Jaguar XJS 3.6 1989 manual
Gauge reading is below normal when driving, when i switch off engine water is forced out into atmospheric tank and sucked back in to header tank but i loose more water each time that happens. when i check the header tank it is full to the neck, seems it does not refill the system just the header tank

 

Hi Jeff,

I'm slightly confused.

By atmospheric tank I presume you mean the one under the front wing and by header tank the one in the engine bay? If so, and the header tank is full to the neck with a cold engine (which is as it should be), how have you concluded that the system is loosing water?

Cheers,
LeeP

 

Hi Lee fitted the tank back in the wing which does work but more water is pumped out than sucked back in, when cold the header tank is full to the neck. When i fill the system up with water i have to take off the small hose to the switch in the middle of the injection assembly which the last time i spoke to you was blocked, its now unblocked, so there is something thats stops the water from passing back into the engine from the header tank, the 6 cylinder engines should self bleed i believe. while running the temp gauge is reading between cold and normal. Another clue is when i switch off the motor i hear a gluck gluck noise as if air is trapped in the system.

Jeff

 

What "switch" on the engine? Have you a photo? Do you mean no. 13 in this diagram?
https://parts.jaguarlandroverclassic.../brand/jaguar/

Is there a vaccuum developing in the system when the engine has cooled dow after a run? ie when you undo the pressure cap does air hiss into the coolant systerm?
Secondly, is the level of water in the header tank right up to the top of the tank when the engine has cooled down after a run?

 

Hi Jeff,

Are you sure you have the correct pressure cap on your header tank?

It is not only a question of pressure rating but I believe that the correct cap has a two-way seal allowing coolant to flow out to the atmospheric tank as the engine warms and back the other way as it cools. If you are not sure I will check the part number on mine as I replaced it a couple of years ago.

Cheers,
LeeP

 

The cap is a jaguar 16 psi original new old stock

 

Hi Greg

I called it a switch because thats how it was explained to me , it has water on one side and air on the other connected to the air intake

 

Is there a vaccuum developing in the system when the engine has cooled dow after a run? ie when you undo the pressure cap does air hiss into the coolant systerm?
Secondly, is the level of water in the header tank right up to the top of the tank when the engine has cooled down after a run?

 

Hi Greg no there is no vacuum more often there is pressure and the water level is up to the neck of the tank when cold.
On a 3.6 engine it should self bleed but i have to disconnect a small bore pipe to allow it to fill up, the thing is why does the header tank not drain water back into the engine

 

You replied
"On a 3.6 engine it should self bleed but i have to disconnect a small bore pipe to allow it to fill up, the thing is why does the header tank not drain water back into the engine"

Which tank do you mean by the "header tank", the actual correctly-named header tank (ie the tank with the pressure cap on it) or the overflow tank, the correctly named "atmospheric tank"?

OK
1) Which pipe do you have to disconnect to allow what to fill up?

2) If the pressure header tank is full to the brim when cold, the engine having cooled down after a run, it would seem the pressurised coolant system is OK. Are you saying you are worried about the overflow atmospheric tank? If so, what exactly is worrying you?

Sorry if this sounds like I am being repetitive, but I cannot fully grasp the problem or the symptoms you are describing.

The "switch" item is nothing to do with your problem, by the way, it is a water heated device for the PCV/inlet body, I read.

 

I remove the small pipe from the PCV/inlet body to fill it up, the problem is the amount of water it loses after a run when i turn of the engine.
This afternoon i ran the engine with the cap removed from the header tank until it reaches normal temp reading, I can see air bubbles coming up into the header tank so i think it has something to do with air trapped in the system. while i am driving the temp is between cold and normal, the viscous fan is actually engaged all of the time

 

Jeff
I still cannot grasp what you are doing? Can you post a photo or video of which pipe you are filling. If the system is working correctly on the engine then you should only have to fill the header tank. You should not have to disconnect anything.

Can you clearly answer the questions I asked above:
1) Which pipe do you have to disconnect to allow what to fill up?

2) If the pressure header tank is full to the brim when cold, the engine having cooled down after a run, it would seem the pressurised coolant system is OK. Are you saying you are worried about the overflow atmospheric tank? If so, what exactly is worrying you?

I suggest if all else fails that you buy something like this, or ask a friendly garage to do it for you, and pressurise the system cold. It will immediately show what is leaking.
https://www.amazon.fr/DHA-radiateur-...%2C152&sr=8-15

 

The pipe i remove is the pipe connected to the PCV/Inlet body remember the photo I sent earlier.
There is no leak in the system.
Water is lost out of the Atmospheric Tank only, water dues get suck back to the pressurised tank when it has cooled down , full to the neck, but engine is low in water which means i need to fill up with about 2 litres of water this is why i remove the small pipe to allow air to escape.
I think the system gets air locked which stops water draining back into the engine from the header tank.
I have fitted a new water pump cleaned both radiators and all the external pipes cleaned, system flushed with bicarb/white vineger, if i drain the water out of the car it comes out rust free and clear. I read an article regarding engine flushing products the one with the best reports is Thermocure Evapo flush which is non acidic and can be left in the engine for up to a week