2-stage brake fluid change?

[mjb]

Is there any problem with doing a hydraulic fluid change over a couple of days (driving the car in-between)? I'm thinking I can do the clutch and front brakes this evening, leaving some manky stuff in the rear brake pipes to be changed tomorrow evening or whenever I can get to work for 8am when the weather isn't too crap...

[djheath]

Once you have done the fronts, it surely doesn't take more than 15 minutes to do the rears too?

Also, I thought you bleed in the order of the furthest away from the master cylinder first, then other rear, then front passenger, then other front?

[mjb]

Once you have done the fronts, it surely doesn't take more than 15 minutes to do the rears too?

The fronts I can do with the car on the ground due to the hefty coupe alloys and massive Brembo calipers, but for the rears I'm going to need to jack the car up and take the wheels off. Given I've only got about half an hour to play with before sunset, I'm not going to get it all done in one evening

Also, I thought you bleed in the order of the furthest away from the master cylinder first, then other rear, then front passenger, then other front?

Haynes reckons the opposite way round with the clutch first...

[djheath]

Once you have done the fronts, it surely doesn't take more than 15 minutes to do the rears too?

The fronts I can do with the car on the ground due to the hefty coupe alloys and massive Brembo calipers, but for the rears I'm going to need to jack the car up and take the wheels off. Given I've only got about half an hour to play with before sunset, I'm not going to get it all done in one evening

Also, I thought you bleed in the order of the furthest away from the master cylinder first, then other rear, then front passenger, then other front?

Haynes reckons the opposite way round with the clutch first...

Fair enough. I cant see it being a massive problem is you take a "brake" (pfft!) between bleeds.

Re, bleeding order, I must check my haynes! I did mine based on my vw bug haynes which is the other way around! Doh!

[jasper5]

It doesn't really matter what order you do the fluid change/bleeding, the important thing is to flush clean fluid through the master cylinder, once you have clean fluid in the master cylinder, it's just a simple bleeding job to flush through any pipe.

I tend to start at the right hand front, mainly because I have a system that I follow when servicing, the right hand front wheel is usually the one I take off first.

I always undo the bleed screw, attach a pipe to the nipple, then put the end of the pipe in a container, pump the pedal until the cylinder is half empty, then fill it up again, pump again until the cylinder is half empty, fill it up again, then bleed through the pipe until clean fluid comes out, leave the bleed screw open for a minute or so, fluid will leak out under atmospheric pressure, then lock the screw up and check if your brake pedal is hard.Now you can go to any other nipple and bleed the pipe anytime you want or can.

To bleed the clutch cylinder, attach the pipe to the bleed screw and use a jar or any container that will take fluid, maybe the one with dirty fluid from the right hand front, submerge the pipe in the fluid and pump the clutch pedal a few times, check when clean fluid comes out and wait a minute for the fluid to drip through, then lock up the screw and test the clutch.

If you have an assistant, get them to press the clutch down and keep it down, lock the screw, let them release the pedal, and repeat until clean fluid comes out, lock the screw then test the clutch....same goes for the brakes if you have an assistant.

[mjb]

bleed through the pipe until clean fluid comes out, leave the bleed screw open for a minute or so

What does leaving it open do?

If you have an assistant, get them to press the clutch down and keep it down, lock the screw, let them release the pedal, and repeat until clean fluid comes out, lock the screw then test the clutch....same goes for the brakes if you have an assistant.

Tube with a one way valve Best thing to come out of Halfrauds

Reminds me I need to nip into Morrisons on the way 'om to get a turkey baster. Sainsburys ones are crap - Used one last time I did this and discovered the nozzle's too wide to hold the fluid

[jasper5]

I used to have one of those one way valve things, I find it easy just to use the tube method, I work by myself all the time, it always works.

[steve_earwig]

I've been nosing through my mate's shop's data sheets: brake fluid capacity of 1.9/2.1 td D8 = 1.2 litres (yeah, I know it's not the same for other cars but it gives a ball-park figure)

By the by, when I was a lad lodging with a mate who was doing a teaching degree, he was doing a project on hydraulics involving large syringes and clear plastic pipes. While sodding around with this stuff I found that if the fluid moves slowly bubbles stay where they are, if the fluid moves quickly it takes the bubbles with it. This is why I said down fast, up slow with regard to the old-fashioned, two-person method of bleeding. Also, using an eezibleed, unscrew the bleed nipples like you mean it, or any small air bubbles are likely to stay put.

