Front brakes are gone

[RoyMember]

On the weekend my front brakes just dissappeared. No resistance on the lever. Thought they might have overheated at first but felt the rotor and not even warm. Lever pulls all the way in the the grip and pumping the brakes makes not difference.

I was thinking it was either air in the line or the seal in the master cyclinder has gone. Leaning towards the seal as I figured even with air surely I could pump the brakes up. Doesn’t seem to be any physical damage at the caliper end and there is plenty of meat left on the pads.

Has anybody had a seal go before and what are the symptoms.

Thanks

[BillMember]

fluid leaking out would be a sign of a damaged seal
try flushing with DOT5
Did it happen while riding or when you parked it

[RoyMember]

I was out riding. First time I noticed it was whilst I was parked waiting. Then when I took of it come good. Then shortly after they dissappeared all together never to return. Made all the downhills very interesting from that point on.

[BillMember]

With all the wet weather we have had it may have water in the fluid from hot caliper quenching it will pull a small amount in and the fluid will absorb it but then when it gets hot it will boil causing an air lock

every time this has happened to me was after a big ride and old fluid in the system

[Mick DMember]

Master cylinder seals do go from time to time, but before you get to excited about replacing the seals try a reverse bleed of the system. Get a large syringe with a bit of clear tubing where the needle would normally go (fish tank air tube will do the trick) Fill the syringe with brake fluid and connect it to the bleed nipple on the caliper. Remove the lid off the master cylinder and wrap a rag around the master cylinder, so that any over flowing fluid is caught by the rag, making sure you can still see into the top of the master cylinder reseviour. Crack the bleed screw and push the new fluid into the caliper with the syringe. Fluid should start over flowing from the MC and any trapped air will also bubble out at the same time. Make sure there are no bubbles in the tube before you start forcing the fluid in and dont forget to nip up the bleed screw when you are done. There is no need to pump the lever using this technique.

If this method fails to sort out your problem then I would suggest your seals in the master cyclinder are in fact rat shit. Most likely fluid can be seen escaping from where the lever contacts the piston in the MC if this is the case. You will have to purchase a seal and piston kit as you cant just get a seal kit.To replace the piston and seals is a relatively simple job. Remove the circlip and the whole lot can be drawn out of the MC and a new one just slides straight in. The hardest part of the whole process is getting the circlip out and back in again. Once you have replaced the piston, do a reverse bleed as described above and all should be sweet.

[AlexMember]

Check both Banjo bolts at each end of the line. If you drop the bike it can loosen one of them and have a slight leak you will hardly notice. Have you tried facing the front wheel, hold it and push knee into caliper to push the pistons in? Pull and flick leaver until pressure comes back?

[BrettMember]

Could be the MC seals are leaking internally, you can purchase the big syringe from a chemist a mate buys from them to measure in a/c oil into compressors.

[Scott TyszkiewiczMember]

Its pretty common for the seals to go in the master cylinder, Try Reverse bleeding it if that fails get a Master cylinder repair kit, ( I know a place that will look after you ) looking at your Display pic i would say 08-09 450/530? RRP on those are $67.30 (you will get OB price)

[RoyMember]

Thanks everybody.

I will bleed it tonight and see how it goes.

You were close Tisco. 09 300.

[RoyMember]

Had a very quick look at my brakes. Checked the banjo bolts and the bottom one tightened up a bit and it looked like there was a fluid leak on the caliper somewhere. Took the cap off the reservoir and not a drop of fluid in there. There is definitely no fluid leaking out around the piston near the lever. Will put the bike up on the stand and check the caliper out more thoroughly tonight. I’ve only done the 5 minute check in the middle of my lunch hour so far.

I did look at the fluid window whilst out riding but I thought it was full. Obviously it was dead empty.

[Eric SmithMember]

Brakes are overrated mate, you’ll be right! Who here hasn’t ridden a drum-braked AG bike down a snotty hill at sphincter-puckering speed and arrived at the bottom in a shower of rocks, dust and sweat… dust and sweat cause that brown stain in your undies, right? 👿

I’ve got nothing to add to help except to hope it works out!

[AlexMember]

Bingo I win.

Edit: nothing further.

[TheBossMember]

Please remember the rules around the Tech Forum fellas it’s the only forum we would like to stay on the serious side that’s you ECKS & Axel

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