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Sigma Radiator (Again!)


Bellissimmo

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I'm looking for a bit of search assistance.

 

My Sigma radiator is pi55ing water again so I'm looking for a replacement. I'm reluctant to upgrade at present - until I manage to cure my unemployed-ness - and I definitely won't waste any money on the standard alu/plastic cr@p (already on my third).

 

I recall seeing a post where the poster had identified an OEM rad for a Seat van(?) that ought to do the job but I'm struggling to find the post now.

 

So, if anyone with a better memory can help or the OP is still around, I'd very much appreciate a pointer.

 

TIA

 

Steve

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Where is it leaking from?

 

If it is the seal between the plastic tanks and the core, it is possible to carefully open up the alloy tabs, remove the tank, apply sealant and crimp them back down with some big pliers.

 

It is a fiddle, and I would still recommend buying a Radtec replacement when you can afford it.

 

Duncan

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Might be me you are thinking of, I have a VW Polo radiator on mine (Caterham had no stock when mine went pop). Involved a bit of re-plumbing as the lower inlet is on the same side as the top hose inlet on the Polo rad. A search for VW 651711 on ebay should find it.

 

You would also need to make some mounting plates from strip alloy as the mounts don't quite line up with the bobbins.

 

Edited by - Molecular--Bob on 15 Jun 2014 20:59:31

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Duncan,

 

Yup, usual suspects, core and plastic have had a parting of the ways. Mainly in the corner where the two top hoses join, so not easy to get to.

 

The frustrating thing is that I did 90 mile round trip on Monday and 70 miles to the club meet on Thursday with no issue and then had a massive leak doing a ten mile trip to the next town. Grrr!

 

Assuming you've done it, how did you get the tabs up - is it just gentle leverage with a screwdriver or something more sophisticated? And what sealant did you use - Sikaflex seems to get mentioned whenever some serious sticky stuff is needed.

 

Steve

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Molecular Bob,

 

Yeah maybe. The story as I recall was that you (or whoever) had found a reasonable alternative (the Polo?) and then posted a PS along the lines of 'I should have used this one', which included a link pointing to a SEAT van rad.

 

The Polo one might be a good interim fix while I save up for a Radtec one.

 

Thanks very much for your help.

 

Steve

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It was me, I used a rad ( the VW Polo 651721) that Westfield use on their zetec cars, it is similar to, but not the same as the 651711. The 651711 (the Seat Terra rad) is a better fit as the core is slightly thicker but a bit narrower. It cools the zetec fine, so assume a sigma would be ok.

 

The 651721 also has a boss on the lower edge that is very tight in the nose cone, leading to a lot of messing around to get the fit right.

 

Edited by - Molecular--Bob on 15 Jun 2014 21:32:35

 

Edited by - Molecular--Bob on 15 Jun 2014 21:33:32

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I used a screw driver to lift the tabs a little, then pliers and I coated the gasket in silicone gasket.

I have to admit that I didn't end up using the radiator after I tried the repair as I decided to buy a Radtec instead. I've kept it in the garage for emergency use, so I may try it sometime.

 

If you can get some reasonably cheap help from a professional, that is probably a better bet *smile*

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Grubbster,

 

That's new news. Any clues on what the construction is?

 

DJ,

 

Well, I was coming to the conclusion that I'd either spear myself or the core before the day was out and with my girlie hands I can't see me being any more successful than the manufacturer at squeezing all those tabs nice and tight. So a local repairer has got to be worth a try.

 

Tomorrow I'll tug it out and take it to a menders for a quote.

 

Thanks everyone. Update in a day or so...

 

Steve

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  • 3 weeks later...

So far so good!

 

I used a company called TransRad in Canterbury and found them very easy to deal with. The guy I spoke to told me up-front that he couldn't guarantee a fix because if there was a fault in the gasket or any 'sh!t' in the joint, then water would find a way through. So he's re-crimped the joint and pressure tested it and told me to bring it back if I had any more issues with it. £36 inc. - much cheaper than a Radtec replacement, although it is still on my long term shopping plan...

 

I've done a fair few long(ish) runs including spending almost all day exploring some lovely parts of Kent. What started as a quick run from Dover to Staplehurst to pick up a new stop light switch and a rivnut set turned into about 200 miles of completely aimless (and grinful) driving.

 

I've regained my trust that I can go for a drive without a bottle of water in the boot and the car is finally getting the kind of mileage that it deserves, particularly with the great weather we've been having recently.

 

Thanks all - and especially Bricol for providing the final solution.

 

Steve

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Good to hear it is OK *smile*

 

I've been thinking about these leaking radiators, and it seems odd that platic tank/alloy cored radiators work fine on many normal cars but always seem to leak on Caterhams. The quality of my Sigma rad looked Ok, and I suspect that they start to leak due to extended periods without use. Certainly mine was problem after a winter where I didn't drive it for a couple of months.

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DJ,

 

That's not my experience. This is my third radiator. The first two failed in fairly quick succession during my first year of ownership when I was driving regularly. My belief is that the rads are poorly put together - just not crimped tight enough and that they fail due to the different rates of expansion and contraction of plastic and Ali. This one failed on a very short run of quite quick driving - having recently performed well on two longer but more gentle runs. So maybe it's connected to the length of time the engine (and thus the coolant) takes to get up to normal running temperature? IDK

 

Steve

 

 

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I think the quality may have improved over the years. My first one failed a couple of months after completing the kit, replaced under warranty.

The second one failed failed when I stuffed the front into an earth bank having spun on black ice so that doesn't really count.

The third is now 6 years old & a has covered somewhere around 23k miles & is still perfect. *smile*

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Martin,

 

You may well be right. Mine would all have been circa 2008/2009 - and it looks like the current one has been fixed (touch wood) simply with a 'little squeeze'. It seems that others have found this approach, or variations thereof, to have done the trick too. My guess is that the design is OK but the assembly process and pressure test, if any, left something to be desired. Be interesting to see if your 23k radiator is any different design-wise to mine

 

Steve

 

Edited by - Bellissimmo on 6 Jul 2014 18:04:13

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