De-pressurising

[hydractive]

Sorry to bother everyone - have tried to do search but ng. Can anyone tell me if the hydraulics on my 2.5 can be de-pressurised without starting the engine?
I am doing some work on the engine and want to change the seal on the doseur without re-starting the engine if possible. The cars been standing 3 weeks and has sunk right down.
Thanks for any help.

[xmexclusive]

Hi hydra

I changed the doseur on my red M reg 2.5 in a hurry last month because of a MOT failure for leaking. Undoing the pipes carefully was all I did about depessurising. Because you have BENDIX brakes you will need to bleed the hydraulic system afterwards including the ABS block. Later 2.5's with TEVES ABS self bleed the hydraulic block.

Regards

XMexc

This post has been edited by xmexclusive on April 24, 2008 10:25 am

[techmanagain]

Thank you for that info regarding brake bleeding or not bleeding. That's the first time I had heard that.
What a mine of information is revealed on this site!

[hydractive]

Thanks XMexc - where is the abs block please?! Regards

[dean]

Hi all

I dont want to go against someone as experienced as xmexc but ...........it is always worth depressurising by lowering the car to the ground via the lever inside the vehicle (with engine running) and once it has settled undo the 12mm bolt (1/2 to 3/4 of a turn max) that is on the pressure regulator then turn the engine off. by leaving the engine running at idle during this procedure the electrovalves stay open allowing all the pressure to be released from the suspension circuit, opening the bolt on the P/R releases the stored pressure for the reserve/distribution circuit. Now i dont pretend to be an expert so if this is nonsense let me know and i will crawl back into my hole but it is always safer to depressurise, after all parts of the circuit can be at up to 170bar and fluid coming out at 170 bar car penetrate the skin, and that isn't something you want.

I am very interested in knowing the procedure for bleeding the abs though, i have always done this with an emergency stop (to activate the abs) mainly because i could never find anywhere to bleed the abs.

Dean

[xmexclusive]

Hi Dean

I take your point entirely, safety is very important. The depressurisation routine is important. It is just that on a 2.5 it is a real sod to do particularly if the suspension is right down despite the anti-sink. I took a calculated risk. Encouraging someone else to do the same was a mistake. Sorry hydractive I should have told you the full depressurisation routine.

It is not just the ABS block there is a specific order for brake bleeding otherwise you risk leaving air in the ABS system which will give false/random ABS action during braking noticable even if the ABS is out of use.

Will look up the instructions for bleeding and add it to the self help ABS entry.

Regards

XMexc

[aengus-xmv6]

When I had to replace the brake valve on mine a couple years back I must admit to cheating a little....

Since the doseur is at pretty well the highest point in the hydraulic circuit, certainly on the HP side, and I was replacing the valve with the HP pipes in one unit (easier than messing with the unions under the scuttle), I opted to do:

1. depressurise system
2. remove scuttle trim etc
3. replace doseur
4. tighten HP feed pipe to doseur, but leave the HP to brake unions a bit loose
5. start up and allow system to pressurise
6. apply brakes several times & hard so LHM fills the HJP pipes to ABS/brakes
7. tighten unions a bit more
8. get assistant to apply brake and fully tighten unions
9. top up LHM
10. road test to ensure brakes are ok (on a quiet/empty road)

didn't end up bleeding the brakes and they are still just fine

Basically used the principle that fluid will fill a void (pipe) from lowest to highest point, the union being the highest point. So long as the air in the pipes on the HP to brake/abs side can escape, you just bled the air out of the system

regards
Dave

[dean]

Hi xmexc

Seems i made a bit of a mistake if i had read hydractives post properly i would have seen that his car has not run for "3 weeks" and has sunk right down because he Has been working on the engine, i would say that you where right as there is no chance of the system retaining pressure for that length of time. It is not necessary to run the car when depressurising, you can open a door which will do the same as running the engine i.e energise the electrovalve and open the hydractive valve to allow suspension pressure to be removed from it as the car is lowered. The only problem is you have about 30sec till the E/V times out and you have to close and then open the door to energise it again

I will be off to my hole now ...............

D