Cheap Thermostats, Problems?

[dickster]

Gents, is it wise to only use genuine BMW thermostats? are cheap thermostats known to be iffy? I've fitted a Circoli thermostat and I'm thinking it's playing up already, my '88 325i Sport was overheating when idling, a new thermostat and properly bleeding it appeared to completely cure it for a short while but now it's doing the same thing again, the car is sitting around unused for long periods of time so I'm wondering if it's just a case of a cheapshit thermostat and not being used alot has caused it to fail in a short time.

[JF008]

I had the same problem and replaced the ECP thermostat to a BMW one and it seems better.

[Brianmoooore]

The OE thermostats fitted to E30s, and later models are far from problem free. They are notorious for the bridge piece holding the 'stat element breaking on one side.
Overheating when idling (and not when driving) is unlikely to be anything to do with the 'stat. Far more likely to be a failed viscous fan coupling.

[DanThe]

Most faulty thermostats tend to overcool rather than overheat

[Brianmoooore]

Most faulty thermostats tend to overcool rather than overheat

As do the BMW ones. With one side of the bridge broken, the disc of the thermostat that forms the valve doesn't lie square on its seat, so it allows coolant through when it should be shut, resulting in the engine being over cooled at idle.

[dickster]

Can I do the newspaper test at idle? I thought there was an issue like something to do with airflow temperature over the thermal part of the viscous coupling in that doing it idle wouldn't make the clutch in the coupling behave in the same way as if the car was moving? Or am I talking horse-shit and just do it when warm at idle?

I did buy a new viscous coupling a few years ago (it was one of the decent makes from Motormec) but it only lasted just over a year, I tried several secondhand units after that before getting one that did work properly.

Interesting to hear of the issues with the genuine BMW thermostats, thank you gentlemen for your input.

[zd3bx]

Have had ECP Circoli thermostat for 2+ years now, no probs so far, but I've got a new BERU viscous coupling too...

I doubt yours would fail so quick, especially since you don't use the car much.