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Anyone cleaned out Air Inlet Ports after AOS replacement?

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Hi All


Took my faulty AOS off a few days ago and noticed there was oil in the air distributor tube on top of the engine after I decided I check it.. 


Realise it’s not normally done during an AOS replacement but I then decided to put a scope down one of the plastic intake distributors down into the engine intake port.. It was all carboned up probably due to oil from the AOS being burnt over time.

I’ve now taken the intake distributor off on the AOS side of the engine so have full access to the ports now. Can see the closed valves and stems. Pretty caked up in the bottom as well.


i feel I need to carefully clean them out (along with the other side which will be the same) and am sure I’ve read someone on the web saying they’ve had to clean them out on an 987 every time they have replaced an AOS.  Unfortunately I can’t find any details of the best way to do it anywhere...


Has anyone ever done this on a 987 engine in situ before.?


My proposed method is as follows:


- Push a new sponge scourer into the bottom of the port and scrape out the top of the port then vac.

- Then use a little brake cleaner with nylon brush to clean top up even more. Vac out again when cleaner has evaporated. This is to keep top end crud away from valve area in the bottom.

- Then lift sponge scourer out and carefully brush the back of the valve and stem with the small nylon brush with some break cleaner on the brush then wipe with clean cloth and then again vac out. 


Is this fine to do? 

The good thing is that the valves are obviously horizontal so any brake cleaner is not going to run straight onto the valve. Saying that, I am not planning to spray cleaner directly into the port..


Assume there could be a lot of engines out there with the same issue after the AOS has been replaced and people not aware? I can’t see it being removed on its own just by clean air going through now..


Any advice would be much appreciated..





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Ps I can try and post a pic tomorrow if it would help..


AOS symptoms weren’t huge. A bit of vac on the oil filler cap/a little more smoke than I would think normal during driving then confirmed by checking AOS outlet hose which had a little oil in. Can see why it may be a good idea to periodically change these now even before symptoms although timescale may be difficult to identify..





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I have just bought a new AOS for my CS too.


Did you have any issues removing it? ( I hear you need contortionist hands?) ... I've got a couple of large & small 90deg needle nose pliers as I gather they are invaluable for this job? 


I'll also be checking/cleaning the ports!

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Yeh it wasn’t as easy as all those YouTube videos make out thats for sure... Well mine wasn’t anyway.


The two Torx bolts were removed easily enough but as hard as I tried I couldn’t pull the AOS out. 
You just don’t get enough room to get a good hold of it.

I ended up tying a thick nylon rope round it noose style with a loop on the top and this with a lot of lateral wabbling eventually got it out.


Am not sure if my torque wrench is out of calibration or the original bolt was fatigued in some way but the head sheared off the rear bolt when I came to tighten it up.  Lost a lot of sleep over it as the engine is obviously alloy and the screws are tough 8.8 Torx bolts. Was another reason to take the distributor out to get at it.  
Originally thought I’d try drilling the screw then using an extractor but thankfully went for the option of a dremmel to cut a slot and used an impact driver to get it out. Was so relieved when it eventually started turning..

Have now ordered two new Torx bolts and am going to get a digital torque adaptor, as I’ll also need to bolt down the distributors. Just don’t trust my mechanical torque wrench. I’ll check it with my new one. 


Dont agree with some videos I’ve seen saying to use the two Torx bolts to draw the AOS down into the two outlets after lining them up. They won’t as mine were very tight and you risk damaging the new AOS brackets.  Going to coat the o rings on the new AOS with oil and after cleaning the two openings I’ll now have better access to push the AOS down whilst the distributor is out. Won’t be torquing the two bolts down until I know the AOS is fully housed.

if you are looking to remove the distributors anyway to get at and check the ports then it might be an idea to remove them on the AOS side first as it will give you much better access for getting the AOS out..


Hope this helps..


Just take your time. We should have plenty of that with the current lockdown eh...




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All done!!


Very surprised how easy it came off tbh 😵


I used my 90* pliers to remove the bottom hose clamp off the cylinder block spigot.


Instead of reusing the original pony hose clamp I replaced with a SS jubilee (muuuuch easier!)


I removed all the tubing & flushed through with paraffin... My old AOS didn't seem that bad tbh! 


Lubed up the block seal on the AOS with silicone grease & copperslipped the mount bolts.



Edited by Mavrik
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