After reading a bit in Palm’s book he mentions the issue with the radiator.
Wouldn’t a simple cross feed hose / tube (1/2in id will suffice ) between the B bank thermostat outlet and the A bank thermostat outlet solve the issue? It would balance out the uneven back pressure between the two outlets under all conditions. The bypassed fluid will see less cooling as it will enter the 2/3 portion of the radiator , so total temperature will have to be monitored but I think that a crossfeed would be helpful. Any thought ?

 

Another way to do it is this:

https://www.becool.com/product/radia...-cool-radiator

Jeff H.

 

Went that thought path waaaaay back, before Computers and associated stuff.

My Rad guy, maintained the Road Train Radiators, reckoned it would be counter productive. Cross flow radiators silt up from the bottom,ANY BRAND OF MACHINE, its gravity and design. So, 5 yearly "tanks off and flush out" will keep it sweet.

That is the path I took. I know removing that Radiator is a 5 minute task, and most owners dont want to waste that Beer Drinking time.

I have never had an issue, even with the Carby thing back in the day.

 

Yeah that’s the way to go for sure. I don’t like to add a bunch of new stuff in it. I keep it original. Coolant filters or a bypass hose is all I modify. This xj12 is pristine and has been very well kept.

 

The OEM radiator design is perfectly OK if functioning properly. If it is not so functioning, it is nothing to do with the internal design of the radiator. It will be one or all of the following things:

• rubbish building up in the external fins of the radiator, condenser or oil cooler
• fan hub torque thingy gone home
• radiator internally blocked
• thermostats not working
• pump not working.

This explains the fallacy of the single pass idea:
https://aj6engineering.co.uk/v12-radiators/

What IS an improvement is the so-called Lutz mod. When cooled coolant enters the head from the water pump (engine warmed and thermostats open) it enters heads of the engine at the front and flows along and through the heads, then out through holes in the heads into the water manifiolds, one at the front and one at the back of the heads. The front and back manifolds are connected by a pipe between them. Each manifold has 2 holes that allow the cooled coolant to exit the head into the manifolds and thus though the thermosats to the radiator. These holes are the same size
This famous Australian racing and V12 engine guy Norman Lutz calculated that because these holes were the same size, cooled coolant having entered the heads would tend to preferentially exit through the front water manifold (and thus go back to the radiator) leaving the rear of the engine less cooled as the flow to the rear of the head would be reduced by the coolant finding an easier path 'short circuiting' though the front manifold. This does not matter at normal speeds but does at higher speeds and load - which 99.9% of engines never see.
The solution is to reduce the size of the front manifold water holes thus forcing more coolant to the rear of the engine by making it harder for it to exit the head through the front one.
I have proved this works, because I have done the mod, and afterwards the gauge read higher than before, this because the gauge sensor (which is in the front A bank water manifold) was no longer being preferentially cooled. Some photos:

Water manifolds and connecting pipe. The A bank thermostat housing is visible on the right manifold

Close up of connecting pipe

Un-modified front manifold

Modified manifold to reduce 'short circuiting' of coolant through front manifold. Many thanks to Monsieur Loriau whose enterprise Lortec did this work for me.

Rebuilt afterwards

 

This is the idea of the crossfeed line. 1/2in id in Red. Balancing the pressure differential between the 2 outlet hoses.
I understand the Lutz mod of internal flow preferences, but this (red line) focuses only on the external pressure differential. The Lutz mod is of course a much more effective solution but for my top speed of 60mph (low rpm) probably not needed.

 

I agree with Grant's point on your other thread. The cross pipe is already doing this to an extent, plus the air purge system also. I think this idea, providing a much greater crossflow might well short circuit, or even stall, the flow to the radiator from one side or the other. I cannot see how it would improve cooling. This, however would:
See post 22 in this thread, plus in the thread various data on under bonnet temps.
https://www.jaguarforums.com/forum/x...-166641/page2/

 

Thanks for all the info. Good to read that cam covers get to 95c. That seems very hot , but if it’s normal it’s normal.

 

Oil needs to be at that sort of temperature to perform properly.

 

oil or cam covers ?

 

It is the oil inside the covers that the temperature represents!

 

so cam cover temperature = oil temperature
no heat loss ?

 

Yes. Oil temp at the top of the engine. No heat loss, as in the oil temp is pretty constant at a given engine load, standard atmospheric temperature and pressure, etc etc. Of course the heat you detect IS heat loss, obviously, but remember that the engine is an oil and coolant heating machine, the radiator and oil cooler, radiant heat loss from the engine exterior, etc etc. keep these temps within allowed parameters if all working as it should.