Brake pedal is pretty soft on my 99 XJ8. The pedal goes all the way to the floor and braking performance is noticeably reduced.

So I thought I would a) bleed the brakes and 2) flush/replace the fluid in the process.

I have already tried the good ole 2 person pump bleed method - twice - with no change in the pedal softness....

I also made the effort to completely flush out the old fluid and replenish it with new during the brake bleeding procedure. Of course, I was careful not to allow the master reservoir to run low/out of fluid.

So I *suspect* there is air in the brake lines..... though it could possibly be the master cylinder seals.

Does anyone have any advice/experience with a technique on the Jag to be reasonably sure the brake lines are free of air?

Just want to make sure it is not air before I take out the master cylinder for a rebuild.

Thanks

 

My Motive Power Bleeder did a great job on the Jag. Instead of pulling the fluid from the slave cyls at each corner like most bleeders, it pushes from the master cyl eliminating the possibility of putting air into the system.

 

I use a piece of clear tubing with a container of fluid at the end so I can see when the air stops bleeding and no air can get back in when the pedal comes back up. This has always worked well for me, but I will say it took longer to get all the air out in my XJ8 than in other cars I have bled. Make sure the cars fluid reservoir doesn't get too low when pumping and pull in air.

 

You have an airlock. I had the same problem a while ago.

Trick is to unbolt each front caliper and rotate it until the bleed nipple faces up.
Bleed as usual, pedal pump until all the bubbles are gone, then nip up and bolt the caliper back up.
Repeat on the other side.

You should then have a decent pedal.

 

Just an update.....

I went ahead and bought a cheap pneumatic brake bleeder system from good ole harbor freight for $25 and bled the brakes with it.

After doing this the brakes are MUCH improved though the pedal is still a little soft but at least it is not bottoming out under a hard stop (or backing out of my driveway!).

This cheapo pneumatic bleeder worked really well... I was pretty surprised. Definitely worth $25!

The only problem I have is I cannot tell if I have actually pulled all of the air out or not because there are always bubbles coming through the line. I *suspect* most of this is air being sucked past the bleeder screw threads or the rubber coupling that goes over the nipple. I teflon taped the screw threads but doesn't seem to solve my problem..... and oh, I only crack the screw open 1/4 of turn *at most*.

After the ole "pump" technique failed me twice (and yes I was doing it right) the pneumatic bleeder has made the difference. On to more bleeding, hopefully I can get it better.

FWIW

 

How is your reservoir cap? It sounds like the system is not sealed and it is open in a way that is letting in air, but not leaking fluid. Or the leak is not visible somehow. Otherwise there should be no bubbles after a proper bleeding.

 

Great info here. Thanks

 

That cannot happen as long as the fluid level is correct.

It is simply that a proper bleed has not yet been accomplished.

A pressure bleeder as opposed to a vacuum bleeder is much better for the purpose. A gravity bleed may also work at this stage.

For some odd reason the hobbyist bleeder tools in North America are vacuum based while the ones in Europe are pressure based. A good place to look is on the UK ebay site.

 

Just to update everyone....

I posted this in another thread when I was thinking the master cylinder was hosed.

Turns out it was not properly bleed (and I am still not sure it is 100%). After bleeding the brakes at least 4-5 times using a combination of the ole 2 person pump the brake method and using a pneumatic brake bleeder, another member suggested that I unbolt the calipers and "point the nipples toward the sky" (please refrain from making jokes :-) ) then bleed them.

That did the trick. It appears the bleeder nipple is not at the top of the brake cylinder and air gets trapped in there.......sounds crazy but it worked.....

 

Sounds like Sean B. nailed it. Hope you are in good shape now - brakes are kinda important.

We should add "point the nipples to the sky" to the sticky. Good words to live by...