Spongy pedal won't go away????

Tommy · Post by **Tommy** » Sat Sep 06, 2008 7:04 pm

I'm having very annoying issues with my brakes right now.

It all started when I personally fitted new discs and pads, after which, I had no brake force and a lot of pedal travel. Fearing the worst I took the car to the garage for them to work out the problem. After they had the car it came back with new OEM rear pads, because they thought the ones I had were faulty, and a new master cylinder. There was no issue before the new brakes were fitted so I don't see how the master cylinder was seen as faulty. Anyway, the issue was better but still bad - a bit more brake force but still lots of travel! I complained and returned to have them fit new OEM front pads. On removing the front pads we found rivets on the pads I supplied were fouling the pistons so the piston did not have a flat face against which to push - therefore, no braking force.

So, now the car had OEM front and rear pads and the issue was just about fixed. Good braking force but rather spongy pedal. I then took my original pads, cut off the rivets so a flat face was available for the pistons, and had them refitted. Again, good braking force but spongy pedal.

I've just today bled all calipers myself but the spongy pedal is still there. What now? Go back to the garage who I've lost an amount of trust in? Could they have fouled the fitment of the master cylinder? (I've read in my Haynes book that changing a master cylinder requires some pro equipment otherwise it's easy to get air in the system which cannot be bled out through the calipers). Could the calipers have been damaged when they were pushing against the rivets?

The garage gave me a big bill last time for work, which in my eyes, did not need to be done. Oh how I wish these things didn't happen!

Post by **Stuart** » Sat Sep 06, 2008 7:16 pm

If the brakes are the same size as BMW intended, then no sorry, I don't know of anything that you haven't covered. If the calipers are bigger than OE you may find the master cylinder is not man enough to deliver enough fluid.

Brakes can be a bloody nightmare in this respect. The Ksports had amazing solidity to the pedal initially, like trying to press concrete (which I loved) but out on track it soon became softer although still firm. I guess 19 stone of sheer brute strength will do that

___________________In the first instance I would ask the supplying garages advice but try to back that up with advice from someone who knows there onions and understands your usage. Maybe PM Gary at APT on here as he has very recently seen my set up first hand.

Mr Fletcher · Post by **Mr Fletcher** » Sat Sep 06, 2008 7:17 pm

sorry mate i don't know which rivets you are on about :oops:

cheers

jason

Gerry H · Post by **Gerry H** » Sat Sep 06, 2008 8:01 pm

Pads are glued on not rivetted :?

You could try bleeding the master cylinder. Slacken off the tube nut while someone depresses the pedal, and holds it down while you re-tighten. Do this a couple of times to each tube connection whilst watching for air. Spilled fluid should be caught in some rag.

Does the pedal improve when pumped?

Is there a bit of free play in the pedal, or does the pedal push rod stay tight on the master cyl. piston?

Is the pedal any firmer with the cap off the M/C?

Tommy · Post by **Tommy** » Sat Sep 06, 2008 9:49 pm

The pads and discs are OE size. The calipers are stock. The pads had shims rivetted to the back of the backing plates and it was these protruding rivets that fouled the piston. I removed the rivets so the shim was flush if you know what I mean.

Gerry, I'll have a go at some of the things you mention but I guess in the first instance I better get back on to the garage. Regarding 'does the pedal improve when pumped?' - yes it does. If I am sat in the car stationary and just pump the pedal, it becomes harder. When you say free play, there is quite some movement at the top of the pedal where it seems nothing is happening at the calipers. With the old pads, the 'free play' was much much less and in keeping with 'normal' brakes.

ScoobieWRX · Post by **ScoobieWRX** » Sat Sep 06, 2008 10:50 pm

What sort of brake fluid are you using??

DOT3, DOT4 and DOT5.1 are the usual mineral based fluids and should give a firm pedal if there is definately no air in the system. DOT5 is Silicon based fluid and does give a very spongy pedal so hopefully you aren't using any of that.

Have you thought about changing the flexible brake hoses all round the car to braided stanless steel types like Goodridge. It wasn't until i changed those from OEM to Goodridge that the brakes on my scooby felt firm and had some good feel to them. Even after initially upgrading the rotors and pads the feel and firmness still wasn't there and prior to that they were pretty lifeless anyway and a bit spongy with more pedal travel than i'd like. The braided hoses made all the difference on my car anyway.

Gerry H · Post by **Gerry H** » Sun Sep 07, 2008 6:28 am

tommySTI wrote:The pads and discs are OE size. The calipers are stock. The pads had shims rivetted to the back of the backing plates and it was these protruding rivets that fouled the piston. I removed the rivets so the shim was flush if you know what I mean.

Gerry, I'll have a go at some of the things you mention but I guess in the first instance I better get back on to the garage. Regarding 'does the pedal improve when pumped?' - yes it does. If I am sat in the car stationary and just pump the pedal, it becomes harder. When you say free play, there is quite some movement at the top of the pedal where it seems nothing is happening at the calipers. With the old pads, the 'free play' was much much less and in keeping with 'normal' brakes.

If the pedal improves with pumping there's definitely air in the system. Can you take the reservoire cap off and try the pedal. Note how far down it goes and if pumping improves it?

By free play, I mean the travel before the actuating rod touches the back of the piston in the master cylinder. The piston needs to fully return in the cylinder.

Shims aren't necessary so I never fit them. The pedal's more 'instant' without.

Good luck but I wouldn't be inclined to spend any more money with that garage. Sounds like you're paying for their guesswork.

Tommy · Post by **Tommy** » Sun Sep 07, 2008 8:00 am

Thanks for the replies. I've just been out in the car and it's not as bad as I was thinking last night. I'll bleed some more today and I may prise off those shims, which I should have done when I Dremel'd their securing rivets.

WRX - it's 5.1 that I have in. I'm not going for braided hoses (not yet anyway

) because I don't believe the current hoses are what have caused the issue.

Post by **Ben** » Sun Sep 07, 2008 9:20 am

I'm with Gerry - if it gets hard after pumping (fnargh) - it's air.

IWANT1 · Post by **IWANT1** » Sun Sep 07, 2008 9:37 am

When bleeding the brakes are you back bleeding or doing it the conventional way???

Iam just guessing now but when you replaced the brakes originally and you first pressed the brake pedal did it go to the floor or did you only push it small amounts to bring the pedal to its original working position after disturbing the pistons etc?

One thing to check also is the flexible brake hoses are not expanding when the brakes are applied doubtful but possible.