L322 Faulty sensor?

Hi guys, so I got my new rad hose today thanks to LR direct who now have a distribution centre in Gloucester so I called them and said I needed it today and 5.20pm I get a call the hose had arrived and I could collect up to 7.30 tonight, great service!

Anyway onto the problem, I refilled the cooling system fired the beast into life and she purred fine, I the car warm up a bit, to the point the oil filter was Luke warm,turned the engine off, I noticed temp gauge was in the centre (normal position) at this point, topped the coolant up, went to restart the car and it just turned over and didn't fire, tried it a 2nd time and it was the same, checked for error codes and all was clear. Tried it a 3rd time and it tried to fire, the 4th time it eventually fired into life but it took a while and was like it was a cylinder at a time coming to life. When it did start I noticed it was over fuelling ( the exhaust fumes stank of petrol) and through the exhaust sounded like it was missing/popping type noise but it all cleared after a couple of mins.

Ran the engine upto temperature, and I noticed the electric fan kicking in for a few secs then off, checked the temperature through the dash and it was reading 111 degrees, so I raised the revs to 1500 rpm for just over a minute and it dropped to 99 degrees, would I be right in thinking temperature gauge gone faulty, or am I looking at something else?
It's a 2003 bmw 4.4v8

Air lock possibly.....i had this once before when an air lock of steam was trapped where the sensor is near the pump.....the sensor was telling the ecu the temp was high so it adjusted the fueling accordingly...when actually the engine was cold and was a bugger to start.

Bleeding the cooling system on the M62 is a pain......

Turn the ignition on but don't start the engine.....set the heaters to full hot and fan down low, this brings on the auxillary coolant pump and opens the heater valves.....I fill through the top hose using a funnel and tube, then into the top of the rad.....refit the top hose to the rad and fill through the expansion tank with the bleed screw open.....fill it to the brim and let it drop the fill up and wait for it to drop again....keep doing this until the tank won't empty further.....

Then run the engine with the cap off and bleed screw open, keep the tank topped up to the brim, run the engine to about 2000-2500 rpm and you should start to get a jet of water out of the bleed screw...try to angle it over the side of the car!! Hold it there for 10 seconds, then back to idle....top up the tank again.....squeeze the top hose a few times to expell any air, and the run the engine back to 2500rpm again.....once you get a good solid jet out, close the bleed screw and let idle and allow the coolant to warm up so the stat opens.......keep the tank topped up, and do the 2500 rpm again with the bleed screw open again....this is to get any air out they may have been trapped behind the stat.

Once you are statisfied you are getting a good stream out of the expansion tank bleed screw.......leave the bleed screw out and allow excess coolant to drain out of the tank until the level is just above maximum.....

Close bleed screw, screw on cap, turn off engine and leave over night to cool....recheck level and top up if necessary.

This is the way I do it and can take 30-40 minutes if the system has been mostly drained.

It also helps to have the car pointing up hill, on a slope or ramps....to get the expansion tank and rad at the highest poimt of the system.

it could have been i've hopefully got it all bled, i do mine slightly differently to you as i've got lpg fitted so extra pipework, but essentially start off filling through tank with heater & fan on, and i just keep topping up, until it won't take anymore coolant, then start it and run at ticker and keep topping again, then i hold the revs at about 1500 until the LPG & heater have warm water, retop the system fit the lid and allow to run to temp. just need to recheck in the morning, but it is possible it was an air lock but i'll monitor it as temp sensors failing on BMWs with M62 fitted is quite common

I run LPG also......

i've test driven it this morning i had to top up with1/4 ltr of coolant, and all now seems ok, i did notice it's now running cooler, i did put a cooling system flush through when i did temp repair on the hose and drove it around 10 miles at operating temp. when i drained it, the water seemed to be clear with no rust scale or anything, but when going up an incline for example i could easily hit 104/105/106 degrees and now it's not going above 98 so must have been some crud that shifted. and it's settling between 90-93 normal cruising (i have 80 degree stat fitted) where before it was 95-99