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Yes I'm pretty sure, the level went too low during my second bleeding attempt.
Could you please explain, or direct me to a picture showing where that O-ring in question is located?
Am I correct in assuming the low pressure hose will come off anyway and becoming bled, as I'm replacing the pump/accumulator unit once it arrives!? I ordered the unit because I can only apply two brake repetitions before the pump is activated. Assuming the accu is due for replacement anyway.
You can see the seal on Jaguar's online parts website. I assume from your questions that you don't have the Jaguar service manual? If not, I strongly suggest that is the first thing you should do. You're running a car that cost the equivalent today of over £60,000. The least you should do is spend £25 on the proper Jaguar service manual. As a minimum, the manual will enable you to understand the braking system.
With due respect to the other posters, you have been given a huge amount of incorrect information in this thread.
1. The problem with your mushy brake pedal is not influenced by your suspension system.
2. You do not have a traditional master cylinder. You have a very complex high pressure actuation unit with integral ABS valve block. You should not try and bleed it as suggested by disconnecting any of the outlet pipes!
3. The bleeding process for your brakes is quite different from conventional bleeding. Do not try and bleed your brakes using conventional procedures.
4. You can not assume at the moment that there is anything wrong with your accumulator and pump. If you have air on the low pressure side of the pump, it will not be able to charge the accumulator. Don't assume either pump, accumulator (or pressure switch!) are at fault at this stage.
Personally, I would definitely not install the 2nd-hand accumulator and pump (and pressure switch?) that you have bought until you have proved there is anything wrong with your existing kit. (And if you did install it, you'll have even more work to do to bleed the system properly. And you'll also need to buy the new seal kits to connect all the pipes.) Is there any reason to assume that the replacement 2nd-hand pump, accumulator and pressure switch are any better than your own?
My suggestion is just to properly bleed the LP side of the system. Once that is done you may find that your accumulator and pump are functioning correctly. I would then use the correct Teves procedure to bleed the wheel circuits. Once that is done, I would run the 32 diagnostic tests via the ECM plug to check the integrity of all the electric circuits on the ABS including the ABS solenoid valves. The tests will take only 30 mins to do.
If your brakes were working properly before the pad and disc change, there is every likelihood that they will work satisfactorily once you have been through the correct bleeding and diagnostic tests.
If so, it is definitely not traditional, and I don't think it's the same as the one in our '93. We'll look forward to following Roland's progress based on your suggestions.
Now I have bought the workshop manual, which I'm reading right now...
I found a note: "Should the front hydraulic circuit fail, pedal travel will increase. If the rear hydraulic circuit fails,
pedal effort will increase."
I've got the increased pedal travel... Closing in on the problem... :-)
Next I'll do the bleeding of the reservoir and the low pressure side of the MC, when I have found the O-ring. (Only close to hundred pages to go through...)
Many, many thanks for the help and suggestions!!! I'm VERY grateful!!!
I'm not an XJ40 expert but I know there were 3 different systems fitted over the years which can make it difficult for owners to know what they've got until they check their VIN. It's not surprising that owners get confused about XJ40 brake configuration!
I'm surprised that your 93 has a different actuation unit? I thought that 93 models used that same Teves actuation unit with the accumulator and pump on the other side of the car?
Roland,
Don't go too much by that statement that "Should the front hydraulic circuit fail, pedal travel will increase." I don't think that's your problem at all. I still believe that you have air in the system which is a very different issue.
At the risk of being pedantic, you're not "...bleeding of the reservoir and the low pressure side of the MC...". Your "master cylinder" is "merely" a small chamber right at the end of the actuation unit. You are not bleeding that. What you need to do first is bleed the LP side of the system whereby fluid passes direct from (one chamber of) the reservoir direct to the pump and accumulator. This LP side has not gone through the actuation unit at all.
Any air that is in the actuation unit (and the other chamber of the reservoir) is bled when you then use the correct Teves procedure to bleed the wheel circuits. You must do it correctly, using the pump to drive fluid to the rear brakes and repressurising the system between each wheel procedure.
