Brake Caliper conundrum

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ianmg

ianmg

Member
Posts
34
Location
Badminton
hi all,

I’ve had an issue with the brakes on my FL-1 L series for some time now.
The brakes are functional but not great.
I’ve bled, re-bled and re-re-bled the system on numerous occasions to no avail. I am more than 100% confident there is no air in the system.
The master cylinder has been tested and is fine.
The flexi-hoses are new too. As are the front to rear brake lines.
Also fitted new pads.

So here’s the issue... yesterday, at my wits end I tried clamping the flexi hoses to isolate the calipers from the system... and hey presto!! Turns out the front drivers side caliper is the cause of the fault. So I duely stripped, cleaned and rebuilt the caliper with new seal, re-attached to the car and re-bled it. It made no difference....
There are no leaks or visible cracks in the caliper.
When I put the hose clamp on again, I got a rock solid pedal.

So... what could it be? My only thought is a pourous casting but feel this is clutching at straws!

Cheers,

Ian.
 
Most likely air lock. Fully compress piston with bleed valve open then bleed with piston compressed. G clamp or sommat will do.
 
Also worth a check yr hose isn't swelling under pressure. If you are working on your own you may not have seen it!!
 
andyfreelandy said:
Also worth a check yr hose isn't swelling under pressure. If you are working on your own you may not have seen it!!
Click to expand...

Also tried that. There were two of us last night. The hose isn’t moving at all.
When we clamped the hose, we clamped it as near to the Caliper end as possible
 
Aren't the brakes a dual circuit system with the front drivers side on the same circuit as the rear passenger side? Clamping the front would pass more fluid to the rear maybe managing to push the shoe against drum. I'd check there if the front brake looks OK. I think there's a flow control/pressure reducing valve in the system somewhere - but it can't do much cos if you lose a back brake you lose everything.
 
My L Series failed its WOF (MOT) on a rear brake imbalance. given the horror stories of what happens when you lose a rear brake, before I even took the drums off to investigate I decided that after nearly 20 years it was probably time to replace everything on the back brakes - so new shoes, drums (AllMakes), cylinders (OEM), springs (LR) and clips (LR). It was a surprisingly in-expensive and easy job.

Bleeding the rears went pretty well. The only problem I've had bleeding the brakes was when I changed the Wabco ABS unit. I found I had an air lock in the unit and it just wouldn't pump fluid through the system. I ended up removing each of the 4 pipes out on the unit and using a syringe to put/force fluid into the modulator. Once the pipes were reconnected it then bled OK - but it did take almost 2 bottles of fluid through the system to get the brakes back working well.
 
Good, firm pedal with the caliper locked off, but spongy only when the caliper "sees" hydraulic pressure?

It must be the caliper. Whether there is air in it, or the piston has corrosion permitting pressure leak may not matter too much - but with new caliper prices being what they are (dirt cheap!), I'd actually replace it rather than waste any more time and effort on it.
 
Both @htr 's F1 and mine are the (yellow-eyed) <=2000 models with he narrow brake servo - same as @ianmg 's.

@htr has complained of similar "The brakes are functional but not great." and driving mine confirmed the brakes were 'more functional' on mine. He has done a lot of work on his brakes to try and improve them but but I don't think things have got much better. He's replaced pads and discs, even trying slotted/drilled discs, and I'm sure has either replaced the calipers or put a new seal kit into the existing ones. Not sure what work he's done on the rears.

I'm sure he'd be interested in the outcome.

I wouldn't write off the back end being the problem, might be the little spring on the adjuster or some other fault with it, or maybe even a pin broke and a shoe just waiting to fall off the cylinder and total loss of brakes.
 
You got it right GG. Carefully O'hauled callipers and replacement discs & pads but the brakes are acceptable but not outstanding. No work done to the rear drums, wheel cylinders replaced just before I bought it. I did think of upgrading the front to larger discs and later callipers but I think that involves upgrading to the later 15" alloys as well - just a wee bit too much co$t at the mo'.
 
Hi all,

Apologies for the delay... I’ve been out of the country with work for a couple of weeks.

Quick update.....
I tried a replacement caliper which had no effect. So still had a soft pedal.
I’m now totally and utterly flummoxed.

The only next step I can think of is to check the nearside rear wheel cylinder for a fault.

As a point to note, it had new rear shoes around 6k miles ago.

Cheers,

Ian.
 
not unheard of wheel cyclinders to leak at such low milage esspeciallsy if recon ones bought cheap

, and also not uncommon for abs unit to become airlocked, I'm at similar situation with my vw golf having had new osf caliper and nsr brake hose, brakes work but approx 30mm of travel before owt happends ( perfectly drivable but if you jump in after a week on holiday its alarming! ) standard proceudre on VW's those it to bleed whilst plugged into the vag com computter scanner while it opens the abs valuve block whilst the brakes are pressure bleed, sadly 2 man job on those with one in car shouting orders of which wheel to bleed and other man runnig round opening the blleed nipples

not sure if thats an option on a FL1 though,

how are you blleeding brakes? 2 man job where one pumps pedal or 1 man whilst pressure bleeding?

if 2 man get one of these http://www.gunson.co.uk/product/G4062

ignore there prices halfords do em for £20
 
Mine doesn’t have abs so it’s not that.

As for bleeding methods. I’ve used gunson eziebleed, a vacuum bleeder and the two man method.
I’m 100% confidet that there’s no air in the system as when the front flexihose is clamped, a rock solid (as in jumping on the floor solid!!) pedal is achieved.

Locking off the front flexi says to me that it’s not the rear wheel cylinder but I’m not sure what else to try!
 
ianmg said:
Mine doesn’t have abs so it’s not that.

As for bleeding methods. I’ve used gunson eziebleed, a vacuum bleeder and the two man method.
I’m 100% confidet that there’s no air in the system as when the front flexihose is clamped, a rock solid (as in jumping on the floor solid!!) pedal is achieved.

Locking off the front flexi says to me that it’s not the rear wheel cylinder but I’m not sure what else to try!
Click to expand...
If it’s any consolation, I had this problem on a mate’s L200. Spongy pedal until one caliper clamped out, then solid. We must have bled litres of brake fluid through the thing. I told him to get a new caliper (£200! Typical pricey Jap parts) and it didn’t make any difference. He called me a c*nt in a friendly way, and it turned out the brake compensator valve at the back still had air in it. Why locking off the front caliper made the pedal solid, I still don’t know.

If it’s not the caliper body, could it be some excess movement in the slides, pads or discs? A small amount of play at the caliper end translates to a lot of brake pedal movement. Get a mate to press the pedal while you watch the caliper bite. Oddly worn pads can increase travel, and a redneck fix is to get up to a good speed on deserted tarmac and lock the brakes right up to reseat everything. Or renew pads and discs... Did you replace the flexi?

It’s not unknown for rear brake adjusters to be assembled with sides swapped, so they dont adjust. In the spirit of checking everything, it might be worth your while to check the adjusters spin the right way (manipulate the shoes apart and see which way the little wheel turns). Check they’re both adjusted for a slight drag.
 
I’ll have a look and see if there’s anywhere else to bleed it but I can see anywhere.

It had new slides and pads 6k miles ago. And I’ve fitted new discs too.
This car is like triggers broom!!!

I’m going to strip and rebuild the drums and whatnot over the next few days so will see what that comes up with.

For clarification, when I say the pedal is soft/spongy.... it also sinks all the way to the floor before any kind of wheel lock up or skid.

Ian.
 
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