Appreciate all the advice. I probably am overthinking it.
It's just a mix of wanting to do a really proper job, so I don't have to do it again for a long time, and learning as I go and not wanting to mess up.
I did make a bit of extra work for myself. The flush left the system running pretty much clear. But, I decided to run a bit of cleaner in it just to see, and with only using half their suggested dilution, I did another run and it came out totally brown again.
It was actually shocking how effective it was. But whether it was worth it or not, I have no idea.
I have now installed the new heater control valve, and that seems to be working perfectly. So the original issue is fixed.
Interestingly, the A/C seems to be working now. Or rather fixing the valve has made it actually effective. Wasn't expecting the A/C to work in a 16 year old KA.
![IMG_20240724_162557.jpg IMG_20240724_162557.jpg](https://cdn.diynot.com/data/attachments/350/350491-7a5245b260f448d9ce32c53ab72507fc.jpg)
![IMG_20240724_171529.jpg IMG_20240724_171529.jpg](https://cdn.diynot.com/data/attachments/350/350493-4316c031a87521c93014390cd8b597ba.jpg)
![IMG_20240724_163331.jpg IMG_20240724_163331.jpg](https://cdn.diynot.com/data/attachments/350/350492-e781306f2d698a1de2e4e7c6c6ceb21f.jpg)
I then decided to do the thermostat, even though the old one was working. I was in two minds as to whether it was worth it, or whether I'd be opening a can of worms.
The retaining screws for the thermostat cap are horrible little things. They are metal screws (that are more like wood screws) and screw into a plastic thread/housing. Feels nice and secure but I was very paranoid about cross threading the plastic.
But, no leaks. Thermostat works.
After doing all this I have notice the valve cover is weeping. So I think that is next on the list.
It looks pretty simple on this, but I'm sure that will be my next post.