temp gauge readings

[123-jn]

I was quite concerned today after having changed the exhaust on 1/3 and repaired the metal coolant pipe that runs from the rear left to the stat housing, I decided to flush out an change the coolant. I tested the strength of what came out and it would only protect down to -15 so was a bit under strength but lovely and clear pink no sign of rust. I refilled with 8 litres of G12 and water to make up. This mixture read -35 on the tester. Now after bleeding and ensuring everything was getting hot all over I took it for a spin and checked for air again (non found). ON heading down the M42 at 55 mph the gauge which used to run dead centre and just to the right of the led up hills was now reading 3mm past the LED although it did not rise any further. On returning home I left her running and checked again for air at the rad and engine etc. None found, all warm, all over. Now after 5 mins ticking over gauge reading half way between led and top. The fan came on speed 1 and stopped it going any higher. Over the next few minutes at tickover it fell back to 1-2mm past the led and the fan cut out. Concern at this point is that previous to the new coolant she ran dead central? Could it be the stronger antifreeze mixture? There is no air in there and all appears good with the fan but it is disconcerting seeing the gauge so far up. Is this normal?

[kevtherev]

Temperature is temperature, it does not matter what your measuring.
three things can affect the temperature of coolant once the thermostat has opened.
1. the thermostat is not opening fully
2. radiator restriction
3, poor coolant flow due to trapped air.

The fan is working correctly
The temp is taken, at the thermostat housing. During warm up, the by pass circuit is open and the temp is taken from the coolant circulating the engine. This bypass circuit is closed when the stat opens, and it measures the coolant returning from the radiator.

Did you use the Baxter bleed method?

[123-jn]

Thanks Kev, I used the bleed process on brickwerks, van level 2000rpm, keep top tank topped up and release air from rad and t/stat housing etc. The only difference is the coolant is much stronger. Now just under 50% previously probably 25% if that. G12. (and the new exhaust)