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She has a Vacuum Booster on the Drivers Side of a (UK) Car and all the ABS Stuff is on the Passenger Side and is a very reliable setup that's not known for going wrong, so from what I know,
In this case you do have a master cylinder, not saying that the rubbers HAVE gone home, much more likely to be a bleeding issue as you say, but keep it in mind, if bleeding does not help, as a possibility even if a remote one.
Agreed! I also think the System needs re-bleeding again as having Started the engine, that could make all the difference except of course its chucking it down with rain!
I would take a slightly different approach and not turn on the engine just yet.
I would bleed the brakes again until I had a very firm pedal without the engine running. I don't know if there's any chance that you introduced air into the m/c, through draining the reservoir or similar? If there's ANY chance that this happened, then I would bleed the master cylinder first by disconnecting the output pipes and confirming that I definitely had fluid exiting the m/c.
Then I'd bleed the wheel circuits again. Then I'd check for any leaks and also look at the seal between the reservoir and the m/c inlet ports.
Then once you've got a rock-hard pedal, I'd hold it and see if it eventually drops. That might indicate that you've got leaking m/c seals.
Only once you've got a sustainable pedal holding at a fixed point, would I turn on the engine. If the pedal then holds at a slightly lower point, that's fine, but if it drops to the floor, I'd bleed the m/c and wheel circuits again! If it still then drops to the floor, I'd suspect the m/c seals. The only difference between pressing that pedal with the engine on or off is the level of additional pedal pressure assistance that you're getting, which could be sufficient to highlight weakened m/c seals.
But Five And A Half Litres Later I May Have Found The Problem!
Hi Paul (ptjs)
Great Thinking and Excellent ideas! especially as today it wasn't Raining down my way, so the very first thing that I did was to Bleed all the Brakes, where I got a nice hard pedal that refused to drop and so was all good, until I started the Engine and then the Pedal went straight to the Floor!
So I Bled them all again and the same thing happened! where in fact I Bled them so many times that I used up Five and a Half Litres of DOT4
Having then Convinced myself that it probably wasn't the Brakes, the next thing I looked at was the Master Cylinder, which I confess I know nothing about whatsoever, even though it doesn't really look that complicated
Though having said that I didn't have any idea of how to Bleed it, even though there were only Two Brake Pipes coming out, where to make matters worse if they could get worse, the Brake Pipe Fittings were also of Two different sizes, which threw me a bit or should I say threw me a lot!
As even with only just Two Pipes, I didn't know what I should do
The Ubiquitous Brake Booster of a 1995 XJS 4.0L this is the later version, that hardly ever goes wrong! (except of course it did go wrong today!)
A Closer View of the Brake Booster Showing the position of the Two Brake Fluid outlet pipes from the Master Cylinder
The only problem being that the Smaller one is 'Bog Standard' but the one on the end is 12mm or something like that! at which point I was tempted to 'Call Paul' as I cannot ever remember seeing a Brake Fitting that Size, so maybe I just need to get out more!
Although at this point I still didn't know the Bleeding Procedure for this Master Cylinder, because there did not seem to be a way of getting any Air Out while keeping the Brake Fluid in
Many Cups of Tea and Jammy Dodgers later, I came up with an idea that I thought might work, although I'd love a Second opinion, as I don't really know
The First thing I did was to unscrew the smaller of the Two fittings on the Brake Pipe furthest back, then when I gently touched the Brake Pedal
Brake Fluid came dribbling out, which then had me thinking that 'Paul' you were Right!
As there could well be Air that was Trapped inside the Master Cylinder! (if it ran dry as it did when I fitted New Calipers)
At which point I was thinking (Help!) what the heck should I do now!
So what I did was to get a Scrap Piece of Brake Pipe and then Bend it into an 'L' Shape as in the Photo below
This is where my New Brake Pipe Bender came in really Handy!
But I couldn't find the most important Photo!, as what I did next was to Screw this 'L' Shaped Brake Pipe, into the Hole in the Master Cylinder that I took the original Brake Pipe out of (Confused? me too but I don't know how else to explain it!)
Then I bent the bit that was Sticking up in the Air into an inverted 'U' so that it went back into the Reservoir!
So basically what happens, is when I Pump the Brake Pedal, Brake Fluid then came out of the Hole in the side of the Master Cylinder and then back into the Reservoir, like in a Sort of Closed Circuit, if that makes any Sense!!
OMG! I just remembered that I made a Video that Shows this Closed Circuit in Action!
