I just fully flushed out the brakes on the XK8, they were a little bit spongy after the rear end rebuild. Fronts went ok but when bleeding the back I was getting an almost continuous stream of bubbles from both sides even after flushing a pint of dot4 through each side.

The fluid filling/top up was done with a Sealey VS820.

There were enough bubbles to fill a balloon so I scratched my head, and went back in doors to do some research.


It turns out if the bleed screw is too loose the siphon effect of the fluid draining from the bleed screw can draw air down the threads of the bleed nipple and into your drain line. Problem solved, I thought I would post my experience here in case anyone else comes across this.


The brakes now feel great!

 

Although not mentioned for the XK8/R, for the S Type and X Type, Jaguar recommend positioning the bleed jar base at least 300 mm above the bleed nipple to maintain fluid pressure and prevent air leaking past the bleed nipple threads.

 

I wasn't aware of this but after doing some research I tried lifting the jar above the nipple and the bubbles immediately stoped.

 

I put PTFE tape on the nipple threads - normally stops this problem and it's there the next time you bleed the brakes.

 

That is the reason I spent the $45 on a pressure bleeder. It makes a half hour job a 10 minute job, and with better results. Pump it up to around 10 psi, and start on the furthest wheel from the master cylinder, and then move from wheel to wheel getting closer to the master. It uses about half the fluid, keeps damage to the master to a minimum, and if you use a pan there is absolutely no mess.......Isn't your time worth at least $45....Be cool....Mike

 

I guess you did not read the original post, this is what I used.


Also read the jag workshop manual, it says start with the closest wheel!

 

I saw the Jag bit about starting at the nearest wheel which is at odds with what I have always done in the past(furthest away first). The instructions with my bleeder also say start at the far point - I wondered why Jag specify this?

 

As I said in another thread recently, it's not obvious (to me anyway!) why it should make any difference wherever you start or finish!

 

I don't know why it is suggested to go to the front wheel, with a Jag, but almost every other car on the planet is bled from the furthest wheel first. I guess that is why Jags are special. I got bubbles out of the rear wheels, and hardly any out of the front wheels. Porsche, VW, Audi. Mercedes, BMW, and Rolls Royce bleed from the furthest wheel first. Also, after bleeding the back wheels first, you slowly pump the brakes, until you get a reasonable pedal, or the ABS unit will give you every bit of air out of that block it can......Be cool....Mike

 

Hi RaceDiagnostics,
I'm thinking of getting the Sealey VS820 as well. Does the 42mm cap supplied fit the XK8 ok or did you need a universal adapter?
Thanks

 

thought I'd jump on this thread as I'm about to do the same - on brembos there are two bleed nipples per caliper - does it make any difference which is done first?

 

The standard cap fits without any adaptor.

 

Thanks RD that's good to know.