Hi there,

I'm getting ready for when my water pump comes and need to do some work on the bypass pipe, as it seems to have had a problem with sludge from coolant mix...

In the bypass pipe is a little bleed valve/one way valve, for air to pass into the fill spout from the radiator.

As it is all clogged up, I want to replace it (I already have the replacement part). How is it best removed? It is pressed into the little pipe so it looks awkward to remove!?

Any tips?

And also, I want to check that the engine is waterproof when the pump has been fitted. My plan was to block the heater pipe (rear left water rail housing), seal the thermostat openings and block the intake to the water pipe with tape or so and then fill it all. Like that - at least by my ideas - I would be able to see where the engine MIGHT leak (after changing all the gaskets, I want that to be right).

Would you do it different?

Cheers

Damien

 

Daim
I would forget the leak test. As long as you have installed all the bits carefully, it will be fine, and you can never reproduce the running pressures properly in a cold engine anyway. As long as the mating surfaces were clean and the gaskets new, you will be fine.



Concerning the crosspipe and filler spout, this is what I did:

• drill out the crud from the spigot at the top of the pipe.
• buy the special pipe that goes to the RHS banjo connecting pipe. This is wider at the spout end than the banjo pipe end. It is still available but dear at 20 quid or so. Alternatively buy two separate diameter pipes and a step down brass hose joiner. The valve will press nicely into the actual rubber pipe just after the spout spigot and work perfectly there.
• Also buy the Jaguar non-return valve, still available and dirt cheap.
• Now the interesting bit: there is a huge correspondence on here and elsewhere about WHICH WAY ROUND this valve should go. Should it allow water FROM the banjo TO the spout, or should it allow water FROM the spout TO the banjo bleeder? This is something that AFAICR Doug, me and the Great Palm agree on (not that I put myself on par with those two gurus, I hasten to add). We three say it should allow water FROM the spout TO the banjo bleeder; thus ensuring no build up of trapped air in the spout. This has to be correct in my view.
• The Great XJS Prophet Grant Francis says forget the bloody valve entirely! and he knows what he is talking about for sure. So it is one or the other!

Greg

 

Well, cheers Greg!

I didn't want to really pressurize the system but more so just do a leak check. I really don't fancy diving into the engine bay again in a few years time when the engine is ready to run to find that many gaskets are leaking...

I've cleaned all the surface areas and made sure, that they will stay clean BUT I really want to make sure no water can escape...

Regarding the little valve. Already bought and it was supposed to be fitted today but I can't get it out. As far as it looks, it has been fitted correctly, allowing air out of the radiator but water not in... So that way it should work...

Isn't it against it's principle if the water can flow FROM the spout TO the radiator? That would mean, that air trying to escape from the radiator (from the banjo bolt) can't escape into the spout!? Making bleeding worse!?

I know that is a believer question but my common sense (at least if you want to call it that ) would say it is a bleeder valve and as it sits higher than the radiator, it should bleed from radiator to spout rather than from spout to radiator/banjo!?

 

aim

Your reasoning re: valve is faulty, I believe, because:

1. The water /air bleed flow is a powered bleed system. It takes air/water from the banjo, across the radtop pipe, TO the inside wing header tank, powered by a jet arrangement within the Y shaped bit at the LHS end of the radtop pipe. This jet is itself powered by a direct feed from the LHS water manifold which provides high pressure water which flows through a jet into an expansion area in the Y which creates low pressure at the expansion point and thus sucks air/water through the banjo bleeder. If you look at the Y piece carefully, you will notice that the bit nearer the centre of the car is a narrower pipe than the bit just after the radtop pipe joins to make the leg of the the Y. This diameter difference is the expansion jet part.
2. This system is required solely in the XJS, NOT in the later saloon V12s (I do not know about the series III V12s), because in the XJS Jaguar could not package a header tank in a position higher than the top of the rad, which would allow natural air bleeding - which is what happens in the saloons, as in all other cars, just about.
3. The crosspipe has a spout solely in the XJS V12 application for the same reason: a high point is needed to fill the coolant system from. Therefore, so my reasoning goes, the spout should not be a trap for air, otherwise the radtop bleed pipe system will not allow air to escape from the spout, where clearly it would collect and be trapped unless a way was found to release it.
4. FYI, you can buy a solid radcap from Car Builder Solutions which is, I believe, the best cap to use on the spout. The normal pressure cap with spring valve has no use in this application, as above the valve the water just goes into the bleed system and does not relieve any system pressure

