The valve for rear brakes is inside the MC and it is mechanically operated by the pushrod (#9, 10 & 11 on the diagram): Image Unavailable, Please Login Here are pictures of the parts related to the valve that I have taken when dismantling a very similar Jaguar MC: Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
I was just reading your MC thread from a couple years back. So this is a MC full rebuild or can I try pulling #10 out the top and see if something is stuck?
I removed #10 after I separated the rear part of the MC from the front: Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login I believe #10 can also be removed from the MC in situ but I do not know if re-inserting it would be easy as its "scissors" need to engage two different spots on the pushrod/piston (see the earlier attached diagram). Otherwise, it is very easy to separate the two halves of the MC - just undo two bolts (one of them seen on the 1st pic above having some yellow paint) and they separate without much force as there is just a large o-ring holding them together. Then you can easily take out the internals from the rear half: Image Unavailable, Please Login Image Unavailable, Please Login It is possible that something has seized in there which can happen if the brake fluid is not flushed/replaced for a number of years.
Thanks all again so far. Obviously the focus has moved to the MC or the ABS block. I'm trying to upload a video but its too big. What its boiled down to is I'm not getting any pressurized fluid out of the port that supplies the rear lines at the bottom of the the MC. I get plenty of fluid going though both front circuits but only a drip or slight pulse coming out of the port that supplies the rear brake lines. Before I pull the whole MC it looks like I can pull off the ABS block. There must be solenoids in there that control the flow/valves to each of the 3 separate lines?
You can check the solenoid resistances as per info on this picture. The solenoid block shown is from a Jag MC but it is the same as the 348 one with same resistances. You can also bring 12V between the "Comm" (Pin 1) and each of the Pins 2 to 7 and listen for clicks. Image Unavailable, Please Login
I'd agree that focus needs to be on the M/C. I highly doubt an issue with the calipers, brake lines or wheel sensors would cause this. The symptoms don't explain it. I still can't help but wonder how that would have affected the hydraulic pump though. I'm wondering if that pump somehow instead caused the fault in the M/C. Maybe the pump lunched itself and spat something through the M/C. The pump has now been fixed by replacing it, however the damage now appears to be somewhere in the M/C. The other option of course is it's a third unrelated issue that caused problems for both the pump and the M/C. Good luck if it is the M/C. They're not cheap One piece of advice I'll give you is to not trust the ABS codes. They may sound like they're pointing to the issue, but they probably aren't. They're measuring a fault at a certain point, but the problem often lies elsewhere. For example, a "failed valve" could actually be a faulty relay and/or pump. Only use those codes as a further piece of information, or clue, but do not rely on them as an accurate answer to what the problem is.
Since on the Teves system the front and rear brakes are totally isolated from each other under normal conditions, and since the rears are controlled by pump pressure, isn't pedal stroke controlled by the fronts? I mean, once the fronts are bleed, opening the rear bleed screws won't allow fluid to bleed from the front system and the pedal will become hard once the front pads are against the rotors. No? Doesn't opening the rears w/o the pump running or system pressured up will only allow fluid to dip out by gravity, even if the pedal is depressed? With the key on, fluid bleeds out the rears when the pedal is depressed because the valve to pressurize the rears in the MC opens. Right? If no fluid comes out of the rears when the system is pressurized and the pedal depressed, then wouldn't that be because either the valve in the MC is stuck closed or the rear circuit inlet solenoid valve is stuck in the closed position when it should be normally open? Assuming no other blockages, which seems to be the case. What about DTC 26, in the OPs 1st post?
That is correct. One more thing that can be checked while trying to diagnose whether it is the MC or not is the delay valve (restrictor) for the rear brakes (#22 &23 on the diagram). I would disconnect the pipe coming to it from the front and see whether the fluid comes out from the pipe faster when the pedal is pressed with ignition in ACC. Image Unavailable, Please Login
I see you're still doing god's work Miro. Good for you man. Thanks for all that you do for the forum members here.
Hi Update from today. I looked into the ABS block/solenoids Checked ohms COMM : 6.1, 3.6, 3.6, 6.1, 3.6, 6.1 the 6.1's fluctuated between 6.1-6.3 depending on how I moved the probe. Is that a huge difference/significant? I supplied 12V to each solenoid and could hear each of them click in turn. Should the female part of the clip that connects to that 7 pin solenoid harness have 12V of power with key on? 12v at all the pins except the comm? I also pulled the banjo bolt on the top of the MC where the line come in from the pump. That was clear and open. Thanks
There are two valves for the rear brake circuit. One (supply) will be normally open, the other (return) normally closed. I'd say that there would be no voltages on the solenoids unless the wheels start to skid. I assume a small spring in each valve keeps them in the correct normal position. I initially thought that one of the springs may have be broken and jamming a valve in the wrong position, but the clicking noises suggest that the valve internals are free to move. Do the clicking noises seem to be similar? If there is voltage on the female plug, perhaps it's an ECU fault sending voltage to one of the two rear brake valves?
Right after thinking about it there shouldn't be 12v in that female harness until its time to tell the solenoids to do something. Each female pin registered like .02 volts.
Your readings are fine. When measuring low resistances, it is normal that the reading will fluctuate depending on how clean the pins you are touching and the probes are and on how hard you press the probes. As Ian has stated, there should be no power on any of the solenoid pins (2-7) unless the ABS is activated during braking.
