Why your Vacuum pump may have failed.

**steane** · 1st February 2016, 03:13 PM

Originally Posted by workingonit

Steane, no leaks at all? Did you reclamp the lid?

No leaks. I didn't tweak anything before fitting it. Just fitted it with the new brake booster.

Will probably crap itself now

**ROAMER_AUS** · 1st February 2016, 03:31 PM

What do they mean when they say that "booster stores the vacuum" This is the first time I hear of this. Is this true? I taught that while brake is not pressed, air is drawn thru the booster either by vacuum pump or engine (non turbo), due to the valve in it being open. Once brake is pressed, it closes the valve which then creates vacuum and pulls diaphragm. Is LR somewhat special with vacuum system?

**bee utey** · 1st February 2016, 04:05 PM

Originally Posted by ROAMER_AUS

What do they mean when they say that "booster stores the vacuum" This is the first time I hear of this. Is this true? I taught that while brake is not pressed, air is drawn thru the booster either by vacuum pump or engine (non turbo), due to the valve in it being open. Once brake is pressed, it closes the valve which then creates vacuum and pulls diaphragm. Is LR somewhat special with vacuum system?

You have it entirely wrong. When a booster is off, vacuum is present on both sides of the diaphragm. When you press the pedal air is let into the rear chamber after the valve between the front and back is closed. Let the pedal off and air stops going into the back and it is drawn through the centre valve until full vacuum is once again present on both sides. This way you get one dose of vacuum assistance even with the engine turned off.

**ROAMER_AUS** · 1st February 2016, 04:50 PM

Originally Posted by bee utey

You have it entirely wrong. When a booster is off, vacuum is present on both sides of the diaphragm. When you press the pedal air is let into the rear chamber after the valve between the front and back is closed. Let the pedal off and air stops going into the back and it is drawn through the centre valve until full vacuum is once again present on both sides. This way you get one dose of vacuum assistance even with the engine turned off.

You live and learn! Thanx for explanation!

Sent from my GT-I9305T using AULRO mobile app

**PAT303** · 1st February 2016, 07:00 PM

I've found fitting them with two gaskets has worked the best,they seem to last years doing it that way. Pat

**BathurstTom** · 4th February 2016, 09:27 AM

Found an interesting post regarding this matter;

"By way of historical explanation I should say that in the 1970's I worked for a UK company, Davies and Metcalfe. I worked on the required brake modifications on the locally built (NSW) British Rail designed High Speed trains, known here as the XPT. Incidentally the eight six car sets built here have now done well over a million kilometres each and that equates to over 25 times (each) around the earth!

Wabco (Westinghouse Brake Company) were D&M's chief competitors for train braking systems so I admit that I have a natural competitive prejudice.

Were I to design (redesign that is) this vacuum pump the piston would have a coiled oil ring and the piston return spring would only be equal to the designed vacuum, so that once that vacuum was achieved in the brake booster the piston would be "held" in the end of the cylinder and the pressure pad would only return to the camshaft lobe once that vacuum was lost. The pop rivets technically are fine, after all, most aircraft external panels are riveted and it's an acceptable method of fixing two components together."

300TDi Vacuum Pump - Discovery Forum - LR4x4 - The Land Rover Forum

Tom.

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