1987 XJ-S v12 non-ABS with inboard rear brakes.

Just had master cylinder rebuilt. I bench-bled the MC.

Using the usual one-man procedure, I started bleeding the front right. After what feels like 200 pushed on the brake pedal and running a LOT of fluid through it, I still see air in the bleeder line. OK...so much for that method.

I brake out (pun intended) my decent-quality hand vacuum pump and try the vacuum method. This goes nowhere. I can pull at the most a 10 inch vacuum and the only thing that happens is that the bottle begins to collapse (and yes, I did loosen the bleeding valve). I still see air in the line and it doesn't move one way or the other. I walk away for 15 minutes, come back and see that the vacuum has held, indicating that the vacuum pump, bottle, my connection to the bleeding screw and not the source of any leaks. See attached photo.

Thoughts?

Thanks,
John

 

Hi John

Over the years, I've tried many different methods of Bleeding The Brakes

Vacuum Bleeding/Pressure Bleeding, as well as tried and trusted methods often mentioned on here

Though from my own experience of trying all these things, nothing but nothing works better for me that simple Gravity Bleeding, which I discovered by Accident when I refurbished the Cage of my 1989 XJS V12 and this will also likely work with almost any other make of Car

(1) No Assistant Required

(2) Don't touch the Brake Pedal until the Gravity Bleeding process is over and in the Case of Marelli Cars don't turn on the Ignition until the process is over

(3) Don't allow the Reservoir to run dry

That is all these is to it and as a result in my 1989 Marelli Car, the ABS Light now goes out in about 20 Seconds instead of 40!

Gravity Bleeding in your case is definitely worth a try

How I discovered an Easy Way to Bleed the Brakes on a Jaguar XJS

 

John,

What is the "one-man procedure" you were undertaking? Is that using some form of one-way valve?

Have you got a picture of this air in the pipe when undertaking this procedure?

Paul

 

If you look at the photo you see the bottle with BF in it. The one-man method is to put one end of a plastic tube on the bleed valve and the other end goes to the port on top of the bottle. Inside the bottle that same port has a short length of tube that ends about 1/2 inch above the bottom of the bottle. The bottle lids also has a vent port.

The idea is that you put BF into the bottle, enough to cover up the bottom of the tube so you don't let air back into the system. Make sure the reservoir is full. Loosen the bleeder valve about a quarter of a tern, then start continuously pushing on the brake pedal. This forces fluid into the line (and supposedly forces air out). The fluid the is being pumped through the line goes into the bottle, and when the air bubbles stop appearing you tighten the bleeder valve and you are done with that particular brake.

When I do this all works as it should...the fluid goes into the bottle...but I still see air in the line.

When I started I had about an inch of fluid in the bottle, and you can see how much fluid there is in the bottle now, so that's how much fluid I've pushed through the system. There are not sign of fluid leaks at any connection.

Maybe I didn't bench bleed the master properly, or the rebuild wasn't successful...I don't know. It's baffling.

The photo below shows the air in the line.

Thanks,

John

 

Looking at your method next orangeblossom, thanks!

John

 

Sometimes you get a system that is difficult bleed. Other times you're done in 10 minutes. My own experience with older Jags, non-ABS, is that they're usually easy.....but you never know.

What I would do in your case, FWIW, is get that master cylinder off the car and into your bench vise. Plug-off the outlet ports. Take tool (screwdriver for me) and start gently plunging the piston while observing the fluid. I can almost promise you'll see bubbles popping up. Keep doing this until there are no bubbles, period. This may take 3 minutes or 30 minutes. While plunging you'll feel the eventually piston firm up and eventually become almost rock hard. Now reinstall the MC and go thru the bleed process again.

Also, make sure you're bleeder screws are not open too far....which might allow air to be drawn in via looseness around the threads.

Oh, a tidbit....

