Fixing the weather / heat shield - another thread

Alan_uk

A2OC Donor
Recently I fixed my weather / heat shield with the help of Matt's (wilco184) excellent thread from earlier in the year: http://www.a2oc.net/forum/showthread.php?30198-Rivnuts . I had some variations in the materials used and fixing.


======= Focus of work =======


The main focus was the shield protecting the fuel filter. As seen in this photo there are 4 fastenings. Note the temporary bracket I had earlier put in place as the shield was hanging down.

Temporary fixed fastening LR annotated.jpg


1. to the floor bulk head – this was replaced by a rivnut, washer and bolt
2. to the fuel tank bracket - this was replaced by a stud, washer and nut
3. to the angle bracket - this was replaced by a bolt, washer and nut
4. to the sill – the self tapping screw was reused but I've new ones on order


I also changed another fastening similar to item 2 on the front facing side of the fuel tank.


As you can see the fastenings and the shield are badly corroded

Rusty fastening and broken shield LR.jpg


Looks like Audi did not use aluminium washers and nuts but either steel or stainless steel. Even stainless steel corrodes next to aluminium. Coatings can delay the corrosion but in places exposed to salty water it will give eventually. See an interesting article here: http://www.stainlessautomotivefastenings.co.uk/index.php?main_page=page&id=11

continues in next post ..............
 
Last edited:
======= Tools and Materials =======

1 Tools and Materials LR.jpg


Clockwise from top left


1. Sheet of aluminium - eBay item number: 261376035009 at £1.95 - I ordered 1mm x 250mm x 250mm. In practice this was too thick but I used it. I suggest 0.5mm but that seller does not sell this thickness.
2. Dremel 4000 – from B&Q at £78.00 with a flexible drive (not used) - it came with 2 x SC456 38mm fiberglass reinforced cutting wheels. I've just managed to get the job done with these 2 and have now ordered a pack of 12 at £11.33 – ebay 182234171640
3. Pack of 10 aluminium socket cap screws M5 x 20mm at £8.25 – ebay 191543249288
4. Pack of 10 aluminium washers M5 (not used) at £2.15 – ebay 201071177847
5. Pack of 10 aluminium nuts M5 at £2.75 – ebay 201546757894
6. Pack of 10 aluminium roofing washers 19mm at £1.95 – ebay 111645337376. These are a compound of aluminium and rubber layers. (I also ordered 16mm but there is plenty of room for 19mm and maybe 29mm would fit).
7. High Strength Thread Lock at £4.50 – ebay 121981725378
8. Pack of 10 aluminium rivnuts M5 at £2.55 – ebay 191666376866

Later I bought/used:
-. Pack 25 Flanged hexagon head zinc plated self tapping screws size 8g x 5/8 (4.2mmx16mm) at £1.39 - ebay 161837981265"
-. Anti-rust fluid, metal primer paint & top coat paint.

I ordered M5s of the above but M4s would have been fine. The M5 rivnuts need an 8.5mm hole which is quite large when one is drilling into the A2 body! Even M3 might do but I cannot find any M3 aluminium bolts.
9. 4mm-8mm Threaded Rivet Setting Tool at £11.09 – ebay 322043320302
10. Rivet Pop Gun with 60 steel rivets £4.49 – ebay user now gone.
11. 100 Assorted Hand Blind Pop Rivets Aluminium Head, Steel Shank at £1.25 – no ebay ref as the price is now £21.25!!
12. Drill and bits
13. Face mask
14. Eye protection (a must have)
Not shown:
15. Ear protection
16. Tin snips and junior hacksaw
17. Assorted files


I think most ebay items had free p&p.

continues in next post ..............
 
Last edited:
======= Removing the studs =======


The back of the vehicle was driven onto ramps for safe working.


Some nuts did come off the studs but others needed cutting off with the dremel. Cutting creates a lot sparks so keep the face well back. Pause to let the cutting disks cool down.

