420R Radiator Woes - Solutions?

[David JLM]

10 hours ago, AlastairA said:

I'm wondering whether using the front right towing loop as a jacking point is the cause of, or at least compounds this problem. When I used this method once, I was really concerned by the amount of torsional stress and twist on the chassis. Of course this happens mostly at the front of the car and must put huge stress on the front vertical plane (i.e. the radiator). Using the towing loop is the advice given by many but I prefer to use the lower front cruciform to get an even lift even though it's a bit of a faff to get two stands under there.

Just a thought!

Not just me then... I used to wince when jacking my Academy car up via the tow loop.  It was the accepted method but it didn't feel right, watching the chassis twist. 

I'll be using the front cruciform with my new car!

[Ainsley]

While this might / probably / does twist the chassis, if the bobbins were loose / flexible enough there should be plenty of flex to allow this.  So perhaps more flexible bobbins is the answer.

I've just built my 420R, but not finished it quite yet.  I will go over the mounting very closely to see if I can arrange it to remove as much chance of stress as possible.

I might try buying an alternative bobbin to see if I can get one even more flexible.

 

[ScottR400D]

11 hours ago, David JLM said:

Not just me then... I used to wince when jacking my Academy car up via the tow loop.  It was the accepted method but it didn't feel right, watching the chassis twist. 

I'll be using the front cruciform with my new car!

It’s the only way. 

[Ainsley]

So just how much does it twist when jacked up at the toe eye ?

5mm - 5cm ?

How much does a properly fitted bobbin move, mine seem to move about +/- 10mm at most.

[AlastairA]

My understanding is that the metalastic bobbins are there to absorb small amplitude vibrations, not large mechanical deformations. I don't have any direct evidence that jacking on one side causes radiator leaks, but when I did do it, the driver side wheel was several inches clear of the ground before the near-side even started to lift. Can't be good!

[ScottR400D]

41 minutes ago, AlastairA said:

My understanding is that the metalastic bobbins are there to absorb small amplitude vibrations, not large mechanical deformations. I don't have any direct evidence that jacking on one side causes radiator leaks, but when I did do it, the driver side wheel was several inches clear of the ground before the near-side even started to lift. Can't be good!

You're right. 

[Geoff Brown]

Unfortunately I have to use the tow eye to jack as the twin horns get in the way being situated close to the cruciform.

No probs after using the tow point for eleven years. And used it on previous Seven for 12 years.

[StevehS3]

According to Caterham Parts the Sigma uses the same radiator and I haven’t heard of them needing such frequent replacement. So if the problem is specific to the Duratec it is perhaps more likely to be the top hose as suggested earlier. It clearly isn’t good as supplied. 

[Ainsley]

I will have a very close look at mine, its a 2024 420R.  

The top hose does not seem to be putting any strain on the radiator, but I will post up some pictures and investigate carefully before I start to use it.

Just finishing the build this weekend and plan to start it up for the first time Friday night.

[Jonathan Kay]

18 minutes ago, StevehS3 said:

According to Caterham Parts the Sigma uses the same radiator and I haven’t heard of them needing such frequent replacement. So if the problem is specific to the Duratec it is perhaps more likely to be the top hose as suggested earlier. It clearly isn’t good as supplied. 

There are plenty of reports of failing radiators on Sigmas:

https://duckduckgo.com/?q=site:caterhamlotus7.club+sigma+radiator+failure

Some of those will be older radiators with plastic tanks, but by no means all.

Jonathan

[MattB]

Supposedly when NSU RO80 owners passed each other they’d hold up fingers to show how many replacement engines they’d had. Perhaps 7 owners should do this to show how many replacement radiators they’ve fitted (although I’d need to be careful as I’ve had 2 replacement radiators so far)?😀

MattB

[BigCol]

1 hour ago, MattB said:

Perhaps 7 owners should do this to show how many replacement radiators they’ve fitted (although I’d need to be careful as I’ve had 2 replacement radiators so far)?😀

🤘🏼

[7Up]

Mine has been on 5 years and on the nose cone has quite a lot of pitting now. Would the wife's turbo hair dryer generate enough heat to flatten it out? Or do I have to borrow a heat gun?

Cheers

 

[raw]

@ScottR400D The leak on the radiator that has just been replaced did not appear to be stress related, I suspect it was a coolant corrosion issue as has been discussed many times before and swapping to blue coolant last year made the leak worse. Thanks for calling my solution a lash up but it works for my car and has done for around 10 years. I only offered it as an alternative.

