Air in the brakes ?? Series 3 E-type

[flyer295]

When I checked the brakes after my rebuild I found I had a problem.
1. The front brakes were not releasing properly. Cured that with a new master cylinder
2. When I refilled the system and bled it I had almost no rear foot brakes (the handbrake's poor as well but that's a different system)
3. Cured problem 2 by fitting a new slave and servo (the costs never end!)
4. I am now left with a foot brake that operates very well HOWEVER, although the pedal feels solid, initially it is more pedal travel than it should be, but NOT to the floor.
If I release and pump it once the travel reduces to what I believe it should be. Maintaining pressure on the pedal it stays solid and does not slowly go down. Indicating that there's no air in the system.

Normally I would diagnose this as air in the system, however, I've bled and re-bled them and there doesn't appear to be any air.
Anyone got any ideas.
?

Bob

[mgcjag]

Hi Bob...i would still think you have air in the system.....how are you actually bleeding the system....where do you start and what do you use....Steve

[flyer295]

Hi Steve,
Initially I had a problem getting anything through the system so by bleeding the front first until I got fluid in the system.
After that I did it as per workshop manual.
Start with the rear rh then left hand then fronts
I've done this 3 times now and all the fluid comes out clear.
I'm just wondering if these vacuum self bleeders might do it better !

[mgcjag]

Hi Bob....yes vacume bleeders are good..dont go for the pressure bleeders.......Iv never had a problem useing the old fasion method......ideally you need 2 people...one in the car......open a nipple...press pedal fully down and hold..tighten nipple......release pedal......then repeat until clear fluid flows with no air bubbles..........no posibility of air getting back in as you release pedal...if pedal is still not firm repeat......Steve

[Whitact]

Hi Bob,
In my experience the brakes on these cars can be difficult. I experienced exactly what you describe on my FHC and no matter what I tried I (including a full brake rebuild by a "well respected specialist") I could not improve the situation so learned to live with it for several years. The car was perfectly drive-able but needed a quick double tap on the brakes to get a firm pedal at the top of the stroke.
The brakes also had a tendency to hang on when the car was very hot, but as this only happened during summer trips in southern Europe I lived with that for a while too. Having tried all the suggestions for lubrication of the reaction valve etc. etc. without success I decided to rebuild the servo again. I noticed that the parts in the rebuild kit seemed to be of a better quality than I had seen before and that the "specialist" had connected the front and back circuits in the opposite way to that shown in the manual.
In any event when it all was back together as per the manual the brakes at last behaved as they should. No hanging on and no double tap required.
I also recently heard a tip for bleeding the brakes that might help. After bleeding the brakes for the first time the suggestion is to leave the car overnight with the brake pedal fully depressed and then bleed again once more next day. I've not yet tried this myself but was told that its a really good way to remove the last bubbles of air from the system.
FWIW I've not found a vacuum bleeder that did any more than pull in air around the bleed nipple, despite greasing etc. I routinely use at pressure bleeder at about 10psi and find it quick and reliable.
In any event it is possible to get the brakes on these cars to work properly but can take some time to do so.
Good luck

[Series1 Stu]

I've had the same problems and wasted days and litres of brake fluid trying many different methods without success.

Then I spoke to a retired Jaguar mechanic who had worked on our cars almost every day of his career and he suggested bleeding the master cylinder first before connecting the pipe to the slave cylinder and then likewise bleeding the slave cylinder without the outlet pipes connected. Then connect the front and rear pipes and bleed as normal.

It worked for me.

Just be careful where the brake fluid goes when bleeding the cylinders.

Regards

[abowie]

Hi Steve,

I'm just wondering if these vacuum self bleeders might do it better !

Positive pressure bleeding is better.

Gunson make a nice kit.

[abowie]

Hi Bob....yes vacume bleeders are good..dont go for the pressure bleeders..

Whereas I would say exactly the opposite. Gotta love the internet.

