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And then pulling up somewhere after a short drive and the poor thing looking like it's got a bad bladder. 😉
There is enough headspace in the radiator that you can fill it once, it will overflow after a heat cycle and then find it's level and stay there. No need to keep topping up and then have the car burp it out again.
It's supposed to be filled to the bottom of the neck, you can see the correct level when the cap is removed.
Park the car on a level surface to do this, rock the car gently from side to side so you can easily see the level.
This ensures that all the rad tubes are submerged in coolant and allows for the expansion of coolant with out it pissing fluid everywhere.
The rads' header tank is the expansion tank.
My experience was that, though the space in the top tank takes up most of the expansion, there's still a small loss of water, especially on a long fast drive. If you haven't added an overflow tank, it's essential to check the level regularly. That means every morning when you've done a decent distance the day before.
If you haven't added an overflow tank, it's essential to check the level regularly. That means every morning when you've done a decent distance the day before.[/QUOTE]
Did you put a overflow bottle on yours and if so how or what did you use?
My engine was completely rebuilt. The block flushed and cleaned. New radiator core and yet I still found that my coolant level was dropping after a good run out and every week I was having to add a litre of water or so to the radiator. On a really hot day after a hot run there would be steam emanating from the over flow pipe. The temp of the engine would be around 70 degrees according to the gauge when it normally reads 55 to 60.
So I fitted an expansion tank. First it was situated under the front wing and just consisted of a plastic screen wash sack. Worked fine but eventually with the hot and cold water cycles it split so I replaced it with a brass tank from an MGB. The tank was bought secondhand from EBay then stripped and polished. The bracket to hold it was bought from the MGOC site and is stainless steel, made specifically to fit this header tank. I converted from positive earth to negative earth which meant I removed the control box, the RB340, from the inside of the inner wing and this left a convenient gap to mount the tank. The tank is polished brass and matches the top of my radiator. Not had a drop of water loss since. I open the top of the radiator and the level is right where it should be on the filler neck.
This is the gap I had after the RB340 was removed. Gap filled with the header tank. Engine bay with brass header tank and radiator top. Header tank set just below bonnet level.
Last edited by Cass3958; Oct 16, 2021 at 03:34 AM.
The link above is a previous discussion with a few ideas. My system was very similar to that of Cass3958, though not nearly as shiney bright. My expansion tank came from a BL Princess - BL used the same, very nice tank on a whole range of ex-BMC cars. I think (it's a long time ago and my car's now in pieces) I had a lower pressure cap on the expansion tank than on the radiator. Some say you should add a seal to the cap on the radiator - I didn't and it worked fine, but perhaps I was lucky.
I have a sprung 7lb cap on the expansion tank and a standard modern sealed cap on the radiator so the hot water can flow from the radiator straight down the overflow tube to the expansion tank and back unrestricted.
I tried a new 4lb cap at first but when putting it on a pressure checker found it to be inoperative & it used to form a siphon for a period & dump lots of my expensive coolant onto the ground. I now run a new & working 7lb cap and if left to it's own devices the level settles. Subsequent to that I have jury rigged a surge tank that always contains some coolant that the overflow pipe terminates in. The system pushes fluid into the tank when hot & sucks it back up as the system cools. Always full. Either system will work fine.
Do not use in excess of a 9lb cap on these cars. The waterpump seal does not like it.
Must be from the BL parts bin. My first though on seeing the tank was Series 2 E Type.
It might be. I had the same tank on my MBG GT V8 which is where I recognised it from but as you say British Leyland owned them all the the 70s so could be a number of cars fitted with them. Someone else said it reminded them of a tank from an Austin Princess again a BL car.
