How a rusty XK engine looks inside, when you remove the core plugs.

 

A lot of people complain about old Jaguars over heating and this helps to explain why. The radiator is going to be blocked with that stuff as well.
Fitting a Kenlow fan to this engine is not going to help an awful lot is it which is why I dislike them so much. Fix the true problem first before sticking a Kenlow on your Jaguar.. When new Jaguar engines were not full of this rust and surprisingly did not have an over heating problem.
My engine on strip down was relatively clean but I still found this in the water pump housing and it took several minutes with a high power hose to wash all the crap out of the block.

Dirty water pump housing on a 3.4s XK engine.

 

Yes ~ trying to fix the symptom instead of tackling the core problem is a common trait. If you are doing a rebuild dump the Block & Head in appropriate chemical baths to clean completely.

If not rebuilding ~ depending on severity because there comes a time that the engine has to come apart. Flush your system with citric or acetic acid (vinegar) until the water runs clean. Fill with a modern longlife OAT or HOAT coolant. Be warned that these coolants will further clean the system. If they don't stay clear & bright do another flushing cycle.

 

In our 100,000 miles (and I understand the PO's 30,000), my Mk2 with a totally OE cooling system never overheated. Driving included sustained high speeds on the German autobahn and the Italian autostrada in the Apennines and climbing Swiss Alpine passes. Without a catch tank, I always topped the radiator every morning (and the engine oil). Neither did it ever suffer a burst water hose or any water pump failure.

The only maintenance to the cooling system was a flush every 3 or 4 years and a refill with 50% anti-freeze and a bottle of the old style Bar's Leaks (I wouldn't use it these days as the more recent versions seem to cause a mass of problems).

When I get around to that stage of the re-build, I might well fit an electric fan and water pump. Why? Because it's possible, interesting, better (possibly). It would free up some space. And I'm sure Bill Heynes and Wally Hassan would have tried them.

 

While I don't recommend stop leak products in the cooling system because they can plug things you don't want plugged. If you must then Bar's latest Aluminium product is favoured by many. Old Bars Leaks had a shocking reputation in SA to the degree that Silverton Radiators would void their warranty if used. Even new Jaguar Welch plugs properly inserted have a habit of weeping slightly. So maybe a little is acceptable & flush the balance out at a later stage.

 

I think the Bar's Leaks from 30 plus years ago had more anti-corrosion and water miscible oil and far less gunge/gunge generator than the most of the more recent types. I presume Jaguar advised it because of doubts about the anti-freeze products that might have been used or not used in the distant past. Many people in warm climates thought anti-freeze unnecessary. I don't understand why Bar's Leaks changed their formulation. Perhaps the old stuff doesn't seal leaks in modern higher pressure systems?

 

I really don't know. Different experiences from different parts of the world.