Peugeot 405 Braking woes

[mkirkby]

Sorry this is a long one...


The brakes on my 405 have always been a bit spongy and slowly got a bit worse over time until it became dangerous. Anyway, bled all the brakes and made no difference so assumed it was the master cyclinder.

Replaced that with a new one and beld all four lines again (using a pressure based Gunson Eezibleed), and still got spongy brakes.

Basically doesn't 'bite' and the pedal goes almost to the floor. Even then, with full effort braking is decidedly 'dodgy' to say the least.

Any thoughts?

My thoughts are:

1) Could I still have air trapped in the system (is that possible with eezibleed?). I didn't bleed the master cylinder before installing, could that have air in it or would the eezibleed release that?
2) before trying with eezibleed I just used a system that had a one way valve to stop air going back and pumped the pedal. Didn't work (probably due to too much air in the system), but I read on one forum that you can rupture a new master cylinder by pushing the pedal to the floor. Might I have done this and need yet another one?
3) Could it be a problem in the calipers or rear cylinders (rear drum
brakes)
4) Might the rear self adjuster be wrong allowing too much pedal movement. (But surely that would still allow a good braking performance when it finally got to bite...which it doesn't)
5) Could it be the servo? But that wouldn't make the brakes spongy would it?

Can anyone think of a diagnostic procedure to try and track the problem down? Is it possible to check the calipers? (replaced rear cylinders as a
matter of course)

Cheers

Mark

 

[Burnerman]

Hi Mark
There are a few reasons that your brake pedal has too much travel.
1) There could still be air in the system
2) There could be a flexible pipe that is 'ballooning'
3) The adjustment is out on the rear brakes (but only with drums).
Try pumping the brake pedal a few times to obtain brake pressure, and hold the pedal there. If it sinks to the floor the master cylinder is faulty.
If the pressure holds, the master cylinder is ok. Release the pressure, wait 10 sec and press again. If there is little feel now, the rear brake adjusters haven't adjusted.
If you can get a reasonable pedal, get someone to hold the brakes on while you feel all of the flexy pipes underneath. There will be 4. Feel carefully for any swelling.
To check the servo, pump the pedal a few times and hold it.....start the engine and the pedal should go down a little.
Personally I'd still be looking at the bleeding process - as you've had the master cylinder off there could still be air up there.....get someone to press the pedal while you crack open the master cylinder unions to allow fluid out.
If your car has ABS they can be very difficult to bleed - I use a device that sucks the fluid out rather than pressurising it, which seems to work for me.
Wishing you luck! Cheers John

 

[^neo^]

If it has a load sensing valve on the back end, make sure this is fully open when bleeding.
Is there actually any air coming out of the bleed nipples?
Have you changed the pads / shoes / discs or drums?
I'd also consider changing the rear wheel cylinders if you havent already. They're peanuts to buy and a slightly knackered seal could be letting in air

 

[mkirkby]

If it has a load sensing valve on the back end, make sure this is fully open when bleeding.
Is there actually any air coming out of the bleed nipples?
Have you changed the pads / shoes / discs or drums?
I'd also consider changing the rear wheel cylinders if you havent already. They're peanuts to buy and a slightly knackered seal could be letting in air

Haven't got a clue about the load sensing valve. Not mentioned in the Haynes manual but I'll have a look later. Presumably it would be a gadget in line with the hydraulic lines..

No air coming out, haven't changed the pads/drums etc, but did change the cylinders (as you say...cheap). Was bad before the change and still as bad so not those.
Thanks

Mark

 

[retirednow]

With some French cars the bleed nipple is not at the top! This can be a problem! Allegedly they are designed so that when the car is on ramps the bleed nipple is at the top.

Years and years ago I had a Lancia Flavia and this had spongy brakes. (It had a Dunlop-Girling system with the discs made of Kryptonite or something. Anyhow the discs never wore at all unlike modern cars where the discs are cheap cast iron) Lancias brilliant parts-man at Ealing informed me that to get a perfect pedal one had to "crack" every union in the system as tiny bubbles of air used to get trapped in the unions. Once this was done the brakes were splendid.

Good luck!

 

[Mursal]

Try sitting in the car and pumping the pedal, when up, keep your foot on the pedal and get a mate to open the passenger side rear bleeder. The pedal will go to the floor, tighten bleeder and release the pedal. Continue until all air has come out. Do the same on the drivers side rear, then both front.

You may have to do this a few times, a small amount of air will leave the pedal spongy.

Hope this helps

 

[Avocet]

Sometimes, after a lot of work and bleeding, you gt microscopic bubbles in the fluid. If left overnight and then re-bled, it can sometimes improve things, even if you thought you'd got all the air out. If it has drum rear brakes, I think they didn't have a load sensing valve, they had a pressure reducing valve in the rear wheel cylinders. Failing that, I'd suspect one or more flexible hoses.