Noisy Hydraulic pump 91 TZD BX

simonineaston · Post by **simonineaston** » 23 Nov 2006, 13:33

Hi Folks,
love my BX but it sure can be quirky - can anyone suggest what the issue is from the symptoms described below...
My hydraulic pump makes a chuckling noise - not a squeek, or a rumble but somewhere in between. The noise occurs every 10 seconds or so, and lasts from a second or so, up to about 5 seconds, at engine speeds of less than about 2000 rpm.
At steady speeds of 35 mph or more I cannot hear the noise. I replaced the pump belt about 1500 miles ago and I am not sure I tightened the new belt properly - I levered the pump, as much as I dared, with a wooden hammer handle before tightening the pivot bolt and the adjuster bolt but the chuckling noise sounds like the belt is slipping to me...
Any suggestions?
Simon, Bristol UK

jeremy · Post by **jeremy** » 23 Nov 2006, 13:45

Is your accumulator working? Simple test - start engine with car at normal height and let it run for a couple of minutes. Turn off the engine and go and sit in the boot. Rear of car should sink a long way and after about 30 seconds - rise to its original position - powered by the accumulator. No rise - flat accumulator.

Another test is to raise the car fully - and see if the frequency of the noise decreases. (The suspension spheres function as accumulators when the height correctors are open)

Happened to me - a couple of days before the MOT - passe with an advisory on a rear seat belt!

slim123 · Post by **slim123** » 23 Nov 2006, 13:54

Hi Simon.

First the belt on your pump does need to be very tight as there is a lot of torque involved when it's developing 175- (2750psi) But having said that, if the belt was loose it would squeal not chuckle.

Check the suction hose from the pump to the reservoir, if there is any air getting into the pump, they will sound very rattley.

Finally, are you sure that it's not just the normal noise of the pump cutting in and out?

The pump is running and pumping constantly when the engine is running, this is controled by the regulator, ie, when you start the car, the pump will run, it sucks fluid from the reservoir and sends it to the regulator, the regulator then sends the fluid off to the priority valve and so on through the system. When the car has reached it's height and the reserve pressure in the accumulator sphere has reached 175- the regulator cuts out with a click. As you use the car, hydraulic pressure is lost due to use and the hydraulic system is topped up with fluid from the accumulator, when the reserve pressure in the accumulator reaches the lower limit of 145-, the regulator will cut back in again so that the pump can top the reserve back up to 175- Hence the occasional "wirr click"

The more often the "wirr click" then the lower the gas pressure in the accumulator sphere.

So is the noise simply the norm??

Regards
Slim.

Post by **Peter.N.** » 23 Nov 2006, 14:48

.......Or it could be that the pump is worn if it has done a high mileage, you can loose the output from one or more pistons which will make it rattle, but if its all working OK I wouldn't worry, but as has been suggested it likely could do with a new accumulator sphere, this will 'cushion' the output from the pump.

Post by **philhoward** » 23 Nov 2006, 20:22

Sounds to me like it could be a mixture of a reseating and new accumulator sphere required. As i understand it, the ball bearing which cuts off the pressure regulator needs occasional (100,000 miles!) reseating (hit it using a brass drift - plenty of instructions listed on this forum) and possibly a new accumulator sphere needed if there's a cyclic noise every 10 seconds or so.

Out of all the Hydo Cits i've owned, not all of them made a perfect "click" noise when the pressure regulator kicked back out, but all responded well to a new accumulator sphere!

jeremy · Post by **jeremy** » 24 Nov 2006, 08:14

If the power steering works the pump will be OK.

As I said I had on let go a couple of months ago - just like yours - ahort bursts of noise from the pump every 10 secs or so - and no other symptoms. - test the sphere first.

If with a good sphere it is still cycling fast - then re-seat the ball -its the non-return valve in the regulator - and the theory is that LHM can escape from the accumulator 3 ways - onward as it should, down the valve in the centre which is unusual and about which you can't do much - or back the way it came - through the non-return valve.

simonineaston · Post by **simonineaston** » 24 Nov 2006, 13:15

Thanks for all the tips folks - now I know what I'm going to do this week-end!