Back at it this morning, restocked with 2 x 12oz cans of R134a. Did not go as expected. Around half of the first can in (so around 500 g/ 17 oz total added) and pressures are on the high side, especially the high side of the system. pressures were 50/270 with an ambient air temp around 90F. I stopped there, after all the warnings about not over pressuring the system. Not idea how much was in the system when pressures were 0/90.
When i first came out, air temp was round 75F and the pressures were lower than at the end of work yesterday, 25/120, not the 35/145 from yesterday. I am attributing that to the lower air temp, and hoping it is not leaks (no sign of dye leaking, yet).
Inside the car, the lowest vent air temps are around 75F. An improvement, and quite pleasant, but not as cool as it should be (for comparison, I fired up the 2004 XJR and got 53F (temps measured using a laboratory grade mercury bulb thermometer - the cheap IR thermometer read constantly lower, and gave different readings at different distances from the target!)).
Hottest temp in XJ40 for the air at the face vents was around 120F.

I had a look at the vacuum operated hot water valve on the engine side of the bulkhead. The hose feeding it from the engine looked a little kinked. IR temps there were 158F on the hose connected to the valve and 176F on the hose immediately behind/below it. The hose feeding the main radiator from the engine was at 180F at this time. Seems like the difference in temp between the two valve hoses is because water is flowing into the cabin and being cooled in the air flow before returning (or is it just that the blocked flow with the valve closed has passively heated one hose more than the other?).

On the visible side of the valve there is lever coming from the vacuum chamber that pivots another lever that is screwed into the valve assembly. I assume changing vacuum makes the levers change position and so switch the water flow? I did not see any change in the lever positions while experimenting with different target temperatures. One remained vertical and the other was around 4 o'clock position. I sprayed lubricant on them and will research testing the vacuum and the valve for operation.

My hope is that it is stuck open, either seized or lack of vacuum and therefore hot air is constantly being blended with the cooled air and so 75F is the current lowest.

Once the car has cooled, I might look at bypassing the in dash radiator for now, long time to winter, and see if that helps.

I will also monitor pressures and temps over the next few weeks and see if there are leaks in refrigerant. Might start saving the pennies for a vacuum pump, scales and R134a tank and do it all from scratch.

Thanks for the suggestion for alternative refrigerants, not sure what is legal in California, and with the system already converted for R134a, I might just stick with that for now.

 

Took the hot water valve out today. Default position seems to be wide open, and sucking on the vacuum port swings the valve shut. Pushing on the lever makes the valve swing quite freely, so I am going to deduce that as a working valve and now reason to swap it out. The vacuum system now becomes the prime suspect as.....I used it as a union to join the supply and return hoses together, bypassing the interior heater matrix such that now there is no heating in the car.
Much improved, air temp at the dashboard is now down to 53F.

My Mastercool gauge set came with no o-ring in the high pressure adapter, and the replacement, other brand set seems poorly engineered and the ball bearings do not slide back in to release from the port, so I cannot take a high pressure reading until my new Mastercool o-rings arrive. Low pressure was around 42 though, with ambient temp around 82F, so room for a little more refrigerant maybe, but I will wait until I can get a high pressure reading too. I am edging closer to buying scales and a 30lb tank.

Fan speed definitely changes as the control is moved, and I verified that both fans are running, but still not as much air flow as a more modern car. I think I need to find a local car to compare and contrast many things with!

So, I need to research testing the vacuum pipe/controller and then there is the leaking fuel tank, dead hifi and one dead electric window, but we are getting there, one problem at a time - and learning so much :-)