 · 09-03-2003, 01:34 PM

MC came off of my other car where it worked just fine, all the flex lines are SS. I don't remember howmuch/if there was any clearance between the brake pedal pushrod and the MC. it doesn't make any sense to me a brake system is pretty simple.

The first time that I bled them I did have a buddy over so we did the two person thing. Could be PValve somehow be introducing air b/c of the bigger front calipers?

I don't want to start replacing parts without a good reason. That is a good way to anger the missus.

914GT · 09-03-2003, 02:20 PM

About the only way you can get air back in the lines is if you have a leak and your reservoir runs low, and that should show up a some fluid dripping out somewhere. Have you checked around the m.c. for fluid leaks? Make sure that the pedal has enough free play for the piston to return fully. It's possible some dirt got dislodged and into the cylinder when you moved it, causing one of the piston seals to leak. If there's air in the p-valve then it's there all the time, it wouldn't be firm right after bleeding. If the valve has a leak to allow air in, it would also be leaking fluid especially when you push down the brake pedal.

johnboy914 · 09-03-2003, 02:33 PM

that is what I thought, but there is no leaking of fluid anywhere that I can see, I will lift up the carpet and see if it is peeing on the floor. I hope not, thanks all, I will let you know how it goes. I travel for work so it drives me nuts that I can't just go out to the garage and fix it. I have to stew about it til the weekend.

Scooter311 · 09-04-2003, 06:11 AM

Hiya Johnboy
Hmmmm, sounds like the same thing that happened to me after my conversion. Everthing worked fine before I changed over, but after a day or two they'd start getting soft. My calipers are 73T also, and before I installed them, I took them apart and cleaned them real good, and put 'em back in. However, the pedal started getting soft, and I couldn't find any leaks anywhere. All my lines are stainless, new and clean, and I have a "T" in the rear, and even stock rear calipers too.
It turns out the left front was sucking a little air, so the swell fellas at Pelican sold me a rebuild kit for 16 bucks - it took a half hour to remove/rebuild/replace and bleed the whole deal. Now it stops REALLY well. I should've done that in the beginning, but live an' learn.
Hope that helps
Ciao
Jeff

johnboy914 · 09-04-2003, 07:07 AM

Scooter -
nice, thank you very much. I am guessing that a caliper rebuild isn't too complex or requires any funky tools. I am definately up for tackling that. That is a load off my mind.