Cheers

Andrew

 

[ScottR400D]

27 minutes ago, raw said:

@ScottR400D The leak on the radiator that has just been replaced did not appear to be stress related, I suspect it was a coolant corrosion issue as has been discussed many times before and swapping to blue coolant last year made the leak worse. Thanks for calling my solution a lash up but it works for my car and has done for around 10 years. I only offered it as an alternative.

Cheers

Andrew

 

I remain of my opinion. And there’s little evidence of any radiator being corroded by coolant. Radtec say don’t use the orange but I and many others have for many years with no issues at all. 

I’m still of the opinion that the main issue with CC rads is manufacturing quality.

As for the hose and bolt ‘solution’ they neither support the radiator nor protect it from vibration. I just don’t get why you would do that.   

 

 
 

 

[Geoff Brown]

Seems opinion on the type of coolant is divided & if it causes any corrosion leading to radiator seam failure. As I related earlier I have used the red OAT in my R400 for eleven years with no problems. Yes still on original radiator.

I still believe the problem is caused by undue stress on the radiator which is not helped by the Duratec natural, subtle but prevalent vibration when on tick over & up to about 1500  rpm ?

[Ainsley]

Can anyone tell me the coolant capacity for my Duratec, complete with heater.  Im just about ready to start the engine and keep topping up the coolant,  but the manual doesn't say how much to add.  Just says fill to the Max level. 

I will of course monitor and top up accordingly once its fired up the first time, but Id like to get close to the max prior.

[Jonathan Kay]

2 hours ago, Ainsley said:

Can anyone tell me the coolant capacity for my Duratec, complete with heater.  Im just about ready to start the engine and keep topping up the coolant,  but the manual doesn't say how much to add.  Just says fill to the Max level. 

I will of course monitor and top up accordingly once its fired up the first time, but Id like to get close to the max prior.

The current Owner's Handbook has:

and Aerobod has just put 6.5 L in:

Jonathan

[aerobod - near CYYC]

2 hours ago, Jonathan Kay said:

The current Owner's Manual has:

and Aerobod has just put 6.5 L in:

Jonathan

Hi Jonathan,

I just checked how much coolant and distilled water I had left in the containers to double check. I certainly used more than 6.0 litres. I’m thinking either the radiator capacities can vary (I have the old style R400D radiator with the M10 bleed bolt in the top), or the Caterham quantities don’t include the amount in the reservoir.

[Ainsley]

OK, so I need to keep filling till I've used up 5.1L despite the fact that Caterham only supply 5L 🙂

I suppose topping the last 100cc with water probably wont hurt, or will it ?

[aerobod - near CYYC]

3 minutes ago, Ainsley said:

OK, so I need to keep filling till I've used up 5.1L despite the fact that Caterham only supply 5L 🙂

I suppose topping the last 100cc with water probably wont hurt, or will it ?

If they supply 5 litres of concentrate as opposed to pre-diluted, it should be enough for 10 litres of coolant at 50/50 mix with distilled or de-ionised water.

[Ainsley]

It was the Orange stuff and on the back it said "do not dilute", so its going in straight from the can.

[aerobod - near CYYC]

21 minutes ago, Ainsley said:

It was the Orange stuff and on the back it said "do not dilute", so its going in straight from the can.

I would try and buy more to keep the mix at 50/50. You may find that it takes more than 5.1 litres once you have purged all the air from the system. Before starting it is worth elevating the reservoir as high as possible, if you have a heater opening the supply valve, and squeezing the top radiator hose until there is no air coming out of the top radiator bleed screw/bolt, if you have one.

[ScottR400D]

34 minutes ago, Ainsley said:

It was the Orange stuff and on the back it said "do not dilute", so its going in straight from the can.

I’d get some more, you’ll need it when the rad starts to leak………. 🥴

[Ant2]

After reading all the radiator woes I had a look at mine.

Mine is a 2020 420s., 5k miles.

At the top of the rad I see yr2022wk38 - 300C004a 

I presume this is the manufacturing date and this radiator was fitted end of 2022, beginning of 2023?

Which would suggest a replacement after 3-4k miles/3 years

Do I just pray to the caterham gods for no more leaks and hope it was a manufacturing defect or is there actually anything anybody is doing about it? - other than trying blue coolant, trying some 620 hoses etc.

The only comment I read apart from checking if it's mounted without strain is ensuring the coolant doesn't sit for 6+ months as this 'may' help with any corrosion issues. I.e give it a few runs before the ice starts and ends and turn it over till hot perhaps once in between?