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Author Topic: Bypass / relief valve creating sucking noise so low suction when in use  (Read 23393 times)

Offline paulwa13

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Hi,

My dc07 has poor suction. It makes a loud sucking noise which seems to come from the relief valve on the filter cover housing and so I assume that the suction is being weakened from this. Suction via the top of the hose seems very good. Can tell the suction is poor because pick up is bad when its being used. It will pick stuff up, but compared to a friends seba (borrowed in desperation) it leaves loads behind.

I checked all the pipes, cleaned filters, replaced the post motor filter and cleared the top of the cyclone unit where it narrows to small holes (blocked up for a very long time, as I know when the plaster dust got there 3 years ago!).

Just wondering if there is anything else I need to look at / consider?  Is it possible the spring in the filter housing could have got weaker so the relief valve is activated the whole time? I also noticed that;

1. the rigid plastic that the sponge filter sits in, is worn where the filter housing's seal should sit. This is a dyson part that originally came with the dc07
2. The replacement sponge filter and rigid yellow plastic for the pattern part we got a little while ago does not seat well in the filter housing - ie I can see a gap between the foam ring for the  filter housing and yellow plastic.
3. The foam ring on the filter housing is a little compressed and is no longer tightly glued to the housing

Having said that, not sure if these affect the by pass valve and nor do I know what "normal" looks like.

Thanks for any advice!

Paul

Offline MV Claire

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Does the valve make the noise only when it is upright or also when it is reclined in the cleaning position?

Online MVacs

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Does the valve make the noise only when it is upright or also when it is reclined in the cleaning position?

We need to know that so we know which part of the machine is affected to be able to give you accurate advice.

Offline paulwa13

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Hi,

Thanks for getting back to me Claire.

I have changed the filter to the newer (ie pattern part). Sucking is fairly constant when upright and is now occassional when being pushed. I've got a sneaky suspicion the older filter (ie dyson original) was fairly grimy,

Any further thoughts welcome!

Thank you.

Paul

PS old filter has been washed thoroughly with bio detergent and rinsed it through a few times. Will see if this works.

Online MVacs

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I have changed the filter to the newer (ie pattern part). Sucking is fairly constant when upright and is now occassional when being pushed. I've got a sneaky suspicion the older filter (ie dyson original) was fairly grimy,

When you say sucking, do you mean the sucking noise at the valve as mentioned above? Or that the suction of the machine is now OK?

Offline paulwa13

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Hi,

Upright the suction noise at the bypass valve is constant. When "reclining" / being pushed it's intermittent (ie better than it was). In terms of pick up, it's improved because I've cleaned the cyclone thoroughly, the pipes and because the newer filter is better than the original. Of course, with the bypass valve kicking in every so often when reclined and sucking when it's vertical, then it's not at full suction, but maybe that's how it's supposed to be?

Thanks.

Paul

Online MVacs

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It is unlikely the bypass valve is faulty (but not impossible). As a general rule that valve blowing suggests a blockage. As it does it in both positions, that sounds like a blocked cyclone unit. When you say you cleaned it, did you take off the top handle (with the three T15 torx screws) and clean it with a jet wash or steam cleaner?

Offline paulwa13

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Re: Bypass / relief valve creating sucking noise so low suction when in use
« Reply #7 on: August 29, 2011, 01:17:03 PM »
I thought it was worth replying on this topic, albeit it's been an age. I finally fixed the problem, as you suggested.

Filters were all cleaned / replaced.
Took off the cyclone section (be careful if you do this, not to break the bin latch).
Jet washed the cyclone section. Inspecting it with a strong lamp, I could still see obstructions deep within the cyclone cylinder (hair, felt, fluff, dust). My jest wash approach might have worked had I tried it again with a bit more precision, but instead I got a skewer and manually cleared the blockages out. This was fiddly, but in the end they all cleared up. Strikes me as more than a slight design flaw to have something that is so small and easily blocked, but I suppose it has been in service for quite some time.

I then reassembled.

And hey presto the machine now works as if it's new. Suction is completely restored and the noise has gone. It's now picking things up with ease.

So my recommendation if you can hear a sucking sound at by pass valve (and you've checked pipes for blockages) is to work you way through the cyclone unit and unblock the top and THEN the exits at the base, with a jet wash or skewer.

Thanks to you here on the forum for your help. I got there in the end and am delighted to have a machine that works. Expect I'll be ordering a few new parts from you soon - was holding back in case I could not fix it. Now it's done it's time to get a few other bits and pieces to make it as new.

Paul

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Re: Bypass / relief valve creating sucking noise so low suction when in use
« Reply #8 on: August 29, 2011, 03:36:09 PM »
Glad to get the feedback and glad your machine is up and running again Paul.  :thumbsup:

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