fourtrak brakes

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hi my mate has a 1996 fourtrak witch had leaky rear wheel cylinders and also the rear brake lines where corroded and since changing them the break pedal seems to go right to the floor but if you pump it a few times you get a good pedal but if you hold the pressure on it starts to sink slowly to the floor.
Has anyone had this problem or may know what it could be.
many thanks john

bled

well thats because they havnt been bled of air

Full of ideas but no time to do them!!

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Bleed them !

Bleed the whole system. Start at the longest 'run' and finish at the 'shortest'. I assume you know how to bleed brakes !

break bleed

hi we did bleed the breaks and it was still doing the same thing so we have replaced the master cylinder as we thought it could have popped one of the seals then we bled them again and still no luck the pedal just seems to sink slowly when you press it.
We have looked for leeks just incase we missed somthing but we carnt find any.
If anyone can shed any light on what it could be it will be appreciated.
many thanks john

Sequence.is essential.

1. You must bleed in the correct sequence. Start with the longest run - distance from master cylinder to brake slave cylinder.[rear wheels] Next the third longest, second, and finish with the shortest. Wrong sequence and you get air trapped at unions.
2. Always use NEW brake fluid of correct rating. [The French always try to be clever and reuse old fluid ... old fluid absorbs water]
3. Make certain there are no small holes in the tube which is used to bleed the brake. The fit to the nipple must be very tight.
4. Do not unscrew the brake nipple further than necessary. Tighten the nipple on a downward stroke of the brake peddle.
5. Bleeding with the ENGINE RUNNING will give better results due to brake servo in operation.

If that fails - two helpers.....
Bleed both rear brakes simultaneously. Then bleed both front brakes simultaneously.

If you have a pressure bleed method make use of it. One man method. I have a spare brake fluid lid/cap modified to take an air feed attached to a compressor ... 5 LBs max air feed. No need to press the brake peddle - the air feed does all the work forcing through the brake fluid, provided the brake fluid reservoir never runs dry.

Note .... with engine off the brake peddle will move slowly down - no brake servo. With engine running the peddle should rise [one press] and lock solid. Does the peddle travel down whilst the engine is running?

bled again

hi we bled the breaks again with no sucsess and the pedal does sink even when the engine is runing.
The break pedal will go nearly to the floor when you press it but not quit all the way but if you pump it a few times even with the engine runing it will get hard near the top then slowly sink.

There is a load sensitive

There is a load sensitive proportioning valve in the line to the rear brakes. This causes two issues. Firstly it has a bleed nipple of its own and you need to bleed this as well. Secondly you need to press the pedal hard and quick each time to overcome the resistance in this valve to get a decent volume of fluid to the rear to push out the air.

I know how you feel, I spent two days bleeding the brakes once. The problem was I was gently pushing the pedal with my hand. Once I got a helper to sit in and press it properly with their foot, the fluid started pouring out of the rear instead of the trickle I had previously. Job done in about 10 mins after that.

Good luck - Alastair.

Totally agree. This is

Totally agree. This is almost sertainly your problem. A lot of Jap 4x4's use this valve. It is a git when it comes to bleeding the system.

Good luck.

Any veiws expresed in this thread by me are purely from my own experience, and (sometimes) falible memory. Hope my comments help, but please don't take them as gospel.

Any veiws expresed in this thread by me are purely from my own experience, and (sometimes) falible memory. Hope my comments help, but please don't take them as gospel.

get a kit

Go and get a brake bleeding kit like gunsons or something, this will pressurise the system from the filler pot right through to all the bleed nipples, which means all you have to do is release them slow to let out the air, easy to use and it works, you do get fluid out of the nipples when you push the peddle dont you??

Full of ideas but no time to do them!!

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Brakes

Have you bled the master cylinder first? most models require this to be done and have a nipple on them. Many aftermarket master cylinders do not have this bleed nipple fitted, so you will have to do this manually.

Get an assistant in the vehicle to press and hold the brake pedal down, crack a pipe until fluid emerges and the pedal is right down, then tighten it up. Release the pedal, and repeat this sequence for both chambers of the master cylinder.

Servo

Hello m8,
This too me seems like it is the servo or the the master cylinder seals, Is there any sign of fluid around the mating faces of m/cylinder and servo.
If so it is the seals of master cylinder these can be replaced (A vice will help a lot here!)
However if the bore of the cylinder is ovulated. The seal may not work. (I have done this on 6 cars and it failed once).
If you have no leak at this join then it sounds to me like servo there is a service test for this in the manual and it seems like this is your gremlin.
However i have assumed the worst on a car b4 and the solution was cheap and quick, So check everything all seals brake lines for signs of rot etc and rebleed if your prob still there with no leaks any where gotta be the servo.
Hope this helps
Scotty