FYI, on pre ABS cars ONLY, it is possible and relatively easy, to do away completely with the radtop bleed system, the OEM header tank and the spout on the crosspipe. This is done by removing the huge screen washer reservoir, installing an aftermarket header tank in its place and fitting an aftermarket screenwasher tank and pump into the wing cavity. Then fitting a 90 degree bleed connector into the LHS radtop solid bleed plug threaded hole, to bleed the rad into the new header tank uphill from it. Fit the removed solid bleed plug into the banjo hole. Remove ALL the flexible pipes to the radtop pipe and the pipe itself. Swap the crosspipe for a non-spout saloon version. Then (as done by Ronbros) the new header tank's main link to the entire system is connected to the heater return pipe just below the new header tank. This does away with the following difficulties:
The radtop bleeder with all its connections
The spout (new non-spout crosspipes can still be found)
The spout bleeder pipe and one way valve
The question mark pipe from the crosspipe to the OEM header tank in the inner wing
The OEM header tank can be replaced by a much more accessible catch tank if desired. But the system will not need one as the expansion space can be part of the replacement header tank as in many modern cars, as long as this tank is made large enough
The cooling system fills like an normal car's system with no special bleeding procedure on filling needed
The many pipes and joins and wormdrive clips associated with the bleed system are eliminated and coolant loss with it.
etc etc etc !


I actually know someone who has done this and the engine cooling is definitely better, I presume because air is absolutely absent and all sorts of turbulence is removed. The engine bay is far less cluttered and more accessible. Also the engine is noticeably QUIETER for reasons I do not understand. Sadly, you ABS boys have probably not got the space to do this demon mod in!
Greg

 

Greg, thanks for your explaination... But again, where does the air, which is in the lower radiator go? There is always air somewhere. When the engine is off, the air in the system will find it's way to the highest point of the system, which is the bypass pipe spout... At least as far as I can remember (my engine has been in parts a little to long now ).

As my bypass pipe is factory still and has the "one way" valve opening into the spot rather than into the pipe towards the rad, I think I'll fit it that way too

I'd love to ditch the system and use one a lot better (starting with a clear water bottle so you can check the level without having to put a ruler in - dunno what Jaguar did it this way. The X300 has a black header tank, the X308 has a black header tank, I assume the modern ones too. I'm used to clear/milky plastic ones), but I'm really limited to my conversion possibilities...

 

Daim
The question you must ask yourself is: "If the spout fills up with air, how can it be purged by the bleed system?". It can only be bled out via the radtop extractor system. My view is that the one-way valve if inserted your way, prevents this. The entire fundamental design problem with the XJS coolant airbleed system, and the reason for the radtop bleed pipe extractor, is that it has to pump coolant air into a low place (the header tank) before it can be purged out of the system. Therefore I hold that ensuring a non-purgable space in the spout traps air is defeating this aim.
My experience is that with the valve allowing fluid out of the spout there is no air left trapped in it; with the valve reversed, plenty.
Anyway, as your system was completely blocked, like almost every other car that has never been serviced in this matter, and as your and all these other cars seem to work perfectly well, with or without a valve, regardless of its orientation, I do not suppose it actually matters much!
We now have three topics nobody agrees upon on the Forum; Brake pads, Oil and now the one way spout spigot valve!
cheers
greg

 

Greg, thanks for your insight. I agree with most with you, but my stubborn brain draws a few connections... Like to my XJ8. The water bottle is the highest part of the cooling system and always has air in it... And you can't purge it from there either... But then again, this is I think a belief...

