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Thread: Why your Vacuum pump may have failed.

  1. 29th January 2016, 09:36 AM #1
    Roverlord off road spares
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    Why your Vacuum pump may have failed.

    We sell a lot of replacement vacuum pumps for the Tdis, customers often are not aware why these pumps fail. Some workshops will now not warrant the replacement pumps unless the brake booster was also replaced it seems.

    Here is a theory why the pumps fail.

    WABCO (Westinghouse American Brake Company). Though they are the original equipment manufacturer for the brake vacuum pump on the 300tdi, the vacuum pump seems to be the most unreliable part on any 300tdi engine. These pumps will either work for years, or fail within a very short time.

    We have been looking into the reason for the high failure rate on these vacuum pumps and have come up with a theory: Whilst there is vacuum stored in the booster, the pump piston is prevented (held by vacuum) to move towards the engine camshaft. As soon as brakes are applied, the stored vacuum is used and the piston is no longer "sucked" away from the camshaft and thus will move towards the camshaft where it will then be reciprocated to create vacuum once again, once there is enough vacuum achieved the piston will again be held by vacuum away from the camshaft (this will occur within a matter of seconds). If there is a vacuum leak, the pump is constantly working to create vacuum, and as there is little lubrication on the piston, constant operation will cause the piston to seize resulting in failure. We suggest that before a new vacuum pump is fitted, the booster is tested for any leaks. If a leak is detected, the most common cause is the brake booster (servo) which will need to be replaced.

    So it seems the unreliable design of the pumps make them just another consumable item for TDI owners.
    Regards, Mario

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  2. 29th January 2016, 05:00 PM #2
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    roverrescue
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    I find that theory a little stretched
    The spring preload in a vac pump is surely far in excess of the vacuum pressure it can create.

    I would be amazed if any amount of vacuum could hold that sucker back into the pump can?

    Having said that defender boosters bring the suck. The only success I have had is to turn the outerplate off a broken booster, clean all paint and residue and silastic this extra outer to the outer of a brand new booster. By doubling up the outer surface of the booster you end up with less flexing with pedal pressure and it is the flexing that leads to the cracking that leads to the leaking. If the booster was made from something with slightly more material than aluminium foil they would never leak.

    S
    '95 130 dual cab fender (gone to a better universe)
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  3. 29th January 2016, 09:21 PM #3
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    rick130
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    Nice tip Steve and agree, the OE TRW booster is pretty ordinary.

    I once tried to mount a dual diaphragm F250 booster as per the 6x6 Perentie but ran out of space.

    I haven't looked at a D1 booster yet, IIRC they are a dual diaphragm style too.

    I should ask Matt/460cixy. He's a brake specialist mechanic and has both a Deefer and a D1.
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  4. 29th January 2016, 11:04 PM #4
    kawaden
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    I am looking to buy a Defender and have so far driven 2 TD5's and 1 tdi300 and all have had very hard pedals. is this normal for Defenders or could it be a vacuum pump issue? if the tdi pumps are a weak point could you replace it with an electric unit?


    Thanks, Dajen
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  5. 29th January 2016, 11:18 PM #5
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    roverrescue
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    It will more likely be the brake booster is cracked as mentioned above
    They be ****

    S
    '95 130 dual cab fender (gone to a better universe)
    '10 130 dual cab fender (getting to know it's neurons)
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  6. 29th January 2016, 11:34 PM #6
    schuy1 Guest
    If, and its a fairly big IF thats the case, then the beefing up of the booster as per roverrescue's and the fitment of a vacuum tank to further prolong the life of the pump would be a good idea. But I tend to agree with roverrescue, It would have to be a very good vacuum to hold against that spring!
    Cheers Scott
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  7. 30th January 2016, 07:14 AM #7
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    If the OE booster is questionable, be very wary of aftermarket boosters.

    How long do you think this would have lasted

    [ame]http://www.youtube.com/watch?v=wU3CyjTFiZ4[/ame]

    Took me ages to work out why pedal feel was ****.


    Martyn
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  8. 30th January 2016, 08:36 AM #8
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  9. 30th January 2016, 12:13 PM #9
    workingonit
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    Roverlord, who put together the quote in your original post?
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  10. 30th January 2016, 09:33 PM #10
    schuy1 Guest
    Quote Originally Posted by Bushie View Post
    If the OE booster is questionable, be very wary of aftermarket boosters.

    How long do you think this would have lasted

    http://www.youtube.com/watch?v=wU3CyjTFiZ4

    Took me ages to work out why pedal feel was ****.


    Martyn
    Yikes!!!
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