Hi guys I wonder if anyone can help me with a problem I'm having, i'm restoring a Sapphire Cosworth that hasn't seen the road since 1998 and i'm having trouble with the brakes, I can't get fluid to the rears, when I first put the braking system back together the motor on the abs pump had no power so I checked all the fuses including the ones behind the glove box and found the one on the green relay behind the glove box to be blown. I replaced it had power to the abs motor but still it didn't work, next I borrowed a new abs unit from a mate but it had also been stood for a while and it also didn't work. I then removed the motor from the abs unit and turned it a bit by hand refitted it and then it started working but it just keeps going and doesn't cut out as they should. I have checked the lines from the valve block down to the rear calipers and all is clear same goes for the pipes from the abs unit to the valve block. I have also tried replacing the valve block and abs ecu but still no fluid to the rear, I have noticed that there are air bubbles coming up in the brake fluid bottle when I pump the pedal and when I remove the pipes from the abs unit the fluid shoots out from the front outputs but even with the abs pump going it just dribbles out of the rear output 😢

 

Think there are load compensators on the rears, around the rear axle area on the brake lines, mine were no good after so long off the road, they restrict or allow flow to rears depending on weight, might be worth a look

 

Silly question but when your bleeding the rear brakes have you got the ignition lights switch on?

 

As you say the fluid just dribbles out of the rear output, so apparently it's not building any pressure there. That will also be the reason you don't get fluid from the rear calipers. On LHD cars the valve block and MC are integrated so I don't know if there are multiple lines from the MC towards the valve block. But in principle it could be that the valve block is causing it, as that will limit brake pressure towards the wheels when the ABS function kicks in.

 

I had the same problem when I bled mine last week,the brake bias valve was faulty,changed it and all good.

 

You are pressing the pedal when the pump is working right?
Of the pumps works on and in then it may be the pressure valve at fault as they need to tell the pump to switch off

 

Is it a 4wd or 2wd car? 4wd's don't have a load valve in them.

 

none of them do if they have abs

thats only on the non abs cars with the valve under the battery tray

 

The 2wds have a valve under the back seat area IIRC, it's to reduce the pressure to the rear brakes.

 

hi ,its worth cracking off the pipes at the master cylinder and checking if you are getting brake pressure from the cylinder itself ,may just be the master cylinder seals are perrished and not building pressure after sitting for so long

 

Thanks for all the advice guys I have cracked off the brake pipe for the rear right at the master cylinder and there is no pressure from the rear output even when the motor for the abs pump has been running for 2 minutes. (the workshop manual says not to let it run for more than 2 minutes) It threw me as I tried the original and a second hand master cylinder and had the same problem with both but then again the second hand master cylinder had been stood for a long time too so I think I might just have to buy a third one that I know has been working on a car relatively recently.