So I had a go at using my 96 automatic disco 1 to help pull some piles out of the ground one hot day a few weeks back. I don't think the temp gauge read hot, but all of a sudden I realized the coolant was just pissing out. I couldn't precisely tell where it was coming from, but it looked like the reservoir tank or a hoses immediately coming off of it. It definitely wasn't coming out of the radiator itself. After it cooled down and I opened the tank, it was completely empty and I couldn't find any indication of a tear or the hose as I was hoping would be the case. Any ideas where to look or what might cause this? Cheers.

 

stock coolant tanks were notorious for the seam splitting under pressure. Hard to see when they cool down

 

i didn't mention that i then refilled it with water and drove it around a bit to see about a tank or hose split and there was no leakage. obviously i wasn't pushing the truck hard, really just got it running so in hopes that the leak location would be clear, but there was nothing obvious.

 

Besides the expansion tank seams splitting check your fan clutch, two most common problems with the cooling system. Check your oil, make sure it doesn't look like a chocolate milkshake, good precaution after an overheat. Your not seeing it leak doesn't mean it isn't going somewhere.

 

Tank will only leak once the system builds pressure. if it is split, it won't build pressure. Been there.

 

So true I had the same problem a couple of years ago.
I replaced everything but the expansion tank, and come to find out the issue was the expansion tank. They are no expensive to replace, while your at it make sure your exppansion tank has a good cap with seal. Once I got everything back together I bleed the system and everything was good to go.

 

Hello,

About my Disco Tdi 300 (may 1998)

Yesterday, I found out where my coolant tank was leaking ; by loosening the 3 retaining nuts and tilting the tank, I saw drops of coolant liquid under the seem at the rounded front outside corner. With the 2 horizontally aligned nuts firmly fixed, I saw that de holes in the coolant tank body and in the lower bracket aren’t flush at all, they are misaligned : the center of the hole in the tank body is about 2 mm higher and about 4/5 mm more to the inside of the engine bay. If you try to get the fixing bold in here, than you must push (bent) down the inside part of the tank and press firmly (squeeze) the whole tank against the upper bracket. It could be possible that these permanent external pression gets tension up the horizontal seem, and when the internal pression of the coolant system builds up when driving, these find a way out through the weakened seem. So I replaced the lower fixing bold by another with half the diameter and a pair of adapted washers ; so I could fix the thank without pressure. Know I’m waiting what will happen.

Kind regards,
Pierrodisco

 

The coolant tank is pressurized same as the radiator, which is why it has a pressure cap that opens up when it has too high of pressure. If they leak, you will see higher temps and lose fluid, eventually blowing the head gasket (and more) I would spend the time and funds to replace it. Been there!!