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Thread: TD5 Manifold depression valve

  1. 31st October 2014, 10:16 PM #1
    PhilipA
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    TD5 Manifold depression valve

    sierrafery recommended that we should replace high mileage manifold depression valves on TD5s in a thread a few weeks ago.


    I did a bit of research and found that the MDV was in function like a PCV valve. It is designed to cut off the flow of gasses from the crankcase breather under moderate to hard acceleration when the intake manifold has a vacuum from gas flow. My old one seemed to work on the "suck test" but that is probably not definitive.


    So I bought one from UK and fitted it, and I believe it has a positive effect on acceleration as all the air going into the turbo is via the MAF without any leakage from the crankcase. It should also cut down oil transmission into the turbo and intercooler as IMHO most blowby and gasses would leak in under load.


    I did some hard accelerations when entering the Pacific Hwy from on ramps and the old TD5 auto picked up its skirts and revved cleanly to 4200 in the intermediates.
    So I think it is worth the $60 .
    Regards Philip A
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  2. 31st October 2014, 11:00 PM #2
    CountP
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    Is this the valve on the pipe from the rocker cover to the intake pipe?
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  3. 1st November 2014, 01:58 AM #3
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    sierrafery
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    @Philip A thanks for confirming that, you're not the first who does it , i'm at the third DCV now and i've always felt some improvement with new one fitted (replaced them after 30-40000 km), i went on simple logic that a plastic bit exposed to those hot crankcase gasses can't work as new forever... so even if it's not completely shot and opens/closes IMO it looses the designed "parameters" in time and i hope we can all agree that excess of crankcase gasses in the inlet/crankcase is not good

    @CountP... yes that one
    Discovery Td5 (2000), manual, tuned
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  4. 1st November 2014, 04:57 AM #4
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    roverv8
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    So I bought one from UK and fitted it, and I believe it has a positive effect on acceleration as all the air going into the turbo is via the MAF without any leakage from the crankcase. It should also cut down oil transmission into the turbo and intercooler as IMHO most blowby and gasses would leak in under load.
    Any pics PhillipA
    Did u leave the old MDV in place or remove it,
    & Did you find a PCV to plug straight into the existing hose?
    Thanks, i seem to be getting a bit of oil in my intercooler hoses
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  5. 1st November 2014, 08:44 AM #5
    PhilipA
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    As the cops say "Nothing to see here"
    The MDV is the right angled thingo that sits on top of the rubber tube from the MAF to the turbo.
    The one I got was from here and as far as I can see is an OEM used by TD5 and Freelander.
    It is just a straight replacement that takes 10 minutes at most.
    Land Rover Defender TD5 Depression Control Valve | eBay


    Regards Philip A
    Last edited by PhilipA; 1st November 2014 at 08:46 AM. Reason: more info
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  6. 1st November 2014, 02:33 PM #6
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    roverv8
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    sorry, I thought you had fitted a PVC valve, instead of the MDV
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  7. 1st November 2014, 06:08 PM #7
    Wasa57
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    Going bush in my Disco is my "Depression Control Valve."
    Last edited by Wasa57; 1st November 2014 at 06:10 PM. Reason: Missed info
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  8. 1st November 2014, 07:51 PM #8
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    bronson
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    Just running in my rebuilt engine, I reckon this is a good investment.

    Cheers
    Bronson
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  9. 6th November 2014, 11:45 AM #9
    CountP
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    $50 from Bruce Lynton.
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  10. 6th November 2014, 03:01 PM #10
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    gusthedog
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    I quite often wonder if my depression control valve works. But then I go off road and have a puckering moment and realise all is good

    Terrible jokes aside, good to know about replacing. Might be a good idea on my bus. I think mine is still the original from the factory.
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