Well done for buying the manual! That really is a sensible approach. It has a huge amount of information. As you've probably realised, the Teves brake system is complex. It really takes some reading to get your head around the full structure of the system.
However, it's just my suggestion, but as I've said, use the Teves procedure that I described earlier, NOT the Jaguar procedure to bleed the wheel circuits.
If you do the LP, then the wheel circuits properly, I have good reason to believe that you can cure your problem.
I'm surprised that your 93 has a different actuation unit? I thought that 93 models used that same Teves actuation unit with the accumulator and pump on the other side of the car?
Hi Paul,
I'm traveling so I can't look at the unit in our '93, but from the illustration there is something that looks different from my memory of our unit. I may be completely wrong. I know that when I looked up the accumulator for the '91 it was a different part number than the one for our '93, but I could be wrong about the actuators!
@ Don B
Yes, that's the reservoir I've got!!! Many thanks for that picture!!!
@ptjs1
Having a LHD, I always begin with the Rear Right wheel, i.e the farthest away from the MC...
Bleeding the LP parts first, makes sense, but I'm thinking why I have to remove the reservoir from it's socket and pry loose the LP hose? Doesn't that only add air to the system? Shouldn't any air bubbles slowly find their way up to the top of the reservoir anyway?
I can't find how to proceed with the reservoir bleeding in the workshop manual... Do I need to plug the reservoir at the bottom and how does that remove air from that little chamber in the MC?
What I have missed, when I bled the brakes is certainly the "repressurising" part and not having waited for the lights to go extinct between each wheel...
I now also realize the difference between braking twice before the pump goes on and the forty times I can apply brake pressure before the pedal goes hard...
AFAIK, the actuation unit should be the same from the time that Teves system was introduced. However, I think the pump and accumulator assembly numbers are different for early and late Teves XJ40s. I THINK the early Teves cars had the pump and accumulator adjacent to the actuation unit whereas the later cars moved the pump and accumulator to the other side of the bulkhead as per the XJS arrangement. Even then the XJS had different part numbers for both the actuation unit and the pump compared to the XJ40!
Frankly, I'm sure Jaguar made it difficult for themselves! It seems they could easily have had one part number for the actuation unit for both XJS & XJ40. And they could have had one pump part number for both early and late Teves and XJ40 & early Teves XJS. The variances in mounting etc seem to be the key reason for such a variety of part numbers.
There is definitely opportunity for interchange of part numbers if one changes faceplates / mounting brackets etc for both the actuation unit and the pumps. Unfortunately, it's a bit of a minefield to plough through to work out what's possible. As the cars get older and more ABS valve blocks are failing through poor maintenance, it's an increasing problem for us owners.
You don't disconnect any pipes at the reservoir. That would only encourage air into the pipes as you say. You bleed the LP side where the pipe from the reservoir enters the pump. This is where the O-ring seal sits. I've tried opening my CD of the XJ40 manual but I seem to have some file corruption. However, I'm guessing it's almost exactly the same sections as the XJS manual where it describes the LP bleeding procedure in the same section of the manual where it describes the wheel bleeding procedure. But remember! Don't use that Jaguar wheel bleeding procedure, use the Teves one that I posted!
As regards LHD and RHD, I take your point but frankly it will make no difference which rear wheel you do first. This is because you do not have a "master cylinder" with separate circuits to the rear wheels. The actuation unit has a single high pressure output to the rear wheels which then splits at the rear axle, with a pipe going to each wheel So, the rear wheels really have have the same amount of distance in pipe distance from the actuation unit.
The air that you may have in the system will probably not be in the "master cylinder" chamber at the front of the actuation unit. If you have air, it will most likely be on the LP side ie BEFORE the actuation unit. If it's in the actuation unit on the HP side, it will be before the "master cylinder" chamber. If somehow, it was in that small chamber, the process of bleeding the front brakes would already probably have removed it.
