Lazy Thermostat

TL;DR yet another saga, for some reason

Super boring long story short, the reference you're looking for is 17670-81AB1. Good luck finding one.

With no reply to the enquiry I sent Caterham through their online form, I had to find the Suzuki part number for a Suzuki Every DA17 on eBay. As far as I known, my dealer was not able to get any information from official channels either.

We got the thermostat out of the car at House of Speed and were able to confirm that what we saw did match the pictures from the listings : the offset piston, the looks of the mechanism and even all the markings on the flange were identical.

On the Caterham 170, the thermostat is not located in the housing that's on the cylinder head (we checked, it's empty), but in a remote housing near the oil filter, where the bottom hose of the radiator is attached (gotcha).

17670-81AB1-000 is a 82°C thermostat with a 48mm diameter that, in Europe, is also used on the Suzuki V-Strom 800 motorcycle.

In hope of a quick shipment and delivery, I placed an order from what looked like an official Suzuki 2 Wheels parts shop. Late on Sunday night (the next day) I got an e-mail telling me the part was not in stock and that it could take weeks. That was far from the excellent experience I got with Electrolux each time I needed anything for the odd appliance at home. We're clearly not talking about next day delivery here.

So I did cancel the order and let the team at House of Speed find some equivalent with their generalist parts supplier of choice. With the Suzuki OEM part number, they were able to find a Valeo 820565 and have it fitted to the car on the same day. Good job there !

Nevertheless, I'm not pleased with the experience : I cannot accept that the only way to find the relevant part number was to take it out and check it if did match eBay listings from the United Arab Emirates and the Philippines. We're following bread crumbs involving an import minivan (look for DA17 and have a laugh) for the most basic yet vital 25 € part you will find in a car.

I'm not even complaining that 3 years and 40 000 km tastes like an early failure. It's so cheap that I don't care. The normal lifetime for a thermostat is around 10 years or up to 200 000 km. With so little coolant, the large radiator and spirited driving, I assume it has to work a lot more than expected. It most likely reached over the 100 000 cycles it was designed to last.

After that it became lazy.

How did I know something was off ? you may ask. The second half of this article seems like a good place to talk about the beginning of the story.

Flashback to the morning of Nov 22nd. It's -5°C outside, all is frosty with cinematic scenery around Spa-Francorchamps. At one point I decide to push hard enough to blip the shift light on a each gear change. That's exhilarating. With the compressed air in the intake manifold at only 5°C, the machine can deploy its fury to its maximal potential.

After that, lift-off and coast... with the CANchecked gauge showing a "COOLANT 114°C" black-on-yellow popup with the angry blinking pink (warning) LED on top. Uh oh...

As I was going to House of Speed to fit the "SEVEN 170 S" stickers on the new bonnet, we discussed what happened in the morning. The most likely explanation was a sticky/lazy thermostat.

Overall, the symptoms were a higher-than-usual "cruise" temperature around 88°C instead of the usual 84°C. For reference the coolant temperature remained around 86°C during the track day in October. Any "hard push" was now followed by a brief spike over 100°C that dropped to 82°C instantly.

There was no rush to replace it: driving around at 88°C was not an issue. I did estimate that the next oil service should take place in March and booked the appointment.

It's now back to normal. I should probably add a thermostat to my list (and stash) of consumables.