I think there will be many other topics with no central agreement Like leapers yay or nay?

 

That is the whole point, Daim. On modern cars, the header tank is at the highest point AND is deliberately made large enough so there is by design an airspace in the top. Thus, as the coolant expands, excess air is expelled, as it cools, air is drawn it. Then an atmospheric catch tank is not needed, and costs and complexity are reduced. The XJS problem is that the purge point (the wing header tank) is NOT at the highest point, and the highest point (the spout) has NO purge if you fit the valve the "wrong" way.
Yes, forgot about the Leaper: Four topics now!
Greg

 

The XJ8 still has the atmospheric catch tank... I'm not kidding... Bit that is all besides the point...

How would you remove that little valve? Can't remember if you wrote that or not

 

Just drill it out of the spigot, then fit the new one into the flexible.
Greg

 

That would be for environmental reasons, as a belt and braces make-spillage-imposible thing, rather than because it is necessary to ensure the system always has enough water in it. In the XJS, Jaguar did not want to risk the header tank going dry, as it is mounted so low down. Hence the atmo tank which (although it always fails, splits and often the pipe to it is blocked) is meant to ensure the wing header is always 100% full.
Greg

 

Ah, ok... I had never encountered an atmospheric in any of my cars before. All of my former cars had a fully closed and selfbleeding setup...

 

That is the reason for doing the mod that I outlined in the second half of my post number above (post number 4). That mod makes the XJS cooling system just like a normal modern one, and just like the V12 saloons' system. The XJS V12 is the only car I have ever come across with this venturi-powered airbleed system - which (takes cover from incoming) is at best a guastly lashup, compared with a normal cooling system. Too bad an ABS car would have a problem finding room up by the firewall for a header tank.

Greg

 

There should be space for a header tank on the passenger side where the ABS pump is. That area is 'less densly populated' compared to the driver's side. Though it would have to be a small pot and would require a lot of plumbing and hoses...

 

The header needs to be about 2.5 litres, shape does not matter at all as long as the bleed inlet at the top is higher than the top of the rad. Plumbing required is:
One bleed line from the rad (steel 6mm tube along the inner wing top apart from the joiners).
One short connection to the heater return (or feed, does not matter, just the nearest engine coolant connection available for the main tank/engine connection)
One connection to an atmo tank (if you bother to fit one).
Plumbing lost is:
The radtop pipe, the banjo, the spout and its pipe, the venturi power and return pipes, the question mark pipe. That's lose 7 put back 2. On ABS cars, Jaguar has already moved the screenwash reservoir for you! My mate who has done this told me that relocating the screenwasher was the hardest bit of the job!
Greg

 

FWIW, I ended up troubled, torn, and distraught..... so I took mine out entirely. It felt a bit cowardly....like I was running away from the issue rather than facing it head on

All's well so far....although I have only 3-4 hours running time on the engine.

Cheers
DD

 

.

Diam; pic shows where i put my high up plastic expansion tank, like any normal cooling system ,it always has about an 1" of air to allow for coolant expansion when engine comes up to temp. it is a sealed system, pressure cap, no over flow, 22yrs and it gets HOT in Texas summers.

the tank inlet connection is just a 3/8" hose from the left side rad outlet(no valve). the lower hose goes in where the factory hose went 1" inside diameter. all air bubbles would go to the tank, and coolant settle to bottom,air stays in expansion area!

this type system should never be filled to the top, heat would expand coolant and burst something someplace.

 

my tank is for a 1975 era VW petrol car.

has a small top inlet barb.

and a large bottom outlet barb.

 

Too big for an ABS model. That area has the ABS pump...

 

move the ABS system elsewhere, or use a different type ABS.

what would you prefer an overheated V12, or a change of ABS?

one of my vehicles has ABS, and it has kicked in ONCE in 15yrs!