cruising on the motorway (lets say at 50mph) and the temperature is displaying a constant 81-82c - nowt wrong with that.
but i blip it up to (lets say 70mph) for about 20 seconds (give it a good kick) and the temperature displayed starts to fall… and fall… and fall… 80… 78…74…70… then it disappears (like when you start the car and its cold). Eventually it comes back to 70, and climbs back to 81-82c
Is it possible that the acceleration could cool the coolant this dramatically? Are the cooling vents really that efficient? And i dont think its a dodgy thermostat… the air coming out of the vents actually starts to cool
It sounds like the spring in the thermostat could’ve gone weak and the increased pressure drop over the thermostat at higher flowrates is blowing it open… I’ll need to get my books out and check …
Yeah, its a bottom hose stat so when its shut it has the pump suction on one side and full engine outlet pressure on the other. The only route for the coolant is either thru the heater core (constantly open) or through the coolant header tank. I cant see how either of those routes could have become blocked so the stat must be getting pushed open?? It should be just open a smidgers just allowing a small amount of cold water from the rad to blend with the recirculated hot water from the bypass/heater circuit. In the summer in higher ambients the stat will be much further open (the water coming back from the rad will be much warmer) so the pressure drop wont be so high and its easier to control.
should i be worried? should i drive it quietly until checked?
Its not going to do it any favours but it wont kill it. My Caterham used to drive like this all the time but I’d get it checked when its convienient.