Brake bleeding problems

I fitted a rear calliper remote bleeding kit from Martin Robey. This involves removing the rear calliper bleed nipples and replacing them with banjos and long flexies to the lower leading edge of the rear sub frame. The flexies terminate at a new bleed nipple and bracket attached to the sub frame at this point.
The new nipples are a simple taper into a conical seating. One had a slight weep and appeared to be poorly machined so I swapped it out for a ball bearing style nipple which seems to seal well.
In bleeding the entire system the brake pedal went to the floor while bleeding the front brakes but only went half way to the floor while bleeding the rear brakes and very little fluid could be expelled. Braking seems poor.
I can’t understand why the pedal won’t go to the floor while bleeding the rear brakes.
The hydraulics are piped as they were before strip down. The workshop manual shows two different pipe connection arrangements at the servo slave cylinder for early and late 4.2 models but Barratts catalogue shows the same servo part number for all 4.2 models so is the different pipe connection in the workshop manual significant?
Anyone got any suggestions why the pedal doesn’t get full travel when bleeding the rear brakes.

A possible place to look: are the brake lines between the pedal and the bleeder in good shape.

A mechanic I used in Boston took half an hour to find a line that had been nearly pinched closed by the flat bed operator misplacing a hold-down chain/hook.

Thanks Craig. Everything is new. It’s a bare shell rebuild, new master c6linder, new servo new callipers and all new lines. My only doubt is the connections to the servo slave. Even though I’ve re piped as per original my only doubt is the connection of the front and rear connections to the servo which the workshop manual shows as being reversed for late 4.2 cars compared with early cars. It the servos are the same throughout the 4.2 models I can’t see why that would make any difference but if that’s the case why did jaguar change it?

Did you remove the little ball bearings from the rear calipers before installing the remote bleeders?

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Remove the pipe connections to the servo slave and make sure that the holes are fully drilled through…it has been know to have no hole drilled…but probably easier to disconnect rear flexi at rear irs and ensure you can fully press the pedal…Steve

Yes, removed with a screwdriver an strong magnet

Good idea I’ll disconnect and check pedal travel, that will give me a clue one way or the other.

FYI…for bleeding brakes many of us use the bicycle tube method…works well…and is done alone (no helper)

FYI…Brake Bleeders are NOT needed…if the feed pipes to the rear calipers are connected to the bleed niple and the bleed niplpe is moved to where the feed pipes went…to the inside…this easily allows enough room to open and close bleed nipples with a wrench.

Mitch

Typical inner tube set-up…

My idea of ‘easy’ is to route the bleeders to the rear flange of the cage…

I (and others) also found the fit of the bleeders in the supplied lines to be poor/leaky and added a ball bearing:

I might be wrong but I think that if you have bled your front brakes and then try bleed your rears, your pedal will only go halfway down because your front circuit is bled and is roughly half the pedal depth.

So I suggest to bleed your rears and it may be that you then get a firm pedal

Dennis

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I think that too.

Dennis and Chris,
Thank you…I learned…
I only have ever used the “bicycle method”…I never understood the pedal problem, and never would have…now I know
I “love to learn”
Thanks again
Mitch

I bled the brakes in accordance with the manual, nearside rear, offside rear, nearside front offside front.
Does anyone know why Jaguar reversed the servo slave connection to the front and rear circuits for later 4.2 models as the servo part number seems to be common to all 4.2 models? Does it make any difference to the bleeding process?

I didn’t think it would make any difference but don’t understand why Jaguar made the change if that’s the case

3rd vote for this being the “problem” but would be interesting to know if pedal is firm after bleeding rears, and if brakes function adequately.

Re: the bicycle tube method, that’s certainly one way to do it; I got a Motive pressurized bleeder which accomplishes the same thing, while also keeping the reservoir topped up and being a bit “neater”.

I’ve tried to pressurise the system, never successfully. I’ve thought of fitting remote bleeders to the rear, but never got round to it. I’ve tried vacuum bleeding - sucking the fluid out through the bleeder - with no success (sucked way too much air through the bleeder).

In the end I’ve always gone back to my reliable one handed bleeding system - a tube with a one way valve in a jar collecting the old fluid. I use the vacuum pump though, to empty the two reservoirs of old fluid before the process begins.

Bleeding the rears still requires a little effort - the front most shock absorber needs to be removed on each side to get access to the bleed nipple .

I just finished bleeding my brakes and clutch slave yesterday. It only took me a little more than an hour. I bought the Motive European Power Bleeder on Amazon recommended by a forum member. It worked great the only issue was fitting the cap on the reservoir. It was a tight fit and I didn’t want to damage the plastic threads. You can see all the bubbles flowing thru the clear tubes I attached to the nipple when pressurized.

Same experiences for me. I usually crack the bleeder open and let gravity work for awhile before the pumps on the pedal especially with the clutch slave cylinder.

David
68 E-type FHC

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I just did a quick check of the Bentley manual, and the only reference I could find to the order of calipers for brake bleeding was in the 3.8L section. The addenda for the 4.2S1 and S2s just reference the 3.8 section. The 3.8 brake system is completely different from the 4.2s - the front and rear brakes are basically hydraulically independent of each other, so I don’t see why it would make difference which order you do the fronts vs the rears. The 4.2 system is another story. It would seem to me that you should bleed the circuit that uses the Master Cylinder reservoir fluid first. That is, the calipers that are connected to the rearmost port on the slave/booster. For early 4.2s, that is the rear calipers, whereas for the later S1 4.2s, and all S2s that would be the front calipers. My logic would be that if you still have air in the lines and calipers connected to the rear portion of the slave/booster, when you pump the brake pedal most if not all of the pedal movement will be used up compressing the air that remains in those parts of the system, and little if any will be applied to the shuttle piston that operates the circuit connected to the front port on the slave/booster. If you pressure bleed the system, this will probably not be such a big issue. As for why Jaguar changed, I can only think that the nature of the design is such that when you press the brake pedal, the circuit that is connected to the rearmost port of the slave/booster will operate first until those caliper pads hit the rotors, at which point the other circuit will receive pressure. If so, the later configuration would apply the front brakes fractionally before the rears which maybe preferable…

The S3 cars that have the same S2 “later” pipe configuration to the servo/slave the servi e manual gives detailed bleeding info…rears first…then fronts…Steve