Leaky radiator replaced

[KnifeySpoony]

The radiator on my 420R developed a tiny pinhole leak in the upper/driver side corner, which apparently is a common failing point. Car has about 3k miles on it, mostly track. Threads on UK fora discuss multiple replacements/failures- some people are on their 4th or 5th radiators on cars just a few years old.  They usually fail in the same place. Theories about excessive vibration transmitted from engine and/or uneven mounting points putting stress on the radiator have been discussed. I ordered a new standalone radiator from CC. They list only the combined water and oil radiators for the 420 road model:

 

https://caterhamparts.co.uk/radiators/7114-radiator-and-oil-cooler-seven-420-road-model.html

 

However, you can get the water rad alone. It says its for the 420 race model only, but mounts up just fine. You just don't need the two little drop brackets anymore:

 

https://caterhamparts.co.uk/radiators/5755-radiator-only-420-race.html

 

 

I put on the new rad, and decided to try to reduce vibration transmission by replacing the distal segment of the top coolant hose. It's the only hose in the circuit that isn't silicone for some reason. Its much stiffer/harder than the silicone hoses and the theory is that it transmits vibration. So I cut the a segment of the top hose and spliced in the 620R top coolant hose: (https://caterhamparts.co.uk/hoses/5758-cooling-hose-top-seven-620.html) which is a short, curved section of silicone hose that is dramatically more supple. I used a short aluminium 1.5" coupler to join. Side benefit is that the hose is flexible enough that I can now pull it out of the way enough to pull out the oil catch bottle to drain it, and will no longer need to suck it out, which is hard when there's just 1/2-1" of oil in the bottom.

 

 

 

 

Edited January 22, 2023 by KnifeySpoony

[MV8]

Beautiful, pricey rad.

I would measure the upper hose outside diameter for the clamp size to use, then add a cushion/adel/MS21919DG or WDG clamp to the upper hose at the greatest bend and another to the chassis X brace tube below it to act as an attachment point without drilling or welding the chassis. This will help to counter the hose pushing the rad forward and leverage on the hose fitting from 14psi or higher in the cooling system and softening from heat. I'd probably install a lower than is modern practice 12 psi cap as well but the clamps should be enough.

Another alternative is to replace the upper hose with rigid tubing, reusing 3 inches from each end of the hose and four clamps.

https://www.aircraftspruce.com/catalog/appages/ms21919clamps.php

[bball7754]

Did you consider Radtec?

[KnifeySpoony]

22 minutes ago, bball7754 said:

Did you consider Radtec?

I have heard of people using Radtecs. I have read about multiple failures of Radtec units as well. Unclear if this is a low quality rad, or something about the fitment. If this one fails too, I will definitely look into a different supplier for subsequent replacement. 

[MV8]

I was thinking crack since you were talking about vibration, but you said pin hole. It sounds like the leak is between a tube and the end plate and a mfg defect versus a vibration issue.

 

[IamScotticus]

so clean....

[KnifeySpoony]

33 minutes ago, IamScotticus said:

so clean....

Leaky one was just as shiny lol.

[KnifeySpoony]

On 1/23/2023 at 4:29 AM, MV8 said:

I was thinking crack since you were talking about vibration, but you said pin hole. It sounds like the leak is between a tube and the end plate and a mfg defect versus a vibration issue.

 

I should clarify - I have not visualized the actual leak point. I had it pressure tested by submerging in water and could see the general area where it was bubbling. I just referred to it as a "pinhole" because it was enough for coolant residue to accumulate on the fins in the area, but not even enough to drip.