Author Topic: Brake Fluid and it's problems, all explained  (Read 10872 times)

guest5079

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Brake Fluid and it's problems, all explained
« on: April 26, 2015, 03:17:24 PM »
I like some others have put up posts about brake problems on the Jazz. My Brother lives in Canada and has a Jaguar XJS. He has experienced brake problems with deteriorating seals in the braking system. The failing seals were blamed on incompatability with Girling Brake Fluid, it was recommended that He use USA made brake fluid!!!! He has just sent me an E mail on Brake Fluid.  Using Google put in 'Girling brake fluid'. There is an article on brake fluids headed 'Tech article, Brake fluid for classic British cars'. It is applicable to us as Jazz owners because it explains such things as why it is imperative to change the brake fluid as per manufacturers service schedule.  This article is NOT for the faint hearted BUT if you are interested, plod on as it explains an awful lot about brake fluid/ brake fade/ failing seals and  allied problems. It contains an awful lot of technical information but to some one like me that is on the borderline between amateur and professional mechanic, it explains a lot. Why do we have clear plastic reservoirs on the master cylinder? It is to obviate the necessity to remove the cap. Every time the cap on the reservoir is removed water is absorbed! It even goes as far as to suggesting checking the seal on the top of the reservoir, that's how important it is to keep it all sealed tight.  Copper brake lines, all the rage in days gone by BUT there is chemical reaction in the pipes. It is far too much to trivialize by trying to precis it BUT it is well worth reading. Even the experts might find some interest. Good reading.

degzi

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Re: Brake Fluid and it's problems, all explained
« Reply #1 on: April 27, 2015, 12:27:21 AM »
Interesting read. It doesn't half go on.

It's just a shame some people don't seem to bother about changing brake fluid like oil changes. It is important when you get into heavy braking and old fluid. Then again same can be said about brake pad materials and a whole barrel of worms.

I just wonder how many garages skip fully changing brake fluid due to stuck nipples  ;D

peteo48

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Re: Brake Fluid and it's problems, all explained
« Reply #2 on: April 27, 2015, 06:47:21 AM »
One thing I noticed, when looking at various independent garages in my area, is how few include a brake fluid change in any service or even provide a price for doing it. One, in particular, highly regarded by many, has 4 different service levels and a brake fluid change is not mentioned in any of them.

VicW

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Re: Brake Fluid and it's problems, all explained
« Reply #3 on: April 27, 2015, 03:00:01 PM »
As far as I know the main reason for changing brake fluid is because of the possible contamination by water vapour which the fluid absorbs readily when exposed to air. The water boils if the brakes get exceptionally hot and the brakes get spongy and hence lose efficiency.
When is the fluid exposed to air ?
The change interval is specified by the manufacturer but many workshops now check the fluid for water content every servicing and will recommend a change if the limit is exceeded.

Vic.
« Last Edit: April 28, 2015, 02:46:19 PM by VicW »

culzean

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Re: Brake Fluid and it's problems, all explained
« Reply #4 on: April 28, 2015, 07:51:21 AM »
I have flushed out brake fluid on Honda cars before - tried using the pressure bleeding system (ezy-bleed) where you can hook up a separate (500ml from memory)  reservoir to your spare wheel valve and screw a cap onto your existing reservoir and in theory just go around loosing off the nipples on each wheel caliper and bleed till fresh fluid comes out.  Only problem is the caps supplied with system were 2 sizes of screw on ones suitable for Vauxhall etc.  and the Honda reservoir caps are twist and click type,  never did manage to get a good seal even with the proper adaptor kit, which is a plate and gasket with a big rubber band to hold it onto reservoir. I lowered the pressure to way below what it says in instructions and still only managed to squirt fluid everywhere.  One solution may have been to get a proper cap from scrapyard and adapt it to take a pipe - in the end I made up a vacuum system to fit onto brake caliper nipple - was reasonably successful but a bit messy.

Apparently DOT 4 fluid is designed to absorb and disperse water to prevent water going to lowest point of system and causing corrosion, and when total dissolved water gets too much it can greatly lower boiling point and also allow corrosion.  Some cars have silicon brake fluid, which is not hygroscopic but if any water does get in it is heavier than silicon and works its way to lowest point (one of the wheel cylinders probably).

If what they say in Girling article is correct and the water will always disperse itself equally throughout the fluid in the system then just frequently sucking fluid out of top reservoir and topping up with fresh should help to lower total water dissolved in system as it will attract water from fluid lower down??  Not ideal, but quick and easy to do at home and better than doing nothing.
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

madasafish

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Re: Brake Fluid and it's problems, all explained
« Reply #5 on: April 29, 2015, 09:57:03 AM »
The Easibleed system sells special caps for Japanese cars.. I don't bother. I use a one way valve bleeding tube and pump the brake pedal and then hold the pedal down using a piece of wood wedged between pedal and seat. Then tighten up nipple and remove wood. Works a treat.

Eddie Honda

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Re: Brake Fluid and it's problems, all explained
« Reply #6 on: April 29, 2015, 03:01:05 PM »
When is the fluid exposed to air ?

All the time I thought. Is the cap not vented with a tiny hole so the system actually operates?

madasafish

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Re: Brake Fluid and it's problems, all explained
« Reply #7 on: April 29, 2015, 03:42:47 PM »
When is the fluid exposed to air ?

All the time I thought. Is the cap not vented with a tiny hole so the system actually operates?

It has to be. Because the level of the fluid falls as the brakes wear.So air must enter the system via the hole in the cap.

VicW

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Re: Brake Fluid and it's problems, all explained
« Reply #8 on: April 29, 2015, 07:40:59 PM »
Good point but I don't think that that air is constantly being changed, there is no flow of air and the level drops very slowly to suck in more air.

Vic.

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