Identifying HP Pump Wear.

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prm
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Identifying HP Pump Wear.

Post by prm »

Can any members advise on detecting BX hydraulic pump condition -- off the car.
The reason I ask. Have two s/h replacement pumps for 16V.
When oscillated by hand, one has no free-play between pistons, but the other has detectable free movement and metallic clack.
Anybody had these pumps apart for repair/inspection, for possible interchange of internals, with the diesel models, which are fitted with the smaller drive pulley.
R
Peter
oilyspanner
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Post by oilyspanner »

I suppose a test rig with a reservoir and a pressure gauge could be rigged, I am in the same situation myself having fitted three pumps to my TZD, all of which were working satisfactorily on the donor vehicles but none of which can raise enough pressure to stop the pressure light from flashing occasionally, if its any consolation I threw away a good GTI pump a few months ago;( I would attempt to dismantle the noisy one though, after all if the likes of pleiades can recondition them then it must be possible.
Stewart.
ps if you want a diesel one for experimentation you are welcome to have one of mine
prm
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Post by prm »

Stewart
That's some of the reasoning behind my posting. Ref your recent post. HP pump wanted/oil pressure light.
If the general static condition is anything to go by, the diesel ones I have, appear to sound far better than the petrol versions.
Time to dismantle a few and inspect. Will advise.
Are you still requiring a pump or is the fault elsewhere ??
Peter
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AndersDK
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Post by AndersDK »

If the pump can produce the common ticks from the regulator - then it works - as the click indicates a system pressure of approx 170bar is reached.
The hydraulic system does not need higher pressure. The pressure switch works at 100bar.
If the pump is noisy it wont work satifactory. The piston clatter noise means the piston return springs are worn (compressed) and the pistons are only doing part of their stroke.
Another common problem is the main (front) bearing worn out usually accompanied by LHM leaks from the axle.
From my own experience with the pump, the first problem is to remove the pulley. This takes methods and tools beyond the average DIY'er, if you want to re-use the pulley.
Next problem is to remove the housing shell. A known method is applying moderate pressure to the intake stud from another pump.
Once the pump is in bits you have a problem sourcing new piston springs. I believe the bearings and O-rings would not be a problem from industry suppliers.
tomsheppard
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Post by tomsheppard »

If the pump stroke is down, then turning the pump at a given speed for a given time will pump out less than the right quantity of fluid. A BX pump does 0.4cc/rev (As compared to that of a CX, 0.28 which is why BX pumps are such a good idea on them and why BXs lift quicker than CXs).
So, turn the pump through 100 revolutions and you get 40 cc from a new pump. 500 revolutions
and you get 200CC which is enough to get an accurate idea of the output. Pump runs at half engine speed so disconnect the output having set the fast idle to 1500 rpm and stopped the engine
Start it up, time it for a minute and you should have 0.4 X 750cc in a measuring cylinder. That's 300cc.
oilyspanner
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Post by oilyspanner »

I believe my pump is tired, sudden demands on the stystem like turning right or braking quite heavily to a stop cause the imperative stop/brake pressure lights to flash, i assume that this is due to system pressure dropping below the 100 bar required by the pressure switch, there are pumps all over the country migrating towards my car! I hope
Stewart
prm
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Post by prm »

Thanks Anders.
It would appear, rotating the pumps by hand, all the s/h petrol versions have at least one partially compressed piston spring as you mentioned. At identical points, with each rotation. Indicated by approx, 10 deg free movement and metallic clack at this point.
Compared to the s/h diesel versions, which are smooth throughout and feel under slight tension whilst rotating.
All units were removed from supposedly fully working hydraulic systems. Albeit, some must have been noisy.
Have access to heavy duty presses to possibly remove/replace pulley, which appears to be heat shrink and splined.
With the metal outer casing, I presume this is lightly screwed on, as this only carries the suction side of the pump.
Any thoughts as to why diesel pumps seem to outlast petrol versions. ?? The only outward difference being, the petrol version has approx 35mm larger pulley diameter to adjust final pump speed.
...........................................................
Tom
Just being lazy, trying to avoid removal and refit of several pumps. Will dismantle and advise.
I believe Citroen's new price is now well over £1000 -- Gulp !!
R
Peter
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Post by tomsheppard »

Diesel pumps will not have been so violently accelerated as petrol pumps and therefore the load reversals will be softer. Another point. Diesels don't get overrevved, unlike petrols. Overrevving the engine probably does the same to the pump. Finally, diesel pumps are mounted differently and may run cooler.
tomsheppard
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Post by tomsheppard »

You, Peter, Lazy? Not the man I know! Reckon you're the man to adapt the BX pump to the CX bracket and pulley then. Just think of it; A CX that could be manoevred at parking speeds!
Once you get them apart, mic up the springs and choose the longest ones. Load one up to get the deflection. There are places that will make batches of springs and if that's what goes, that's what we'll need.
prm
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Post by prm »

Tom
The petrol versions have the larger pulley to give approximately similar final pump speeds, with both variants, But agree with being able to overrev petrol versions by at least 1000rpm, when compared to diesel.
You also could be on the right track with pump temperature.
The 16V pump is mounted lower down in the engine bay, within the air track over the near side. Fine with moderate outside temps. But with any excess, cold or hot, would possibly effect pump internals.
Now I know why a TZD steering is more responsive on really cold mornings, when compared to a 16V.
Will let you know how I get on with repairs. Then poss, your CX mod.
R
Peter
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