Carry on

[steve_earwig]

I used to have one of those one way valve things, I find it easy just to use the tube method, I work by myself all the time, it always works.

Oddly enough, I never got on with them, I found unless the bleed nipple was a spot-on fit the air used to get sucked past it into the brakes

[Longintooth]

The correct procedure for bleeding brakes/changing fluid is to start with the furthest away. The reason is that the pipe expands a little when the brake is pressured so if you bleed the longest first when you shut the nipple there is enough pedal movement with the expansion to allow the others to follow through.
If you start with the shortest the expansion is least ( shorter pipe) and the pedal movement is reduced making it more difficult to get the fluid flowing to the others. Dual master cylinders (divided front rear) create a more difficult effect than what used to be mono lines. It makes very little difference whether the clutch or the brake is done first on a shared MC. All apprentice trained engineers will/should have been taught this procedure from early days. In bleeding the system whether you use a vacuum extraction or not always get an assistant to press and hold the brake whilst shutting the nipple each stroke - this ensures that the fluid is drawn quickly into the barrel of the MC to get full charge of fluid. If you use a jar you will see when the fluid runs clear. Make sure you put the rubber cap back over the nipple. It is fair to say that bleeding from an empty system is more susceptible to problems than changing/flushing albeit that you only get a short stroke on each
wheel - the divided lines restrict the pedal travel.

regards
John

[jasper5]

We were talking about changing fluid, the key is to empty the master cylinder of old fluid,fill it with new fluid, then get new fluid to each brake, the old fashioned method taught in the old days on old type braking systems, does not matter these days, every apprentice was taught to bleed the furthest away, with modern systems, it really doesn't matter, there are so many types of systems, the only thing important is that you get the old fluid out and the new stuff in, without introducing air, it's personal choice which way you bleed them.Once you have new fluid in the master cylinder, you only need to flush out the pipes with clean fluid.It is quite easy to pump fluid through the system by pressing and releasing the brake pedal, once you have clean fluid, leave the bleed screw open for a minute to let atmospheric pressure do it's job.

I do at least one fluid change each week, every single one successfully completed using my preferred method.Experience counts for more than theory.

When I do the service on my own car, I will photograph what I do and post it on here or the Wiki site.

[Longintooth]

Hi
It matters more on modern systems because they are all split divided systems and nothing changes in hydraulic theory or practice. There is a group operating in the uk that occupies 75% of garages they are called Boggit & Leggit Co Ltd , beware since they have no procedures worthy of the title skilled. Where do you get this idea of "Letting atmospheric do its job" - Please explain what you believe this does.

Regards
John

[mjb]

It doesn't matter anyway, I think the slave cylinder's toast

Airbox out
Nipple cap off (eventually, felt like it was welded on)
Ring spanner over the bleed nut
Tube over the bleed nipple and into coke bottle
Crack the bleed nut, undo half a turn
Reservoir cap off
Press pedal slowly a few times
Pedal stays on the floor. Zero pressure on it other than the spring. Observe brake fluid everywhere but the bottle (but the tube's still firmly over the nipple)

Dick around for a couple of hours giving myself a stinking backache

Dry the gearbox off. Take tube off.
Open bleed nut, pedal to the floor, close bleed nut, slowly raise pedal. Repeat 20 times.
Observe dry gearbox

So how do you get the hydraulic pipe off the slave? And lets start taking bets on how long it takes the bastards at Peugeot to get me a new slave

I'm no longer having fun with this car.

[steve_earwig]

Seems to depend how common the part is. I'm not really sure which yours is to try it. Service Box also seems to list a master cylinder both ends of the pipe

[Longintooth]

Mj
I had trouble bleeding my slave - there is a small rubber seal on the end of the connecting pipe that blocked the pipe when trying to bleed it. Remove the pipe and examine the rubber seal.

John