Shop Vac Burning Smell

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Established Member
29 Mar 2018
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This week my shop vac (Metabo - only a year old) has started to produce a slight burning smell from the from the exhausted air when switched on. Once the vacuum is switched off the burning smell disappears instantaneously, and so attempts at locating the source by immediately opening the vac up after use haven’t discovered anything.

I appreciate the exhaust system moves the air through rapidly, but, if the motor was the culprit, I would have expected to find the smell still present near the motor straight after powering down.

Does anybody have any advice or to potential causes or remedies? I’ve cleaned all the filters, but that doesn’t seem to have made much of a difference.

I've done a bit more investigating this morning, and at the bottom of the motor housing there looks to be a potential 'issue' (attached photo). I'm not sure if this is related to the smell, but it is the best I have to go on for now.

I'm guessing it is not meant to look like that. Does anybody have any suggestions of what type of fault this could be symptomatic of?


  • Vaccum Motor Housing.JPG
    Vaccum Motor Housing.JPG
    1.2 MB · Views: 258
Looks like you have sucked in some fluid of some kind and its burning off in the motor or from the impeller blades, or at some time it has overheated and it's the bearing grease attempting and escape to freedom.
I appreciate everything in its path will get sucked into the vaccum, but it’s never been used specifically on liquids so I’d be surprised if the limited amount of liquid that must have passed through it would have made its way into the motor housing.

The marks almost seem to have a metallic shine to them, almost as if they were solder, so you’re probably right in that it is something coming from within the motor assembly, e.g. bearing grease. When switched on there’s no problematic noise that can sometimes be associated with bearing issues, but the smell is instantly present so it’s not like you have to wait for it to overheat under prolonged use.

I guess it could be worth adding lubricant into the motor, but its looks like it could be a sizeable disassembly operation which I’d sooner avoid if possible.
Almost all motors nowadays are "sealed for life" bearings.
Have you washed the bag? Are the hoses clear?
restricted air flow will produce burning smells, even the air will smell of burning if it cant escape.
It’s got a new fleece bag in it. I’ve cleaned the filters. I’ve opened up the top and cleaned all accessible areas with compressed air and a cloth. I think realistically it’s as clean as it’s going to be for a used vacuum.

I’ve also tried using it with all non-essential components in an effort to locate what could be the causes (either source of smell or restricting air flow). Even without the hose, bag, or even filters the exhausted air is still coming out the back as if something is overheating.
Try running it without any bags, just the motor. If you still get the burning smell the windings are cooked and you need a new one.
Agree with Bob, it's cooked, give it to your OH let them keep using it until it stops working preferably by not bursting into flames then blame them and make them buy you a new one.
Yes, if I remove the hose/bag/filters and just with the machine on (essentially not trying to use it as a vacuum, just as close as I can get it to testing the motor in isolation) the smell is immediately present in the exhausted air.

It’s a Metabo (although essentially it’s a rebadged Starmix I Pulse), so it’s a pretty disappointing failure after little more than one year’s use (not even under the considerable greater stresses of a professional environment).
Where did you buy it from? That would be my starting point. Let them deal with metabo.
Quite right, your first port of call is the retailer, not the manufacturer.
I emailed Metabo customer service for general advice, but am yet to hear anything back. I think the previous time I tried contacting Metabo (different subject) I never heard back, so I don't have high hopes at the prospect of having to deal with them.

It was bought off Amazon (supplied by them, and not a third party seller), so I will have to try with them and see where I get to.
If you payed with PayPal get them involved, the manufacturers don't like a bad review or a PayPal dispute being started.