924Board.org

[Johnny_Haywire]

Hey guys, trying to figure out what to do next with this issue. I've bled the brakes twice (in proper order, and I'm getting clear fluid and no bubbles) and the front calipers have new pads, and I'm still getting little to no braking and the pedal gets very hard after about 1/4 or 1/3 of the way down. I can mash down on it, but the results are pretty minimal.

A bit of background - the car sat for approximately 10 years before I got it going again. When I replaced the pads, I really had to work on getting the calipers to slide freely. It's possible that they are still binding a bit, but I would figure that once I got them loose enough to install the pads and lubed them up, the hydraulic force would be able to get them moving freely.

Could this be the master cylinder? Or the booster? The vacuum hose for the booster is at least 10 years old. it doesn't look bad, but I will try to change it today to see if that makes any difference.

I did notice that the idle kicks up a hundred RPM or maybe a little more when I push the brake pedal down.

I have changed about 95% of the vacuum hoses on the car so far, but still have to do a few of the odd ones and the hoses that have different sizes on either end.

Thanks in advance for any advice or tips!
_________________
1981 924 N/A 5-speed

[fiat22turbo]

Rebuild or replace the calipers and the flex hoses.

Make sure the rear shoes are adjusted, lubricated and working as well.
_________________
Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[Ozzie]

booster
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

[Johnny_Haywire]

Thanks for the input, guys.

I did test the check valve on the brake booster and it is working properly, for what it's worth.

I also took off the front pads again tonight and noticed that the calipers weren't sliding very freely. I had freed one of them up a few weeks ago, but the other was still pretty stiff. Now they both slide freely. Braking performance improved around 2% after doing that.

The first pump of the brake went all the way to the floor smoothly while the calipers were setting up. For a second, braking almost felt like a normal car in terms of pedal feel (not the all the way to the floor part ; ).

What I did pay closer attention to were the caliper pistons. They were both very difficult to pry back in order to get the new pads in. I've had some difficult ones in my day, and these definitely rank high up there. The ends of the pistons that are visible are really rusted and corroded, as well. I'm thinking I should start with calipers first?

One of the rotors has some deep grooves, so those should be replaced, too.

Which then leads me to my next question... should I just upgrade the calipers and rotors to something a little bigger? I remember someone telling me that VW GTI rotors and calipers were bolt on (to some extent) and were bigger than what I've got on my 4-lug set up now.

I know I'm kind of putting the carriage before the horse, but if I'm going to get calipers...
_________________
1981 924 N/A 5-speed

[ideola]

[Johnny_Haywire]

I haven't been having any fluid loss from the master cylinder, though it did sit inop for ten years, so it's not likely in "great" shape.

What do you think in terms of the rusty pistons in the brake calipers being the culprit?
_________________
1981 924 N/A 5-speed

[Johnny_Haywire]

I suppose I should add that I haven't had the rear drums off yet. Hoping to get to that this weekend, but I was going to try to adjust the rear shoes first (I have the orientation and adjustment directions for the adjustment wheels). Could that be a source of the issue? The e-brake works, but not until it's pretty high up there.
_________________
1981 924 N/A 5-speed

[Paul]

The next step is to properly adjust the rear brakes.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[Johnny_Haywire]

Thanks for the advice, Paul. That'll be the next thing I do, and should be able to get to it this weekend. I'll report back with my results.
_________________
1981 924 N/A 5-speed

[Johnny_Haywire]

It's been a bit of a journey to pull the drum(s) off, but I finally got around to it today. I managed to break my breaker bar last weekend when trying to get the 36mm nut off, and so armed with a new one today, I was able to loosen the nut and remove the passenger (RH) side drum.

The shoes were making no contact with the drum and it slid right off. Both adjusters were rusted stiff, with the forward one all the way in and the rearward one about 3/4 of the way out.

I was able to get the forward one out with persuasion and a lot of penetrating oil, but the rearward adjuster required some fire. In the end, I got them out, so that's a positive.

The wheel cylinder was pretty stiff and wasn't moving much until massaged a bit. When I compress both pistons now, the forward seal leaks a bit of brake fluid, hence the tourniquet. There was a bit of wetness when I got started, but I don't think it was leaking too badly until I got it moving.

New wheel cylinders have been ordered and are on their way. I have new shoes and hardware here already, but will probably throw the old hardware and pads on temporarily while I turn the car around and tackle the driver's side. Those adjusters are frozen, as well.

Any tips on what to lubricate the adjusters with when I reinstall them? I'm on the fence between using high-temp bearing grease or anti-seize.

Here's the passenger side after getting the adjusters out:



And here are the stubborn ba$tards once released from their rusty caves:


_________________
1981 924 N/A 5-speed

[Ozzie]

when I did my brakes I replaced both cylinders, freed up the adjusters and used anti seize. The cylinders were full of snot and had seized bleed screws.

Make sure you get the 19mm not the 17mm cylinders if you replace them.
believe it or not it is a big difference.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

[MikeJinCO]

You have to find someone who can turn VW drums, most folks can't do it anymore. When I adjusted them they were dragging more than I was first comfortable with in order to work very well. I got Porterfield street pads, more expensive, but figured they might be a little better. Hard to say the result.

I got a NOS master cylinder from a retro automotive Porsche place in NH and it still needed to be rebuilt(old and dry).
_________________
Mike


'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild)

[Johnny_Haywire]

Thanks for the tips, guys.

I ordered the 19mm cylinders (3/4") and I also ordered two rebuild kits for them in 19mm, as well. The rebuild kits were very cheap, I think USD$1.56 each, and the cylinders were pretty cheap, too, at around $13.50 each. Both are coming from rockauto.com.

I just found a place that turns drums and rotors. Not too far away, either. i am thrilled, as one of my rotors has some grooves in it (might not be salvageable). The drums look good, but I'll just have them all turned. Haven't seen a local place that turns rotors for decades, but here it is:

http://www.supremeautoltd.com/Chicago-machine-shop-services.html

Thanks also for the tip about the Porterfield shoes. I was wondering who, if anyone, made performance shoes. I will definitely look them up as I am going to stick with the current brake/suspension set up for a least a year, if not permanently.

I suppose the master cylinder will be my next battle, but I'm curious to see how the braking is after getting the new rear cylinders installed along with actual working adjusters.

I will be sure to post an update once I make some progress. Cylinders are due to arrive on Friday
_________________
1981 924 N/A 5-speed

[Johnny_Haywire]

I had a little time to work on the car tonight, so I temporarily buttoned up the passenger side drum and spun the car around to tackle the driver's side (my garage is pretty narrow).

Pulled the driver's side drum and here's what was waiting for me:



Sweet Melissa. Like something they pulled out of the Titanic...

The rearward piston is frozen in this wheel cylinder. The forward piston began moving freely after a squeeze. I think that one was working on some level.



The adjusters are frozen solid, and this side is actually worse and rustier than the passenger side. I removed the shoes and springs and hit it repeatedly with a wire brush and penetrating oil, and did the same to the brake line and bolt for the wheel cyl. I think some fire will be involved in this removal, but I'll give it some time and a few taps. The forward half of the adjuster index spring is no longer there, so, I've got that going for me...


_________________
1981 924 N/A 5-speed

[ideola]

I admire your determination and methodical approach...a rarity among toofah owners!
_________________
erstwhile owner of just about every 924 variant ever made