As you will see from the Next Photo, there is still some Air in the Master Cylinder and that is because ideally, I also wanted to take a Pipe from the end of the Master Cylinder back into the Reservoir as well, so that both outlet pipes from the Master Cylinder
Would be returning Brake Fluid Back into the Reservoir at the Same time, as I figured if that didn't happen I would never get all the Air Out
Where the only reason that I haven't done that Yet! is that at the time I didn't have the bigger12mm Brake Pipe Fitting
But I have got one now and will hopefully be able to rig it all up Tomorrow or at least ASAP
But am I on the right Track here? by having the Brake Fluid coming out of the Two Outlets from the Master Cylinder and then back into the Reservoir when I slowly pump the Brake Pedal (although I only have one of those Two Pipes doing that at the moment)
Also what would happen when I removed those Pipes that were carrying Brake Fluid back into the Reservoir
Would Air get back into the System and could I just leave the Brake Pedal alone in its normal (foot off) position or would it need to be held down, although when its all back together with those Pipes removed and the other Pipes back in
I expect that in any event I would be have to Bleed the Brakes all over again! and hope that this time it Works!
Alex
To make 100% sure the M/C is bled, I advise two pipes, one on each fitting, and have them poking UP, and if you want bent a bit sideways over the reservoir, but they must have their ends ABOVE the M/C and so you can get a finger on each. Have loads of rags round so any spillage is OK. Then, enlisting Madamoiselle on the pedal, she pushes the pedal down and holds it down. You then place a finger over the end of each pipe to act as a non-return valve. Then she lets the pedal up. Repeat 4 times. She can let the pedal up and you can take your fingers off the pipes. Then unscrew the fittings one at a time and re-attach the brake pipes one at a time. You might not have to rebleed if the pipes are full when reattached, but if you do have to, you do!
Last edited by Greg in France; 07-29-2023 at 09:06 AM.
But first of all I've got a Major Problem, as I cannot undo the 12mm Fitting on the End of the Master Cylinder and while the Smaller of the Two, responded to a Clump with a FBH on the Side of the Spanner that I was undoing it with
I cannot do that to the one on the End or even Counter Torque it, as there is nothing to Grip onto and I don't want to break it, or that will be horrendously expensive to put right
Having Bled the Master Cylinder today with just one pipe and Bled all the Brakes all over again, I'm getting exactly the Same Results as before, a very Hard Pedal until I Start the Engine but then as soon as I do the Pedal just goes to the Floor
Does that Bigger Fitting on the Master Cylinder, do the Front Brakes or the Rear ones, as I'm completely out of ideas at the moment
Search me Alex! The trouble is that if the M/C seals have gone, no amount of bleeding will help as the fluid just leaks past the seals. BUT, if when bled the pedal is rock hard and you cannot push it at all, engine off, then I would say the M/C seals are NOT the problem. But I know nothing about the system thereafter, so I cannot help further.
The front fitting does the front brakes on my car, so I expect on all of them.
The pieces of the Puzzle are now Starting to come together, as every time I've Bled the Brakes I have never seen any Bubbles of Air in the Tube I use for Bleeding and the Pedal is Rock Solid every time (so that sounds like very good news, as far as the Seals in the Master Cylinder are concerned)
Its only when I start the engine that the Problem occurs, where instead of being Solid the Pedal goes down to the Floor with no effort at all
I've even tried starting the Engine, while my Foot is still pushing the Rock Hard Pedal, where exactly the same thing happens, as soon as the Engine catches, this once Rock Hard Pedal then goes to the Floor with No Resistance and No Effort at all
So based on what you've been saying, it does look like the Front of the Master Cylinder is the problem and is probably Full of Air from when I took the Front Calipers off
So with the benefit of hindsight, I should have done something to stop that Brake Fluid from Draining Away
So now its looking like come Hell or High Water, that Front Master Cylinder fitting has to be undone
Except the Sway Bar is right in the way and that won't undo either, as if it did then I could possibly Clamp the end of The Master Cylinder with 'Mole Wrenches' to Counter Torque it while I try and undo that Front Fitting
That as you say does look like it is for the Front Brakes
'Note to Self' I must try harder! but these Cars can drive you Crazy if you let them
Who put that Sway Bar right in the way of undoing that Fitting on the End of the Master Cylinder, as if that wasn't there I could get a grip on the end of the Master Cylinder to Counter Torque it while I undid that Front Fitting but I can't undo the Sway Bar as the Bolt that holds it won't undo at least not yet
After you changed calipers, and went to bleed the brakes, was the master cylinder reservoir completely empty? If not, I suspect the problem is not the master cylinder, but rather the ABS unit on the other side of the car. Below is the factory bleed procedure for the ABS hydraulic control module in 1995.25 cars. It sounds like it can take a long time and many attempts.
