I was very impressed with Ian's (squiglyzigly) thermostat modification and vowed to copy it. It's only taken me a year and a bit, but here's my take on the mod that Ian has pioneered. The hardest bit was probably getting hold of Renault Clio/Megane/Scenic /Kangoo thermostat housings in aluminium. It seems that Renault have moved to plastic for these components, which I didn't really want. I'm sure that modern hard plastics will do a perfectly good job, but I just prefer metal.
I then acquired a standard Mini thermostat, but in the hot climate (74 degree C) version - part number GTS102. The 84 deg C (temperate climate) version is GTS104 and the 88 deg C (cold climate) version is GTS106. I got mine from Rimmer Bros (
www.rimmerbros.com) who charged me a paltry £4.32 inc VAT for the privilege. These stats are fractionally larger than the Renault housing, but a few seconds with a flap wheel in an angle grinder soon encouraged it to fit snugly.
The lip on the Renault housing has a depth of 3.5 mm and the i.d. is 53.5mm, so I tracked down a suitable o-ring to fill the gap. I got a pair of Viton o-rings (you need two) from simplybearings for £6.47 delivered. They are actually a British Standard (BS 828) and measure 3.53 mm in cross section and 46.04 mm internal diameter. They serve a dual purpose of sealing the thermostat on both sides and stopping it flapping about loose in the housing.
Both housings (you need two) have a small relief port, one of which will need to be closed off. I removed the spigot on one of the housings and then had my local welders seal the port with some weld inside and out. If using plastic items I guess a hacksaw and some epoxy resin would work.
The last thing I needed was a gasket. I'm sure I could have tracked down the Renault part, but instead opted to make my own from some 1mm thick gasket material I had. On reflection, tracking down the Renault gasket would probably have been simpler. I haven't done final assembly of the unit yet (the bolts in the pics below are just finger tight, but when I do I shall probably use Threebond liquid gasket, as that has never yet failed me when being used on motorbikes. Again, probably overkill but I hate doing jobs twice.
So thanks again to Ian for the initial inspiration and here are the pictures.
I hope your in-line thermostat mod works to your liking. Mine has covered around 1.5k miles now and for me it’s been all positives and no negatives.
I like your detail of welding up the un-needed 2nd bleed pipe on one of the housings. I promised myself I’d do the same if it works but so far I’ve not got around to doing it but it’s on the list.
I’ve got a 75 degree stat with no bleed hole and it runs in the lower green most of the time only rising to mid green when idling and driving hard.
I did find a stat with a bleed hole warms up a little slower and it’s apparent that warm water water does pass the bleed hole when cold and thus slows warm up slightly. But it’s no biggie. I only discovered this when swapping different temp stats for testing purposes. You don’t actually need a bleed hole in the stat because the housing self bleeds via the bleed pipe that you return to the expansion tank.
Your choice of hunting down a pair of alloy housings is a good choice in my opinion and I have done the same for the same reasons as you. There are many aftermarket plastic housings for sale for many cars and the reason for that is simple, the plastic ones distort and crack more often. A friend has had 2 plastic housing failures on 2 cars (a Ford and a Mazda) in the last 12 months.
Hope your test goes well
Ian
