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Hi all.
I changed the Accumulator the other day for a new one as my pump would come one with every push of the pedal. No problem swapping the old one out however I now seem to have a problem. New accumulator pressurises in about 20 seconds so all ok there but when I press the pedal and hold it down the pedal slowly drops the pump cuts in but pedal still drops until it goes hard. While this is happening I can see brake fluid being returned to the reservoir. Some advice on this would be much appreciated. I haven’t bled anything since swapping the accumulator.
Rob.
You are not going to believe this but I have exactly the very same problem on my red XJS 'Cherry Blossom'
Just to make sure we are on the same page, this is what happens on my Car
Turn on the Ignition the Brake Pump primes and then the Brake Pump cuts out along with the ABS light, just like its supposed to (so far so good!)
Then with Foot Pressure applied to the Brake Pedal, the Brake Pedal suddenly drops, almost as if its dropped down to another level, at which point the ABS light comes on and stays on until the ABS pressure has built up again
Then when you push the Brake Pedal down, its a 'Rinse and Repeat' as the Pedal drops down once again!
If you can confirm that exactly the same thing happens on your Car, then we can compare notes and try and fix it
Good job I came across your post, as I was just about to order a New Ball, which as it turns out may not be the cause of the problem
The Brakes on 'Cherry Blossom' have never been the same, since She came back from her MOT last Year, when the Brake Pump also started running Hot, so watch out for that one on yours
I haven't tried Bleeding the Brakes yet, as I've been getting my other Car '50 Shades of Grey' ready for her MOT Next Week, so if you find a Solution please let me know
P.S. Was it the Wabco Ball you put on STC 2784 and if so was it an easy fit as its just a little bit wider than the OEM where we were thinking the Sway Bar might have got in the way
Morning Alex.
Yep happens exactly as you have said. Can’t say I noticed it happened before the accumulator change but I haven’t actually been anywhere in the car since it was delivered at the beginning of February. This is the accumulator I fitted as recommended on another post on here. I managed to get this through one of our work suppliers £73.00 inc vat delivered.
Rob.
I also changed the Ball last Year and just like you everything worked great, up until the time I changed the 'Ball' and took her for an MOT
Where like yourself I also didn't Bleed the Brakes, because I thought that I wouldn't need to
Which with the benefit of Hindsight, looks like a major mistake!
So as we've both got the same problem, created the same way, it now looks as if what we need to do now is to Bleed the Brakes and see if that makes any difference, which I have a feeling that it will
Don't forget to Bleed the Low Pressure Side of the System, from the Reservoir to the Brake Pump which is 'Gravity Fed' and needs to be done 'on the fly' with Brake Fluid flowing out of the Plastic Elbow that goes into the Brake Pump
Ignition OFF at all times!
(1) Fill the Reservoir with Brake Fluid both side of the divider as you look into the Filler hole of the Reservoir
(2) Pull the retaining Pin that holds the Plastic Elbow into the Brake Pump
(3) Jiggle out the Plastic Elbow, held in by an 'O' Ring being Careful not to break the Plastic Elbow, then let the Brake Fluid Free Flow for a few seconds to get any Air Bubbles out and then put the Plastic Elbow back into the Brake Pump while the Brake Fluid is still flowing out
(4) Protect all the Paintwork from Brake Fluid while you do this, or as you know it will Strip the Paintwork Off!
(5) Stuff Rags round the Brake Pump to catch any spills and have a bucket of Soapy Water Handy just in case!
(6) Then Bleed the Brakes According to the method described by Paul (ptjs)
Then let me know what happens as I will be preparing '50 Shades for her MOT' as this lockdown stuff has pushed everything back
That will be very useful but I don't think the problem we have is all that complex, as this only occurred when we both changed Accumulators but didn't bleed the brakes
So when I get another New Accumulator, then I am going to bleed the Brakes and see if that makes any difference but if you get there before me then please let me know
Hi Alex.
I certainly will. I need to flush all the old fluid out anyway so need to order a 5ltr can of brake fluid. I don’t know how old the fluid is in mine but it’s certainly not a nice golden colour. I think I will siphon as much as I can get out of the reservoir then top up with new then bleed.
Rob.
This is only a 'Theory' but what I think we might need to do is to also Bleed some Air out of the High Pressure side of the ABS Brake Pump, where that Pipe goes into the Brake Pump under the Black Ball, maybe with the Ignition off as I would think there could be enough residual pressure to do that
Looking at your Photo where the Ball screws onto the Pump, there looks to be quite a lot of space in and around the feed tube where Air can be trapped and wondering if you were thinking of Loctiting the thread of the Ball, so that it can't come unscrewed, which was maybe why it was so hard to remove in the first place
That 'Dab' of Red in your Photo could be from Loctite? as if it unscrewed itself when driving then all hell could break loose, as those are the kind of pressures that you might find in a bottle of Welding Gas
Hi Alex.
