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Raize
Joined: 18 Sep 2013 Posts: 337 Location: Scotland
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Posted: Sun May 11, 2025 5:41 am Post subject: |
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Did you ever get this sorted?
I have my 4-wheel discs now but same old soft pedal, worse if anything tbh.
Will flush another liter of Typ200 through it but it’s a damn expensive process at nearly £20 a can. |
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coup85

Joined: 12 Aug 2024 Posts: 54 Location: Madrid
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Posted: Sat May 24, 2025 2:49 am Post subject: |
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Update:
The full hard line rebuild is now complete — all new copper-coated steel lines fitted, along with new soft lines and a fresh set of fittings throughout. I also installed new crush washers and sealed every union with care. I then filled the system using a pressure bleeder (1 bar), checked for leaks (none), and ran a full bleed starting with the master cylinder, followed by all four wheels in sequence.
The good news: the system holds pressure perfectly, and the bleeding went cleanly.
The bad news: the pedal feel still isn’t quite right. With the engine off, it’s firm but doesn’t fully harden like I’d expect. With the engine running, it travels about a third of the way down before firming up — much more than I’d expect for a fully bled system.
I’ve double-checked for leaks and re-bled the system twice. I also adjusted the rear drums to increase shoe contact (even tested with them dragging slightly), but the pedal behavior remains unchanged.
At this point, the master cylinder has been ruled out via a blanking plug test (pedal went rock solid), so my next focus is on the rear wheel cylinders and front calipers. If the wheel cylinders are retracting too much or the caliper sliders are sloppy, could that explain the excess pedal travel?
I’d really appreciate any insights. I’m especially curious if anyone has seen worn front calipers or rear wheel cylinders contribute to similar symptoms, even without visible leaks.
Thanks again for all the input so far — this forum has been a huge help.
Raize wrote: | Did you ever get this sorted?
I have my 4-wheel discs now but same old soft pedal, worse if anything tbh.
Will flush another liter of Typ200 through it but it’s a damn expensive process at nearly £20 a can. |
Sadly, no. System fully rebuilt, bled multiple times, still the pedal seems off.
And yeah… I also feel the pain of burning through expensive fluid bottle after bottle. Let’s keep each other posted! _________________ 924 - 79' |
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Raize
Joined: 18 Sep 2013 Posts: 337 Location: Scotland
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Posted: Sat May 24, 2025 4:00 am Post subject: |
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I'm suspecting at this point it's because the 924 has numerous high loops in the system and there is air trapped in these which is impossible to ever get out.
I am not even using the original brake setup and it's still mushy. Can't blame the original components now in my case. Fixed calipers should NOT be mushy and I had the disc runout down to 0.05mm on all 4 discs.
I might try reverse bleeding it next. (pushing fluid from the caliper up to the resevoir and taking the fluid out the resevoir with a baster as it fills up) |
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coup85

Joined: 12 Aug 2024 Posts: 54 Location: Madrid
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Posted: Sat May 24, 2025 4:35 am Post subject: |
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I never thought about trying reverse bleeding, but it might be worth a try. Do you have any tips on how to do it apart from the obvious? Thanks for the idea! _________________ 924 - 79' |
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Raize
Joined: 18 Sep 2013 Posts: 337 Location: Scotland
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Posted: Sat May 24, 2025 6:25 am Post subject: |
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coup85 wrote: | I never thought about trying reverse bleeding, but it might be worth a try. Do you have any tips on how to do it apart from the obvious? Thanks for the idea! |
I have a pressure bleeding thingy that you fill with brake fluid so I guess you’d just attach it to the bleed nipples instead of the brake reservoir cap. Then watch the level in reservoir slowly rise, hopefully observe some bubbles, and remove fluid as needed.
I expect you’d need to put some PTFE tape on the bleed nipples to stop it from leaking back up the threads. |
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Karlio
Joined: 17 Nov 2019 Posts: 99 Location: UK
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Posted: Sat May 24, 2025 7:02 am Post subject: |
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Small compressor and a vacuum bleeder from sealey, wasting your time otherwise
Last edited by Karlio on Sat May 24, 2025 7:06 am; edited 1 time in total |
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Karlio
Joined: 17 Nov 2019 Posts: 99 Location: UK
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Posted: Sat May 24, 2025 7:05 am Post subject: |
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And start with the cailper/piston furthest away |
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coup85