Hey OB, I've been trying to figure out what is happening as if you have a rock hard pedal? And lose it when you start the engine. Where is the trapped fluid going??? When you start the engine??? I have a suggestion, pull the vacuum line off at the booster, and see if there is any brake fluid in it??? I have seen a booster go bad, and pull the brake fluid out of the master cylinder, and suck it into the engine. Just a possibility
I too am lost when it comes to ABS, and bleeding procedures. As there is some VOODOO afoot me thinks. Have you ever heard of, or seen a reverse bleeder? It injects brake fluid from the wheel cylinder or caliper bleeder nipple, and pushes the fluid and air back into the master cylinder. Which I've found works 99% of the time. I hadn't heard anyone mention it. It just might fix the problem? Hope it helps
Alex
I am not sure the front part of the M/C is the problem, not with a rock hard pedal, engine off.
To remove the wing bracer you need HUGE pozi (Pozi 3 from memory, could be bigger if there is one). Undo the wing one and loosen the bulkhead one and swing it out of the way.
Those pozi screws are not made of the finest steel I can tell you, so be VERY sure to engage the driver fully and place all you weight on it while you undo it. In my car I have replaced them with stainless bolts.
Mind you, by the time you have sorted this and bought a new M/C etc etc the car will be so good you will not be able to bear to, sell it! Maybe the Jaguar Gods are telling you something...
Where is that Brake Fluid Going, when the Pedal goes down??
All of the Calipers Bleed Ok and as of yet, I have never seen any Air Bubbles in the Bleed Tube
But before I start to Panic anymore than I'm doing already, I think I better go with 'Gregs' suggestion, that there may be air Trapped in the Front end of the Master Cylinder
So First Job is to get that Sway Bar out of the way, where in order to do that I've been doping their fixing Bolts with Oil and am going to try a 'Star Bit' in the end of my Smaller Impact Wrench
Then I can Grip the end of the Master Cylinder with a 'Mole Wrench' to Counter Torque it while I give that Fitting on the end a good pull with a Spanner and maybe Tap that Spanner with a FBH as that's the only way I'll know if there is any Air Trapped in there
I'll also try your suggestion of pulling the Vacuum Line off the Booster to check for Signs of Oil
Hoping 'The Wizard of Oz' may 'Chime in' as when all else fails then that is what you do, although the Brakes were Working OK before I changed the Calipers and the Pedal wasn't dropping, when I started the Engine
I also think we need an Emoji that says 'Grant Help Me Please!' and of course the same for 'Greg' who I have nicknamed 'EL Jefe' and 'Better Call Paul (ptjs) 'The Yellow Pages' of all things Jaguar!
I will probably need Counseling by the time I've finished this, although it would be easier if I only knew what was wrong
The Good News it's not Raining but instead it's Blowing a Gale and probably enough to release the Self Locking Bonnet/Hood Struts and have it Crash Down, so I'll have to be careful (either that or go and cut the grass!)
- If that video indicates the end-point of your master cylinder bleed, then you definitely still have air in the cylinder. With a single port output, you would have fluid squirting in a single jet on each press of teh pedal if the air had been expelled. The small amount of fluid that is dribbling out tells me you have air in there or it is being drawn in somewhere.
- You HAVE to get that port at the end undone. I'm really surprised that a simple adjustable wrench won't undo it, without you needing to undo anything else. There seems to be enough room to get an adjustable king dick or similar there?
- Once you've properly bled the m/c, try plugging both ports with blanks and then try the pedal. It should be rock-hard with even less movement than previously. Now try starting the engine. What happens? If the pedal drops to the floor still, it's air or m/c seals imo.
- Some people talk about a sinking pedal if the check valve has failed in the servo. I don't really see how that can happen. If the check valve has failed, you end up with no vacuum on the m/c side of teh diaphragm and I feel you would have no power assistance and, therefore, a harder pedal. So, I don't think it's a faulty check valve.
- When you say the pedal is hard without the engine on, how hard are you pushing? The servo "merely" gives assistance to the push of the m/c input rod. But it has a ratio of about 6:5:1 which in pressure terms is enormous. So try pushing MUCH harder with the engine off and see if the pedal then also drops.
- If you had a leak on the back of the m/c to the servo, I think you would notice it in terms of the fluid dropping with the number of times that you have tested this. So, I don't think the problem is there.
