Greetings

Assistance with understand the following, please.

Right side top of the radiator is a banjo fitting, with two outlets to three expansion lines.

One goes to the filler cap on the right side of the engine.

The other runs to the left side and splits into the expansion tank and the block.

Why does the expansion line run to three different points….? And is it really necessary that its run this way….?

I need to replace the metal tubing so would like to understand this set up before I do.

Many thanks

Darren

 

its mostly for bleeding air around ,

and if and when the water does expand its an escape route

just replicate what is original, and everything should work fine if the correct filling procedure is followed

BB

 

Yep,

They are air purge lines, and the V12 creates plenty of air just being what it is.

That banjo bolt needs modifying whilst in there.

I would also replicate what is there, as it works and works well.

Overheat a V12, and the national debt will seem very small. Hotspots also reek havoc, and that system bleeds that air out constantly, so no hotspots.

 

Hi Grant,

what are the mod's to the Banjo Bolt...?

Thanks

Darren

 

This is the engine and radiator air bleed system. Because the radiator top is lower than the engine, there has to be a system to purge air from the entire system,as it will not automatically collect at the filler cap. It works as follows:

The banjo you refer to allows any air in the rad to escape into the thin line across the rad top. The rubber line from the central filler spout to the metal pipe that goes to the banjo allows trapped air to get out of the spout and into the thin metal line.

The double pipe at the LHS that is joined to the thin metal pipe running across the rad top is the "motor" for the purge system. If you look carefully you will see that one end of this two is wider than the other, and the diameter chnages about in the middle where the thin radtop cross pipe joins it. The thinner end is connected to the water pump and takes high pressure water from the pump. Where it joins the thicker end inside (and the thin radtop pipe joins there too) it forms an "escape jet" at the join. This means that, because the water is suddenly decompressed it creates a low pressure area that "sucks" air and water from the radtop thin pipe and thus purges any air in the system. Technically it is a 'venturi', remember 'ground effect' Formula One cars? same thing.

So to ensure the system operates as required:
1) ensure the spigot exiting the centre fill spout to the rubber pipe is free flowing (often blocks itself, drill the blockage out carefully if necessary).
2) ensure the pipe is free to the banjo. Jaguar fitted a small non-return valve into this rubber pipe (allows flow TO the banjo, prevents flow FROM the banjo to the filler spout) which is still available and cheap, but the acknowledged expert and fellow Aussie Grant Francis says this is not necessary, and he knows best, believe me. Will not do any harm though!
3) ensure the banjo bolt is not blocked (often is) and that the banjo ring lines up properly with the banjo bolt holes (often do not because washers are the wrong size etc etc)
4) ensure you can blow through the thin pipe and the venturi system pipe on the LHS end and that all parts of the Y they form are clear.
5) ensure the rubber pipe FROM the thicker end of the venturi pipe TO the overflow tank on the wing with the pressure cap is clear.

Having all this working is essential to ensure the V12 with this configuration purges air properly.

The thin pipe that runs across the radtop is pretty fragile and NLA. You can safely replace it with a decent flexible strong walled pipe, as long as you retain enough thin pipe where it joins the steel banjo bits and the venturi bits and connect to them securely.

Greg

 

thanks one again to all for all of the assistance, will make sure is as advised when i make up the new pipe.

all good

Darren

 

Here ya go.

Need more, ask, got heaps.

Bleeding the V12 cooling system.doc

Those drillings MUST be elongated, and there is no "near enough" with that thing.

 

So when I find that pre 1980 XJS with the quad headlights and a tasteful little leaper at less than 7k ,not too far from home GF will be my first stop?...this bloke just needs to drop the price and I go from tyre kicker to serious looker!

Colour is only an option if you are buying a 2015MY car!!!!!


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thanks again....absolute gold....will be up early in the morning to look at the "atmospheric tank"...now i know it there, hidden inside the guard.....!

 

Interesting front bumper treatment.

Just make sure it is an Aust delivered car, as there are a lot of Private Imports, mainly UK, getting around, and as good as they may be, there can be issues. Rust is one, particularly the PreHE's.

Top side, is that 1980 was the year that a few of the 10:1 comp cars got out, and those suckeres Mumbo.