Hi. I've replaced all of the brake pads front and rear. Front brakes bled pedal came up. The rear brakes will not bleed. Do I need to run the motor while doing this or is there something else I am missing Thanks Malcolm

 

Shouldn't need to run the motor, but you will need to make sure the handbrake is off when trying to bleed the rear.

Edited to add:
Should mention when I did that it was on a non-ABS car (1986 MY). You don't need to start or turn on the ignition to bleed those, but that's probably different for a car with ABS.

 

You don't need to run the motor but you will need to turn on the ignition.

Assuming you have discharged the accumulator, top the reservoir to just below the neck. Then open one of the bleed nipples, fully depress the brake and hold it down. With the pedal down, turn on the ignition and wait until the fluid flows free of air bubbles, probably at least 15-30 secs. Close the nipple and then slowly release the brake pedal.

Then you will repeat for the other side. Make sure you do not let the reservoir level drop too much or you will re-introduce air into the line.

Cheers,

Allan

EDIT: This is for ABS cars. In another thread, the OP had said his was an 89 so I assumed he had ABS.

 

Is it an ABS or non-ABS car, the procedure is very different. Or check out my blog from the link in my signature how I did mine.

 

If you don't run the motor you will probably have a better feel for everything, but no power assist obviously.
I don't know what you mean by the rear brakes not bleeding, If you are opening the bleed screw and pumping the pedal or applying pressure otherwise, fluid WILL come out, if it isn't there is something blocking your rear line.



The parking brake should make ZERO difference. A manually operated brake separate from the service brakes will have NO effect on the hydraulic system.


More importantly...WHY ARE YOU BLEEDING THE BRAKES AFTER CHANGING THE PADS??? Changing the pads in NO way introduces air to the system, all you need to do is pump the pedal a few times to seat the pistons on the new pads.

Either way you can still bleed the brakes, no air will come out since nothing changed though.

 

In ABS cars the front circuit is static. The master cylinder acts only on the front brakes so bleeding these in the normal fashion works fine.

The rear circuit is dynamic and pressure to the rear brakes is supplied by the accumulator through a control valve. That is why you can't bleed them using the normal pump method. You have to use the method outlined in my previous post.

Cheers,

Allan

 

Right, didnt bother checking his profile to see his year.

Still don't know why he is bleeding brakes after changing pads...

 

I agree that is not necessary. Perhaps just to be sure?

To the OP, if you have disconnected any of the components in the hydraulic circuit, you will need to bleed the pump circuit before you bleed the brakes. You did not indicate this in your post so I didn't mention it but Sidescrollin's comments made me think about it.

Cheers,

Allan

 

Thanks for all the info.I hope to get at the car in a couple of days. I'll post how it goes. Thanks again Malcolm Peddie 1989 XJS 12 conv.

 

Well, no it won't have any difference on the hydraulics, but when I was doing mine having the hand brake on made it so that when you pumped the brakes, nothing came out of the rear bleeder valves, nor did the pedal drop when the valves were opened. Took off the hand brake, re-pumped and voila, pedal dropped, fluid came out, and was good to go. My car's non-ABS, though, as mentioned, so may be different in ABS models.

 

AlanG, Would you be so kind as to explain what you said about the master cylinder not supplying hydraulic pressure to the rear calipers? This goes contrary to everything I thought was true about hydraulic brakes. If you re saying that accumulator stored pressure is all the rear calipers get when stopping then it is no wonder we have failure to stop in these cars because accumulators fail. That is scary info.

 

Hi, Thanks again for all of the info. Turned on the key and everything went as it was supposed to. The reason for bleeding the brakes is I bought this car and everything I was told about the car was very vague and as I am checking out things I'm finding that the former owner did things very very cheaply, that is why I wanted to bleed the braking system, one of many things that need to be addressed. Once again thanks. Malcolm Peddie

 

RagJag,

Jaguar used this system from MY89 through MY94 XJS, they changed back to a simpler servo + master cylinder arrangement in MY95.

Perhaps this drawing will help visualize the system.

brake system.pdf

As you can see, during normal operations, the master cylinder only operates on the front brakes. The rear brakes are directly operated by the hydraulic booster. Under anti-lock conditions, the main valve is opened so that boost pressure can now act on the master cylinder and thus on the front brakes.

Cheers,

Allan

 

Relieved to hear that Jaguar went back to a simpler system.
RagJag

 

Hmmm. That's really weird! I can't think of an explanation for this but I never argue with success

Cheers
DD

 

This could just mean you didn't have enough pressure built up, but when you tried again you blew past the bleeders. Or if there was build up or debri, it had to be blown out with a bit more pressure.

I'm not trying to argue with you even though you seem to feel like that is a trick that worked. The hand brake literally has absolutely nothing to do the hydraulic system and any combination of applying it or not applying it was merely a placebo effect.

 

Hi Got the car on the road today, and the brakes worked perfectly. Now I need to get the parking brake to work. The handle works but the brake doesn't have any effect. The car continues to move. Any ideas on how to adjust it. Thanks Malcolm Peddie

 

Jaguarmack, I can not answer your question with certainty for my 1996 has outboard brakes and yours may have the inboard type. On my '96 the parking brake is inside the brake rotor and I found my little shoe linings were completely worn out and even loose from the shoe. I replaced the shoes and all is well now, until I forget to release the parking brake and burn the shoes off. Happens quite often with these cars for the park brake light is not easy to see in daylight.
Cheers, RagJag

 

On your 1989 you have inboard rear brakes. These have a separate handbrake caliper on each rotor mounted incredibly inaccessibly above the footbrake caliper. it is yunlikely to be just an adjustment problem, I am sad to say. I suggest a bit of diagnosis to start with, from the back and work forward, asking and answering these questions roughly as follows:

• Are the handbrake caliper lever return springs in place (one each side)
• Are there handbrake caliper pads in place (two each side)
• Is the handbrake cable properly engaged in the caliper levers
• Is the cable intact
• Is the cable properly engaged in the lever in the cabin

If the handbrake pads are missing/worn down, replacing them on car is a ROYAL pain, if not damn nearly impossible. I always remove the cage to do any maintenance on the handbrake calipers! If you have to do some work on them, further advice from the guys here will be forthcoming!

Greg

 

If the hand brake isn't working when you pull it, but you can feel tension so you know the cable is connected, you probably have a seized adjuster spring.

The parking brake cables don't really need adjusting on the XJS because there is a spring on the parking brake calipers that keeps them at the correct distance as the pads wear.

Definitely a bit of a headache to fix your parking brake