Did you, the first time, bleed the front calipers with the ignition off? Was the system also depressurised? This is a bit far fetched but might be a possibility: one cause of the pedal having no travel, and only when the system is pressurised, could be faulty Main Control Valve (#4 on the diagram). During the ABS operation, while the relevant solenoids are activated to relieve pressure in the caliper, this valve is also activated to apply pressure on a piston inside the MC to push the brake pedal back up. If this valve is faulty (leaking in its "off" position) it may keep the "back pressure" on the pedal preventing it from being pressed down. To test for this possibility, you would need to have everything connected back and the reservoir filled with fluid. Keep the ignition off and the system fully depresurised. Bleed the front calipers and then, with the ignition still off and the system depressurised, open one of the rear caliper bleed nipples and check whether now you have some pedal travel. If you have certain brake pedal travel in this case, close the rear nipple, switch the key to ACC and fully pressurise the system. With the key in ACC, try again bleeding one of the front calipers. If the pedal is now very hard (almost no travel), it might be the mentioned Main Control Valve. Image Unavailable, Please Login Image Unavailable, Please Login
1. Small initial movement of the MC before it starts pushing the fluid 2. Small initial movement of the pads before they start pressing against the discs 3. Expansion of the rubber brake hoses 4. Compression of any air in the system
Here is my point Miro. The OP stated he had no brakes. But then he goes on to say the opened the front bleed screws and successfully bled the front brakes. No problem with pedal stroke with the front bleed screws open. No problem with front calipers. Then he closes the bleed screws and gets no (or minimal) pedal motion with the rear open. But isn't it trued that with the Teves system the front system is completely independent of the rear? Thus the only time there is any coupling is through the high pressure circuit IF ABS is activated. So isn't the pedal stroke limited by the front brakes regardless of whether the system is pressurized or not? Formm the point of pedal stroke, pressurizing the system only adds boost to the pedal motion. Depressing the pedal once the fronts are bled and bleed screws closed make the pedal motion limited by the items you listed for the font part of the system. As for the rears, depressing the pedal does not displace any fluid in the rear system. It only opens the valve to the high pressure loop so, as we all know, opening the rear bleed screws won't vent fluid, if the system is not pressurized, when the pedal is depressed. When pressurized it should vent. Since the OP claims there is not fluid vented from the rears with the bleeds open when the system is pressurized and pedal depressed it seems that since he said he had code 25 or 26 (I'm suggesting it was 26) that the problem is with the rear inlet solenoid valve. Op said resistance measures OK and solenoid clicks, but that doesn't mean the valve is actually working. I would disconnect the rear brake line from the MC and see if fluid can vented there when the system is pressurized and pedal depressed.
Yes I have done this and the answer is basically no. Disconnected the rear line directly from the MC. Fronts are closed, pump is on, pressure is present and only a drip or very slight pulse of fluid comes out of the rear port when pedal is depressed. And the pedal only travels about an inch (vs the full stroke I can get if the fronts are open). Thanks
Can you feel the "boost" when you depress the pedal when the system is pressurized compared to when it is not? If you can then it indicates that high pressure fluid is getting into the MC and then that would seem to me to mean the rear entry solenoid valve is the problem. In my car (95 355) with no pressure I can push the pedal to a hard "stop". If I turn on the key and press the pedal I can feel the same "stop" but with a little more pressure I can depress the pedal a little further and I can hear the rear bakes come on. I can modulate this last pedal movement and hear the rear brakes release and be applied. If I turn off the key can continue this last bit of pedal modulation I continue to heart the rear brakes being applied and released until the pressure in the system is depleted at which point the pedal feel has the same hard stop as before the system was pressurized. Of course the caveat os that my car is a working system.
If I remember well, my brake pedal travel was also about an inch (perhaps a bit more) when bleeding the rears. This is normal as the front calipers, with the bleed nipples closed, are limiting how much the pedal can be depressed. Despite of this, I managed to bleed the rears well. Perhaps your problem is actually only the binding of both rear brakes. What John said in his post above "the problem is with the rear inlet solenoid valve" is a valid possibility. Perhaps the solenoid valve is seriously clogged/seized allowing, under high pressure from the MC/Pump, some pressure to be built onto the rear pistons but does not allow it to fully relax thus keeping the rear pads fairly hard against the discs. One way, fairly cheap but taking some risk, is to buy a Jaguar MC and use parts from it for experimenting. There are currently two on Ebay UK - https://www.ebay.co.uk/itm/JAGUAR-XJ6-XJ40-RHD-MASTER-CYLINDER/313139207478?hash=item48e88d1d36:g:IE0AAOSwOWdfBBYX and https://www.ebay.com/itm/Jaguar-XJ40-XJ6-BRAKE-MASTER-CYLINDER-1989-94/224051259196?hash=item342a7ee73c:g:CSkAAOSwTQlfB3js. The whole MC is very similar to the 348's MC except that the pushrod external section with a fork that connects to the pedal is much shorter. The Jag valve block is same as the 348's but it has its connector mounted on the valve block itself, i.e. does not have the extended loom with a connector separately mounted like on the 348. I haven't tried it, but it looks like, if you mount the Jag valve block onto the 348 MC, you can still plug the connector of the incoming harness into the connector on the valve block. You can see the differences on these pics: Image Unavailable, Please Login Image Unavailable, Please Login
Yes, with the front bleeds closed, once the play in the pedal is taken up (not much), the stroke to a hard pedal is about an inch when the system is depressurized.
