 | Home > Puma (Tdci) > Brake system overhaul - spongy pedal - Help/Advice |
 
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| mrfirepro Member Since: 07 Nov 2020 Location: kent Posts: 219   
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HI all,
I have a 2007 90 2.4 tdci, (with ABS) I have replaced all the calipers and disks using the LOF stainless piston calipers, I've also replaced the rear lines with Pioneer lines and replaced all the old brake fluid. I have also replaced all the wheel bearings. I can't get rid of the spongy brake pedal, which does not really bite until nearly on the floor.... 
To replace the fluid I sucked the old fluid out with a syringe and used a pressure bleeder to push new fluid through the system starting at the NS rear, OS rear, NS front and OS front, I have pushed 1.5L of fluid (DOT 4) through the system and there is no sign of any air in the fluid coming through. I also have nanocom and have done a bleed of the actuator and pump lots of times with the brake pedal depressed. I don't seem to be getting anywhere by keep pulling brake fluid through the system. I can't see any brake fluid leaking any where. Any help or suggestions appreciated.  Click image to enlarge Click image to enlarge Last edited by mrfirepro on 2nd Dec 2023 10:02am. Edited 1 time in total |
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30th Nov 2023 11:04pm |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 250 
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I feel you pain..
After reading your posts I was left thinking that you only have the master cylinder and any flexi hoses in the system left to change.. Now you are saying the master has been swapped over with no change.. What flexi hoses have you in the system that have not been changed.. It would only take one to be expanding a bit through age or defect to cause your issue I think |
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2nd Dec 2023 10:19am |
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| ickle Member Since: 22 Jul 2010 Location: South Vendee Posts: 1728  
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can you set up a dial gauge to see if there is any movement in the disc when the brakes are applied?
HTH Keith |
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2nd Dec 2023 10:31am |
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| Ashbyandy Member Since: 17 Dec 2015 Location: Leicestershire Posts: 219  
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Have you checked the entire length of the vacuum pipe, and it’s connections 🧐, just a thought
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2nd Dec 2023 10:39am |
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| Nuclear Nick Member Since: 21 Aug 2021 Location: Southwest Posts: 251
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Grabbing a straws here, is it possible there might still be some air trapped in a calliper? I wonder if exercising the pistons through full stroke might dislodge some air? You’d need some worn pads or spacers to facilitate this. And maybe pushing the pistons back into the calliper with the bleed nipple open might shift some trapped bubbles.
Is it drivable with the brakes as they are now. Perhaps getting some heat in the system might do something? Also, I notice in your pic of the fronts that the inner pad is showing proud of the disc perimeter. Is this normal/correct? |
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2nd Dec 2023 10:40am |
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| geobloke Member Since: 06 Nov 2012 Location: Nottinghamshire Posts: 4410
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Spongey brake pedal feel is not a straight forward issue to solve I am afraid, but you have done most of the work already.
Travel in the pedal then the brakes apply is indicative of either warped discs or play in the bearings. Both would push the pads and pistons back into the callipers. When you come to need the brakes the extra distance between the pads and discs is the pedal travel, but it is not a spongey feel. Just travel. Plus you have just replaced the callipers, discs, pads, flexi-lines and fluids, so as long as the bearings are seated properly there is nothing that can be wrong there. Spongy pedal feel can be the clutch master cylinder, the servo or the ABS modulator (if you have one fitted), you have just replaced the MC and whilst it is possible that the new MC is duff, it is unlikely. Plus you swapped out and proved the new MC is better than the old MC. So, possibly the servo or the ABS modulator then. Lack of brake pedal feel, spongey or excessive pedal effort lead onto the servo. This is essentially a black box of magic to most people but there are moving parts inside: one or two diaphragms, pressure valves, springs and rods. All of which need to be sealed to maintain the vacuum provided by the engine. The lack of vacuum feels like the pedal is heavy and the effort required to brake is enormous, so I expect your vacuum and pump are ok. The only two things that are left are the ABS modulator (if you have one) and the brake servo itself. Unfortunately it could be either of them, obviously if you do not have ABS then the number 1 suspect is the servo. This is absolutely my experience of diagnosing spongy brakes and others may have other ideas. |
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2nd Dec 2023 10:55am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 16893 
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As a first step I'd clamp all the brake hoses. If the problem stops, the fault is in one or more caliper. If it doesn't, it's upstream of the calipers.
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2nd Dec 2023 11:39am |
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| geobloke Member Since: 06 Nov 2012 Location: Nottinghamshire Posts: 4410
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That is an excellent suggestion Blackwolf, but I suspect he has just fitted braided hoses
 The only downside to braided hoses in my experience is the inability to clamp them.
Well you can clamp them, but they don't really like being un-clamped again...  |
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2nd Dec 2023 11:42am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 16893
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In that case disconnect the hard line from the hose and blank the end of the hard line.
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2nd Dec 2023 12:07pm |
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| mrfirepro Member Since: 07 Nov 2020 Location: kent Posts: 219
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Thank you all for the assistance it really is appreciated. I've now spent about three days on this in total.
I'm not sure it will help anyone but on the third attempt the only thing i did differently was to also pump the brake pedal around 10 times on each corner, and carried out numerous pump and actuator bleeds using Nanocom, whilst using a pressure bleeder. Being by myself I was not able to see if any air was released but the feel on the pedal is now about what it used to be. My next issue is that the front right ABS sensor is now creating a fault and the TC light is coming on. I have checked everything with a dial gauge but I plan to do this again next weekend. On a side note I'm quite impressed with the LOF gear, its been good quality and LOF have been really easy to deal with. Thanks for all the comments |
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6th Dec 2023 12:01am |
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