8 Fuel tank stud removed 1 LR.jpg


6 Bracket stud to be removed LR.jpg

Once the nuts are removed, along with one self tapping screw,

4 Self tapping screw LR.jpg


the shield to the fuel filter is removed. For the exhaust shield only 2 studs were removed so the shield remained in-situ. Instead it was easily bent out of the way of these 2 studs.

continues in next post ..............
 
Last edited:
======= Drilling out the studs =======


1. to the floor bulk head


When cutting off the stud to the floor bulkhead I over did it a bit and lost position of the stud so it might be worth noting the position by measuring beforehand. I increase the drill size when drilling out the bulkhead from a few mm to 7.5mm and then filed out with a round file so the rivnut fitted. I didn't have an 8mm bit and whilst the rivnut is 8.7mm outside diameter it is easy to drill oversize in soft aluminium.


Sorry, seem to have lost the photos.


2. to the fuel tank bracket



Drilling out the studs on the fuel tank brackets was much harder and obviously caution was need. The drill kept slipping to the side of the stud. Eventually it came out or disintegrated.


Again no photo but here is a photo of the rusted fasteners and the arrow marks the top of the stud.

23 Rusted fasteners LR.jpg


Behind the stud is a partition wall. Again no photo but here's Matt's photo

IMG_5538.jpg
http://i1237.photobucket.com/albums/ff461/wilco184/IMG_5538.jpg


but my A2's bracket seem slightly different with a larger partition wall, less distance from the stud to the front edge of the bracket, and a part number embossed on the bracket.


So I decided not to remove this partition wall or to drill to the side as Matt did. Instead I just carefully removed a few mm by enlarging behind the hole in the bracket – a bit like drilling a tooth cavity for a filling – bigger on the inside. The material seems to be a rubberised compound so relatively soft.


3. to the angle bracket


Drilling out the studs on the bracket was quite easy. I made a 5mm hole to match the bolts.

13 Drilled bracket LR.jpg

continues in next post ..............
 
Last edited:
======= Replacing the studs =======


1. to the floor bulk head



The stud to the floor bulkhead was replace by a rivnut. I practised on the sheet of aluminium and watched a YouTube video using a similar tool. The key is to remember that the tool uses reverse threads and not to over squeeze.


2. to the fuel tank bracket



For the studs to the fuel tank brackets I took a 5mm bolt and cut off the head. Probably would have been better to have parred down the head by trimming off the flats. I then fixed it into the fuel tank brackets using epoxy resin applied with a match stick into the enlarged hole.


As the mixed resin tends to run I taped any gap either side of the bolt with masking tape. Another strip of masking tape ran from the bracket over the bolt end and back to the other side of the bracket to maintain tension and stop the bolt sliding out. It was left 24 hours to harden.

15 Stud glued into fuel tank bracket 2 LR.jpg


3. to the angle bracket


The angle bracket was fitted with a bolt with a little Thread Lock below the head and temporary tightened with a roofing washer and nut.

continues in next post ..............
 
Last edited:
======= Fixing the wasted shield =======


Using the wasted shield what was left of the hole I traced the outline onto cardboard of the repair piece.

9 Marking out the cardboard template LR.jpg


I then cut out the card and used it as a template onto the aluminium sheet using the side with a protective sheet. It was then cut out with a mixture of snips, dremel and hacksaw.

10 Aluminium sheet marked out LR.jpg


Using a vice the repair piece and shield were aligned and 3 rivet holes drilled and the rivets applied. The reverse of the rivets were quite proud so I cut them down. Not pretty but seems OK.

11 Wasted aluminium patched 2 LR.jpg

12 Wasted aluminium patched 1 LR.jpg



continues in next post ..............
 
======= Replacing the shield =======


First the holes in the roofing washers were slightly enlarged by putting them in a vice and giving a few seconds with the drill until the bolt slipped in. It's the rubber part that binds the bolts. These large roofing washers help to fix the corroded and enlarged holes in the shield.


As the rubber part compresses it provides tension so I did not use tread lock or locking washers or nuts. Whilst the glue studs seemed strong I didn't want to tempt fate by using locking nuts. Anyway the shield to the fuel filter needs removing occasionally to replace the filter.