I didn’t use any loctite when I fitted the new accumulator. Just nipped it up as tight as I could. The old one is a bit of a job to get undone. I wedged some small pieces of wood between the pump and it’s bracket and sprayed a bit of PB Blaster on the joint and it cracked open. There was no pressure at all in the old accumulator And no loss of brake fluid. I tried to syphon the old fluid out of the reservoir but due to the the design you can’t get much out. I think when I bleed the low pressure line to the pump I will be able to drain most out there.
Rob.
Yes, agree on that as its probably better to change the Brake Fluid by Bleeding the Low Pressure Side as you say but when I undid the Ball the First Time, then all hell broke loose as Brake Fluid came Spraying out and went all over the Car and everything else
It will be interesting to see if that slightly smaller Bosch Accumulator works as well as the Standard OEM
Right I have my 5ltr of brake fluid. So let the fun begin. The little plastic RH pipe in the pump moves ok it twists from side to side and moves out a bit when pulled. The clip came out fine. I have sprayed a bit of PB Blaster on there and will have a go at removing it tomorrow.
Rob.
Having looked at the Links you gave me and although I am not sure, there seems to have been a solution that worked for one of those guys, that might work for us and that could be a Stuck Valve maybe caused by some sort of gummy Brake Fluid and so I do not think that either of us have any thing to lose by Clicking the Valves
It could well be down to our style of driving where the ABS Valves are seldom if ever used and so to hit them with 12v might just loosen them up and get rid of some crud, where sometime ago I made a very short Video, on how to go about this for which I used an old unit as I didn't feel the need to Test the one that was in my Car
But I do now!
Link Below Robbo about halfway down Page: 80 of my 'Cherry Blossom Restoration Thread'
The Sticking Valve Scenario is really drawing me in but how strange we should have the same problem both at the very same time
In order to try and find out for sure, you could first of all see if the New Accumulator Solves the Problem which it may do but in the event that it doesn't, do the Click Test with 12 Volts as in the Video
its been 3 months since I removed the master cylinder along with ABS valve block on the 92 and replaced with the Bosch Accumulator.
At the same time I just replaced the ball on the 89, im getting ready to sell. With the 89, there does seem to be some oddness, as I didn't bleed the rear just did the ball. I do notice some slow peddle travel after holding. will bleed in the coming weeks and see whats up.
Now the 92, I completely took it apart. I rigged my own cleaning system with brake cleaner and a fuel injector pulse box on the ABS valve block. that worked perfectly, a ton of gunky brown brake fluid came out and the solenoids got louder and cleaned themselves. I also cleaned the master cylinder as well. Now with the new calipers/pads/hoses and it all back together. the brakes on that thing are 100% I have never driven an xjs with brakes this good, went down the driveway (having been used to the old brakes for years) when I hit them it was instant. caught me off guard and went sliding in the gravel, while the ABS did its thing. stopping before I hit the wall im quite happy with the end result.
But if you get tempted to take the Reservoir off the Master Cylinder Actuator in order to clean it out
Do be aware that even if you think that you have siphoned all the old Fluid out, there will still be plenty in there that you cannot see that will come pouring out of the Spigots underneath as well as the gravity outlet to the Brake Pump
Yes it’s pretty rank. I don’t really want to take the reservoir off so hopefully will be able to get most of the crud out of the low pressure pipe. Looking at the reservoir it looks like the lowest point.
Rob.
My Car has a New Valve Block which I put on a couple of years ago and I also change the Brake Fluid every year regardless of whether I really think it needs doing or not
I'm getting very disenchanted with this ABS System in general, as while there may be some advantages its not much good if it goes wrong as much as it seems to on my 1990 while my earlier Coupe has the Vacuum Booster System and that has never given any problems
Update.
I managed to get the plastic elbow out quite easily drained the reservoir and then flushed it through with new brake fluid. Also flushed the pump and accumulator with new fluid. I made sure the new fluid was running freely with no air bubbles from the elbow the popped it back in followed by the clip. I haven’t as yet bled the high pressure pipe from the pump back into the reservoir. Pedal problem still remains.
Rob.
05-24-2020, 04:10 PM
Help with ABS please
im quite happy with the end result. 