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Advice on removing under trays please UPDATE

drmark

Well-known member
Joined
7 Feb 2009
Messages
452
After reading couple of threads on here I have decided to have another (proper) look at the underside of our 12 year old 997. I have had the wheel arch liners out before, but now have the car up on axle stands and plan to take everything off.
The belly pans look to be held on by (corroded) bolts - are they are major pain to get off?
Are there any tips on where to start to make it easier?
Plan is to jet wash the underside once plastic is off. Clean up and then wire brush and rust treat any trouble spots, and then cover the whole thing in Bilt Hamber UC.
I will check the rear drains too (it's a cab).
Any comments / advice gratefully received (I am ham fisted).
I will take pictures as I go if anyone is interested.

PS the car is on four good axle stands with wheels under each corner should the worst happen. Safety first ;)
 
The majority of the fixings are self tappers and should come out without a problem the clip that they screw into will most probably be pretty rusty

Speednut 91242501 £0.39 + vat from OPC someone mentioned you can also get them from Wurth.

The rest is held on with a plastic nut on a stud just be gentle with them and all should be ok.
 
Sounds a useful project... please do post up how you get on.

I imagine it would be a hard job to do without lifting the car quite high up.
 
Robertb said:
Sounds a useful project... please do post up how you get on.

I imagine it would be a hard job to do without lifting the car quite high up.

I am going to have to breathe in - and put may reading specs on ;)
 
Deffo post some pics please, I'm going to do this to my car too!

Best of luck!

:thumbs:
 
You may find pressure washing is overkill for most of the hidden areas. I was more successful with the bucket and sponge/micro cloth, just working steadily from front to back. I then sprayed ACF 50 on as it gets in all the cracks and is safe for everything (except brake discs!)

The studs can corrode and snap off, but a soaking with penetrating fluid and gentle pressure should see them off ok.

A very satisfying job, even though only you will know it has been done.
 
Can't wait to do mine too. Probably in the summer when my mates garage has a ramp free for a few days.
 
You'll probably find it's clean under the Undertrays, aside from the brake pipes slowly rotting in silence.

I'd remove any sill end covers and clean them out, maybe cavity wax the sills and any other cavities while the Undertrays are off

Oh and waxoil or similar the brake pipes if they are ok, unclip them and get it in around any clips
 
Update

Thanks for all the tips. Plastic is all off and I am astonished at how good the underside is. Only two parts are corroded (fixings aside) and it is just some superficial rust on thediagonal braces that run back from just in from of the rear wheels. Even the brake pipes look like new.

I knackered a few of the plastic bolts and all the clips are corroded. My OPC sent me a full pack of replacement clips, self tappers and plastic nuts for £20 inc postage.

I have treated and sprayed the braces. Used Dynax S-50 in the sills, and covered the underside and arches in Dynax UC (clear).

One problem I did discover is that both rear drains (it's a cab) were blocked so I had a lucky escape there.

Was it worth the effort? Probably not as the car looked good for another decade without my help. But it was very satisfying and kept me out of the pub. I won't be doing it again though.

I am puzzled as to why some cars on here have had bills for 2- 3k for the work (because of corrosion). Our car has done 54k and is 11 years old and doesn't get washed that often (monthly) and is used all year around. Perhaps I have just been lucky - or they have been very unlucky. The quality of the rust protection on mine appears top grade - as you would expect. Now to the pub.
 
I don't often see rust on these cars .. a bit of surface here and there but that's about it .

Rear drains blocked and you just saved yourself a fortune .. trust me .. you have !

Remove the rubber disc behind the arch liner .

I have to say .. my hat off to you for removing the undertrays whilst on stands .. not an easy job when working that close to the panels.

Just reading this makes me glad i use a ramp :D


Btw .. a car near a coast .. i know as i live near one will suffer far more than one inland .. salt air !
 
deMort said:
I don't often see rust on these cars .. a bit of surface here and there but that's about it .

Rear drains blocked and you just saved yourself a fortune .. trust me .. you have !

Remove the rubber disc behind the arch liner .

I have to say .. my hat off to you for removing the undertrays whilst on stands .. not an easy job when working that close to the panels.

Just reading this makes me glad i use a ramp :D


Btw .. a car near a coast .. i know as i live near one will suffer far more than one inland .. salt air !

Thanks. Not easy on jack stands! Why is the rubber diaphragm there? Happy to remove if you advise.
 
Porsche don't explain these things to us .. many training courses but we are still left to figure out on our own how some things work and what the reason is for others ..

My guess which is the same for the stupid drain bungs next to the battery is to stop rodent ingress to the car ... pointless as they find other ways in .

The rubber disc merely holds leaves , pine leaves etc and slows the water exiting the car from this area ..

I can say for a fact that the drains can only just about compensate for a large downpour of rain if totally clear .. i've sat in a stripped out car and watched in a car wash as these almost fill to the brim ..

The slightest obstruction and it will overflow ...

At first under the rear seat base then into the carpet area and under the seats .. control units there and you're in trouble basically .

Either way .. remove that rubber disc ;)
 
Will do. My guess is road noise rather than rodents, but either way they are gone.
 
Last update :)

Just checked front drains - the 4 rubber plugs either side of the battery - and they were blocked too. Please check yours.
 

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