Hydraulic system check/analysis:strange symptoms

[adamskibx]

Right: Ive got no problem as such, but this BX confuses me. Something needs replacing in th hydraulic system but I cant work out what. In other BX's, any stopping of the engine would result in rapid loss of braking (this was done at low speed in a planned and controlled way). In this BX the brakes feel even sharper, and never seem to fade, no matter how many times they are pumped off and on. Does this mean this is the only BX I have had with a good accumulator sphere? Its just that its also the only BX that doesnt rise with the engine off when you press down on the front or rear.The self leveling with the engine on works fine however. I would have thought that if the car doesnt change height as it should with the engine off then the accumulator sphere is flat. There is no regular clicking but there is however, a hiss that can go on for a long time, or until the accelerator pedal is jabbed to take the revs up to 1500, then the hissing stops for another 20 seconds or so. Just want to make sure the components are all in good order so that I know it drives at its optimum. Regards, Adam

[jeremy]

I wonder - 2 possibilities

1. Air in the LHM due to a leak on the inlet side of the pump - look in the reservoir with the engine running and see if there is any evidence. - green milky LHM.

2. leaky non-return valve in the accumulator? Turn car off and sit in the boot - car drops and by the time it should rise (which would be about a minute or so) - the pressure has leaked away from the accumulator?

Hissing/ticking should be longer than 20 seconds - nearer a minute. Non return valve is under the accumulator sphere - remove sphere, remove plate and bolt (10mm head?) from accumulator face on regulator. collect ball bearing (which will probably fall in your face). Stick ball back in hole with a dab of grease and strike it ONCE smartly with a BRASS punch, reassemble.

I have done this job on my TD with the regulator on the car from underneath. You must use a brass punch - a steel one will put a flat on the ball. Similarily you must only tap it once - this creats a seat - do it more than once - you create one each blow which will not be concentric and the consequent mess will leak!

Nice effective cure - and its FREE!

[AndersDK]

Even BX'es with high mileage (and thus a supposedly worn hydraulic system) will have several full blows left on the brake pedal after a HP pump stop (or engine stall). My wife tried it when a HP pump belt snapped ...
... in city traffic ...

She had countless brakings due to traffic - and only when reaching home after some 30mins driving the suspension was getting low & bumpy and brake pedal feeling hard. Still sensible to drive when I tested it for fault finding
This was our (at present) 248Kmiles '89 16RS.

[DLM]

Sounds like a reasonably healthy one - though you should also note when making comparisons that your old blue estate was one with a very recent doseur valve refit.

In my experience the dropping front you've previously experienced could be something to do with strut seals - but depends on exactly when it occurs.

As the struts age and seals degrade, there's a greater tendency for sit-down - but particularly when you get into the car after it's been parked up. If the front drops as soon as you get out, then it's all part of a healthy hydraulic system with a healthy accumulator that's just compensating for the rise in level immediately after you get out of the car - the mirror image of the car rising immediately after you get in but before you start the engine.