18 Bolt secured into stud with roofing washer 1 LR.jpg

19 Bolt secured into rivnut with roofing washer 1 LR.jpg


One of the fuel tank studs has two shields and the repair, so 3 thickness's. There was just enough stud showing for the nut, but as mentioned above, if the bolt head had been parred down and not cut off, then more would have been protruding.

17 Bolts secured into studs with roofing washers LR.jpg



I would recommend cleaning the corroded parts of the shield to remove any iron oxide residues – I forgot so will do them later.


continues in next post ..............
 
======= Further work =======



All the self tapping screws are beginning to corrode. Most of them seem to go into the boot. There must be at least 10. I presume they are all self tapping screws and not bolts.

20 Corruded sheild and self tapping screw - to be fixed LR.jpg


The only 3 ebay suppliers of aluminium self tapping screws was in China at £1.06 for 30, shipping included! Ebay ref 222214531442. They are now on a slow boat from China. Let's see if they arrive! I get the impression the 3 suppliers are the same company – no doubt there is only one factory supplying the whole world.


There are a further two badly corroded studs on the rear end of the fuel tank but they are above the rear axle and awkward to reach. As I'm intending to replace the rear axle with a refurbished one, so the replacement of these 2 studs will be left 'till then.

22 Rusted fastener above the axle 2 LR.jpg


All the studs on the exhaust tunnel are fine.

24 Tunnel studs OK for now LR.jpg


End of thread (for now)
 
Fixing Heat Shield tank rear studs

Well I decided to finish the job before the winter.

First job was to go back and remove the earlier repaired shields and wash the parts of the shields with the corroded holes with meths and when dry treated to some anti-rust fluid. When this was dry they were reassembled. All further corroded shields were similarly treated when

being repaired.

=========== Corroded studs on rear of fuel tank

There were a further two badly corroded studs on the rear end of the fuel tank but they are above the rear axle and awkward to reach but can be done with thin hands! The bracket are different to the front of the fuel tank. On the front the bracket protrude off the side of the tank but at the back the bracket are below the tank. This makes it more risky when drilling out the stud.

The fasteners on the rear tank studs came off easier that previous ones - i.e. no need to cut them off with the Dremel.

25 Corroded tank rear stud LR.jpg
25 Corroded tank rear stud

The Dremel was used to cut off the corroded stud. I then used an electric drill to remove some of the plastic to create a recess for a new stud. I used a 3 or 4mm bit and wiggled it around to removed the plastic. I also tried to drill out the stud head. I was reluctant to press too hard on the drill as if it suddenly went through then I would drill into the tank!


26 Corroded stud cut off LR.jpg
26 Corroded stud cut off

I had bought a pack of 10 cutting disks which was good as they soon blunt.


27 Dremel with steel cutting blade LR.jpg
27 Dremel with steel cutting blade

My first attempt at replacing the stud failed. As on the front of the tank I cut the head off an aluminium bolt and then epoxied the bolt into the bracket recess and they held. But on the rear of the tank, despite leaving the exopy 24 hours, when I tightened the nut up the stud came out. Not helped I discovered by the resin that had run down the thread. I was reluctant to drill a deeper recess so Plan B was needed.

Taking a new bolt I cut of just some of the head to make it T-shaped. After the photo below I thinned it down a bit more.

28 Alumin bolt with T-shaped head LR.jpg
28 Alumin bolt with T-shaped head

I then cut an aluminium plate about 15mm square and drilled a centre hole for the bolt. I also cross hatched one side of the plate to give adhesion.

29 Bolt with T-shaped head and square plate LR.jpg
29 Bolt with T-shaped head and square plate

As there was a small gap between the hole and the bolt head, I secured the bolt below with 2 strips of insulation tape (see photo below). On the second bolt head I put little blobs of epoxy either side of the head and left to set. Trying to solder the gap did not work.

Next I fashioned a 30 cm / foot stick about the thickness of a small finger and with a chiselled shaped end. I then made up some 10 minute epoxy and waited a few minutes for it to get a bit thick otherwise it will run down. Using the stick I scraped up about 1/2 the epoxy and applied it to the bracket recess. Best to use eye protection in case the epoxy runs down.

