Spoiler alert: fitting the radiator didn’t exactly go to plan: Fixings were missing from my supplied kit (I am beginning to expect that) and one massive mistake on my part. As a result I hope that this post helps future Caterham 420R S3 builders not make the same mistake I made!

Fitting this radiator currently is not documented in either manual, and I think isn’t really understood by Caterham’s parts picking process for 420 kits. By way of an example, my kit included an oil cooler fitting kit and brackets (which are not longer needed with the new combined unit)

Considering the lack of information I had for this step, I decided to find all the fixings I thought I needed before starting, and this was where I ran into my first problem. Although the correct length fixing is now supplied with the radiator for the top mount, I didn’t have any M8 bolts short enough for the lower bobbins. I thought I would use a longer bolt as a temporary measure, but in the end didn’t bother.

Next, I decided to find a spanner slim enough to fit within the gap between the radiator and the bent bracket. I fitted the drop brackets and the lower bobbins after. Note, I didn’t secure the bobbins with nyloc nuts; nyloc nuts can be a nightmare to remove from a disinterested rubber bobbing. I have only ever seen Caterham use standard nuts with spring (split lock) washers on bobbins.

I then realised it would be a good time to finish tidying the headlight wiring, by making up the Econoseal connectors and tie wrapping the wires into place. The process is simple, connect the two halves of the connector and match the wire colours. Push the wires into the connector until you hear the click, no click means you haven’t oriented the pin correctly. Finally tie wrap the wires to the chassis tubes. I didn’t go mad, because there is unfinished business here. Until the front wings are fitted and the side repeaters are fitted, I am missing a green wire, so I didn’t fit the yellow locking element into the Econoseal connectors.

I also connected the horns (using the purple and yellow wires).

Now the fun really began. The bottom hose isn’t connected to the radiator in same location as my previous 360R, it’s actually almost 1/2 way up the radiator. This led me to trying different locations for the dry sump hose (top of dry sump tank to right-hand-side of the radiator) and the bottom hose. To rearrange these two hoses I removed the catch tank, which proved to be a) the limiting factor and b) the cause of my mistake.

The only route I found for the dry sump hose and bottom hose was routing the dry sump hose under the steering rack and the bottom hose one top of the steering rack (where I had it to start with). However, every Millimeter is needed, and I had to move cables to get the dry sump hose to fit this tight route.

So, I proceeded to cut the top hose to length, and decided to use a hacksaw to cut the hose on my marked line. This worked well with a little rubber lubricant.

The photo of the cut hose shows my big mistake: I measured the top hose with the catch tank removed. The result: a hose cut too short!

So, with no lower fixings present and a top hose cut too short that’s where I had to stop the radiator fitting process for now. (UPDATE below)

I decided to try and attach the cooling fan, mainly for protection of the delicate radiator. Normally, the plastic mounts are just a push-fit, but not this time. I had to lubricate and locate them with the aid of a rubber mallet. The final step was to attach the fan to the radiator, and even without any washers there just isn’t sufficient thread through the nyloc, so another frustrating fixings problem to solve.

UPDATE – Please see David’s comments below on heating these plastic mounts, it might save some trouble.

Type T M6 nyloc nuts fitted to the cooling fan

UPDATE – I have now fitted M6 Type T nyloc nuts to the cooling fan and the thread is now clear of the nut. I was advised with my 360R build this would be an IVA fail, so its well worth the effort sourcing the correct nuts.

UPDATE – I obtained two options for the lower radiator bolt, M8 x 12 and M8 x 10. I wanted to use the longest bolt possible, but unfortunately the M8 x 12 bottoms out in the bobbin before pulling up on the radiator. Therefore M8 x 10 are the bolts to get. Then I stumbled into the next problem, my thinnest 13mm spanner was still to wide to torque the bottom bolt. So I purchase a thinner spanner, a Facom 31 Extra Slim open ended spanner (https://www.facom.com/uk/). With the M8x10 and the very thin spanner the radiator was finally fitted. There will be a separate post on the top hose.

Tools Used

  • 13mm slim spanner (Facom 31 Extra Slim)
  • 13mm combination spanner
  • 13mm 1/4″ drive socket
  • 10mm 1/4″ drive socket
  • 1/4″ drive ratchet
  • Side cutters
  • End cutters
  • Junior hacksaw