Strange warm-up behaviour (Airlock ?)

[FFMan]

Went out in the Griff 500 yesterday which I hadn't done for a couple of months.

Whilst it was warming up, the temp gauge stayed on the bottom longer than I expected, then when I looked a moment later it was up near the red, and then it after a minute it settled to normal and was ok for the run. when I started it again to go home, it did pretty much the same.

we've had some very cold weather (-5) since it was last used, but its always got a good concentration of anti-freeze in it, but I wonder if this might be related ?

any comments appreciated.

[blitzracing]

The water flow pattern in the inlet manifold is not ideal-but it depends how TVR plumb in the heater. If the heater circuit always allows water to flow around the head and manifold if its on or off things should work OK. However if shutting the heater valve stops this flow, then you can get hot spots forming behind the thermostat before it opens, so you get a sharp rise in temp before the stat' opens. The workaround is to have a 5mm hole drilled in the top of the thermostat so there is always some water flow past the stat, but it can increase the warm up time in colder weather. You can see the hole with a brass insert on this 'stat, but not 'stats all have them.

Edited by blitzracing on Thursday 4th February 15:59

[FFMan]

ok thanks - this could be the issue, as on the second occasion I fiddled with the heating controls and I got the impression this helped.

is it therefore perhaps better always better to ensure I start it with the heater valve open ?

[blitzracing]

TBH Id be surprised if TVR had got the heater valve system that wrong, Id expect every car to do the same thing if thats the case. Certainly all the Ginetta G33's where wrong so every car shows a sharp rise in temp to around 95-100' before the stat opens then the temp drops rapidly back to normal as the stat opens. I dont know if any one can confirm if the heater valve is simply open / close or a two way one that bypasses the heater when its off- you need the latter? Certainly running with the heater on works just fine on the G33 if you dont have a hole in the stat'.

[Colin RedGriff]

Pretty sure the TVR arrangement has a bypass when the vlavle is closed

[stevesprint]

Precats definitely have a heater bypass in the passenger footwell and it seems from this thread 500s don’t.
http://www.pistonheads.com/gassing/topic.asp?h=0&a...