Before bench bleeding a MC I use a tool like this to initially force air out of the MC. It doesn't eliminate bench bleeding. It just pushes out most of the air so you have less bench bleeding to do. You fill the syringe with fluid and push the fluid into the MC via the outlet ports.


https://shop.advanceautoparts.com/p/...B&gclsrc=aw.ds


Cheers
DD

 

Not the cheapest option but I absolutely love these things. I have them on 3 motorcycles and the XJS.

stahlbus®-bleeder valve

 

John,

If there's air in the pipe, I think it can only be for one of 6 reasons:

1. There's still air in the systems that is being forced out
2. You've let the level in reservoir drop too low before topping up and air has got pulled in
3. It's getting pulled in at the joint between the reservoir and M/C
4. It's getting pulled in around the joint of the tube to the bleed nipple as you push fluid through with pedal pressure
5. It's getting pulled in around the joint of the outlet pipes to the M/C as you push fluid through with pedal pressure
6. It's trapped in the pipe because its quite high above the bleed nipple and fluid is passing under it as you push the pedal

Suggestions:

1. I think that's possible but quite unlikely
2. Only you know the answer to that! If there's any chance, just bleed again
3. Check and re-bleed
4. The most likely imho - See below.
5. Detach, check flares and joints and bleed again
6. Try and move the jar much lower so the outlet pipe from the bleed nipple is going straight down and not arcing above the caliper.

I know it may be difficult for you but try and get another person pressing the pedal whilst you control the bleed nipple and watch the pipe. If air is getting pulled in around the bleed nipple, it's often lots of very small bubbles which then coalesce into bigger air bubbles.

Good luck

Paul

 

Thanks for the comments!

At the moment I've got it back in the vice but have run into another issue....blocking the ports.

I was able to find a 10mm 1.0 bolt to block the smaller port. The larger port seems to be 12mm 1.0, but I can't find anyone that makes a bolt that size locally. I see them on e-bay, but I was hoping to push the project forward rather than waiting on another part, but I may just have to wait.

I have the Dorman "universal" kit with which I initially tried to bleed the MC, but of course those fittings are plastic and the larger port leaks with the port-to-hose fitting screwed all the way down, so time to put on the thinking cap and figure out a way around that little issue.

Thanks,

John

 

Hi John

Find a Brake Pipe Fitting that will Screw into those Ports, then get a piece of Cupro Nickle Brake Pipe and put an SAE Double Flare on the end of the Brake Pipe that goes on the end of the Fitting that is being Screwed into the Port

Then the the Free end of this that is open, as it hasn't got a Fitting on the end can then be bent and Crushed with some Pliers in order to Seal the Pipe

Or You could put a Fitting with an SAE Double Flare on each end of a Piece of Cupro Nickle Brake Pipe and then Screw each of those Fittings into each of those Ports to Form a Continuous Bridge and then Seal it off that way

 

When I fitted a new M/C to a friend's car I had similar trouble. This is what worked for me:

• Madame in driver's seat operating the brake pedal
• The two outlet ports to the callipers disconnected
• Pedal pressed and held down (rag collecting any fluid)
• My fingers over the ports, Madame releases pedal
• Repeat until fluid flows out perfectly with no bubbles
• Reconnect outlet pipes

What I concluded was happening (before the above fix) was that there was so much air in the M/C that no, or hardly any, fluid was being drawn into it, and when the brake pedal was released, air just re-entered through the ports rather than the cylinder filling with fluid. Once no air could enter the ports, the fluid HAS to get into the cylinder. It only took about 5 or 6 goes to fix it.

 

I worked out a substitute device to block the larger port. It's the plastic part from the Dorman bleeder kit, a skinny bolt, a nut and two o rings. The larger o ring goes into the port, then (after running to bolt through the plastic part and tightening the nut) screw the assembly into the MC port. Viola! a tight seal. OH, the o ring not shown in the picture went over the nut/plastic part joint.

As Doug suspected, I got some bubbles out the the MC. After pumping on the MC piston a bit I now can't move the piston at all, so it seems the air is out of the MC.

So today it goes back in the car and I'll try again.

Thanks,

John