I changed my radiator for a larger alloy one and am now having real difficulties bleeding the system, to the point I'm thinking I may have another problem. I'd had a suspicion my stat was on the way out for a little while, the car seemed to be running hotter under bonnet temps wise although on the obd temp scan it seemed to be within normal ranges. This was prior to the new rad going on. So I changed the rad, had the front end jacked up as per the guides and filled till coolant came out of the bleed nipple, no problems. Ran the car and top hose hot, blowers in the car hot, bottom hose cold.
So stat out and true to form it's stuck closed in boiling water. Changed that (genuine honda one),refilled had it running and still the same, top hose hot, blowers blowing hot, bottom hose staying cold. Fans have come on, bled air out of the bleed nipple numerous times, bottom hose still not getting hot. Despite the car been running for 20 mins or so I can still put my hand on the thermostat housing, which although warm is certainly not hot by any means.

Any suggestions of what else to try or what else could have failed. I've read through all the previous threads on bleeding ect, but I'm at a bit of a loss as to what to try next.

 

You either have a leak or haven't bled it properly sorry, they are bastard to bleed when you've basically removed all the coolant etc. A sticking stat will cause high temps, typically sticking.

I ran mine (engine running) for ages with it jacked up and watched the level fluctuate with the rad cap off, finally it calmed down without bubbles appearing - i slowly topped it up and squeezed the pipes occasionally. I ran the car around and also cracked open the bleed nipple slightly and put aquarium tube over the bleed nipple and put my chops over the rad cap and blew, thus a few bubbles came out of the aquarium tube, a day later i topped it up and that got rid of all the air never topping it up again.

 

Will have another go at it tommorow. Never had this much trouble bleeding coolant system before

 

Did you remember to test the new stat before fitting? I'm sure you did but so many people don't think to because it's brand new.

 

I had the same problem when fitting a F20C into my kit car. Tried everything over about a 2 week period. In the end I drilled another 5 mm hole on the stat and it cured the problem straight away.