HELP Brake pedal goes to floor slowly (1 Viewer)
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Thanks!, of course I had the wrong one.
Hi, I am having exactly the same problem as the original poster. I have changed out the master cylinder still have the same problem. firm pedal with the truck off, but with it on, it slowly goes to the floor. I have tried the power bleeder combined with pump bleeding with and without the truck on. It doesn’t result in any bubbles, wondering if I should continue to try bleeding?
It’s a 91 hdj 81. Brakes worked great before I swapped calipers out in order to move to the larger 96 Fzj hardware in the front and back.
Pedal is rocksolid with the master cylinder, Outputs plugged. Also feels pretty good with the front brakes port plugged. Suspecting that there is air trapped in the calipers, but I have not been able to find anything. I also capped off the line right before the caliper on either side, and had the same result, so it doesn’t seem to be one side or the other.
At a total loss and would love to have this rig up and going again. Any comments or suggestions would be helpful the.
It’s a 91 hdj 81. Brakes worked great before I swapped calipers out in order to move to the larger 96 Fzj hardware in the front and back.
Pedal is rocksolid with the master cylinder, Outputs plugged. Also feels pretty good with the front brakes port plugged. Suspecting that there is air trapped in the calipers, but I have not been able to find anything. I also capped off the line right before the caliper on either side, and had the same result, so it doesn’t seem to be one side or the other.
At a total loss and would love to have this rig up and going again. Any comments or suggestions would be helpful the.
ppc
M Go Blue
Slowly going to the floor indicates some type of leak, a ballooning rubber brake line etc but not air in the system. Is the brake fluid level in the reservoir remaining at the same level? Typically this is a leak within the internal seals of the master cylinder, no external leak. Where did source the master cylinder, if it s a remanufactured unit from your local parts store I would start by replacing with a genuine Toyota new or rebuilt.
It’s a brand-new master cylinder from advics (oem supplier for Toyota). It will only go to the floor when the truck is running. Flexible brake lines are all brand new.
There are no signs of a leak and the fluid level does not drop at all in the master cylinder reservoir after repeated use.
In any case, the old master cylinder and system works great prior to swapping to the larger rotors and associated hardware. I suspect it is still good as the problem is the same either way.
Trying to decide whether I should try putting the old calipers back on temporarily or start looking at the brake booster or continue to try to bleed it? Or something else…
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Update… I tried swapping back in the old calipers with no effect. Also checked the pedal adjustment and master cylinder to booster pin clearance (both were ok). Re bleed everything and decided after a test drive that the pedal probably was the same as it was before the upgrade. Still not as good as I would have expected, but the brakes are operating satisfactorily. I probably just never stood on the brakes long enough before to notice how low the pedal goes before settling (about 2.5” off the floor if I put all my force into it with the engine running). I read in another blog that this is common with diesel 80s. Maybe the hydraulic vacuum pump produces higher vacuum at idle….
other things I may try to see if it improves the pedal feel are:
-swapping to the 1-1/16” t100 master cylinder (seem to be getting hard to find a new advics one though, currently I have a 1” bore)
-replacing and/or removing the lspv (it is currently frozen up in a condition where the supply to the rear is fully open, ie no flow back through the return line that tees back into the front brakes)
I need to order the parts to try either of these. Not sure if I should order a new lspv, or go right to deleting it and adding manual proportioning valve. Any suggestions on what to try first would be appreciated.
Thanks for the help
other things I may try to see if it improves the pedal feel are:
-swapping to the 1-1/16” t100 master cylinder (seem to be getting hard to find a new advics one though, currently I have a 1” bore)
-replacing and/or removing the lspv (it is currently frozen up in a condition where the supply to the rear is fully open, ie no flow back through the return line that tees back into the front brakes)
I need to order the parts to try either of these. Not sure if I should order a new lspv, or go right to deleting it and adding manual proportioning valve. Any suggestions on what to try first would be appreciated.
Thanks for the help
Hi,
I did my best to check the clearance per the FSM (using a depth gauge and calipers, as I didn’t have the SST tool). It was within spec with both the old and new master cylinder, so I didn’t adjust it. Brakes also feel exactly the same with both the new and original master cylinder…
Thanks,
Byron
Dave 2000
Not all Land Rovers are useless!
I am up there with fluid passing the MC seals, and air being trapped as well. The booster doing its job compressing air trapped somewhere in the system.
Sometimes there can be a mismatch between different components of MC and booster. Try this, first get some washers that will fit over the booster studs. Cut a section out of each of them. Turn the boost pin anticlockwise half a turn from where it is now, ghat is making it longer. In the glove box put the washers and a spanner, remember you want at least two for each stud. Go for a drive, nothing special 20 -30 minutes should be enough?
If nothing happens and all feels good leave it alone for a couple of days, if you find as you drive the brakes start dragging pull over and stop. Loosen the booster nuts and ease the MC forward and slip a washer on each of the studs, dropping a nut at the side of the road can be a RPITA, but that little collection of cut washers saves you undoing the nuts all the way. Make sure you put the washers on all studs, you don't want the MC sitting crooked. Now go for a drive and see how things go, if you have a good pedal and no dragging of the brakes, then you now know by the thickness of the washer how far the pin needs to be turned in, once done remove the washers, a little juggling adding or removing washers could sort this issue you have, the 80 is not the only vehicle I have done this with, the LR Discovery is a classic example for instance, I have even used the SST and no joy, the washer trick is foolproof.
Regards
Dave
