Possible overheating problem

I had a similar problem, only got hot towing up hill or if the weather was really hot, eventually after checking everything and finding nothing wrong the radiator burst climbing a motorway sliproad with a defender on the back, new rad cured everything

sierrafery said:

As long as the system is OK there's no reason for coolant nor air to be released through that valve so once it worked as to make the hoses to shrink there is a problem already. In normal conditions the pressure in the system doesnt exceed 1.2 bar to activate that valve

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Quite and that is what it is designed to do. But if the driver doesn't realise what has happened or does, but is too thick to do anything about it, he deserves what he gets, I suppose.
Even if all you do is take the cap off and put a bit of plain water in, with the engine running, you will save the system, unless the leak is catastrophic. In which case you shouldn't be driving it anyway. Oh and leave the cap off to prevent coolant escape just watch the temp like a hawk!
Have had to do similar in the past, have already related here my story of having to pee in the rad, in an old Mini!

sierrafery said:

That's what happens, i've seen it myself

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Got you. So one way valve it is then. Thanks

NPG said:

Got you. So one way valve it is then. Thanks

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Looking at it again, there is nowhere near enough gubbins, or space for any, inside it for a two way.

Shows how one works and how big it would have to be!

Stanleysteamer said:

Shows how one works and how big it would have to be!

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Better not compare a radiator cap which is in direct contact with colant with an expansion tank cap which is a completely different thing with other purpose

sierrafery said:

Better not compare a radiator cap which is in direct contact with colant with an expansion tank cap which is a completely different thing with other purpose

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I wasn't comparing it with anything, I was simply putting it up so peeps could see the internal works of a two way valve cap. It does say quite clearly that it is a Rad cap!
To my mind there would be nothing wrong with fitting a two way valved cap to an expansion tank at all. In fact, if it also was piped up to yet another tank with spare coolant in it, it would work the way that one was originally intended to work, i.e. the vacuum would suck spare coolant in from the expansion tank. Or "Reservoir" as it used to be called. You will note the connection on the left hand side of the drawing.
In fact the modern method, although simpler, is not, in many ways as good. I'd rather have one on my D2 to protect the tank and the rest of the coolant system from being overpressurised by the atmospheric pressure in the case of massive loss of coolant. Then you would not see flexible pipes collapsing!
I think they are just saving a bit of money, but then you'll tell me the modern expansion tank is a lot more complex than the simple expansion tank used to be.
I built a system with a plain rad cap on the rad, no valve at all then with a two way valved cap on top of the expansion tank. This was normal back in the seventies, see Morris Marina for instance! This worked constantly to allow pressure to escape but coolant to re-enter the system under vacuum when things cooled down. Not that different at all from the system on the TD5 except that it allowed vacuum to draw air back in. LR could have done it but they must have saved a few pennies on the single valve expansion tank cap.
You only have to work for 5 minutes on kit-cars to discover that cooling the blasted things is one of the major problems with them, especially the ones that are copies of 1930s Roadsters etc! some even use computer fans!

Sorry to interrupt for this interesting discussion.... I checked the viscous fan immediately after driving when the temp is high. I filmed myself turning the fan with my hands and it felt a little too easy. What is your thoughts?
Dear sierrafery, i know you think my car is acting normal, i belive the tempratures are not abnormal high but i am going to say probably somthing stupid, i feel something is not o.k. i drove this car a year ago same roads and same climate and it wasn't like that. I feel like the temps climed by at least 3-4 degrees and i am afraid to miss somthing

Checking te fan was a good ideea, too bad i forgot to tell you that... the best test is to try to stop it with a rolled up newspaper with engine running when the radiator is hot. If you can stop it you need a new one.

I did that test and couldn't stop it. As i said, next step is probably check the rad

That fan would be moving very easily even when cold, but when it is hot? I would say that was too easy.
But would have to compare it with my own to be sure. Too busy today to do it for you but will do it tomorrow if you ask me to.
Looks to me as if the viscous part of it isn't working at all. BUT you need to have the engine at slightly over normal to get it to lock up, so if I was to test it I'd make a rad muff out of cardboard or something to ensure that not enough air can pass through the rad to keep it at normal temp. the viscous should deffo lock up then, but you may need two peeps to ensure you don't overdo the getting-it-hot bit!
I'd be inclined to take it off, fix it solidly to its bearing part using longer bolts, or a strap wrapped from a bolt to a fin or two, or something, (never had to do it so cannot tell you how) and drive around with it solidly locked to the drive. You can find ways to do this on the web.
If that don't cure your problem then it is something else.