I have rebuilt and bled literally hundreds of brake systems. I replaced the front calipers on my 1990 XJS convertible recently, having previously completely rebuilt my rear calipers and ebrake system without removing the IRS to do so. I followed the bleeding procedure for the rear brakes (ignition on, pump comes to stop, pressure pedal by assistant, open bleeder, rinse and repeat). I also had an accumulator failure in traffic on the highway and replaced it without issue. Months later when driving around locally, I found the rears to be smoking. Up on the lift, I found them to be not releasing, but I was able to manually loosen them. Test driving seemed successful, but I thought that I would check the front calipers and found them to be also not fully releasing. I bought a rebuild kit and removed the calipers. I was unable to get the pistons out no matter what I did (air, soaking in my tried and true acetone/Dexron formula, Krol) but I finally got one out and found it to be bad and the cylinder walls scored. I ordered and received a new set from Rock Auto, installed them, and attempted to bleed them (I did not try to bench bleed them, as I would with any master cylinder), getting nothing but air bubbles into clean Dot 4 (with my son and able assistant pumping the pedal multiple times). Gravity wasn't working either. Teves II systems are clearly complicated (perhaps to clever by half, IMO), but I believe I understand how the system works.

I then consulted THIS forum and saw numerous posts from Grant, Orange Blossom, Paul, Greg....and frankly, the methods suggested contradict one another. I intend NO disrespect. I have read many many of your posts and you are all extremely knowledgeable WRT the XJS. I have learned a great deal from you, but this one issue has a baffling variety of opinions.
For example:
* bleed rear calipers first
* bleed front calipers with assistant pumping pedal without regard to the rear calipers since they are activated via the pump
* bleed front calipers using gravity
* bleed front calipers but don't touch the brake pedal
* bleed the hydraulic pump before bleeding the front calipers
* remove the reservoir and clean out debris before bleeding
* ignore the XJS manual directions and follow the Teve II instructions (can't find them anywhere so far)

My head is spinning. I would love a discussion that shows what the consensus agrees is correct. I'm counting on y'all to help get this straight for me and all others to follow with these questions.
It could even be a sticky or whatever this forum calls our knowledge base. Thanks for y'all's consideration.
Eric

Eric,

I'm not sure what "Pre-Uplift brakes" are, but I'm guessing you're just referring to the Teves II system?

If so, the nature of the system and specifically the operation of the Actuation Unit means that IMHO, you really need to do it in this way.

1. If you have no reason to believe that air has got into the reservoir:

- Bleed the rear brakes using the Teves procedure, not the Jaguar manual procedure.
- Bleed the front brakes using conventional pedal pressure technique
- If pedal doesn't feel right (with engine running) after the procedure, - Repeat rear then front again


2. If you believe that air may have got into the reservoir:

- Bleed the low-pressure side of the system (this is bleeding the feed to the pump, not the pump itself)
- Bleed the rear brakes using the Teves procedure, not the Jaguar manual procedure.
- Bleed the front brake using conventional pedal pressure technique
- Repeat rear then front if pedal doesn't feel right (with engine running) after the procedure


I respect others viewpoints, but I don't agree with trying to gravity bleed the rear of a Teves II XJS. I don't understand how it can work.

Cheers

Paul

Thank you for your response, Paul. I mis-wrote....I meant 'facelift' and of course I meant the Teves II system. No one suggested gravity bleeding of the rear calipers....it was for the front calipers. I'll check again, but the reservoir is at the correct level, so I don't think air got into it. Of course when I removed the calipers initially, there was brake fluid, and even after I capped the line, there was some leakage.

My bleeding problem was that i never got any fluid to flow whilst pedal pressure bleeding...from either side (mine is an LHD car so I began on the right side) and got nothing but air bubbles into a clean jar of Dot4.

Am I given to understand that we should have done the rear calipers first even though I had no reason to believe that they needed bleeding? And then gone on to do the fronts? Based on my understanding of the Teves II system, the rears should be completely independent of the fronts, which are in themselves entirely conventional. If you think that doing the rears first is the proper approach, I will go ahead and do that. I had intended to rebleed them anyway.

Eric,

Just to clarify, Teves II was also used on facelift cars for 4 years from 1991. It's only the very late facelift cars that went to Teves IV system.

Returning to your car, I'm no expert but have what I think is a pretty reasonable understanding of Teves II. If you merely remove a front caliper, cap the line, then replace the caliper, you shouldn't have to touch the rear ones first IMO. However, if the calipers were removed for some time, and you mentioned a line leak, you COULD have air travelling back up the line, to the ABS valve block or even to the Actuation Unit further up. And you also mentioned you had a problem with the rear brakes not releasing. Naturally this could be for a number of reasons, from a simple sticking caliper piston, through to a collapsing flexi-hose or even a failing ABS valve block valve. So I'd always start with bleeding the rear because of how the fluid is driven to the rear under accumulator pressure through the Actuation Unit, not pedal pressure. You need the sequence of Reservoir to Pump Accumulator to Actuation Unit to Valve Block to Rear Brakes to be air-free before you do the fronts. If you have air in the early parts of the system, it can be quite laborious to fully bleed it.

As regards your front caliper, were you "pushing" air bubbles under pedal pressure, or were they just slowly coming out? In theory, if you're not sucking air back in air somewhere on the release of the pedal; if you slowly repeatedly press the pedal you must force fluid through the caliper as the bleed nipple is higher than the fluid entry point. Unless as mentioned, there's now air earlier in the system. You could try one other approach, which is to push the pedal down, hold it and tighten the bleed nipple. Release the pedal, loosen the nipple, press the pedal down, hold it, tighten the bleed nipple. And keep repeating that sequence. This could prevent air being drawn back in during the bleeding.

Cheers

Paul