Peugeot 405 brakes power assist fault

Much to my surprise this morning on the way to work, I nearly rammed the car ahead when it stopped in a country lane and I couldn't.

So I stopped to have a lookie at the vacuum system. It's a Pug 405 GLDT, and I can only see one vacuum pipe which appears to go directly from the pump to the master cylinder. I removed the pipe at the master cylinder end, and there was a little bit of suck with the engine idling (not enough to suck my finger hard onto the pipe though). If I revved the engine then it would suck a bit harder.

Driving wise after that point, on the motorway the brakes appeared to be fine. The power asssist only stopped working when travelling slowly, and giving the car a bootful in neutral would return the power assist temporarily.

So, does this sound like the vacuum pump, or could a leaky seal somewhere in the master cylinder explain it?

The car is on 227k miles, so bits are bound to be rather worn.

Cheers!

Tony

Reply to
tony.jackson
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at tickover it should drag your finger in, so it sounds like the pump is worn out

Reply to
mrcheerful

OK, cheers. Wasn't sure how much suck it should have, but it's not enough to do finger-suckage at idle.

Experimenting on a bit of empty road on the way back, if I accellerated up to 60mph and just coasted in neutral, if I pumped the brakes a bit the vacuum would all go.

Then if I held my left foot on the brake while slowly bringing the revs up, I could feel that by 2000 rpm there was a bit of vacuum and by 3000 rpm there was enough that it felt like "normal braking."

I don't think there are any leaks in the air system because if I revved it to develop vacuum and then cruised in neutral for a mile or so, then there would still be enough vacuum to brake normally.

So sounds more and more like the pump.

Seen a few scared faces in rear view mirrors today as I've braked up behind people with the engine thundering. :P

Reply to
tony.jackson

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