My TT normally runs at about 75-78 degrees on the motorway, off boost. (Consult temp from the ECU sensor). This seems a bit cold compared with most cars, but I guess this is normal with a 76.5 deg C thermostat? The dash gauge is just marginally under horizontal.

 

If I drive at constant 50mph a couple of minutes after a cold start, it takes over 10 minutes to reach 70 deg C. Ambient temp 10 degrees. Is this normal or could the thermostat be stuck open a bit?

 

During warmup, at what temperature does the ECU stop fuelling rich, is it a threshold or does the enrichment gradually reduce as the temperature rises? What temperature enables full boost?

 

Thanks!

If I drive at constant 50mph a couple of minutes after a cold start, it takes over 10 minutes to reach 70 deg C. Ambient temp 10 degrees. Is this normal or could the thermostat be stuck open a bit?

 

Yes very likely, the viscous fan could also be locked, having said that it would be very noisy if it was.

 

Thermostat issues can occur and will result in all manor of problems, not too expensive to replace, the fuel saving from a quicker warm up will soon pay for it, 10 mins at 50mph to attain 70deg is too long.

 

I did a tech about this very issue, see link below

 

http://www.300zx.co.uk/forums/showthread.php?t=126426&highlight=thermostat+tech

 

Another thing to consider if a stat with the wrong temp has been fitted, see link beow.

 

http://www.300zx.co.uk/forums/showthread.php?t=133014&highlight=thermostat+tech

 

Jeff TT

Thanks Jeff, that's very useful. Pretty sure the fan isn't locked because after an initial roar on cold startup it quietens down, plus you can spin it by hand when it's cold.

 

Coasting down from high speed off throttle the temperature can sometimes drop into the low 70s, so I'm a bit worried the ECU will switch to "cold" fuelling and safety boost. Economy is pretty good, though (25-28 mpg at 70ish).

just out of interest, what should the temperature be? (i just got my OBD1 interface, so can check it properly) :)

The "desired" temp is 80c once up to temperature this should be fairly stable whether the engine is at idle or at higher revs, the thermostats job (with the radiator) is to regulate and react accordingly to maintain 80c, 2 or 3 degrees either way is no biggy providing its stable,if the temp sensor reads in the low 60`s then saftey boost is an issue as you mention but you are well above that.

 

Jeff TT