Hi all,

I recently went to bleed the fluid through on my 1989 as I noticed the fluid was slightly darker than the fresh stuff is, so I thought it would be good to change out.

I started bleeding the front drivers side brake using standard 2 person bleed procedure, & not sure how this happened exactly but I now have absolutely no pedal pressure/resistance - the pedal just pushes straight to the floor.

I disconnected the flexible brake line at the caliper and have absolutely no fluid dripping out the line due to gravity. the reservoir is fully topped up.

The motor/accumulator side of things still seems to be charging normally (i cant pump the brakes to discharge it though obviously as I have no pedal resistance!)

Does anyone have any ideas what might have happened? When I replaced my calipers I don't remeber having any trouble just gravity bleeding them.

 

You probably have a sticky solenoid valve, try applying 9v power to each one, some where in the forum is a procedure for this... If one of those valves is in the open position, fluid will justt return with out allowing pressure to the caliper... Just a thought...

 

Thanks Alpecsa.
I've done much reading of the forum and have now tested the valve block with a small hobby 12v battery, ground pin being the one closest to windscreen. I get an audible click for each of the 6 solenoids. Some louder / more satisfyingly clicky than others but they all make a sound.

I've left the car overnight with the brake line disconnected at the caliper & in a container to see if anything would happen/if it would start gravity draining(this is what it did in the past) but nothing... pedal is still completely soft & goes to the floor with no pressure or resistance after 10hrs.

Accumulator still recharged fine FYI, I could see it pulling the reservoir fluid down slightly whilst charging up.

I also tried sucking on the brake hose at the caliper and can pull absolutely no fluid through. It just holds a vacuum.

I found a Teves manual linked on the forum (thanks to original poster) & looking at the below diagram, I think I have one of the following issues:



either:
- main valve not working/blocked
- central valve (is this like the traditional master cylinder?) Not working/blocked/somehow damaged/airlock?
- the 'first' solenoid valve in the valve block is blocking fluid flow.

As I just have 0 fluid flow when with vacuum It doesn't really feel like a seal issue, more total blockage/shutoff.

Does anyone know which of the valve block electrical pins corresponds to the solenoid valves for the front right caliper? I'm thinking if I hold power to them and apply vacuum to the brake hose at the same time, perhaps it will pull some fluid through from somewhere.

 

Update - last page of the manual had a wiring diagram -pin1 is the inlet valve, pin 2 is the outlet for the RH front.

Powering pin 1 does nothing (as expected I guess)
powering pin 2 allows fluid to drip out the brake hose - I guess this makes sense as this is the pressure return/reduction path used during ABS, so activating it opens up a free flowing path between the reservoir & caliper.
Activating both at the same time does nothing, which I don't really understand - I would have expected fluid to still flow to caliper?

Looking at the diagram, does anyone know if it's possible to do a static test of the 'main valve'? I notice it has a simple 2 pin connection.
As I think I do have working hydraulic pressure in the accumulator side, if I bridge this/activate it, will this force this high pressure fluid through the system/to the caliper?

 

Ok one more update - I have a solid pedal back...
Spent a while staring at the system operation diagrams in the Teves Mark2 ABS manual.
I decided no harm could come from bridging the Main Valve (the 2 pin connector on the end of the master cylinder) & see what happens. It made a clicking noise, just like the valve block.

Ayway surprise surprise, something actually did! After leaving it connected for 10 seconds or so I tried the brake pedal & there was an actual sensation of fluid being pushed about in the system - I think activating this valve used the high pressure from the accumulator to flush through/put fluid somewhere where it previously clearly couldn't get to.

No fluid coming out of the caliper bleed when I pressed though, I only got 'one depression' of the pedal before I was back to 0 resistance i.e it didn't recharge itself, & the pedal was obviously still soft, but at least there was -some- resistance now...

So next, based on the info in the system diagram, I propped the brake pedal half way depressed (to activate the control valve) & energised the main valve again.
This time I could hear definite fluid movement noises from the master cylinder, albeit very faint. I was hoping to see fluid rush out at the caliper bleed under pressure, but it didn't. Hindsight, I should have tried this step whilst simultaneously activating the valve block solenoids to see if anything additional happened.

So I closed off the brake caliper bleed, basically repeated the above a bunch of times (I cycled the ABS pump through approx 3 full recharges) & ended up with a firm pedal.

