Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Changing the air filter on a Sigma 4/4.

This might sound a daft question but to remove the lid from the air filter box how to you access the torx screw behind the rad fan with the brace bar in the way? the only way I can see is to remove the 2 large filter housing bracket nuts and possibly remove the whole lot which seems overkill for changing an air filter.
While its off I'm looking to swap out the filter to a K&N KN33-2877 otherwise I'd leave well alone.

Thanks.

Alpha. Think the lack of replies says it all. I gave up & let the garage do it, but not sure how many times my K&N gets cleaned.

Hi Alpha,

I use the tox bit (just the bit) with a spanner attached on mine.
I can just get the small bit into the screw head and then turn it with the spanner a 1/4 turn at a time.

Hope that helps ?

I thought there would be a fair number of DIY enthusiasts that would of come across the same issue so an easy one to respond too.

I’m not sure I have the room with the brace bar in position.

If Pauls tip helps, perhaps a ratchet wrench like this may help to save some time?

I often use it with a piece of adhesive tape on one side to avoid screw heads or bits slipping through.

You have already described the solution yourself. It is much easier if the two large nuts of the airbox bracket are removed. It is really quick to do. Please make sure that you do not lose all the washers. (at least my 2014 4/4 had a few of them). I would place them exactly the same way when reattaching. Otherwise the filter box may touch some struts at the front and then it will rattle when the engine is running. I say this specifically because sometimes the nut comes loose, then all is well as far as the washers are concerned. But sometimes the whole bolt comes loose from the motor housing and then the washers would be without lateral control.

Once you have loosened these two main nuts, you still can't remove the airbox. It is too big when screwed together with the cover. But now it can be moved back and forth so far that you can easily reach all the screws on the cover. This way you don't have to disconnect the valve cover vent hose, which can be quite tight. You only have to loosen the MAF sensor connector that is attached to the cover. To do this, first pull up this red plastic piece of the locking device. Then you can remove the cover.
If you want to use a K&N you can just put it in the filter housing because the K&N is very flat. Later on, make sure that the cover is in the right position so that it fits very easily.

If you are using a normal new paper filter that is deeper, then the side screws of the airbox holder may protrude a little too far into the filter paper. you can feel this when the old filter is removed. Also, there may be scars or tears on the old filter paper at this point. However, this is the reason why a new paper filter cannot be placed smoothly in the airbox right away. If you don't know this point, you can despair why it doesn't seem to fit properly. So you have to place the filter at the position of these screws with gentle force and some bending past the screws.
At the end, check that the rubber edge of the filter lies evenly on/in the filter box.

Now screw the lid back on. Be very careful! These plastic threads are worse than those of cheap Chinese plastic toys from 1967! Although I was very careful, my threads broke out completely after three filter changes (in 8 years). So only tighten with gentle force. That's why it's so important that the rubber lip of the filter fits really well in the box.
I now have to use screws with nuts and washers which makes it even more complicated.
Then you screw everything back on. It sounds more complicated than it is.

BTW I tried the K&N and didn't really feel much effect, in fact I find the 4/4 rides a bit more powerful with the paper filter in the lower rpm to mid band. But that's really a matter of individual taste. I go on holiday with the normal filter box that I leave installed. But for most of the weekend joyrides, I use an open K&N filter placed under the windscreen. I just unscrew the metal pipe that goes to the front and I use a different hose with a second MAF sensor and a different hose for the valve cover vent. Maybe I will find some photos later. This filter really makes a difference especially at the higher revs the engine is much freer and more powerful, but it is also louder and for long distances it can be annoying. But that's just by the way.

BTW if you use the OEM airbox, Kevin, this post could be of interest,

http://www.talkmorgan.com/ubbthread...ment-sigma-4-4-oem-air-intake#Post673108

Wow Heinz that is some detailed response 😊
I’ll digest all that and take on board just how fragile the fixings are.
Really interesting to read how the OEM paper filter performs better in the low to mid range than a K&N panel filter, wouldn’t of expected that .

Thank you very much for your time posting such a comprehensive reply. 👍

Kevin, I think the danger to the threads is when the filter is not inserted properly flat, because then you "pull" the lid forcefully against the rubber of the rim of the filter because there is still an air gap and you keep turning and turning. It should be stable enough when the filter is properly inserted and you can feel the defined end point of the screws.

I forgot one more point. There is a small green sponge in the air filter box where the valve cover breather hose connects. Remove this small sponge and rinse with detergent, rinse and dry. It is best to put it back in upside down so that the "new" sponge surfaces are in front of the inlet hole. It makes if only little difference to the performance. Without the sponge, more unwanted oils would be able to touch the MAF sensor.
(I know this is the case when I use the open K&N. But it doesn't have to be if you use the OEM airbox and can use the protection of the sponge.