What you have also missed, is not just the repressuring of the rear brakes, but the fact that you do not press the brake pedal down as per conventional bleeding to move the fluid (and air) to the rear brakes. It is the pump that is pressing the fluid to the rear, NOT repeatedly pressing the pedal. If you re-read the manual and Teves procedure, you'll see that you only move the pedal initially to open the inlet valve from the pump. The pump and accumulator then pump the fluid to the rear brakes. It seems strange, I know, but you have to get your head around the idea that it's not the pressure of brake pedal that is "moving" fluid to the rear brakes. This is in contrast to the front brakes where the normal (not ABS-initiated) brake operation IS driven by brake pedal pressure (albeit that it is aided by boost pressure driven from the HP pump circuit!).
I hope all this is helping. I'll try and keep an eye on this thread, so let us know if you have any other questions.
You're right, it's not easy trying to re-program an old rigid brain like mine... Am I getting warmer, that I only have to remove the "reservoir retaining clip", loosening the hose and letting out what ever air is in there while soaking up any fluid spill and then rinsing with a lot of water, when the hose is re-attached properly?
After that, complete the bleeding, using the Teves procedure you posted earlier... Fingers crossed... :-)
Bleeding the LP side of the pump, involves removal of the pipe that comes from the reservoir AT THE POINT THAT IT ENTERS the pump. Do not disconnect anything at the reservoir end!
I think you must read the section of the manual where it describes bleeding of the LP side of the system so that you understand what you're looking for. If you remove the pipe elbow (can be tight) and immediately direct the pipe into a jar, then you should be able to minimise any fluid splash.
Sorry I'm not that good in explaining my self in English... I meant removing that small metal clip (that looks like a ring and is referred to as the resrvoir retaining clip) at the pump side with a pointy pliers, like the picture in the Workshop Manual is showing and then pulling out the hose along with that O-ring...
If possible I could try to place a small vessel/jar down there to collect the spill.
Apols if I didn't understand correctly. Yes, your description is correct. You really need to get a jar there as you have to let the fluid flow from the pipe until there is no air. Try and pull the pipe carefully to avoid splashing fluid. Make sure you have the reservoir well topped up before starting and at each stage. You will be getting through some fluid during these processes!
Will the air bubbles follow the fluid down on their way out, or will the air bubbles rise up through the hose and if so, how will I be able to see when there is no more air in the fluid?
You think 2 Litre fluid will be enough for the whole operation, including the bleeding of wheels?
You'll either see bubbles or else the fluid flow will change from a dribble to "filling" the pipe (if you see what I mean!). Even if it starts up running freely, let it go a few seconds in case there is air "behind" the initial fluid flow
2 litres will be fine for a full bleeding sequence.
After having bled the LP side and then bled the wheels, using the Teves procedure to the letter, it's much better... No FAIL codes or anything after resetting VCM and the pedal feels fine... BUT still it happen a few times that the brake light flicker or light up intermittently for a few seconds...
ABS light is now working perfect, but the brake warning light takes a bit longer to go out...
All in all, much better, but not convinced it will pass MOT, should the brake warning light come on while there...
It's good that your bleeding procedures seem to have improved pedal feel and braking efficiency.
How many brake warning lights do you have on your 1991 XJ40? Do you have an ABS warning light, a Brake Warning light and a separate Brake Pad wear light?
If so, and it's just the red Brake Warning light coming on occasionally, then I think this is just registering low fluid level. If so, the sensors can become slightly jammed. Check for a sound wiring connection and that the float sensor is working properly.
I have a yellow "Antilock" lamp and a red brake warning light, but no brake pad wear light.
The fluid level is on the full mark.
HOWEVER, the left front pad wear connector is damaged by previous owner, so I have "looped" the connector because the new pads did not have a wear sensor...
I can imagine that if the wear sensor has a built in resistance, then the zero Ohms in the loop could perhaps mess things up in the ECU... !? What do you think?
07-24-2015, 10:53 AM