I'm basically back where I started, albeit with all brand new fluid throughout the reservoir & pump/accumulator rather than the yellow/orangey coloured stuff. I'm fairly sure I still have issues but that's for another day.

I know there's a few people who know a fair bit about the Teves ABS so perhaps they can explain why what I did worked.

 

I could not tell from your note what bleeding procedure you were following.. Did you do this? :


TEVES brake bleeding procedure
You do this for both rear calipers, then you should bleed the front ones as normal. I assume deviating from this procedure can cause issues.
I don’t know enough about the charging and discharging of ABS valve. You should not have to do that to bleed the brakes.
Chuck

 

Before doing anything drastic, put a line clamp on each brake hose. See if the pedal is hard. If it is, the problem is not the master. If it is not hard, it is the master or air in the lines. If it is hard, remove the line clamps one at a time and see if the pedal drops. If it does, you have located the area of the fault.

 

I was following the Teves guidance on how to bleed the brakes i.e. 2 person method using the pedal, ignition on.
I didn't bleed the rears first in this instance as per the picture above, but as I hadn't done any work on the system i.e. no fluid had been lost or air introduced, I don't think that was necessary? I was just looking to introduce fresh fluid into the system.

I bled the left hand front this evening & that was a gravity bleed with no messing about, so clearly there is/was something up with the right hand front circuit. Pedal is nice & firm.

 

Asdrewq,

The symptoms you describe could well be symptomatic of a jammed open valve in the ABS valve block.

As you probably know you don't have a "Master Cylinder" per se. The section referred to as the master cylinder is merely the small chamber at the front of the Actuation Unit.

I THINK that what likely happened, is that your introduction of new fluid caused a disturbance of the micro-sediment in the old fluid in the ABS valve block. It's why you should also change fluid via the rear calipers first. (You mentioned that you only did the front caliper?) The reason why one starts at the rear calipers is that the fluid is moved to the rear brakes via accumulator pressure, not pedal pressure. This changes more of the old fluid with the fluid passing through the ABS valve block via accumulator pressure. That leaves less dirty fluid to be cleared through the front circuits under pedal pressure (with minimal boost assistance)

With the process you undertook, I think that possibly some micro-sediment jammed under the seat of the reservoir return valve of that front circuit in the ABS valve block. So although the solenoid was working when you tested it, the valve was fractionally jammed open. Thus you had an open circuit back to the reservoir and couldn't get pressure applied to the caliper circuit.

When you activated the Main valve, I believe it allowed a greater volume of boost fluid to be applied to the front brake circuit and then fortunately the sediment in the jammed seat valve cleared, thus closing the reservoir return and allowing pressure to the front circuit and the correct pedal pressure.

If I were you, I would now flush through the rear circuits using the Teves procedure, because that is the only way you can flow the new fluid through the pump and accumulator and pumped under pressure to the rear circuits. "Gravity bleeding" can't do that and push the fluid through the high-pressure pump circuit, as the control valve opening the high-pressure circuit is closed if the pedal doesn't activate it.

Hope that helps.

Good luck

Paul

 

Thanks Paul, yes will be bleeding the rears at some point. It's been a few years but I think I had issues with the bleed nipples last time I attempted it.

I've just taken the car for a test drive & it brake straight & true from 40mph, no diving to either side and a good firm pedal so for now i'm happy. I can't confirm if the ABS is actually working or not but there are no warning lights. MOT test will be soon so that's the acid test!

Interestingly I found this post on another forum (scroll down the thread), which is a screen capture from Facebook of someone who it sounds like had a very similar problem to me albeit on a 3.6 XJS, solved in a similar way using the main valve to help bleed the front: https://forums.jag-lovers.com/t/brak...1-xjs/423984/8

 

Asdrewq,

A jammed valve seat won't show up as a fault, but I'd also perform the Blink Test to check and then clear any fault codes stored in the ABS ecu.

Cheers

Paul

 

Paul,
Just a question, if there is no abs or brake light on, is it possible to have a code stored in the ecu? What I mean, should one run the code procedure even without any warning lights?

 

alpecsa,

Generally the ABS MIL will illuminate with a fault code. But there are some codes which may not throw the light, predominantly the wheel sensor signal faults. So, it's worth doing a check just to see if there's anything still stored.

Cheers

Paul

 

Thanks so much, will run the codes just in case.

Cheers
Alfredo