Cooling system flush block radiator and heater.

No pics for this one which is more of a placemarker.  I've had a coolant leak under pressure around the top of the rad for a while now.  Coolant collects in the weld seam gulley at the back top of the rad.  I suspected the otter switch seal....  But it could be the brazed seam itself.  Further,  the heater isn't working too well so I suspect its time to drain the coolant (probably overdue) and flush before refilling with new.

I decided to remove the thermostat to get a good flush through the block.  Mainly because Im nervous of removing the block drain plug.  Anyway I did it as follows:

Undo filler cap,   disconnect rad bottom hose and drain.  I collected the fluid but my local recycling centre has no idea what to do with it!
Remove themostat cover and thermostat...  Replace cover.
Disconnect top hose at rad.
Disconnect heater hose at water valve.
Using domestic water hose flush block through top hose and out of bottom.
Open and close water valve to ensure water can exit thru the valve when open and flow stops when closed.
Backflush thru open water valve into block
Flush heater through the water valve hose
Flush rad through top hose entry
Reconnect bottom hose,  fill rad and remove hose to drain again.
Repeat until draining water is clear.

I found the bottom hose was perishing so I fitted a new one.  I also removed and cleaned the otter switch. The seal was brittle and so I cleaned its seat in the rad with P1500 emery paper before fitting the new seal (buy several and keep one in the car) and old clip. The seal has to be fitted first dry,  and the switch then pushed in.  I used a little wash-up liquid as its very tight.  I took advantage of the opportunity to clean and tighten the spade connectors.  They slip easily out of the covers if you depress the correct tab.   Took loads of trial attempts and I can't remember which one worked!
I refitted all the hoses,  cleaning up their junctions and applying corrosion block grease.

I removed the thermostat cover again,  cleaned off any old gasket remnants on cover and block and wire brushed the studs.  I would have removed these to clean properly but they were pretty tight and would, I think, snap before coming out.  I did the best I could to remove caked-on crud around their bases.  I could  then fill the block and rad through the open thermostat housing before refitting the thermostat ("top" to top)  with a new gasket (no sealant) and topping up through the access plug.

Run the motor,  check level,  then replace the plug and run it up to temp (thermostat opens).  Allow to cool and check level via access plug. Again.

I had intended to use some K seal if the rad still leaked, but to my surprise the new otter switch seal has so far cured the problem.

I can also say I have improved the heater no end...  Not through the flushing, but because I hadn't appreciated that the water valve only really opens in the last few mm of its travel.  Mine wasn't set right and left about 0.25cms of movement when the cable was tight.  A simple matter to adjust the position of the solderless nipple on the cable and sorted!

Nb I had bought a "winter" thermostat with a higher opening temp.  This however also lacked any bypass hole and so filling with the thermostat in place would be impossible.  I refitted the old one and Im hoping that the water valve adjustment will be enough to restore heater function.