The rest of the epoxy was applied to the cross hatched plate with the T-shaped bolt. This was then pressed against the bracket and held with the fingers until it was firm.

30 T-headed bolt and plate epoxied in place LR.jpg
30 T-headed bolt and plate epoxied in place

After waiting 24 hours an aluminium plate, roofing washer and nut were secured to the bolt. This time it held.

31 Plate, roofing washer and nut 1 LR.jpg
31 Plate, roofing washer and nut 1

One of the studs secures 2 heat shields and due to more extensive corrosion a longer plate was needed.

32 Plate, roofing washer and nut 2 LR.jpg
32 Plate, roofing washer and nut 2

That concludes the fuel tank stud repairs. Next up are 2 "bowler hat" shaped fasteners.
 
Last edited:
  • Like
Reactions: Tsu
Fixing Heat Shield bowler hat fasteners

================ Bowler hat fasteners ====================

Two further fasteners were rusted.

33 Rusted fastener LR.jpg
33 Rusted fastener

I thought I would need to remove the studs and drill for rivnuts but when the fasteners were removed there was little corrosion.

34 Fastener removed - clean stud LR.jpg
34 Fastener removed - clean stud 2

Instead I cleaned up the fasteners, applied anti-rust fluid,

35 Fastener after anti-rust treatment LR.jpg
35 Fasterer after anti-rust treatment

then metal primer and finally top coat.

36 Top coated fasteners LR.jpg
36 Top coated fasteners

After cleaning around the shield hole and applying anti-rust fluid, I carefully reassembled to minimise damage to the paint. But as the thread will cut into the new paint I then applied a coat of lacquer using a brush.

Next up are the rusted self tapping screws.
 
  • Like
Reactions: Tsu
Fixing Heat Shield self tapping fasteners

================ Self Tapping Fasteners ====================

The aluminium self tapping fasteners arrived on a fast boat / plane from China via Malaysia in about 3 weeks

37 From China via Malaysia LR.jpg
37 From China via Malaysia

How do they do it for just over a £1 including postage?

Unfortunately they were only 10mm long and not 20mm.

38 Aluminium self tapping screws LR.jpg
38 Aluminium self tapping screws

This would be OK for a straight replacement for the corroded fasteners but not long enough to add a roofing washer to overcome shield corrosion.

39 corroded self taping screws LR.jpg
39 corroded self taping screws with one new unsuitable screw

A further hour or so on the internet did not find any longer aluminium self tapping fasteners so I went for zinc plated self tapping fasteners. Zinc is close to aluminium on the anodic - cathodic scale. See http://www.bssa.org.uk/topics.php?article=89 I found these screws on ebay (ref. 161837981265) size 8g x 5/8 (4.2mmx16mm).

40 zinc coated self taping screws LR.jpg
40 longer zinc coated self taping screws with one corroded screw.

Most of the corroded screws came out easily if pressure was applied but one got damaged and needed to be cut out.

One shield hole was rather corroded so an aluminium plate was used. Care was taken not to over tighten the screws going into plastic.

41 Zinc plated self tapping screw and plate LR.jpg
41 Zinc plated self tapping screw and plate

42 Zinc plated self tapping screws LR.jpg
42 Zinc plated self tapping screws

Adendum: As the aluminium shield was not corroded in the above photo I didn't need to use a roofing washer. But now I realise that the zinc plated screws are longer (to accommodate the washers). So would be wise to check the longer screws are not going into anything critical, like the battery. Alternatively use suitable short screws or add the roofing washer. As these screws are zinc plated they may eventually start to rust after some years due to salt etc. and should be replaced before they corrode the shield. Alternatively, use the short aluminium screws from China.


Job complete. If I ever need to replace the exhaust it might make sense to replace the shield above at the same time but the exhaust looks good for sometime yet.
 
Last edited:
Alan, thank you for reminding me of yet another job I've to address on my TDI, but more importantly, thank you for detailing your repair work so impeccably.
 
Back
Top