Joined: 12 Aug 2024 Posts: 54 Location: Madrid
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Posted: Sat May 24, 2025 9:50 am Post subject: |
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Karlio wrote: | Small compressor and a vacuum bleeder from sealey, wasting your time otherwise |
Thanks for the advice – I’ve been using a pressure bleeder (like the Eezibleed type, around 1 bar) to flush and purge the system.
Do you think there’s a big difference in effectiveness between using a pressure bleeder and the vacuum method you suggest? _________________ 924 - 79' |
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Karlio
Joined: 17 Nov 2019 Posts: 99 Location: UK
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Posted: Sun May 25, 2025 7:09 am Post subject: |
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With vacuum bleeding you pull through from the reservoir so therefore all the air and all the fluid gets pulled through. Using this system for at least 12 seasons of racing not had any brake issues. The easibleed things are s**t |
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coup85

Joined: 12 Aug 2024 Posts: 54 Location: Madrid
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Posted: Sun May 25, 2025 3:46 pm Post subject: |
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Karlio wrote: | With vacuum bleeding you pull through from the reservoir so therefore all the air and all the fluid gets pulled through. Using this system for at least 12 seasons of racing not had any brake issues. The easibleed things are s**t |
I actually have a vacuum bleeder kit, but the bleeder's seal went bad, so I'll need to address that before trying. Thanks for the tip _________________ 924 - 79' |
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Raize
Joined: 18 Sep 2013 Posts: 337 Location: Scotland
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Posted: Sun May 25, 2025 8:07 pm Post subject: |
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coup85 wrote: | After capping both rear flex lines, the pedal became much firmer with a significantly reduced travel |
In case vacuum bleeding has no result:
Have you tried capping the front flex lines or all four flex lines yet?
Capping at the MC confirmed the MC is good. Just make sure you have the end of the line pointing up and there is fluid welling out of it so that there's no possibility of having some air behind the cap.
If the pedal was just as hard as it was with the MC capped, it would rule out the brake lines completely and it would have to be an issue with the brakes themselves. |
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coup85

Joined: 12 Aug 2024 Posts: 54 Location: Madrid
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Posted: Fri Jun 06, 2025 8:04 pm Post subject: |
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I feel half stupid, half angry. After endless attempts bleeding the brakes, I finally opened up the rear drums… and found the problem: the brake cylinders are completely shot. One side expands much more than the other and not evenly at all.
The reason I didn’t check them earlier is because I trusted the garage I took the car to when the problems first started. They told me both front and rear brakes had been checked and were “fine”, and were clueless about what was going on. That turned out to be very far from the truth.
Video: https://imgur.com/7cU18Zw
Lesson learned: if you’re still chasing a soft pedal after replacing nearly everything else, don’t rule out the drums just because someone said they’re okay. _________________ 924 - 79' |
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Beartooth
Joined: 05 Apr 2022 Posts: 280 Location: Roberts, MT
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Posted: Sat Jun 07, 2025 4:28 am Post subject: |
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Ah, glad you found the problem! My wheel cylinders were shot - leaking, some rust, and probably un-repairable, so they got replaced. It does seem like the drums are the source of a lot of issues. Not so much failures, but obviously there's the adjustment aspect, plus a lot more pieces to potentially go together wrong. The good news is, they work well once everything's fixed, where it needs to be, and adjusted.
I've had similar experiences with shops telling me what is or isn't wrong. I had new tires put on my truck back when, and they said "you've got some wheel bearing noise," which I'd been starting to hear myself. So I replaced all the wheel bearings (like an idiot, not even stopping to think when they all looked great), and the noise was still there. Turns out it was the driveshaft center support bearing. So I only take someone's word, saying "it's fine" or "that's your problem" if I they have a good track record or I can confirm what they say myself. Sadly, on older stuff at least, you typically find you know more and can diagnose better than the average full-time mechanic. _________________ 1980 931 diamond in the rough |
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coup85

Joined: 12 Aug 2024 Posts: 54 Location: Madrid
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Posted: Sat Jun 07, 2025 4:15 pm Post subject: |
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Entirely agree, the problem is you still need to rely on your mechanic from time to time. I think the better way to proceed is to find the problem first by yourself and then, if you need help or some extra machinery, go to the shop, just for that specific task. Nothing else. Bring the piece, agree on a price, and that's it. I recently changed the sleeve that goes in the flywheel, something out of reach for me, as I can't disassemble the transmission by myself. I bought the piece myself, and printed the diagram from the manual, told him to send me pictures during the process, and that was it. _________________ 924 - 79' |
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Raize
Joined: 18 Sep 2013 Posts: 337 Location: Scotland
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Posted: Mon Jun 09, 2025 6:25 am Post subject: |
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Glad you found it.
I had a mechanic assemble my handbrake bar backwards once somehow, needless to say it all barely worked. They put an MOT on it like that though.
100% agree with do anything you can yourself. |
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