Vacum

[sp00k]

Hi guys, hope you can help.

This is a discovery 200 tdi engine.

Is it normal to lose brake vacum after being parked with engine off? I recently noticed that my brake pedal was rock hard for a few seconds after I started the engine. Since then I've been checking and it seems that the vacum in the braking system is lost when the engine is off. I'm sure in the past, it used to retain pressure. I know it can only generate pressure with the engine running

I'm not having any problems with the brakes and the vacum builds quickly once the engine is started.

I had a quick look tonight and I can see that the base of the vacum pump where it sits on the engine is slightly damp, but there is no oil as such dripping or anything. Is it common to have a leak from here and is it worth replacing the gasket?

Any tests anyone would recommend?

Cheers!

 

[lynall]

Follow the vac pipe along the bulkhead, there is a t-piece the hose splits near this.
Ignore that just twigged its a 90!

 

[sp00k]

Follow the vac pipe along the bulkhead, there is a t-piece the hose splits near this.
Ignore that just twigged its a 90!

I'm not talking about a dyson here

The vacum pump pipe runs direct from the engine to the master cylinder - it's ony a couple of feet long.

 

[Jonnyb1990]

Mine has the same issue, although its a 300tdi,

Found flushing brake lines and renewing fluid helped a lot, but it still requires tweaking

 

[Kwakerman]

There is a non-return valve attached to the servo (the right angle union where the vac pipe attaches), could possibly have a slow leak?

 

[sp00k]

There is a non-return valve attached to the servo (the right angle union where the vac pipe attaches), could possibly have a slow leak?

Yeah I would agree with you. It has to be something simple like that. I guess I can easily test that with a quick suck and blow on the pipe . I cannot stress enough that the brakes are working perfectly. I only noticed the vacum issue because after I started her the other day, I dropped the clutch hard thinking I was in neutral and shot off down the drive. When I jammed the brakes on, I could feel the resistance. Once the engine has been idling for a few seconds, the full assistance is there.

I just did a little test before. After I turned off the engine, I used up the vacum until the brake pedal was hard. I then applied the brakes fairly hard and started the engine. After a few seconds, the pedal sank nearly an inch. This indicates to me that everything seems to be working normally, so maybe I've got a very slow leak from somewhere.

 

[tottot]

As they get older it's not unusual for pin holes to develop in the servo diaphram.