HELP!! No brake pedal after rear disc conv.

[Kwakshack]

I've recently replaced my rear drums on my samurai with a disc conversion and now cannot get the pedal to hold pressure.....

I've replaced all of the calipers (well, the back ones were rebuilt Girling ones), replaced pretty much all of the brake lines including new braided lines, replaced the master cylinder/servo with a good s/hand unit and bled the system so many times my local parts place thinks I've shares in a brake fluid refinery!

No matter what I do I just can't get the pedal to be firm, it goes straight to the floor with very little resistance. There are no leaks and everything should be right - I've totally ran out of ideas and in my 30+ years of working on cars I've never seen anything like it. the feeling at the pedal is similar to when you replace some brake shoes but don't adjust the handbrake up (my handbrake is one the transfer box btw).

Once on the floor, the brakes actually feel okay and stop the car okay but I'm at a loss as to what to try now to get a pedal that actually feels right - anyone got any ideas???

[Jordi]

Are you bleeding the brakes with the caliper in the correct position?

[Kwakshack]

Are you bleeding the brakes with the caliper in the correct position?

Hi Jordi, thanks for the quick reply, rear calipers are 90 degrees towards the rear - are you thinking there may be air trapped in the caliper due to this position?

I'm pressure bleeding them so surely this would expel all the air, wouldn't it??

[Jordi]

Not necessarily as the air can get trapped at the top of the chamber. 99% sure the caliper is designed to be fitted in the 12 o’clock position for the bleed nipple to be the highest point.

I’d try bleeding them with the caliper in the top mount position.

Have you also bled the whole system or just the new rear calipers?

[maxaret]

If nothing else works could it at least partly be that you have 4 new discs and pads and that they all need 'bedding in' (burnishing) ?,I have had cars where when you replace brake friction components the Brake Pedal feels very 'springy' and can be pushed quite easily further down than usual,after 50 miles or so the pedal has hardened up.
Alternatively is the master cylinder big enough to supply the correct volume of fluid and/or are you sure the MC is holding pressure (ie no internal leak past seals).

cheers/rgds max

[Kwakshack]

Quick update - rear caliper brackets modified and rotated to allow the calipers to sit at a more conventional position and the system rebled...success!!!

The pedal now feels like it should, well it would if it didn't blow a rear brake line, but after all the hassle I've had, that's an easy fix!!

Thanks to everyone who replied and especially Jordi - was almost ready to throw the towel in and bloody sell the thing if I couldn't get this sorted!!

[Jordi]

Pleased you’re sorted bud.

[maxaret]

Great you got the brakes working Kwakker

[Grey Man]

Hi, Just reading up on the problem you had regarding brakes. I have a SJ413 with rear disks fitted by the recently previous owner, so taking stock of what to do at the moment. I have 2 used calipers to fit to the rear disks and I'm not sure what vehicle they came off. So I need to fit the calipers and sort out a handbrake. Any advice would be appreciated. Images show my calipers.

Cheers

[Jordi]

Standard aisin calipers off a Japanese SJ i think.

If not already fitted you may need to swap to a transmission handbrake.