924Board.org

[wombat]

Hi Guys,

I havent been around alot lately as I have had a lot of work on and not much time to fix up my baby. The head is back on but it has yet to run after this for any great amount of time. So it is sitting in my garage looking pretty but not going far. I have dropped in for time to time but only posted about 3 times in the last 6 months and I appologise for this.

One of the problems I now face is a reoccuring brake issue. quite strange this one and it has been there for a while. I have rebuilt the rear drum cylinders, replaced and adjusted the shoes, Installed new front rotors and pads and put in a new master cylinder all of which improved the situation slightly and got it good enough to pass a RWC but after time (and not much) the brakes go soft again. A few other things I should mention on this are that I have considered rebuilding the calipers and fitting new rubber brake lines and, that you can not blead the brakes effectively unless you do the passengers front wheel last, if you do anything else last it just dosent firm up totally however myself, my mechanic and a friend of mine who works at Mercedes as a mechanic cant seem to find any obvious reason for this. Most things are brand new the only things I can think of are calipers (hence the idea of rebuilding them) and posibilly the lines. I have declared this problem fixed a few times but after time it softens again??

Hope someone can give me some ideas.
Thanks
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1977 924 2.0 Auto

[Cedric]

hm,. soft pedal. Have the same problem on my n/a. Have rebuilt mc + calipers, new brake lines and so on. The only thing not touched is the rear brake cylinders. I havent got rid of the soft pedal, you really have to push it down a bit before things happen. But the brakes works fine at the track, its just the pedal feeling wich is a bit irritating. So i hope someone has any answers ?
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1980 924 Turbo
www.instagram.com/garagecedric/

[Harm]

Hi, Wombat.

[Smoothie]

No personal experience with them here, but Gohim has mentioned several times that the rear drum brakes need readjustment at freakishly frequent intervals - possibly once a month..? If so, this could be that.
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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

[Chrenan]

I usually adjust mine once at the start of the summer driving season, lasts all summer, but I don't put many miles on my car.

When I refurbished my rear brakes, I did everything, drums, pads, springs, retaining clips, the works. Everything inside, and the drum, all new, the only original part left was the backing plate. My brakes have been very good since, I once had to avoid an accident at highway speed when a load fell off a truck in front of me, I locked up all four wheels in fifth. Must have forgotten my threshold braking, too much time in crap new cars with ABS.
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1987 951 - M193 Version for Japan

[POORscheMAN]

I found a vacuum leak in the line feeding my brake booster, once I repaired that the pedal was much firmer feeling and brake response was greatly improved.
All that for the price of a hose clamp.
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1978 924
Audi 5K Throttle Body - 10:1 comp
Stage 1 Cam -MSD coil- Crane XR700 ignition - Headers
260# springs -26mm rear TBars-
poly bushings -Weltmeister sway bars

1980 924 N/A -- stock
1982 931
1988 944
1994 968 M030

[zedex]

If you have no fluid leaks or air {vacuum leaks}, try a pressure bleeder. A proportioning valve may be sticky or there may be a blockage. How are the hoses?? If they are old, they can break up internally but look fine on the outside.

A note on the brake hoses: I had a Fiat X-1/9 that needed new hoses and could not find any at any of the parts stores. I took the old hoses to a hydraulic hose shop and they used the original ends and made fresh hoses using slightly thicker walled hose lines. They performed as well as SS hoses in resisting pressure expansion. A firm pedal was always there. Speaking of which, I am going to do the same for this little car.
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You get more with a kind word and a gun than a kind word alone--Al Capone

[gohim]

924/931/924S/944 do not have a proportioning valve (951s do).

I used to drive about 4K miles a month driving to LA to work. the brakes needed adjustment every 4-6 weeks to keep the pedal high and tight. I adjusted the rear brakes so many times in the three years I wrote to LA every day that I got the time factor down to less than 15 minutes.

Absolutely the best modification I have ever made to the car was the four wheel disc brake conversion with braided stainless steel covered teflon hoses. More powerful brakes with better pedal feel, and no more rear brake adjustments. AND, I got to bolt on a set of phone dials, which are lighter than every other factory 15" 924/931 wheels except for trashcan lids.

[fiat22turbo]

You could have flex lines that have failed internally. Removing them and cleaning them out is a cheap and easy thing to do. Sometimes when lines fail internally, the collapsed rubber acts a one-way valve or you can get other wonky issues. I would strongly recommend braided stainless steel replacements baring that, a series or plastic zip ties on the lines will improve pedal feel by reducing the flex of the rubber lines.


Make sure you connect the lines to the proper ports on the master cylinder and that the master cylinder does not still have air in it. Sometimes bleeding at the joints can tell you where a possible restriction might be in the system. On my old X-1/9 that bleeding the clutch and even the brakes was best done by cracking the fittings loose one at a time and bleeding the air out along the system after a master cylinder replacement. Once the system was bleed, then normal maintenance bleeding was all that was needed (provided the car didn't sit too long and the master cylinders failed internally, like they did on the Fiat)
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[Doodle]

My brake booster was full of fluid so I had it rebuilt. Installed a new M/C, brake hoses, rebuilt calipers, cylinders, shoes, pads, etc. After bleeding and adjusting, the pedal was very spongy and still went nearly to the floor before engaging. I finally adjusted the brake booster rod where it attaches to the pedal. This solved the problem. I believe there is a procedure in the Haynes. If all else fails...

Apparently when the shop rebuilt the booster they removed the pedal clip and didn't mark it so I would have a reference point to re-install.
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Doodle
Pre 77.5 Mars Red

[968rz]

Just be careful adjusting the rod. I did mine once and it was a little too much, I drove about 4 miles and the fronts were smoking hot (literally).
It only took about 1/4 turn back and it was fine; Just saying.
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Rick
79 924 coupe Petrol Blue 3spd auto (wife's DD)
93 968 coupe Amazon Green 4spd Tip (my DD)

[mgatlag]

I had the same spongy brake issues as well last year. I replaced the old rubber hoses with SS and things got much better. I still do have to adjust the rear shoes about every other month to keep the pedal nice and tight. From what I hear it's just the nature of the beast with the drum rears. That's why I'll be doing the 5 lug conversion as soon as I get a few more things. All disc brakes and more wheel choices sounds much better to me, and no more adjusting!
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Michael
'77 1/2 924 N/A- 5 speed Audi box
'04 Ford Taurus - gone!!
'92 Jeep Cherokee Laredo - gone!!

Porsche... better than tea with Miss McGill
(Slap Shot)

[pmcaya2]

Spongy brakes and rear drum adjustment seem to go together. Replaced my master cylinder and brakes were still spongy. Rear brakes were not engaging the drum and needed replacement and adjustment.

The car only has 180K on it - might be original brakes since they weren't being used much! I noticed that if the emergency brake was slightly engaged, the spongy brakes symptom was not as bad.

My mechanic says that this is common. Hope that this helps. - Peter