High CHT warning

This is in a new -12 with first flight last Saturday. We did not fly too long as the CHT went into the yellow. We tried the climb to 10,000 but as we passed 1,500 the CHT went in to the red and it cooled down as we returned to the airport.
OAT low 60'sF.
Rotax 912 with the newer CHT probes that actually measure coolant temps.
Zerex Dex-Cool 50/50 coolant.
Cooling system has been purged of air and topped off.
The CHT sensors have been checked against boiling water and the give the correct resistance and the reading on the Skyview matches.
On the climb-out at 75 KIAS the temperature peaked at 270 when we aborted the climb. The oil temps were in the green.
The radiator was pulled and back flushed.

Any other suggestions? Van's had none.

N4212C

Even though the cooling system has been purged of air, check it again to be sure.

CHT's match, both sides hot?
Fluid level still normal after landing?
Factory built or kit built?
Air duct unobstructed?
Hoses properly routed and unobstructed?
CHT normal on ground runs?

Post a photo of the cooling air inlet on your cowl.

CHT's match, both sides hot?
Right side ran 5 - 7F higher than left.
Fluid level still normal after landing?
Fluids topped off after first flight but o.k. on 2nd and 3rd flights.
Factory built or kit built?
Kit built E-LSA
Air duct unobstructed?
Air ducts clear.
Hoses properly routed and unobstructed?
Hoses look good but will double check for crimping where they are routed through the engine mount.
CHT normal on ground runs?
Mid/upper green on the Skyview.

I am thinking coolant flow problem. Either an obstruction or a bad impeller in the pump.

After the first flight I could grab the upper hose into the radiator. It was very warm, but not hot enough to burn. The lower hose was comfortable to the touch.

Here are a couple of shots.let me know if you need other images.

tadpole rider said:

Here are a couple of shots.let me know if you need other images.

Click to expand...

Ok.
Cowl looks good. I imagine you have confirmed that teh duct seals well to teh radiator.

Next thing I would check is for some type of blockage (as you mentioned).
Confirm that none of the shipping plugs were accidentally left in the radiator nipples or the water pump or expansion tank on the engine.
This might be a long shot because it should also cause a rather rapid heat up of CHT's just idling on the ground, but it needs to be ruled out.