After having extensive bled my brakes with both a pneumatic bleeder and using the ole 2 person "pump" method; I now believe my master cylinder is hosed.

If the pump the brakes 3 times real quick then hold steady pressure, the pedal falls away from me.

Does anyone know if rebuild kits that are out there for the Jag? I've tried searching but have had no luck. Has anyone done this?

Are there other master cylinders that will fit/work with my 99 XJ8 (i.e. a ford etc..)?

Thanks for any insight.....

 

My XK has an aluminum master cylinder and I could not find a rebuild kit when I thought it had failed. Not being able to rebuild and facing a $450 - $700 replacement I tried bleeding the brakes again. That was after the first two efforts but the third time fixed it.

I do not believe I have ever heard of a failed master cylinder.

 

Yeah, I keep going back and forth on this.... is it the master cylinder or air in the lines?

I've bled the crap out of the brakes.... I don't know how I could do this differently. I thought about getting one of those pressure deal that forces fluid from the reservoir down.

Gonna try some of these tests to try and figure out wtf is going on....

Shop manual for automotive brake systems - Google Books

 

Ron, I posted the fix in your other thread on bleeding. I spent 3 days trying to get a pedal with an eze-bleed hooked up to the spare tyre. After this I also suspected the master cylinder.

https://www.jaguarforums.com/forum/j...26/#post245593

The eze-bleed did a good job of getting the fluid into the system, but I still had a spongey pedal.
I even jammed a broom handle cutoff against the pedal and floor stiffener under the seat overnight, hoping to force any air up into the reservoir. This didn't help. I'd turn the car on and the pedal would go further to the floor once the vacuum assist got a hold.
At this point I was set to buy a master cylinder. But looking at the bleed nipples on the ATE calipers the penny dropped.....
My answer was to unbolt the calipers at the front, at the risk of repeating myself, get this done and you'll get a proper pedal. The nipple is located in such a way that once air is above it, it's impossible to flush out because it's trapped. If you unbolt the two caliper bolts, with the pressure of the eze-bleed hooked up, rotate the caliper until the nipple is pointing to the sky, undo the nipple a half turn, you'll get all the air out. No need for a new master cylinder. I've told you the answer, go and do it, and thank me later!

 

Was it just the front that exhibited this problem? or should I unbolt the rear ones also?

I don't have a pressure bleeder so I will do as you suggested and use my pneumatic "sucking" one and see if that does the trick...

 

Just the fronts.....the sucking version should work just as well. Or, someone to push the brake pedal down as you release the bleed nipple, 2-3 downward strokes should see clear fluid. As you know on the last stroke have them hold the pedal flat to the floor as you tighten the nipple up. A small amount of air compresses down working at this brake pressure, so your not looking for large bubbles, just a little "fizz" will give a spongey pedal.
Keeping a critical eye on the reservoir to make sure you don't go anywhere near the minimum level, as this can very easily introduce more air back in the system.

Do the caliper nearest your ABS pump first.

Once both fronts are done, fluid topped off and car running, you should have a good pedal, good luck!

 

Well, you were right.... I was skeptical but after doing the fronts brake pedal is much, much better. I can't even believe the difference it made.

I should also mention that though I don't think this had much to do with it, my left front outer pad was pretty well stuck in the carrier. Took a bit of effort to get it out and then I wire brushed out the "slots" and greased them such that the pad moves freely "back and forth".

Another thing to note, I too was experiencing a hard pull to the right. After doing this bleed out that pull is quite noticeably improved. Just drifts a little bit now and that will be taken care of next week with an alignment (hopefully). I really don't understand how un-bled brakes can cause this condition, but it does.


Geez.... only Jaguar could make a simple, routine procedure a colossal pain in the a$$ :-).


So note to anyone bleeding your brakes - take the calipers off.


Also - note the admins.... feel free to take these last couple of posts and move them over to my bleeding thread then nuke this thread if you'd like.....


Thanks again..... I don't think I would have ever figured this out by myself

 

I feel warm all over, nice.

 

Being a certified aircraft mechanic in no way makes me an expert, but I've owned Jaguars for a number of years. The simple way to bleed air out of brake lines on aircraft should work on cars as well. We use a hand operated pump oiler....like an oil can with a pump built inside. Connect a small rubber hose to the oiler and connect to the bleeder at each wheel and pump brake fluid toward the brake resevoir from underneath. The air is easier to expell going up to the top instead of trying to force the air to expell out the bottom. If you run out of fluid, uncrew the top while you keep the hose connected and top off the oil can. Tighten the bleeder screw before you remove the hose and oiler.