Radiator woes again!

[MattB]

My 9 month old Caterham built 420 has just had its radiator replaced by CC under warranty.  I'd been monitoring it closely, having read this and other similar threads, and thought I'd got away with it, but it started leaking from both sides at just under 6000 miles.

CC asked no questions once I said it was a radiator problem, and just booked it into their first available workshop slot.

It appeared that the leaks were where the matrix tubes entered the side tanks, so I'm wondering if the mounting arrangement is too tight horizontally, leading to the tubes expanding into the immovable side tanks when hot and breaking their seal. Perhaps slackening off the bolts and elongating the bracket holes on one side and allowing the radiator to expand horizontally as a whole might lessen the chance of another leak?

MattB

[Jonathan Kay]

Thanks for adding that experience.

I don't think that anyone has previously suggested thermal expansion of an otherwise well-fitting radiator as the cause of failure. That's a very interesting idea.

Did you ever check the fit in the brackets and the mechanical load from the hoses?

Jonathan

[MattB]

The fit looked good, the bobbins didn't appear stressed or twisted, and the hoses didn't look to be pulling/pushing on the radiator.

[Jonathan Kay]

Thank you

Jonathan

[Jonathan Kay]

[MattB]

Thanks Jonathan - you are the Turnimator ....

MattB

[John Vine]

I note that the old design had much longer bobbins.  These are the ones on my 2008 R400D:

 

I don't know what effect (if any) that would have, but yours do seem quite short and squashed.  Also, presumably your mounting bolts pass right through the bobbins?  I could see that being a conduit for vibration.

JV

[Jonathan Kay]

John: Are your bobbins made with a separate stud at each end?

Thanks

Jonathan

[John Vine]

Indeed they are, Jonathan (which, of course, is what triggered my comment).

JV

[Jonathan Kay]

Thanks

Jonathan

[ScottR400D]

All those bobbins should be two separate studs. No point otherwise. I'm sure the OPs will be. 

Then again, it's a CC built car, I wouldn't put anything past them. 

[ScottR400D]

As an aside,  and it may be a silly question, but if this was a design issue wouldn't CC have sorted it out, it's been going on for years? 

Though I guess the same question could be asked if it was just poor quality radiators. 
 

 

[John Vine]

Re #36:

Yes, I think you're right, but (according to the Assembly Guide) with one stud and one female thread:

 

 

This looks like the bobbin in question.

The description suggests that it was originally intended for the 485 exhaust, so using it as a rad mount looks like a bit of a bodge.  I think it could do with a lot more rubber.

JV

[ScottR400D]

1 stud and 1 female is OK, plenty of rubber mounts like that. It's effectively the same as one with 2 studs, you still have the separated rigid mounts. 
 

I agree that these mounts might benefit from a bigger rubber mount though I'm still far from convinced this just a vibration issue.

[Billy.Whizz]

#26, I've also just had a new rad fitted under warranty on my 17 month old 420R, I noticed it leaking from the top 3 tubes above the top hose, looked a bit like bottom picture at #30. Mileage when first noticed was around 3500, the service manager told me that it's a manufacturing problem and nothing to do with fitting.

[ScottR400D]

#40 I guess there's a chance that 'they would say that' though in this case I think it could well be true.