Did you replace the rubber O-rings to each brake caliper? You have to completely pull out the piston to get to the O-ring. That maybe swollen due to wrong fluid. Also replace with correct brake fluid. I had to do this before and I noticed no one mentioned this....

 

Loosen both front brake tubes at the ABS module and see if both rotors spin now. Also look to see if any brake fluid comes out where you opened up the brake tubes at the module.

 

I have replaced the o-rings when the seals were replaced. That was it's own headache. Getting the seal to tuck into the lip was a test of patience.

You hit on my second check tomorrow. I will check stack up on front pads as mentioned earlier and if not the issue I will start pulling lines one at a time to see what happens. I did a quick once over on the hard lines and all seem fine.

At this point I may just snap and rip the entire system out of the car in rage. Just rebuild the entire thing from new.

(ironically I bought this car and my other jag-sold to hold me over until I build a Cobra) I've damn near built this one from scratch......

 

If your going to check your pads and rotors for dimensions ,

front pad thickness 17.5 mm
front rotor thickness new is 28 mm

rear pad thickness 17.3 mm
rear rotor thickness new is 20 mm

note , depending on brand or make of disc pad , they will vary by up to 0.5 mm .

 

Thanks. Will check tomorrow, needed a day off. I believe everything is OEM Jag parts. The previous owner spent eye-watering money on this thing.

 

L front
19mm O pad, 28mm rotor, 18mm Inside pad
Piston out 17mm


R front
17.5mm inside pad, 28mm rotor, 18.5mm Outside pad
Piston out 19mm


Stack up is off, but piston has enough stroke on both sides to go back more.

 

Col , you have removed the Master Cylinder and refitted it , it has no oil in it , pipes are disconnected , rear calipers are off and now front brakes dismantled .

I would suggest you take a break and start again .
Even the best of mechanics would have trouble with this one .

The symptoms you are experiencing are more consistent with pressure build up or incorrect pedal geometry .

Sid

 

I love a good mystery: I don't ever impugn the skills of a mechanic, pro or amateur, still, I have found, personally, that when something is not working correctly, I have made a mistake.

I fail to see why the piston sticks out more on one side than the other: I am missing the physics/hydraulics; when you have fluid in the system and have bled it, can you push the overextended piston back in with either a c-clamp or water pump pliers? If not, why not?

secondly, one side has bigger pads than the other (?), can you sand them down? Both appear larger than suggested, why is that?

With the calipers off, will the rotors (wheels) spin more freely, or is there a binding in the bearings. This isn't rocket science.

I can feel your frustration; it is painful! But the car seems worth your effort.

 

Mine do not spin as freely as I would like either.

Looking around the internet at descriptions of freely spinning
hubs did not help me.

One of the things to remember is that the front hub bearing is
a preloaded cassette bearing which is tighter than the old type.

No, I haven't figured it out yet. In my case probably need a caliper
rebuild.

BTW, the piston seal goes in one way. This is by design to allow
the piston seal to retract the piston.

 

Well, the saga continues. It took me a few days longer than I wanted to get back to it. I got new lines put on and started to swap the Master cylinder. After priming and bench testing it I go to put it in and duh. Bolts don't match up. Go look and I got a 3-bolt MC instead of a 4 bolt.

I'm interested in knowing what the difference is between the two if anyone knows.....
Back online to figure out why I may have ordered that and see that it is very difficult to source the 4 bolt for less than $500.

I'll look into finding someone local tomorrow who may be able to help.

Also, I found that no matter how tight I put the driver rear parking brake it seem to find a way to run/scrape. Anyone have the spec's for rear parking shoes?

 

The last thing the OP needs now is to confuse him further about which way the piston seal is installed .

The Caliper seal on this car has no inner or outer side , it is a square cut design , it is not bevel shaped , meaning it can go anyway .

Directional seals that do go in one way are commonly used on motor cycle Calipers .

I mean no disrespect to anyone on this forum .

 

Col , Are using a second hand master and booster assembly ?

 

Bought a re-maned one but wrong mounting. Looking for another.

Was not planning on replacing the booster assembly. Any reason I should? I'm assuming the rubber seals on the MC are bad and blocking the return ports.

 

No reason at this stage to replace the Booster assembly , even if the master cylinder ports are blocked it will have no effect on the Booster operation .

Even though the Booster is incorrect , you will find that the master cylinder will fit either Booster .

Col , if the ports are blocked , contaminated brake fluid can cause the seals to swell , but more than likely the push rod between the Booster and master cylinder may be out of adjustment . To correct this the brakes need to be assembled and the car driven , then you can then carry out further tests if needed .

The previous owner may have tampered with that rod , there is no reason that he should have but you don't know .

 

I've read the thread a few times and don't think I saw a suggestion to open a caliper bleeder to see if any fluid is expelled and the hub turns freely.

If this makes no difference, then it's not the master cylinder or booster.

 

I bought a remaned MC, not booster. The 3-bolt and 4-bolt MC have different mounting.

I have bled the brakes both pressure and gravity a number of times. Nothing.

I checked the push rod. Seems to aligned perfectly with the right amount of travel before engaging.
I may have mentioned before but I am believe most of the issues are with the MC. I have enough other things going on that leads me to believe that there is more than jsut that. From what I can tell the MC is causing problems but is not the only thing.

Seeing as I dont have the correct MC I plan to assemble all the new parts I have and drive. New front calipers, new brake lines, cleaned MC.

I may need to get new rear parking shoes though, even backed off a bit they still seem to catch and drag. Test drive will show.......

 

Assuming the calipers are new or remanufactured ready for install, and the pads are the right thickness, after rebleeding I would bet it all works.

 

Once the the brakes have been put back together and the car driven , you can then start to crack brake lines and see if it is a pressure problem .

 

Explain the physics behind your "pressure problem" please. The problem is too much material between the calipers. When was the last time anybody saw an issue with too much pressure from a master cylinder?

 

The OP is correct that it's possible, albeit a one in a million chance that it affects all four wheels at the same time.

If the piston in the master cylinder does not retract fully after brake application, residual pressure in the lines and calipers can keep the pads in contact with the rotors, creating drag. The condition usually affects only one set of wheels at a time as almost all cars have a dual piston M/C.

Troubleshooting consists of opening a bleeder on one caliper to see if the pressure is relieved. Not sure if the OP has done this, as stated above.