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Post by indianajones on Feb 24, 2020 9:19:42 GMT
Hi chaps!
Long time no post, been rather busy of late, wife just gave birth to your third (and final!) child.
Been having a tinker with the Jag, brake pedal has been soft and going to the floor if I sit on it. Now I managed to source a M/C re-build kit, so go the M/C off and rebuilt it, reinstalled it, bled the system.....and the brakes, while feeling a little better, are still going to the floor should I sit on them.
Now the XJ40 does have a rather interesting booster system (ran from a hydraulic pump system rather than a vacuum servo), but I don't think that should be causing this issue.
So on that note, any ideas? lol
Is it a cause of bleeding more? I have done it twice since the M/C rebuild (got the mrs to help on the pedals). I have read of one method where you keep the brake pedal pushed down overnight to help get air out of the system. Another avenue is to check the flexi hoses by clamping them off in turn and checking the brakes (I dare say the they would benefit from a replacement regardless).
Cheers all,
Andrew
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Post by dave1800 on Feb 24, 2020 10:06:44 GMT
Hi Andrew
Congratulations, more sleepless nights to come - and a Jag to sort out!
I've had a quick look on the forums as I guess you have but nothing very helpful. Certainly worth checking the rubber hoses aren't acting as balloons before delving further as this alone could provide your answer.
Some mention priming the booster pump but not sure how that works. Is the brake pedal hard with the engine off?
David
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Post by indianajones on Feb 25, 2020 10:12:30 GMT
Cheers Dave, yup, sleep is a thing of the past at the moment lol.
Not sure what they'd mean by priming the booster pump, unless they're referring to pumping it before bleeding, to remove residual pressure from the system.
They brakes seem harder with the engine off and I'm fairly sure that the pedal doesn't go as far with it off, but will need to go back and confirm that.
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Post by andrewa on Feb 26, 2020 16:31:46 GMT
Congrats to you and your family!
I've sent you a pm with a link to Toyota site which i used when bleeding the brakes on my Toyota - which has a hydraulic pump - may be of some use - or absolutely none at all!!
Cheers
Andrew
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Post by indianajones on Feb 27, 2020 20:11:32 GMT
Cheers Andrew, saw that thanks, will take a look and see if there is something useful within it  |
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Post by indianajones on Mar 1, 2020 23:10:10 GMT
Took another look this weekend just gone, used a locking plier to clamp off the top of the front driver's side flexi hose and the pressure to the pedal felt a bit better.
So the next course of action is to order/make up a new set of front hoses and see how we get on.
-Andrew
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Post by indianajones on Aug 17, 2020 20:35:54 GMT
So got new front hoses made up, still getting the low pressure warning on the dash and the pedal still seems to feel soft.
Also, a week after doing a bleeding session and firing up the car, I bled the rear brakes again and noted that air was coming out of the nipples instead of fluid (though the fluid wasn't too far behind it) with the near-side wheel being worst.
Is this a sign of air entering the line? if so what could be causing it? I have read about knackered piston seals drawing air in once the brake pedals are released.
Cheers,
Andrew
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Post by tonymark3 on Aug 18, 2020 19:58:40 GMT
Logic says that for air to enter some fluid must be displaced or leak. Doesn’t need to be much. I remember a servo seal leaking and it emptied the reservoir. A shock when I reached a junction and no brakes, swift use of hand brake and spun round in road!
dismantled servo and it was full of brake fluid.
Has the reservoir level dropped at all?
Is it a vacuum pump like diesel engined cars?
after I had renewed all the brake lines etc on Muddy I couldn’t get a hard pedal. Turned out to be a tiny leak at one front calliper
Tony S
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Post by indianajones on Aug 19, 2020 0:35:17 GMT
Cheers Tony,
Reservoir level doesn't appear to be dropping (well by any noticeable level), it's a hydraulic assisted braking system (there's a separate pump with provides pressure to a booster which is behind the master cylinder).
Might get off my bottom this weekend get the wheels off and see if I can notice any obvious leaks.
Also glad to hear you got our of your tricky situation in one piece!
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Post by indianajones on Oct 19, 2020 23:13:02 GMT
Update on this one, I replaced the brake accumulator on the hydraulic system and that seems to have got things sorted, touch wood. Will continue to monitor, though I'm sure all 4 calipers could do with a refurb.
Cheers,
Andrew
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garry
New Member
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Post by garry on Dec 29, 2020 18:45:35 GMT
Hi Guys, I had something similar once years ago with a Vauxhall Carlton, tried everything to get the spongey feeling out of the brake pedal. Just as you have. After scratching my head i found that if you bled the brakes with the engine running (full servo assist) it solved the problem. If it works with your situation, Happy Days |
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Post by jeff on Dec 29, 2020 20:23:38 GMT
Well with all my years on the tools I found that I made mistakes that even a careful boy wouldnt.
Last summer I fitted a new master cylinder to my landcrab. Me and Mrs bled and bled getting through 2 cans of fluid..I kept seeing bubbles in the bleed tube and a continued soft pedal.
Result: I decided air must be getting in. It was. I hadn't seated the master cylinder pipe connection properly. Each downstroke let fluid out of the bleed nipple with air. Then I locked the nipple before the return stroke. That return stroke pulled air in from the poor connection. I hadn't noticed anything wrong until out of frustration I locked the nipple up and asked mrs to pump fast and hold it when it went hard. (Ahem!) By luck I saw a very fine spray of brake fluid across the back of the engine bay. Well worth a check. Even a microscopic crack or miss fitted joint will let air in.
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