Can not bleed rear brakes

Hey all,
I have an early XJ40 (vin number 579970). I had a problem with what i believed to be a caliper sticking on. I have since removed the caliper and rebuilt it.
I can not get my rear brakes to bleed up at all. There is no fluid coming out of the bleed nipples.
I am aware that the car needs to be running with the pedal depressed for the fluid to pump through. But this just isnt happening :frowning:
I have opened the pipes slightly that come from the master cylinder at the ABS module and it appears to be pumping fluid.

I suspect the ABS module is not working. I removed the cover - i do not hear any clicking from the relays when the ignition is switched on. In any case i swapped the 2 relays out from another spare module i have - and no difference.

I probed around the connections where the relays go with a test light and did find power in a couple of places, for what that is worth.

I am really stuck, does anyone have any ideas?

Ryan

oh i have forgotten to mention, that my brake system has been converted to an xj6 vacuum booster , with the accumulator etc. removed.

Welcome to the club. I’m having the exact same issue. I’ll be working on mine more this weekend and will let you know if I figure anything out.

sounds great - Im confused as to what the ABS module actually does. From what i understand there is no motor in these early modules , so i cant understand why im not getting any fluid pumping.

brett, did you make any progress?

ryan

Unfortunately not. I have my own thread going on this issue if you want to track my progress. From your description, your symptoms and even the course of events coincides exactly with what I’m dealing with.

I can’t see how rebuilding a sticky caliper caused the ABS module to fail, and I don’t think the ABS module failing would prevent brake fluid from reaching any of the calipers when the pedal is pumped.

If that was the case and it failed when driving, not only the ABS would stop working but also the brakes.
Also, if you applied the brakes with the ignition switch in the off position the fluid would still flow to the calipers and the brakes would work, so not hearing a relay click, although it still may be a problem, should not prevent fluid coming out of the bleed nipple when the pedal was pumped.

Are you aware that each caliper has to be bled in the correct order ? Because it’s a dual system it’s possible air has found it’s way into other parts of the system when you had the caliper off.

I’d try bleeding the entire system in the order described in the manual before going any further.
Best of luck.

Casso, this did not start because I was having caliper issues. Actually, it happened after I had all of my brake calipers powder coated. Since putting them back on the car, I’ve been unable to bleed the rear brakes. Front brakes have been fine since reinstalling them.

Despite the brake lines for the front brakes routing through the ABS module, they are still serviced and bled just like any traditional brake. Its only the rear brakes that are different. If all four corners were affected by the ABS module, it would make sense to me that the front brakes could also be bled by utilizing the ABS module. However, we know that they can’t.

Currently, if I disconnect the rear brake line at the ABS module, it is dry. Therefore, I know the rear brake lines are dry from the module back to the bleeders. I’ve tried bleeding them using the ABS module with the brake depressed, using a vacuum pump (both manual and air compressor driven), and even the good old up-down method with a helper sitting in the driver’s seat. I’ve been unable to get them to bleed using every method I know.

Despite what the XJ40 e-book says, I don’t think these brakes are simple. In fact, I’m starting to believe no one understands how they work. It seems like most of the knowledge out there is based around the Teves system, and not the girling or Bosch system or whatever the earlier one is called.

Brett,

I’m not too familiar with the pre-Teves brake system on the earlier XJ40s but it is my understanding that in exactly the same way as the Teves system, the rear brakes on your car need accumulator pressure via the master cylinder for the rear brakes to function.
Since you have installed a vacuum brake servo system and removed the accumulator, how does the master cylinder get pressure to activate the rear brakes? Without that pressure, no wonder you cannot bleed the rear brakes.

Bryan …

Um. are you saying that the vacuum servo conversion systems don’t operate the rear brakes.

Since normal vanilla vacuum brake systems don’t have accumulators to operate the master cylinder what would be the difference? Are we talking about the ABS ?

Just to clarify, I have NOT done any kind of vacuum servo upgrade to my car. My car is bone stock with the exception of the rear shock retrofit which was done about 20 years ago. Not sure where that idea came from, but I wanted to clarify so that we can keep the conversation on topic.

Hi Brett,
I have been following your thread I know your problem didn’t occur following caliper issues, It was meant for Ryan who mentioned it in his post.
Reading that he only removed a caliper for repair made me doubtful the ABS module would have been affected, and for the reasons I mentioned I thought he was jumping to a wrong conclusion.

The braking system from the earlier cars may be different to the later Teves system, but both are designed so the brakes will still work normally if any part of the ABS failed, if Jaguar hadn’t put a warning light on the dash you wouldn’t even notice a difference until you needed it and it wasn’t working !
The three solenoid valves within the modulator can only increase, maintain or decrease pressure at the caliper, none of them can actually block the flow of fluid. . In a ’ No Current ’ situation the valve ports are all open.

As it’s a dual system and the front brakes bleed ok could it be possible something inside the master cylinder has gone awry and the outlet to the rear is either blocked or there is no pressure because of a collapsed seal or something ?

