Odd Temperature problems

[Dodsy]

My 450 has been running very cool lately, temp gauge on the dash barely moving and lukewarm air from the heater. Fuel consumption has been poor as well.

Assuming it was the stat a new one has been fitted but problem still exists. I'm not sure the stat is working properly but I think there is something else going on here.

This is what I see (Using my ECUmate)

1.Running up to temp I should see a step temp reduction as the stat opens then it should climb again until the fans cut in. I dont get this, it just climbs steadily to 92 then the fans cut in.
2. Heater is a bit warmer than before the new stat but still not toasty hot like it used to be
3. When driving around yesterday on a steady throttle the temp was hovering at ~ 71Deg then over a few seconds jumped up to settle at 117Deg (yikes!). Stayed there for a short while then slowly dropped back to 105. After a few minutes it then dropped fairly quickly back down to ~70. During this the dash gauge didnt move from 68deg , oil pressure was fine and no misbehaving from the engine. I have once before properly overheated the engine and had low oil pressure plus erratic running before it boiled over. It doesnt feel like that.


My suspicions are either an airlock somewhere in the system or maybe a tired water pump. Or maybe sludged up cooling system ?

I'm going to get it into Str8six asap for a proper look but scared to drive it now in case some damage is done.

Its had a new valley gasket fitted (not by Str8six) recently , could the cooling have been incorrectly replumbed after that ?

Coolant level in swirl pot is to the top , expansion tank at its normal level.

[Bassfiend229hp]

Dodsy said:

3. When driving around yesterday on a steady throttle the temp was hovering at ~ 71Deg then over a few seconds jumped up to settle at 117Deg (yikes!). Stayed there for a short while then slowly dropped back to 105. After a few minutes it then dropped fairly quickly back down to ~70. During this the dash gauge didnt move from 68deg , oil pressure was fine and no misbehaving from the engine. I have once before properly overheated the engine and had low oil pressure plus erratic running before it boiled over. It doesnt feel like that.

What were you using to tell you that the temperature was 117 degrees?

[Dodsy]

I was using my ECUmate which reads the temp the ECU is getting from the engine temp sender. I guess the engine temp sender could be broken but that still leaves me with a cooler than normal heater.