407 HDI Brake Problem » Peugeot 407 forum » Peugeot Central

Posted: Sun 31 May, 2009 9:17 pm

Hi All

I am not in the UK, in South Africa, but I am hoping to find a solution to a problem with the brakes on my 407 HDI that I have had for over a year now.

The problem started when they changed the pads and discs at a service and the car came back with spongy brakes. Of course I was told this was normal but they could not convince me that the brake pedal fading to the floor was so they changed the master cylinder 3 times and also bled the system numerous times which did have a lot of air in it.

The problem did not go away and has been getting progressively worse. Its not that the car doesn’t stop, rather that the pedal is floppy and this means you can apply too much breaking force too quickly which sends the break assist and ABS into a panic and triggers it erratically and prematurely.

As it stands now my car will activate ABS when stopping at speeds less then 5kph and it is not possible, with very little force, to push the pedal right down to the floor. If the car is idling you can push the pedal straight down to the floor with very little resistance which would seem to indicate a master cylinder bypass problem but if you pump the pedal, you get to a stage where it stops, which it should, but then fades slowly all the way to the floor which rules out a total failure with the master cylinder as the first scenario would suggest.

They have just replaced the ABS pump which has not solved the problem and I am getting desperate as the car is not pleasant to drive. I should add that there are no fluid leaks, or ballooning pipes and no air in the system so we can’t figure out where the fluid is going to when the pedal floors.

The brakes are also ok at speeds over 30kph when the car has enough momentum to overcome the agressive braking but you can still floor the pedal if you are not careful.

Has anyone got any ideas or heard of anything like this before?

Thanks

Robert

Posted: Sun 31 May, 2009 9:44 pm

Did they use Planet to bleed the system also?

You could have a vacuum issue.

Posted: Sun 31 May, 2009 9:54 pm

Hi Canyondust

If by planet you mean the Peugeot system, then yes they did use this. All in all, the car has been bled 5 times now.

I raised the suggestion of a surplus vacuum problem but apparently Peugeot France rules this out as apparently the 407 HDI 2.0 has a separate vacuum pump which they claim cannot produce enough of a vacuum to cause this problem.

I also keep getting told that this is normal for a 407 HDI 2.0 yet the 3 I have driven don’t do this.

Posted: Sun 31 May, 2009 10:10 pm

I've test driven hundreds of customers 407's and never had that happen.

I would still suspect a vacuum issue i.e. pump not working properly or a leak.

What happens if they look at live brake pressure data using Planet?

Posted: Sun 31 May, 2009 10:19 pm

Everything on what they call the "PPS" system shows up normally but you have given me an idea that I am going to ask them to do tomorrow and that is take mine and another 407 HDI and disconnect the pipe from the vacuum pump on both of them.

My feeling is that if they are both the same with no vacuum assist and the engine running (to rule out some other system causing the problem that may not be present while the engine is off) then the problem must be the vacuum system which they should be able to test with a vacuum gauge and compare both cars.

Will post an update once this has been done and thank you for your replies.

Robert

Posted: Mon 01 Jun, 2009 6:15 am

PPS is Peugeot Planet.

Specifically ask them to look at live data in the ABS/ASR ECU. Within that there is a brake pressure parameter which is obtained from a pressure sensor on the base of the master cylinder. I would be interested in that value as a peak and also if it is maintained over say 20s.

I put an inline vacuum gauge between the pipe to the servo and the servo and also monitor that. I am about to change that to an electronic guage which I can log using a data recorder.

Posted: Mon 01 Jun, 2009 3:45 pm

Hi James

The local dealer has decided that they don't want to be responsible for this problem anymore so have no handed it to Peugeot South Africa so I couldn’t get much done today other than find out that this will be raised by one of the technical managers at a forum in France tomorrow.

What I did do is to remove the vacuum assist pipe and see what the pedal action was like with the engine on and off. In both cases I can push the pedal down half way with moderate force i.e. I don’t need to wedge myself against the back rest to do it.

As far as I can recall this is not normal?

Thanks

Robert

Posted: Mon 01 Jun, 2009 3:55 pm

Doesnt sound right to me pal.

I think your close to finding your problem.

Posted: Mon 01 Jun, 2009 3:58 pm

Hope so but what is confusing me is for what is happening to be happening, the brake fluid has to be going somewhere or the car is compressing it which I would normally say is impossible but it seems that nothing with this car is impossible Confused

Oh Peugeot South Africa say to please thank you for your input.

Posted: Sun 30 Jan, 2011 8:48 pm

Hi I have a 407 with exactly the same probem. (Today)

It has been left for 6 weeks on its own and now the brake pedal will push almost to the floor slowly. The car will brake but the pedal feels lower and the brakes dont feel as good as they used to. The feel is that the front brakes only are working these are locking up and the ABS cuts in as designed to stop wheels locking up.

I have a mechanic background so have learnt some tricks in the past.

You said no leaks anywhere and no bulging pipes. But the pedal sinks.

The brake master cylinder could be at fault. When the footbrake is applied a valve/s close the master cylinder reservoir off so that fluid in the cylinder can not go back to the reservoir, instead of applying the brakes. The fluid then trapped applies the brakes. For safety reasons the brakes are dual circuit meaning the master cylinder has two seperate circuits built into its body.

To test these valves apply the brakes hard and have someone watch the master cylinder if it level starts to rise then the valve/s responsible for locking the fluid in the master cylinder during braking are not working.

I am going to carry out this test tommorow. If Peugeot come up with a fix please let us know.