I took the filter assembly apart, now I can't get it back together. There's a silver medal ring, a big cotton back, an inner plastic seal and an outer plastic seal. Somehow, they all fit back together. It's not in the factory manual. Nilfisk GS 90 Cannister.

That's the thermal cut off circuit. If the motor gets to hot it trips and shuts it off. When it cools down it will turn on again but it is generally an indicator of one of the following; the cone filter needs changed or the inner filter ring that sits above the motor inside the unit is shot. One is an easy change the other requires dis-assembly, better carried out by a vac tech if you aren't comfortable taking it apart. In the meantime remove the cap out of the top of the vacuum, that will let it exhaust heat better but I strongly recommend getting that filter ring changed.

One shouldn't take things apart if one cannot re-assemble them :D
Take it to your local vac shop.

That is more than likely the problem, NEVER put wet or even damp filters back into your vac

Check this URL:
http://dl.owneriq.net/c/cfa73431-8b5e-42a3-8f48-1ca8fc2bcdd4.pdf
You should find your solution there. If not, please let me know and I will see if I can find an exploded view manual. Paul

If the plastic insert has come off then that is not normal. It should be all one piece to the hose. You might have a hose problem that needs replacing.

Check its assembled correctly . Sounds like something is out....

look in the instruction manuel

Steve, The o-ring goes inside the turbine assembly on the metal shaft.

I’m happy to assist further over the phone at https://www.6ya.com/expert/robert_b96ba3f038cf317c

I had a similar problem - the hose had very low suction and made a loud hissing sound whenever I went to use it; and there also seemed to be some overheating at the bottom. I spent a lot of time checking the vacuum for clogs, from top to bottom, over and over (including the u-shaped piece already mentioned, and the filters) and made sure everything was completely clear and clean - and yet it made no difference. It was really frustrating and I was ready to go out and buy another brand vacuum cleaner! In desperation I called Dyson customer service, and a very helpful young lady quickly figured out the problem and talked me through how to fix it. The culprit was a rubber seal ring that wraps around the very bottom of the inner assembly inside the clear plastic bin where all the dirt collects. Set aside the clear bin, and you will see what looks like a fat black rubber band approx 1" wide and about 4' across. It has grooves on the inside that match ridges at the bottom of the silver grey cylinder. Mine had slipped out of the track and had ridden up the cylinder about an inch, and hence there was no seal and dirt was escaping. This was causing the problems and way overclogged the hepa filter. I just had to slip the rubber seal back down into place where it belonged, and also thoroughly wash the the filter, let it dry overnight and put back in. After that the hissing noise was gone and I again had suction in the hose. It was a very simple fix, and yet it wasn't something I would have known to look for - and I could have very easily have ended up spending money unecessarily at a repair shop. And yet nowhere in the leaflets or online instructions that I read was any mention made of this seal and the importance of making sure it's properly in place and how easily it can mess up the cleaning action.

Mine was a simple fix. Hope yours is too.

You need to take the unit apart to get to the cord reel. If you don't know how to take your unit apart, here are some instructions on how to take apart most of the Miele canister units.

http://www.sannerud.com/house/miele.html

Once it is apart, you will need to take out the cord reel. There is a small rubber hose which needs to be removed on the outermost part of the reel. Then there is one small silver screw that you must remove as well. One these two items have been removed, carefully lift the entire cord reel assembly upwards. When you are doing this, ensure that you are also lifting the black and white wiring along with the reel - just make sure that you're not yanking it and possibly breaking the connectors off. As you lift the entire reel assembly out, you can also remove the white wiring harness which connects to the main switches on the vacuum.

Now, here is the trickiest part - not really that tricky if you are good with your hands.

First, make sure that the cord is retracted fully. Then, start pulling the white plastic cord reel away from the black plastic assembly about 1 inch or so. Between the black assembly and the white reel, you'll notice a copper-like metal spring which is attached to the white reel. Make sure that as you are removing the white reel further, that you are maintaining visibility with the copper-like spring. DO NOT LET THE SPRING OUT OF ITS OWN WHITE REEL (the spring has its own reel which is difficult to wind up again, so be very careful!).

Make sure that the spring is fully retracted at this time. If it is not, wind the reel so that the spring is not wound up anymore around the white reel. Carefully slip the spring out of the white reel and leave the spring as-is ensuring that it does not unwind itself out of its own reel.

Now that you have the white reel off the black assembly, inspect the inside of the inner part of the white reel. You'll see two copper rings with 'wings' on them. These wings transfer power to the vacuum. There may be some grease (black) which you should wipe off with a paper towel. Also wipe the metal rings on the black assembly which touch these 'wings'. (the wings touch the metal rings to send constant power to the motor. The wings are there so that as you wind and unwind the power cord from the vacuum, there is always constant contact with the metal rings on the black assembly.

Now, carefully pull the wings up and out. If you can picture it in your head, what you're doing is ensuring that there is a good contact between the copper wings and the metal rings on the black assembly. Do this for all 4 wings on both the inner and outer copper rings within the white reel. Make sure that the 4 pads are clean and grease/dirt free.

Once you've done this, it's time to put the white reel back on the black assembly. Do everything you did earlier, but in reverse.

Carefully take the copper spring and align it to the white reel - you'll see a specific slot where the spring slides and grabs onto on the white reel. You'll probably have to place the white reel slightly onto the black assembly rod in order to achieve this - again, you must be good with your hands to do this without breaking anything.

Once the copper spring is attached to the white reel, press the rest of the white reel onto the black assembly. HINT: turn the white reel slightly so that you're applying some tension on the spring - this will make sure that the spring doesn't fall out of the white reel.

Reassemble the cord reel assembly (black and white parts) back into the vacuum. Make sure that the black and white power cables are out of the way. Once seated, wrap the black and white cables around the assembly and reseat the white wiring harness. Reapply the black rubber tube to the cord reel assembly and replace the silver screw to hold the entire harness down.

Close the vacuum casing, replace the control panel (power and cord buttons). Close the unit, plug it in, and power it on!

If it worked for you, congrats! If it didn't, sorry, you've got a much bigger problem with your unit.