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        General >> Off Topic Subjects >>   Bleedin'  
        
(Message started by: mr._floppy on Oct 7^th, 2008, 12:55am)

Title: Bleedin'
Post by mr._floppy on Oct 7^th, 2008, 12:55am

Not quite off topic but, on the Crown Victoria USA site is a dramatic, heated and raging ( well, not quite :)) debate re brake bleeding.

Your views are welcome.

The question being should the bleed screw be loosened when the caliper pistons are pushed back in to facilitate fluid displacement or should one leave the little b****rs undisturbed ? Or do it make no difference ?

The future of centuries old Anglo/American diplomacy is at stake that's all, it could be The Boston Tea Party all over again.

So answer with care. @

Title: Re: Bleedin'
Post by Snoopy on Oct 7^th, 2008, 8:14am

Really, it should not make any difference as the fluid will be pushed back into the brake fluid reservoir as the self adjuster is wound back. Loosening the bleed nipple might, just might let some air into the system which would require the system to be bleed.

Title: Re: Bleedin'
Post by peteHull on Oct 7^th, 2008, 8:31am

If the nipple is open then fluid would be pushed out, this would have to be replaced no doubt and this should be with new fluid, a slight benefit although not important I would have thought. ;)

So long as no muck is allowed to enter and the system is bled properly I don't think it makes any difference, but then... Who am I?

hth ;)

Pete

Title: Re: Bleedin'
Post by Highlander on Oct 7^th, 2008, 9:41am

I've never opened a bleed screw when resetting a piston, no need to, and as already stated it could let in air.

So I'm in the "dont touch it" camp, whatever side of the Atlantic that puts me on :)

Title: Re: Bleedin'
Post by mr._floppy on Oct 7^th, 2008, 3:42pm

The theory is that if you don't open the bleed screw then dirty brake fluid is pushed backwards through the system causing problems with the seals and valves in the sensitive ABS system. :-X

Title: Re: Bleedin'
Post by cossie_al on Oct 8^th, 2008, 7:55pm

If dirty fluid gets pushed back into the sytem then surely its time the fluid was changed anyway???got to admit I am with Highlnder on this ;)

Title: Re: Bleedin'
Post by Highlander on Oct 8^th, 2008, 8:12pm

Hmmm yep, dirty brake fluid??
Doesnt make sense to me. How is it dirty?
if theres dirt in it theres a problem.

I've never seen or heard of unscrewing the bleed screw when resetting the pistons, the reservoir cap yes but never the bleed screw.

Why would you run the risk of letting air and indeed dirt in by unscrewing it?

Title: Re: Bleedin'
Post by Tompion on Oct 8^th, 2008, 9:12pm

I thought one of the reasons was that the reservoir could overflow, but I wouldn't undo the bleed screw.

Title: Re: Bleedin'
Post by mr._floppy on Oct 8^th, 2008, 9:41pm

Thank goodness for good British common sense.
Them colonials, you can't tell 'em nowt. :-/

In fact, my service schedule for my Crown Vic doesn't even mention changing the brake fluid at all, yet advises changing the fuel filter every 30 000 miles .

Weird ???

Title: Re: Bleedin'
Post by Simmo on Oct 9^th, 2008, 7:14am

The other practical point, having removed the cap from the fluid reservoir, which is done to allow the 'pressure' to release, is to surround the neck of the reservoir with rag to collect any fluid which spills out. ;)

Title: Re: Bleedin'
Post by cossie_al on Oct 9^th, 2008, 1:22pm

on 10/08/08 at 20:12:57, Highlander wrote:

Hmmm yep, dirty brake fluid??
Doesnt make sense to me. How is it dirty?
if theres dirt in it theres a problem.

Brake fluid is hygroscopic (absorbs moisture) so after a good while will appeer discolored or dirty.
But as you say Highlander opening the bleed screws will pose more chance of getting actual dirt in. :-/

Title: Re: Bleedin'
Post by peteHull on Oct 9^th, 2008, 1:46pm

on 10/09/08 at 13:22:33, cossie_al wrote:

Brake fluid is hydroscopic (absorbs moisture) so after a good while will appeer discolored or dirty.

Hi Al

I have always wondered about this, I know about brake fluid absorbing water and that is why car manufacturers and main dealers recomend it to be changed. However I haven't decided why the water would be absorbed into it in the first place, it is sealed into the brake system. Similarley, Heating boiler manufacturers and heating engineers also recomend de-scaling your radiators and pipes, costs a bomb....

If these systems are sealed and bearing in mind they are nowadays, so the only scale would be the small amount introduced in the initial filling stage which wouldn't even be enough to coat the inside of the pipes.

Anyway, these are just my thoughts on these two particular examples, there are more, I'm sure.

The one thing that is clear though, that is they both cost lots of money to have done.... ;)

Pete

Title: Re: Bleedin'
Post by cossie_al on Oct 9^th, 2008, 2:16pm

Pete,
Are both systems not vented?
Again I am no expert }{ but I always thought the gubbins inside the fluid resevoir cap was the venting system.