I replaced my rear rotors and front pads. Now my brake pedal goes nearly to the floor when I start the car. I bled the brakes and the pedal is fine when engine is off. Goes way down when started and barely stops car.

Brakes were OK before the work and I've done this work before with no problems. Any help greatly appreciated.

 

One of the real techs pointed out recently that the Jaguar caliper bleed valve is not at the true top of the internal reservoir when installed. That creates a situation where you cannot get all the air out. Solution was to remove one of the bolts so that you can tilt the caliper to make the valve becomes the top and bleed again.

I bleed mine 4 times before I got all the air out before this advice.

 

Interesting. I'll Mityvac again. Still concerned about the cause though. Done this brake maintenance before and never had this low/mushy pedal afterwards.

No leakage. Pedal perfect until I "fixed" the brakes. Car stops straight. Could some other component, e.g. master cylinder, be failing?

Thanks

 

I was at the point of buying a $700 master cylinder trying to fix my brakes. Aluminum with no repair parts available. Tried bleeding one more time and it worked. Probably ran 2 quarts of DOT4 through the system.

Never heard of a failure of this master cylinder.

 

I'm waiting on the delivery of 4 quarts of LMA (Surprisingly hard to find around here). I'm going to flush the whole system when it shows. Also planning to bleed from farthest to closest rather than Jag's way.

 

I hope you won't take this the wrong way, but.....

Are you really sure that the pedal is lower than before? Broadly speaking it's typical to have a somewhat low, soft pedal on ABS-equipped car.

It's also typical to be hyper-sensitive to brake pedal feel after bleeding the brakes. I came across this quite often in the repair business.

I often do the servicing on family members' cars. Years ago, to prove my theory, I played a mind game on a couple of them by telling them I had bled the brakes when I really hadn't. As expected, and right on cue, they complained that the "brake pedal feels low".

Anyhow, it's just a thought. I'm not discounting the possibility of an actual fault but, OTOH, I'd hate to see you pour money into fixing a non-problem.

Cheers
DD

 

Check here, common problem when bleeding fronts....

https://www.jaguarforums.com/forum/j...kes-xj8-55730/

As Test mentions, the way to get your pedal back is to unbolt and rotate the front Ate calipers so the bleed nipple points skywards, bleed as normal and you should get a bit of air out, nip up and your pedal should be as normal.

I spent two days and a couple of litres of fluid before I managed to suss this out.

 

I wondered that myself but I'm virtually certain it's lower than before. At any rate the fluid needs changing so I'll give it another go using the "bleeders up" method.

Thanks guys

 

First, thanks for the help so far. After running a quart of fluid through system with a Mityvac the brake pedal is high and firm... until I start the car. The pedal then goes very low (with effort I can bottom it out) and feels spongy. The car will stop, but pedal bottoms out, and the the pedal improves slightly with pumping but returns to the lower state.

Sorry to repeat myself but I have replaced pads and rotors on this vehicle before and never had this problem. This time, did back rotors, no problem. Immediately did front pads and down went the pedal.

Should I keep bleeding (the car, that is) or could something else have gone wrong (damaged caliper?) when I did the brakes?

Sorry for long post and thanks

 

I will re-affirm the my thread on the topic referenced by Sean B. It seems beyond stupid to have to unbolt the calipers to bleed them but it is necessary.

I too tried the suction method (many times).... unbolting the calipers did the trick.

I will also note that I can bottom out my brake if I push REALLY hard with the engine on.

If you can hold the brake at a certain foot pressure and the pedal doesn't "fall" away from you then it is probably not the master cylinder. (make sense?).

 

Yeah, I'm a believer. It really does feel like there's still air in there. By the time I got to the front brakes I was getting lazy and didn't turn the calipers. I will now.

Thanks

 

Also remember when you bleed the brakes the proper sequence for the X308's is opposite of most cars due to the design of the ABS plumbing. Even though the bleeder nipple is not at the true top of the caliper resevoir, if you use a good push system pressure bleeder, it shouldn't be an issue.

 

I used the "bleeders up" technique on the fronts and bled all 4, for a while. Have yet to take it out for a good test but pedal is back up and solid.

Along the way I found that I had reinstalled the anti rattle springs on the rears incorrectly causing the pads to rattle.

Much thanks to everyone.

 

One thing I found the hard way is that the caliper "anti-rattle" clips are confusing to install to correct way. If you put one or more of them on incorrectly it results in excessive movement of the caliper - and a soft/low brake pedal. I bet your had a combination of things happening; the incorrect installation of the clips on the rear was enough to make you really notice the pedal in the first place, then you probably improved it through bleeding but only fixed it once the clip was reinstalled properly

 

I'll bet that's what happened. I should have known that if the clips go on easily you're doing it wrong! I've never had a low pedal problem with this car and was scratching my head as to the cause.

Well, live and learn. Now I've got fresh brake fluid. Thanks for the explanation.