Brakes - bleeding the system from new

ChrisC · Post by **ChrisC** » Thu Jun 09, 2011 7:38 pm

Chaps,

My new braking system is 100% empty of fluid (or was until tonight) and i am trying to pump the fluid round the system but the level of the brake reservoir is not dropping implying that the fluid is not being going anywhere when i pump the pedal. The reservoir on the servo also has fluid (and also not dropping) and none of the joints appear to be loose.

As the fluid is delivered to the brakes from the servo cylinder - do I need to have the engine running in order to get the fluid moving? I would have thought some of it would have been pumped unaided.

I have never built a braking system from scratch so this is new territory for me....

Cheers

Post by **1954Etype** » Thu Jun 09, 2011 7:45 pm

Chris,

I use an Easibleed. On your car, start with the bleed nipple furthest away from the master (n/s rear) then the o/s rear followed by the n/s front then the o/s front.

I can almost guarantee you will have a leak somewhere. Check, tighten where required and bleed again if necessary.

Angus

ChrisC · Post by **ChrisC** » Thu Jun 09, 2011 8:17 pm

Thanks Angus. I am hugely nervous of easybleeds after I had one spray fluid all over my TVR bodywork (I thought I had washed it all off but I missed a few little blobs which eat the paint) ever since then I have reverted to the old fashioned one way valve in a jar...

I guess I need to go round all the joints again but the servo is the bit I cant get my head around....

Post by **1954Etype** » Thu Jun 09, 2011 8:20 pm

Chris,

You don't need the engine running to bleed the brakes.

Angus

christopher storey · Post by **christopher storey** » Thu Jun 09, 2011 9:26 pm

Well... I am sorry to disagree with Angus in one sense .... although theoretically it should not be necessary to have the engine running, i have found , and confirmed again only 2 weeks ago, that if you can't get fluid through the system, starting the engine and thereby providing vacuum to the servo can make an enormous difference. Quite why this should be is hard to explain but sometimes it does work

The other thing to do if you get stuck is to loosen off the union at the input from pedal cylinder to servo, and bleed that far - washing down thoroughly once the union is tightened - and then bleed in stages from the servo onwards

ChrisC · Post by **ChrisC** » Thu Jun 09, 2011 9:46 pm

ah now that makes some sense... i could at least prove the pedal master cylinder is working... i will try that now

ChrisC · Post by **ChrisC** » Thu Jun 09, 2011 10:11 pm

yep fluid is getting to the servo cylinder fine but nothing is coming out from the servo. I have no way of using the servo to pump the fluid any further so although I know I can bleed the brakes without the engine running it feels like I have to defer this job for a few weeks and go back to the electricery to get the engine running.

christopher storey · Post by **christopher storey** » Fri Jun 10, 2011 2:17 pm

Chris C : the other thing you could do if you have access to a vacuum pump is to create vacuum in the servo front ( I think I mean the front ) chamber with it , as though the engine were running, and then use the pedal

ChrisC · Post by **ChrisC** » Mon Jun 20, 2011 9:24 pm

Aha and then again not....

I have now changed the brake master cylinder and fluid gets to the rear callipers with no problem at all and the pedal is nice and hard. Trouble is absolutely nothing is getting to the front callipers - in fact nothing even comes out the servo cylinder at the front. SO I guess the servo cylinder is stuck (or something).

Ideas please gentlemen...

The pipe to the front callipers is fitted to the front outlet on the servo cylinder which looking at the parts manual is correct so its not that.

<<<written with a cringe because my gut tells me the servo cylinder is toasted..>>>

christopher storey · Post by **christopher storey** » Tue Jun 21, 2011 9:39 am

Chris C : the usual genesis of this problem lies in the fail safe mechanism built into the servo cylinder to prevent total brake failure in the event of a hole in either front or rear circuit. Too complicated to explain here but if you study the workshop manual diagrams showing the fluid flows etc you will see how it works

The remedy, I'm afraid, probably lies in getting vacuum to that servo, which provides much of the motive force for the shuttle which operates the front pipe hydraulics . If you can't get it from your own engine or a vacuum pump, what about bleeding off the manifold of an adjacent running ( petrol) car using a long pipe? - or indeed off a running diesel with a vacuum pump

ChrisC · Post by **ChrisC** » Tue Jun 21, 2011 10:22 am

Ah thats interesting thanks Chris.

I will stop panicing for a minute then and wait until I get the engine running and then see if I can bleed the fronts...

Lovely.

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