-In summary, I think you either still have air in the m/c or else you have failing seals which only shows up when the huge difference in pressure is being applied with the servo operating. I don't THINK it's air in the ABS module.
Oh, FWIW, the rear port on the m/c (the one you have disconnected) is the primary circuit and applies pressure to the front brakes, (via two separate ABS circuits), and the port at the front (the one that is seized) is the secondary circuit, and applies pressure to the rear brakes (via a single ABS circuit).
Oh, FWIW, the rear port on the m/c (the one you have disconnected) is the primary circuit and applies pressure to the front brakes, (via two separate ABS circuits), and the port at the front (the one that is seized) is the secondary circuit, and applies pressure to the rear brakes (via a single ABS circuit).
Paul
This is the opposite of what I thought was the case Alex, so follow Pauk in all ABS matters:
Managed To Undo That Pipe On The Front Of The Master Cylinder!
Hi Paul (ptjs)Atrocious Weather Conditions, Blowing a Gale and looking like Rain but even so I managed to cut the Grass before the downpour as I didn't want to risk the Wind Unlocking the Bonnet/Hood Gas Struts in case the Bonnet/Hood decided to come Crashing down!
When suddenly it went from Showers to Sunshine and the Wind dropped down to nothing more than a Gentle Breeze, at which point I was thinking that come Hell or High Water that Fitting that is on the End of the Master Cylinder just has to come off
Even before I had the Chance of reading your reply, as I figured this would be what you would want me to do
Except it wasn't as easy to do as it looked!
For although I had A Very High Quality Spanner to do the Job and got it on that Fitting without any problem, it didn't matter how hard I pulled, it quite simply wouldn't undo and I also wanted to 'Counter Torque' it, to lessen the possibility of me breaking something
Obviously overlooking the fact, that the Master Cylinder was made of Cast Iron! 'But Anyway........'
So I decided to remove that 'Sway Bar' to give me a bit more room to Maneuver and 'Greg' certainly wasn't kidding when he said that great big Screw would be hard to undo!
But then to my Surprise and delight, the only 'Star Key' that I had was the Perfect Fit! although I had to put a Tube on the end of it, to give me more leverage but even then it wouldn't undo, until suddenly I heard this massive bang! like a Shot Gun going off, as it finally came undone!
And I was able to Sway it right out of the way!
With the 'Sway Bar' now out of the way, it was time to have another try at getting the Fitting on the end of the Master Cylinder undone. so trust me when I tell you that this was a 'Nightmare' to undo and required some Serious Clumping on the Side of the Spanner with a FBH!
Having Clamped the M/C with a Pair of 'Mole Wrenches' it still took quite a lot of 'Clumping' with a FBH to get this Fitting undone!
Until finally against all the odds I was able to unscrew it from the End of the Master Cylinder, 'Spanner Tight' from the First Thread to the Last!
As I then pulled the Pipe out of the end of the Master Cylinder not a Single droplet of Brake Fluid came out! even though the Reservoir was completely Full to the Brim
But then when I unscrewed the Cap on the Top of the Reservoir, that was when Brake Fluid started to run out and so I think it must have been the Vacuum of the Reservoir Cap, that was holding it back, although this is only a Guess as I don't know
And so to Stop the Brake Fluid from running all away, I put the Cap back on the Reservoir and also Screwed in one of the Pipes I made, just as a Temporary Measure, as I am Totally lost about what to do next
To prevent the Reservoir running dry, I just screwed one of the Pipes I made in the end of the Master Cylinder as a Temporary Measure, with the open end the same height as the Top of the Reservoir
At which point I decided to call it a day, as it Started Raining again and so there really wasn't much more I could do
Except in answer to your question, when the Pedal is Solid without the Engine Running, you can really stand on those Brakes and the Pedal stays as Solid as a Rock!
But once you Start the Engine, even the lightest feather light touch, is more than enough to send that Pedal straight down to the Floor with no resistance whatsoever, just like the Pedal is not connected to anything at all
As such I just don't have a Clue about what's wrong or what I should do next, so if you can come up with the Answer, as you are the ABS expert, you won't just be helping me but loads of other people who might one day have this problem
Probably my turn to say 'Good Luck' to you, as I haven't a Clue!
Well done getting the pipe union undone without rounding it!
With the engine off, what happens when light pressure is applied to the brake pedal whilst the union is removed? Does any brake fluid come out with the reservoir cap in situ?
07-27-2023, 03:19 AM
