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R4 bleeding front brakes problem.

branty

Enthusiast
Messages
22
Hi
I wondered if anyone had experience of the front 2 brakes not being able to be bled?
I have recommissioned my R4 and the brakes were very spongy. The master cylinder has been overhauled by a R 4 expert in the last 2 years.

The rear brakes pump out fluid on bleeding but the front 2 don’t. It seems strange and I wondered if this is likely a problem with the seals in the master cylinder?

As always, insights and advice would be greatly appreciated.

Best and thanks
Jon
 
If your car has the bendix discs brakes at front did initially have problems with mine due to a lot of sediment in the actual calliper cylinders, the rear of these seem to rust where it is natural casting, also are the flex pipes deteriorating internally, I rebuilt callipers and changed all flex pipes on mine and have had no problems since.
 
Hi Branty

The procedure which works for me on R4s is to bleed the rear cylinder furthest away from the master cylinder first, then the other rear. Once I'm happy the rear are bled properly, I move on to the front, ie the furthest away of the two fronts from the master cylinder first and then the nearest. If still spongy and especially if I have worked on the master cylinder too, I would also bleed at the master cylinder. If still spongy I would then start to inspect individual brake components.
 
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I had a motorcycle with the same problem. There was yust a tiny needle (dirt) clogging the pinhole on the bottom of the canister. So the actual plunger wo'nt refill after pressing oil to the brake. Thus no pressure bildup.
I,m not sure but some cannisters have 2 holes. 1 for front and one for rear brakes. Or the rear was allready pressurised.

I should try to press brake fluid trough with an surringe from the brake calliper to the master cillinder. So the other way around. Maybe you flush something out. You can check if level rises.
 
Hi Branty, the same happened to me but only on one side. So I removed the bleed nipple completely and found it blocked with a tiny piece of sediment. Once cleaned, it worked perfectly.
 
Hi Branty, the same happened to me but only on one side. So I removed the bleed nipple completely and found it blocked with a tiny piece of sediment. Once cleaned, it worked perfectly.
Hi everyone
Thanks for the replies.

I did the rear furthest away bleeding first but when I come to the front they don’t bleed put any fluid despite really loosing the bleed nipples. So I don’t think it is the nipples. Also, as it is on both fronts equally I wondered if the master cylinder was to blame....?

I will have another think- maybe it isn’t the output from the master cylinder to the fronts- is this a separate thing, if so it would seem to be likely to account for them being equally affected.

Thanks
Jon
 
Hi Jon

You might be along the right tracks. The later R4's had a tandem master cylinder. Even though you had the master cylinder overhauled at some point in the past, this would be a good starting point for further investigation.

Best Wishes
 
If its the tandem system I would definetly try to press the fluid back from brake to master. Maybe pull off the cannister en check the holes. I still think its clogged.
 
If its the tandem system I would definetly try to press the fluid back from brake to master. Maybe pull off the cannister en check the holes. I still think its clogged.
Hi Jon

You might be along the right tracks. The later R4's had a tandem master cylinder. Even though you had the master cylinder overhauled at some point in the past, this would be a good starting point for further investigation.

Best Wishes
Hi both,
Thanks so much.
After 2 years off the road the brake fluid was empty. So, after bleeding the rear brakes no problem, the front brakes did not let fluids through- it was not due to clogged nipple valves as still did not happen when taken out completely (not sure you should do this)!

So, disconnected the 2 front brake tubes at the master cylinder (rear brakes had single master connection), then saw some bubbling and eventually brake fluid. Reconnected and rebled with no problem. Now all sorted..

I think there may have been an airlock but I really can’t be sure.

R4 GTL 1984 40,000 miles reasonable condition. Any rough idea of the value?
Thanks again for your inputs
 
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