924Board.org

wmrae · Posted: Sun Aug 02, 2009 11:04 am Post subject: Brake problem

New to the 924, just bought an 80 and I am trying to sort out a brake problem. records show that the former owner put a new master cyl in recently (2yrs) but the pedal is really soft and i dont consider the brakes safe. just tried bleeding today per haynes instructions and no change and now i have the brake warning light on the dash lit so something got worse. i have a friend coming over with a vacuum bleeder tomorow but i am looking for ideas from the experts.

Thanks for your help

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Can you put the year and model in your signature (go to the profile page and add the info there). I'm assuming your car is an NA with drum brakes in the rear. It may be difficult to get a firm pedal without adjusting the rear brake shoes, which do NOT have self adjusters on them.

That said, I've learned to never trust anything claimed to have been done by a previous owner...even receipts from "reputable" shops may not be conclusive proof that good quality parts were installed and professional workmanship were executed. Check the master cylinder for leakage, particularly into the brake booster. Easy enough to remove it to see if there are signs of leakage.
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erstwhile owner of just about every 924 variant ever made

wmrae · Posted: Sun Aug 02, 2009 11:49 am Post subject:

It is an NA, 4 bolt wheels. I havent gotten into the drums as I thought that the manual adjust drums were just on the 77 and earlier cars. I will look up the procedure and check that out. Still gonna have to clear up the warning light issue since I'm sure the adjustment wont fix that.
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1980 924 NA

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Which warning light is coming on? The one on the dash or the one on the center console or both?

Are you certain the handbrake lever is fully seated? Is the handbrake switch functioning correctly? Is the wire to the handbrake switch intact (they have a tendency to rust from moisture and fall off or break)? BTW, upon adjusting the rear drum brakes, you may also need to adjust your handbrake lever.

Also, double check the electrical leads coming off of the switch on the brake master. Don't assume that the soft pedal and the warning light are necessarily related. They quite possibly could be, but it would be just as likely that you have a simultaneous grounding problem, and one that could have been made worse by rooting around with the brake system to begin with.
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erstwhile owner of just about every 924 variant ever made

wmrae · Posted: Sun Aug 02, 2009 12:13 pm Post subject:

Its just the light on the center console, the hand brake light in the gauge cluster is working fine. The light was not on before i started messing with the system. I have unplugged both pressure sensors and checked their connections.
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1980 924 NA

Smoothie · Posted: Sun Aug 02, 2009 12:28 pm Post subject:

How's your oil pressure?
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

wmrae · Posted: Sun Aug 02, 2009 12:36 pm Post subject:

why do I suspect the oil pressure question is a loaded one... Can't really say at the moment as the oil pressure sender is bad, I have confirmed that it is a bad sender and have one on order. Are you telling me that the oil pressure is somehow linked to the light labeled brakes and not to the light with an oil can symbol?

As far as adjusting the drums this is what i see when i pull the plugs, how do i adjust?

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1980 924 NA

wmrae · Posted: Sun Aug 02, 2009 12:44 pm Post subject:

scratch that, just found a how to on the adjust, apparently mine are just a little stuck as it wasnt budging for me.
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1980 924 NA

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Yes, the oil pressure signal will go to the brake light in the center console. So as I said earlier, the flickering light there may not be related to your soft pedal, particularly if the oil pressure sender is known to be defective or not correctly connected or shorting out on the foil heat shield behind the head.
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erstwhile owner of just about every 924 variant ever made

gohim · Joined: 02 Nov 2002 Posts: 4459 Location: Rialto, CA

There are two adjustment stars on EACH side. One is for the front brake shoe, and the other is for the rear brake shoe.

Each rear brake adjuster (total of four) has to be set correctly for the any of the brakes (front and rear) on the car to work.

The reason is that the 924 has diagonal braking. Each rear brake is tied to the front brake on the opposite side. Rear brakes must be adjusted every 2500-3000 miles. Otherwise, the clearance between the drum and the shoes becomes excess, and when you step on the brake pedal, the fluid flow is used to close the gap between the shoes and the drums instead of being used to press the shoes against the drum.

Unfortunately when the rear brakes are out of adjustment, the front brakes don't work either, because the fluid flows in the direction of least resistance (rear brakes out of adjustment/excessive clearance provide no resistance to fluid flow when pressing the wheel cylinder pistons outward).

This is one of the primary reasons that many 924 owners switch from rear drum brakes to four wheel disc brakes. Reduced maintenance with improved reliability, and performance.

wmrae · Posted: Mon Aug 03, 2009 5:20 am Post subject:

Got the drums adjusted, re-bled the system with the vacuum bleeder and the light went out, handbrake even works now! Stopping still isn't great it wont lock up the wheels but it is far better than it was.

thanks for the tips
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1980 924 NA

gohim · Joined: 02 Nov 2002 Posts: 4459 Location: Rialto, CA

You probably don't have the rear brakes tight enough yet.

The way I used to adjust them is to pull the parking brake handle up five clicks, then adjust the brake shoes till they stop the wheel from turning (leave the wheels on the car and try to turn them by hand (both hands).

The other way is to pull the parking brake handle up three clicks, and adjust the shoes till each one is barely dragging on the brake drums. Then check your adjustment by pulling the handle up two more clicks to make sure that the brakes are locked up tight. If you can still turn them at all, then you need to go slightly tighter.

Scorpio · Posted: Mon Aug 03, 2009 2:58 pm Post subject:

Jakkq · Joined: 29 Sep 2008 Posts: 810 Location: Omaha, Nebraska

It seems as though I am having some similar issues. When braking not always, but sometimes, it takes extra time to completely brake. E.g. I will brake gradually, but even when pushed all the way to the floor, she still rolls a bit before coming to a complete stop. DO I need mroe fluid or what?
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1979 Porsche 924- Snailshell
http://porsche924workblog.blogspot.com/