Seems to be a recurring theme, this one. Mine's been overheating under pressure for a while, mitigated by slapping the heater on full blast and roasting my wotsits off. I've tried different thermostats, new water pump, compression test, hydrocarbons in the coolant tests, coolant pressure tests, flushing the system, jamming the fan, all to no avail. The problem is the unconventional setup on these cars.

Having finally got miffed to the point of sweariness with it all, I decided to strip the lot down today. Now, our beloved Sporties have the thermostat in line with the COLD flow from the radiator. This seems daft but, when it works, it's not a bad idea at all. The minor difficulty is keeping the head from cooking while the block stays cool (heat rises) and thus the thermostat staying resolutely shut. To mitigate this, Daihatsu fitted a bypass path for when the stat is closed to ensure the head and block coolant is still circulated and remains at an even temperature.

Guess what was blocked up to buggery? It's not obvious, this pipe. There's a spigot behind the outlet on the head that it attaches to, under the distributor. It then goes to a metal pipe which is bolted under the inlet manifold in two places (12mm), becomes rubber again and connects to a spigot near the thermostat. It's an absolute bugger to get off as DH in their wisdom used those awful spring clips on the rubber hoses that we all know and hate. Better still, they put them on so the release tabs are against the block where you have zero chance of getting at 'em

Cleaning this monstrosity out and replacing a buggered bit of pipe from the outlet end and all is well in Sportyville. Something to bear in mind if your precious keeps getting hot-headed. It's not an easy job at all, but I'll bet a pound to a pinch that a few of these Sporty overheating problems are blocked bypass paths.

BTW, Gates make a thermostat for these that works flawlessly - and sits in the hole while you get the housing back on unlike the sodding BluePrint part. Part number TH29478G1, opens at 78 degrees (standard config rather than 82 for EEC, gives you a bit of overhead) and is fully open when the 84 degree Quinton Hazel (spit) stat is still thinking about it. The baffle and jiggle pin are in the correct places, too.