Brake bleeding after caliper change?

[steve_m]

I intend having the front calipers replaced; as there is no work going on at the back is it necessary to bleed the whole (Teves) system?
If we were to clamp or block the front hoses, would the loss of fluid from the front calipers only, affect the whole system?
If it is necessary to go to the hassle of bleeding the (inboard) rears would it be worth fitting the bridge pipes as per the advert?

http://www.ebay.co.uk/itm/201390714123? ... EBIDX%3AIT

Has anyone done this and is it an easy fit?
Thanks.

[davidr]

Hi Steve - I would say it's not necessary if you clamp off the hoses. They will "gravity bleed" to a fair degree. Then you can bleed them conventionally to get the last bit of air out without the need to run the accumulator pump.
As for the outboard bleed nipple conversion for the rear, the thought occurred to me when I rebuilt my IRS but I came to the conclusion that I can use my pit to get under the car if necessary so not worth the effort for me.
Regards
David

[steve_m]

Thanks David, that will be a relief for my wallet!

[ptjs1]

Steve,

Remember not to let ANY fluid get pushed back up the pipes when removing the pads and calipers. It's probably the biggest single cause of failed ABS valve blocks. Undo the caliper bleed valves then clamp the flexi pipes.

Good luck

Paul

[steve_m]

Thanks Paul, not something that I was aware of.
It won't be for a couple of weeks yet; the power steering pipework on the X Type is dribbling badly so I'll have to trundle off to work in the other one until I can get that fixed.
Ho hum, the joys of Jag ownership.

[steve_m]

Well, that was another bust; changed the calipers and there is no difference.
I guess that the problem lies with the valve block as we couldn't get any fluid to the caliper although it looked like there was air pressure pushing the pads out?
I figure that when the discs and pads were changed that caused the problem as the pads were pushed back in to remove the calipers (who knew?).
The thing is, I don't have any ABS warning lights on other than when I start up and then it goes out after about 30 seconds.
We even tried sucking the brake fluid through with a little pump but nothing came out.
Any ideas?

[ptjs1]

Steve,

I know that in theory, you haven't disturbed the low pressure side, but you could try and bleed the LP side first to ensure that the pump is receiving its supply of fluid and there are no air locks in the LP side. After that, try and bleed the brake circuit again. I know you probably know all this, but do ensure that the pump has come up to pressure before bleeding the wheel circuit.

If you've still got problems after that, you need to pray to the Jaguar gods that it isn't the valve block. First of all, roll the car as far as you can with the ignition on so that the system doesn't think that one wheel has locked and initiated the ABS valves. It shouldn't happen but you never know.

Then if you still can't get fluid out of the bleed valve, disconnect the pipe at the caliper and see if fluid can be pumped out of that. You can at least eliminate the caliper as being the cause if you get the same problem. I'd then disconnect the pipe before the flexi and try again so that you can eliminate a collapsed flexi. If you still have a problem, connect it all back up and try bleeding a few more times with ignition on and off in-between. because if you've still got a problem it feels like a stuck ABS valve and you just don't want that!

Cheers

Paul

[steve_m]

Thanks Paul.
Could you just remind me which is the LP side and how to bleed that?
The calipers are new (recon) units and the fault is exactly the same, offside front not working (so that was a waste of money but at least they are nice and shiny).
The pump is definitely getting fluid because I can hear it slow down and stop when it gets up to pressure.
When we were bleeding the offside caliper (no problems with the nearside) brake fluid was coming back out of the reservoir which is a bit odd.
Anyway, had to bolt it all back together in a rush as I had 5 minutes to get to the MOT station!
It passed with 2 advisories for front tyres which are badly worn on the inside due to tracking being wildly out (thanks Wiltshire council for the lovely state of our road: only done a couple of thousand miles).
Brakes passed but only at 60% on the accelerometer; not bad for a 3 hydraulic/1 pneumatic system!
Interestingly enough the ABS light behaved differently on the way back; it is now extinguishing immediately the engine starts whereas before it would always stay on for a little while.
The pedal is a bit spongy so I figure another go at bleeding and see if there is any improvement in the whole system.
And get some more tyres.
Did have one result though, managed to finally fix the erratic tailgate window on the Freelander.
Now just have to sort the airbag light on the Alfa before I sell it; anybody fancy a nice Twinspark Spider?

[steve_m]

Bled the offside front again today and fluid came out so that's a result.
Balance is much better but still pulling a bit to port when braking but not as much as it used to plus warning light is not on nearly as long as it used to be.
We'll give it another bleed in a couple of weeks to see if it improves anymore.
Justxjs has a recon valve block for £850!

[davidr]

Steve - I have a pair of braided brake hoses that will fit your car. I bought them in error thinking they'd fit my Celebration.
They're yours if you want them - price is a pint

[steve_m]

Sounds good to me but I'm away for a fortnight and your pint will be flat by then!

[ptjs1]

Steve,

If you've still got pulling to one side and inability to bleed, you MAY still have a valve block issue. Suggestion, don't pay £850 for a recon, I may have 2 cheaper suggestions....

Paul

[poprivet]

The valve block has for a long time been widely regarded as witchcraft. As a purely mechanical piece of kit I see no reason not to service and clean it, obviously with the usual caveat of care and done by someone with sufficient mechanical aptitude.

Yes, it is part of the braking system and is critical but many here will happily service brake calipers, suspension components and other things that would result in tears if not done correctly.

[steve_m]

Thanks guys.
We'll give it another go when I get back as there is now fluid coming through the pipework which wasn't before and the braking is much improved.
I think I'll take up David's offer of the flexi hoses as at least that will eliminate the possibility of collapsed rubber one.
I agree about the witchcraft thing; I remember the similar sense of dread if the overdrive ever packed up on the MGC; nobody wanted to touch them as they 'couldn't be repaired'.
I'll have to wait a couple of weeks now anyway.
Paul, what are the 2 cheaper options?

[ptjs1]

Steve,

Give me a call and I'll explain!

Paul

07966 202314