Dennis,

No - just trying to introduce some ‘lateral thinking’ in to the problem solving. :slight_smile:

I think Casso is on the right track. Surely the problem has to be something amiss with the Master Cylinder? Wasn’t there a requirement to bleed the Master Cylinder to overcome this sort of problem? I can’t find anything in the XJ40 archives on that subject but this from the E-Type forum may be of interest.

Bryan …

“Lateral thinking” … lately I’ve had trouble just connecting two dots !

Thank you all for the excellent replies! I think what has been said makes sense, so its definitely something I will look into. If some of the theories are correct, I might actually be dealing with an ABS issue and a separate brake hydraulics issue. The link to the E-type topic does indeed seem very similar to our issue, so I’ll try to glean some advice from it as well. I probably won’t have time to work on it again until this weekend, but I’ll be sure to update you all on any progress I make.

OK, I think I have my rear brake bleeding issue figured out. In my situation, I wasn’t getting brake fluid through the ABS module. It was reaching the incoming ports (H and V) on the base of the ABS module, but was not exiting the rear brake port (h upper connection). I was getting fluid to come out both the front brake module ports though (l and r upper connections).

After trying several things, including attaching a spare bleeder valve directly to the outgoing module port, I came up with a theory. Casso’s comment about the fluid still being able to travel through the module even in the event of an ABS failure makes complete sense, especially from a safety perspective. Additionally, if the brake fluid enters the bottom of the module, travels upward through the module valve, and exits the top of the unit, possibly it needs to be gravity bled to a degree. My thinking was that if the lines were dry from the module to both rear calipers as they were for me, possibly the fluid could not pass upward through the module valve.

What I ended up doing was disconnecting the h port on the top of the module. Then I took a short piece of hose and slid one end over the flared end of the metal brake line and placed the other end directly into a bottle of brake fluid that I had wedged between the module and inner fender. I then went to the back of the vehicle and began bleeding the rear brakes like normal. Doing so pulled the fluid directly from the bottle and essentially filled the brake lines. Then I removed the hose and bottle of brake fluid, reconnected the metal brake line to the h port, and bled the rear brakes again. I was hoping the first step would leave only a small section of air in the module while the rest of the line would be filled with fluid. Now I was able to bleed the fluid through both rear calipers pulling the fluid through along with the air.

I haven’t driven the vehicle yet, but the pedal feels firm now. Keeping my fingers crossed, but hopefully the issue is now fixed and I’ll be able to drive my car again soon. Also, I’m still working on the electronics of my ABS system and have eliminated many of the possibilities. If I get it figured out as well, I may post a writeup on how I went about doing it in case anyone else deals with the same issue. Thank you all again for the awesome responses and debate about this topic!

I think the key needs to be turned to ON or maybe the engine needs to be running. I forget how I used to bleed the brakes on the older Jags with the engine driven and electric pumps.

bob

thanks for your help brett - im glad you’ve finally solved the problem! I have also had some success . I managed to borrow a pressure bleeder - a tank that uses your air compressor to force brake fluid through the lines. This appears to have been successful :slight_smile:

I’m glad to hear that Ryan. Sounds like a fairly simple fix too. I own several types of bleeders including the one you mentioned, but got no results from it. Hopefully my fix will be able to benefit someone else in the future. By the time I’m done with these brakes, I will be an expert!

I am new to Jaguars although not new to car repair. I have, fairly recently acquired a 1994 XJ40 V12. It had been sitting up for 6 years in a guys back yard. It has only 83k miles on it though. The brakes needed overhauling as you can imagine. I have two brake pumps with the accumulators. Both accumulators were bad. I replaced all disks, rear calipers, all pads, and ordered rebuild kits from classic Jaguar in England as I could not find front calipers anywhere. I also ordered a “new” accumulator. Manufacture date 8/15/17. I then proceeded to bleed the brakes following the procedures found here. I have a good firm pedal, but… When I press on the brake pedal with 1 to 2 seconds the pump starts to run and then the ABS light and Brakes lights come on and a little bit later the pedal gets very firm. I realize the last part is normal as the pressure bleeds down. The pump seems to run an inordinate amount of time (60 to 90 seconds) the ABS light goes out the Brake light goes out, then when the pump stops the Brake light comes back on. When depressurizing the brakes to check accumulator it takes 15 brake applications to start to get a hard pedal so I believe the system is pressurizing properly. I have tried both pumps with the new accumulator and the only difference is with one pump when the Brake light goes out it stays out until pressing on the brake pedal. I have a hard time believing the accumulator has lost its precharge in 3 years, but that may be it. I have bled approximately a quart of fluid through the system for all 4 brakes. Is it possible there is still air in the system? Do I have a bad pressure switch? Or should I send the accumulator back and request another one. I have read and read and read the forums and am still stumped on this problem. Any help you can give me will me much appreciated.

Thanks,
dldstrock