Changing seal for hydraulic brake boost pump switch

[moore]

I am about to change the seal on the pump switch, which is leaking fluid, is it simply a case of unscewing the switch, fitting new seal and screwing back in, or are there things to watch for, ie pressure in system, fluid loss etc

 

[Dave Wilkinson]

Mike,

It's not a job I've done so my knowledge is very much based on heresay but I have a feeling that getting the original unscrewed is no mean feat, possibly necessitating the removal of the complete pump in order to get access/leverage etc.

Once removed, the switch will leave the hydraulic circuit open so I would assume once the replacement is in place the whole primary hydraulic circuit will need bleeding including the pressure container (the "bomb"). I believe there is a specific process for doing this and be aware that the pressure is VERY high.

If you have not done this before I would strongly recommend consulting someone who has.

Regards

Dave

PS. As I mentioned before, due to the complexity of the system and the work involved in restoring it to working condition, I would have been tempted to replace the switch as well.

 

[NeilW]

I doubt you would be able to unscrew the switch from the pump with the pump still in the car. Luckily, the pump is easily removed from the car. It is held in place by two bolts attached to rubber mounts, two electrical connections and the in/out fluid lines. Access is good and removing the whole pump/switch unit from the car should take less than 10 minutes.

However, separating the switch from the pump is less easy. Mine refused to budge even after being held in a vice and applying a great amount of leverage. I didn't want to apply too much brute force bearing in mind the cost of a replacement pump! So, I took it to my local garage complete with spare switch and o-ring and asked them to do it. The switch eventually came out albeit in pieces. Perhaps yours may come out more readily since it's leaking. I had a different problem whereby the switch was not extinguishing the 'under pressure' light even though it was correctly stopping/starting the pump.

As Dave says above though take care with the high pressure system. I don't remember any high pressure feedback from the 'bomb' side, so there might be a non-return valve. But in any case I'd de-pressurise the system before doing anything.

Good luck.

P.S. You'll need a pressure bleeder to bleed the primary/feed circuit, bomb, and diff solenoid block when you're finished. My pump used to run for almost a minute from cold start, which reduced to 40 seconds after bleeding.