I've mentioned the catch can in so many blog posts but never actually covered the install of the can, I think it's time. This one is a retrospective post, I believe the catch can was installed towards the end of the first month.
The installation of the can be split into two phases, mounting the catch can bracket to the chassis and then adding the required hoses to the can itself. As I installed the bracket first, I'll detail that step first.
On the 420 the catch can is mounted using a bracket which is attached to the nearside chassis structure immediately behind the front suspension strut mounting. The bracket is identical in shape to that used by the wash wipe bottle, although the process of fixing the bracket is a bit more complex.
The bracket is riveted to the chassis which actually isn't that difficult in principle. Unfortunately the process is made more challenging on an S3 chassis as the top chassis tubes limit access with a standard power drill. There simply isn't the length to get the body of the drill into place, so drilling the rivet holes can be difficult. I opted to purchase a cheap 90-degree air drill for my air compressor. Whilst the drill had easy access it did lack sufficient torque and kept jamming.
Fitment of the bracket requires removal of an existing rivet, and reuse of the resultant hole, plus the inclusion of a new hole for an additional rivet. Drilling out the existing rivet with the air drill was quite difficult, as mentioned the air drill wanted to jam and also kept skipping off onto the body panel, hence the few additional marks in the photo. Drilling the additional hole was easy enough, mark with a punch and drill.
Once both holes had been prepared adding the rivets to mount the bracket was also straightforward, there was just enough room to fit my air riveter between the chassis tubes.
The can then slides down the bracket and into place.
The catch can is a cheap simple moulded plastic bottle, but it's missing an additional aperture needed to accommodate a hose between it and the output from the engine, in this case, the breather port at the top of the dry sump reservoir.
The hose used between the catch can and the breather is actually a length of coolant hose, secured at the breather with a jubilee clip and the other end passed through the top of the can down to the base of the can. The hose is approximately 340mm in length, and the hose total diameter approximately 26mm.
To get the hose into the can you need to drill a hole of similar diameter to that of the hose, about 26mm, however you can leave it around 25mm to create a snug fit as there is some flex in the hose. I didn't have a drill bit of that size so I marked the location by drawing around the hose end with a Sharpee whilst positioning the hose in approximately the right location. I then used multiple smaller drill holes and finished off grinding the remainder with a Dremel bit. It made a little mess, although most of the bits fell into the can, a quick rinse through under the tap and all detritus was removed. At this point the can should be ready to go, having a nice smooth aperture for the hose to be inserted.
Don't forget to fit the can onto the bracket before adding the top coolant hose!
If you are reading the blog before starting your build, I'd also recommend fitting the bracket before the engine and suspension are fitted. it will be much easier being able to work whilst standing inside the chassis, and the presence of the bracket won't impact the install of the engine.
I understand the existing hose pre-fitted to the can is for additional venting from the can itself, and should be fitted down through the car to the floor.