Taffia 2021 Prep, Goes Wrong!

As I mentioned in a previous blog, 2021 has been a quiet year with regard to Caterham ownership, general speaking there's been little opportunity to stretch the legs on either Seven. A lack of activities isn't something that's been isolated to ourselves on the Isle of Man either, the Lotus 7 club has also experienced a reduction or change to its regular event calendar. One such event is the Taffia Fish and Chip run, an event which we'd previously attended in 2019, and had a fantastic time. Normally the event runs in May, however this year the event has been rescheduled, and is now running in late September. Even though a late September run increases the probability of inclement weather, along with shorter days, the opportunity is too good to miss. So we've made plans, booked ferry travel and are currently looking forward to getting away.


Attending The Taffia (as it's known) will mean clocking up some serious mileage in the Seven 420R, and so as a responsible motorist I took the opportunity over the recent Super Manx Bank holiday, (yes 4-day break) to fully inspect, spanner check and detail the 420R in readiness for the road trip.


Over 3 days the entire car was checked, starting at the rear and moving forward. Everything was cleaned, detailed, protected and the mechanicals verified as appropriately secure. I also carried out an interim oil change just to be doubly sure. Where appropriate surfaces were also ceramic coated to ensure maximum water repellency and protection. I'll avoid becoming tedious about detailing, if you do have an interest, below are some images from the process which illustrate the depth of cleaning and protection taking place.


As I mentioned earlier, the weekend is known as the Super Manx Bank Holiday. We're given an extra day on the Friday before the UK Bank Holiday on the following Monday. The additional day replaces what would have been the Senior Race Day Bank Holiday which normally occurs during the currently suspended TT festival. Given the special nature of the weekend, the Manx Government had also arranged for the Red Arrows to perform their usual TT aerobatic display in Douglas bay. As I live on the headland at one side of the bay, my detailing efforts were temporarily suspended by some noisy low flying. A couple of quick videos are below for your enjoyment.






I eventually made it to the front of the 420R having been briefly distracted by the awesome skills of the RAF. The nose cone was removed and I started to inspect, clean and protect the various components. It was at this point things went a little sideways! As you can see from the image below my radiator has started to leak, not much, but very clearly leaking.

Failed radiator Caterham radiator failure
Failed radiator, leaking down the edge of the passenger side end tank

In response I washed the radiator through with a gentle stream of water from a hose, removing all traces of coolant. I then refitted the nose cone and bonnet and went for a short test drive, ensuring I got everything nice and hot. Upon returning home the nose cone and bonnet were removed to check for additional traces, sure enough, there was ample coolant staining all the way down the edge of the radiator core. Not good. Travelling to the UK, up and down Wales with a failing radiator would not be a responsible thing to do, so at this point, the Taffia road trip looks very unlikely. Sadly it wasn't just the annoyance, we'd paid out for two cars on the ferry and made three different commitments in terms of accommodation, so there was considerable financial exposure too.


Time to seek some support!


On the following day a good friend (Mark) visited to assist with the diagnostics. He brought a radiator pressure testing kit to help understand what was taking place. Mark has considerable experience with heavy plant machinery and is always super helpful with these sorts of problems. I actually spoke to Mark the night before and during the conversation, he suggested the radiator might be repairable if the failure was suitably positioned. We might get lucky then. We tested the radiator, and in doing so could see coolant slowly flowing from the very top vane, but couldn't actually see the source. Mark's conclusion was such that it would be very difficult to repair if not impossible.


With that, I turned to try and understand what had happened, and why. If you look back through my blogs, you'll notice this isn't the first radiator failure, and furthermore, prior failures have been in exactly the same region. I started to inspect the region of the radiator where the failure occurs and it became apparent very quickly that the revised mounting system now used by Caterham was in fact contacting the radiator inlet port. I figured this was likely the smoking gun. Chassis vibration would be transmitted directly from the bracket onto the inlet and over time cause sufficient fatigue and failure. The following picture shows contact from both the mount and rubber hose.

Hanger and hose interference with inlet Caterham radiator failure
Hanger and hose interference with inlet

Just the hanger, no hose
Just the hanger, no hose

As part of my investigation, I slacken all the bobbins and attempted to move the radiator to gain sufficient clearance to see if the issue was avoidable. With some force I did manage to increase the clearance very slightly, so you could see light between the bracket and port, but we're talking the thickness of a piece of paper. While the hanger wasn't making contact the rubber hose continued to make contact, and I suspect that would have generated sufficient fatigue as the hose is pretty stiff. I am also unconvinced the radiator position wouldn't drop back considering the distance moved and pressure needed. Given the radiator supplied and my chassis I was left feeling this was unavoidable and probably repeatable. I turned to the Lotus 7 Club BlatChat group to seek advice and to check my conclusion. A lengthy and supportive discussion with regular members (big shout out to all those that helped) took place, drawing a similar conclusion. Fatigue from the chassis was ultimately responsible, being caused by the tight packaging. Packaging that is needed to fit the 420 race radiator under the S3 bonnet.


I was left with two problems, a replacement radiator to ensure the Taffia road trip takes place and additionally ensuring we learn and avoid further repeat failures. Some new thinking is required! My boss at work loves to quote Einstein,


"definition of insanity is doing the same thing over and over and expecting a different result?"


Seems appropriate! We're not out of the woods yet. With some luck I'll be following up with some sanity, so check back!


As a footnote, the current radiator is the third which has been fitted, the first failed immediately, while the last two have been reliable for approximately 2000 miles.



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