Chattering sound from hydraulics

[B-Hive]

I have had this issue for as long as I've had my MK1. My money is on a flat accumulator that struggles to maintain top pressure. Its almost like slow machine gun fire especially with high pressure demands like high position setting or braking at idle.

Good luck

[Linegeist]

Nope. A flat accumulator will result in a constant ticking from the bypass valve as pressure in the HP side fluctuates rapidly, kicking the pump in and out of circuit all the time.

Once my PR valve pops shut, it'll stay that way for almost a minute, on idle, indicating that (a) I don't have too much in the way of leak-off (good) and (b) The accumulator sphere must be holding enough reserve pressure to feed the system for the top end of the timescale recommended. (Anyway, it's a new one )

Once that minute's up, and the PR valve pops open again, that's when the problem starts. Once pressure's back up to normal (a matter of 10-15 seconds or so) off it goes again - hissss ..... hissss....... tap-tap-tap ....hisss.
(Howzat for a Citaerobics impersonation then? <bows deeply, blushes, etc> )

A blip on the throttle obviously snaps it shut and it all goes quiet again. So, I suspect that the valve's not shutting off cleanly - I just want to make sure there's nothing to bite me in the derriére when I whip it off (like, do I need any new pipe seals f'rinstance).

[citronut]

Bob wrote
"young man. "

i aint bin called that for a lonnng time, thats the young bit

regards malcolm

[mnde]

Resurrecting an old thread here but...

My car has always had the same symptom, that the idle revs drop when the pressure valve lifts, and sometimes, but not always this is followed by a "continuous" hiss, and cut-out won't happen until I blip the throttle.

When crawling along at slow speed, I can feel the extra drag through the drivetrain when the pump cuts in, and the "release" when cut-out happens.

Can anyone explain why this could point to incorrect ignition timing or a problem in the HT/LT circuit... or indeed why this would cause the drop in revs? It is not enough to labour the engine - except when the engine is very cold. I always thought it was due to a weak pump or the extra friction of the LHM flowing through the pump at high pressure, or old LHM.

Should there be NO discernable drop in revs when the valve lifts?

I have to say I don't own an HT tachometer so have always set the revs by the revcounter to what I estimate to be around 850 rpm (BX16 manual).



Mark.

[Kitch]

Mines done this ever since I got the PAS working again having fitted the new FDV. Thought it was the dosuer drawing a shitload of LHM as it was knackered and was probably losing shitloads to the return side, but no change since I fitted the new dosuer. Can go for a minute without ticking sometimes, but is always brought back by applying the brakes. Drives fine, just annoying!