weird overheating (but not really) problem

[Sheck]

Ok, i bought a new thermostat i little while ago because it was opening later than the fans would come on. The one i bought was a 180 deg F one which opens ate about 82 deg C.

Now when i first start to drive the heat comes up to mid way on the dash and stays there for a while then it proceeds to go half way between the mid way and the H at the end before the thermostat opens. Once it opens the temp goes to about 80 and sits there for a while before stabilizing at around 86-94C depending on whether or not i'm in traffic or on the highway (at speed). Also the dash gauge goes back to the normal position of just befoer half way.

Last night i tried running the heater full blast so as to keep the temp at the half way point, but this only prolonged the time it took for the thermostat to open, and it still went to the 3/4 point before opening.

I'm running a PWR 40?mm radiator with a custom under tray i made to direct air to the IC and rad instead of around it. (i ditched the stock plastic one) It doesnt have sides yet, just the bottom.
This problem is the same during the day or night.

Any ideas??

Cheers!
Dave

[siu_loong_bao]

seems like u got the same probs like me (b4 I stored my MX5 to go to Dubai)...

thread: http://www.aus-cartalk.com/viewtopic.ph ... highlight=

I still havent figured out my probs and will do it in 3 yrs' time after my Dubai job posting...

[JBT]

Have you tested the engine temp sender? Maybe it's faulty.

[Okibi]

Sorry I can't be much help but i'd love to see your DIY undertray.

[Sheck]

JBT: Yea, its only 3 or 4 months old! Bought as new one cause of idle problems (mechanic suggested it as a fix).

siu_loong_bao: No mines only when i first start, kinda like the thermostat doesnt realise it should be opening untill its really hot, then once its open everything is fine.

I'm guessing maybe its cause one side of the thermostat is cold and the other hot, big radiator plus lots of air flow makes the water in the rad extra cold, and the water in the engine has to heat up that extra amount to get the thermostat to temp??
I may try drilling a small hole in the thermostat temp thingy so some/more of the water cuirculates earlier..

Thanks for the ideas guys!
Dave

PS i'll get photos up once the new engine is in.