[mgcjag]

Hi All...the only reason i wouldnt recomend the pressure bleeder if for the mishaps that can happen....if you know what you are doing all well and good.....but asking here intimates that your not sure....bad fitting lids and to high pressure can cause brake fluid to go everywhere.....someone only a few days ago mentioned useing 30psi on his pressure bleeder......Steve

[AshM]

Having restored all braking components over the winter (plus new callipers) I have a completely 'dry' front end to bleed. Hence my research on here to pick up as many tips as possible before I start.

Stuart - in this string of posts you reference bleeding the master cylinders BEFORE connecting the pipework up. Could you give me a few more details of what you actually did please?

Also, I plan to fill the system and let gravity to its work for a few days - do I loosen off the bleed nipples on the callipers?

Nervous about the new reservoirs too as there is lots of discussion on those at present so will add small qualities initially to check for cracks. Using Silicone so at least I won't have paint damage risk.

cheers
Ash

[Series1 Stu]

Stuart - in this string of posts you reference bleeding the master cylinders BEFORE connecting the pipework up. Could you give me a few more details of what you actually did please?

Yes, of course.

Disconnect the brake lines from the master cylinder and arrange cloths and trays etc. to collect any spills and squirts. Ensure reservoir has enough fluid in it and gently pump the brake pedal until fluid flows out of the master cylinder outlet.

Reconnect the brake line at the master cylinder and disconnect it from the slave/servo cylinder. Pump some fluid through the line and reconnect it to the slave cylinder.

Disconnect the outlet pipes and the supply pipe from the reservoir from the slave cylinder (plug the end of the reservoir pipe if there's fluid in it). Pump the pedal gently to expel air from the slave cylinder. Reconnect the slave reservoir pipe and bleed the slave cylinder again. Ensure your get air-free fluid coming out then reconnect the brake lines to the front and rear brakes.

You should now be able to bleed the brakes as per normal procedure.

I think the problem with this system is getting the fluid to centralise the piston in the slave cylinder. Until you've achieved this you are unlikely to get both circuits working

Regards

[mgcjag]

Hi Stuart....Have you actually used the above procedure........i cant see how you stop air entering back into the system during the "pumping" ...Surely as you release the pedal air would be sucked back in becaus you have open pipes......Steve

[Series1 Stu]

Like I said, it worked for me on the 420, which is basically the same system as the Series 2.

It's about bleeding the cylinders at first. As you reconnect the pipes you bleed them with each subsequent operation.

Makes sense to me.

PS Yesterday I had to bleed the oil supply pipe to my central heating boiler and the procedure entailed cracking open the joints and bleeding each section in turn.

Regards

[Ole-xke1974]

If I remember correctly then a spongy pedal is caused by air in the system.
If you can pump the system, its caused by excessive brake pad travel. Mostly seen in drum brakes that need adjustment, but I'd expect a disc brake where the caliper isn't centered on the disc will show similar symptoms.
What am I missing ?
Cheers ......... Ole

[flyer295]

I think I've cured it !!!
I bought one of those pressure self bleeders and to start with I still had the problem, HOWEVER, after a lot of thought I tried pressurizing the rear brake reservoir (left hand down near the screenwash bottle ) opened BOTH bleed nipples, then closing the l.h.one then the r.h one then both until no air noticed. (I've modified mine by running a copper pipe from the bleed nipple socket down the rear subframe and coming out just below the subframe. This means no removing of the rear seat etc. ):bigrin:
I then, without touching the pedal removed the pressure gismo and fitted it to the front bulkhead reservoir feeding the front brakes/master cylinder. Slowly pumped the foot brake r.hand wheel first then the left by the conventional method of bleeding. It was not necessary to have anyone in the car to do the rears but only for the fronts.
After leaving the brakes for half an hour (tea break) the pedal was still very firm and held pressure without slowly going down. I have yet to test them on the road but I've had to delay due to a rear engine mounting problem.
Talking of which, anyone got a pic of the underside of the V12 showing the rear engine/gearbox mounting ?Mine is wrong and I'm not sure but I think the C42202 is missing and the mounting bush (CAC3227*) is missing.
I can't see where the rear mounting bracket fixes.
Bob

[Ole-xke1974]

Hi Bob,

will this help ?