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Discussion Starter #1
I THINK the tank is leaking, the center depression always is partially filled with coolant. Is this because my cap is leaking or is releasing pressure?

Also, the switch in the cap no longer functions, the dash light was flashing continuously for weeks until I hot-wires the 2 leads together that plug into the cap. Yes, the tank was at the correct level.

I see aftermarket aluminum tanks on ebay for the price of a replacement cap. Sounds like a valid upgrade, anybody use one?

I figure it would be no different than the good old days when you actually had to look under the hood to check coolant level, kind of like I have to now with the cap wires jumped.

Mostly wondering why my coolant tank has coolant in the center depression.
 

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The coolant is getting in the center depression as it it overflowing
The system is closed so the cap shouldn’t leak
It can cause overheating
Lao I think the metal coolant tank is for older models
 

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Big question - is your coolant expansion tank the original “black” one? If so, they fail, usually along the seam joining the upper/lower halves. I suggest you get a new “white/opaque” replacement.
 

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I had the same issue with my '91, where there was always a small pool of coolant in the dimple on top of the expansion tank.
It went away after recoring the radiator and replacing the water pump, thermostat, and coolant hoses.
Unfortunately I have no answer for what specifically was causing it, but it hasn't reappeared since.
My guess is the radiator; it's amazing the old one could move water at all, and maybe it was causing excess pressure buildup in the expansion tank.

If you're considering upgrading your cooling system, I've always relied on some advice from the Arizona LRO page: http://www.azlro.org/chad/rrcadvice.html
I'm still using the original black expansion tank, but Allisport makes excellent replacements from 2mm thick aluminum: https://www.allisport.com/model-series/range-rover-v8/
 

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Buying a new radiator is the best thing I did for my '83. I was going to have the original overhauled and found it had cracked as well. Then I could not find a radiator shop and then found new aluminum radiators are cheap and plenty available.

Cooling capacity of a new radiator is just amazing!

I do agree when people say radiators are like batteries an expense basically.
 

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Discussion Starter #6
My coolant tank is white opaque.
I have been considering a new radiator for years, but there have been no symptoms of overheating, at least not indicated by the temp guage. And the temp guage DOES indicate an overheat condition; I blew 2 hoses many years ago, and as I saw the steam and coolant spraying out going down the road, the temp guage was pegged.
I still want to replace the radiator, but does the coolant-tank cap release pressure, like an old-school radiator cap, as part of it's normal safety function?
 

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No it doesn’t have a pressure release....
Take the radiator to a radiator shop
They can tell you if it’s clogged
 

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As the other poster's advice, I'd too try to verify you radiator condition.

The original system cooling spec is a fairly high capacity on these, usually making it quite a distance into impairment before you see any real obvious signs of it generally.

The radiator can be affected by reduced flow internally, usually created by using a system sealant that ends up resident in the fine radiator cores. Or using it without corrosion inhibitors / antifreeze, resulting in system corrosion. Aluminium oxide is a pretty simple way to reduce radiator effectiveness. Both of the above are certainly at odds with running this system to its best.

Another is if the radiator has been in there a long time, the matrix just gets blocked externally with general debris, especially at the lower regions. They just sound different when running with the airflow clear as it draws so much more air straight through it rather than just churning it around inside the fan cowling.

The temperature guage gives clues rather than shouts about things in my experience. Generally it'll run juuuuuuust under halfway and be repeatable at that If healthy. If it runs just onto halfway or slightly above, then that's usually it's first indication that something is wrong, just a few minutes of arc to the hotter consistently and it's really telling you something.

Although as you found, if it definitely says really hot, for sure you're in trouble.
 

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Discussion Starter #9
No doubt it's time to pull the radiator, but regarding my previous question about the coolant-tank cap providing a pressure relief: Is that how a "modern" closed cooling system in a car operates? No relief valve?
 

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Yes that's correct, there's usually arrangement that allows you to open the cap safely by about one turn to let it bleed pressure out but that's it.

Significant over pressure is ultimately dealt with via the core plugs failing if that eventuality arose. I've never seen that though.
Check that the two small hoses connected to the top left of radiator are going to the right destination as they have different internal levels inside the radiator, one to the expansion and one to engine manifold. These assist the self bleeding of airlocks while the system is closed and can give problems if swapped.
 

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Yes....
I have also have a 04 Ford f250
It has a closed system
The good thing about the rover is the radiator is easy to remove
The bad
No drain cock
On my 91 when I removed the radiator
It was clogged with unseen crap
 
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