Brake Question

porschenewbe · 01-06-2007, 06:03 PM

OK, I have already searched the forum and found some good info but does not seem to answer my question.

I changed my front brake pads on my '83 944 NA and then I could not get any real pedal even after bleeding the brakes. It acted like the master cylinder was bad so I changed it out . . . still no pedal.

My wifes leg is about to fall off from bleeding the $*^&(* out of the brakes but still no better. We have used two bottles of fluid so I feel like all the air should be out. I am bleeding with a piece of tubing attaced to the bleeder and submersed into a bottle of brake fluid, I also bled the master cylinder itself before hooking up the lines. With the car off we can get a nice firm pedal but as soon as we start the car, down to the floor it goes. Been a LOONNGG time since I have had a booster problem on any car and I really don't remeber the steps to determine if there is a problem. You guys have been great in helping me so far so THANKS in advance!

Rusty

pdx944 · 01-06-2007, 06:15 PM

Slave cylinder?

Razorback1980 · Razorback1980's Garage

Most important advice I will give you. Power bleeder is cheaper than the cheapest attorney out there!

Did you have good brakes before changing that pads?

porschenewbe · 01-07-2007, 01:11 AM

Yes, I had good brakes before changing the pads. I've never heard of a power bleeder, how does it work? I have bled brakes on many many cars and trucks over the years and never had a problem like this one. But then again, I have never seen a "valve cover gasket" this hard to change either.

Baza · Baza's Garage

It may sound funny but try bleeding your rear brakes

Lawrence Coppari · 01-07-2007, 03:21 AM

Fill the master cylinder reservoir to the brim with fluid. Mine has a weir in it so if you don't fill it all the way up, the front half doesn't fill. The front half is for the rear.

Power bleeders work really well. I got another reservoir cap and made my own.

Razorback1980 · Razorback1980's Garage

Hey Rusty,

The part I don't understand is how or why there would be air in the system after just changing the pads. Did you open the bleeder valves to move the pistons back? If you did that would explain it. I generally use a large C clamp so I don't have to open the hydraulics.

Here is a write up on the motive one, but there are many out there. I have the motive one as well.

Review of Motive Power Brake Bleeder

Basically it just allows you to force the fluid through the system with small amounts of air pressure. A lot of times when I'm changing fluid which I do about once a year or so (I'm not sure if that is the right interval or not, it's just part of my January maintenance), I will put a different color brake fluid in the master cylinder and when I'm at the wheels, I will see the new color come through and that tells me all the old fluid is out. Sounds like this might be the right opportunity to change your old fluid out as well....of course by now you already have.

I agree with Baza, bleed everything especially if you put on a new master cylinder as that put air in the back system as well.

Good Luck

porschenewbe · 01-07-2007, 08:05 AM

I did not open the bleeder when I changed the pads but after changing and not being able to get a pedal I first tried bleeding the brakes. I used a C clamp to compress the caliper and since I could not get a pedal after changing the pads I thought forcing the fluid back through the old master cylinder may have caused some damage to hardened seal. So, I changed the master cylinder and still no luck. I looked at the pictures for power bleeders and I am pretty sure I can make one next week and give it a try. As far as bleeding goes, I always start at the right rear, left rear, right front and then left front. I have done this multiple times. We have tried slow steady pumping, agressive fast pumping and everything in between. I plan on bleeding the clutch system but I don't think the two systems are connected in a way that will cause the problems I am having. Sounds like you guys are pretty convinced I still have air somewhere in the system so I will keep working in that direction!

Thanks for all the responses.

Razorback1980 · Razorback1980's Garage

Sounds like you are doing everything right. I agree with you on the clutch system. They only share the same fluid reservoir I am pretty sure. Should not change your problem here. Be nice to put a pressure gauge on the master to see what pressure you are getting from it. Air may still be in there although you would think it would be long gone by now.

A power bleeder isn't the problem here...it just gets your wife out of helping you and you out of trouble!

Lawrence Coppari · 01-08-2007, 05:15 AM

The clutch system is easier to go get into trouble with than the brake system. Why not get one straightened out before working on the other. The fluid pickup for the clutch system is in the upper half of the rear wheel portion of the reservoir. If you get air in this system, it is more difficult to remove than air in the braking system. It is easy to get the fluid level below the pickup level for the clutch.

Power bleeders are best to use. Besides making it a single person job, you also avoid shoving the piston in the master cylinder beyond the normal point. If you have a crud buildup in your master cylinder beyond where the piston usually travels while driving the car, you force the piston past the crud, possibly causing problems.

Slam · 01-08-2007, 10:39 AM

Any damage to the rubber brake hoses? How old are they? You could also try jacking up the rear of the car high enough so the front of the brake fluid reservoir fills properly. There is a baffle in it, as Lawrence says. I also understand that air can get hung up in the proprotioning valve (it does on 924s), which is why some of the power bleeders work well on these cars - sucking the fluid through instead of pushing it. Otherwise, I'm at a loss... I hate stuff like this. My wife's 924 burned up its front brakes when the calipers locked and we replaced the calipers and the MC. Took about 2 weeks of adjusting and bleeding before we got it sorted.

JonA · 01-08-2007, 05:03 PM

You are doing everything right, if air was your problem you would have gotten it by now. Are you sure you didn't start a caliper leaking when you replaced the pads?
Also, I understand the clutch hydraulics are a bear to service, I'd stay away from them. The clutch is not causing your problem.
How soft is the pedal? Did you have the rotors turned? When I was young and poor I would replace the pads withour turning the rotors and the pedal would be just a little soft until the new pads seated into the imperfect rotor surfaces.
Good luck.

Jon