i seem to be loosing coolant from my radiator. there are no obvious leaks from any hoses, water pump is brand new, thermostat is working well and the temp is good.. ive got no idea why its loosing it but it seems to loose a bit from the top tank over the course of a half hour drive. could it be a pressure problem? or am i just not doing something right.. im using one of those ebay rads so not sure if the cap is the right one or not..

sorry i cant describe it a bit better but ive got no idea why its happening..

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Potato

Head gasket?

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Size DOES Matter!!!

dont think so, no discolouration in the oil and the car runs great..

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Potato

how much is a bit? do you have a overflow bottle. if no overflow the water is gonna expand when it gets hot and you are gonna lose some.

maybe not fill it up after it s lost its bit and take it for another drive and see if it loses any more then it s original lost bit . if no losses after it's lost bit ,, no problem .

thats how see it anyway, i probably got no idea ,,,
fiji

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PrOuDlY aSkInG qUeStIoNs FoR uR aMuEsMeNt

it goes half way down the top tank on the radiator, or all the way if i run the car for longer... on the way back from the grand day out it took about a third of a bottle of coolant before i left for home... not many mk1's had expansion tanks? ive not seen one loose that much coolant purely through expanding...

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Potato

mmmm fair enough.. thats my idea shot.
one for the experts.

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PrOuDlY aSkInG qUeStIoNs FoR uR aMuEsMeNt

air in the system from when radiator/water pump were removed and coolant refilled?

I was going to suggest expansion but it seems to not be the case...

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tim
68 Deluxe 1293, HIF44, megajolt/EDIS4, daihatsu alternator..

'a mini is for life, not just for christmas!'

nah, cap isn't sealing...

tape a plastic bag over the neck with the radiator cap on and run the engine and I reckon the bag will blow up

To be loosing that much and if there is no obvious leak, then it would have to be head gasket or a cracked head or even a cracked block. It may not show up in the oil and there may not be any noticable deterioration in performance.

A seperate header tank (overflow tank) is a very good idea on any car, but if your running an alloy radiator, it is VITAL to stop corrosion of your cooling system.

I reckon Simon's right, you're blowing coolant out past the radiator cap.

Mine did this really badly, if I could see coolant in the radiator it would blow it out, even with a brand new 13psi cap. One brass overflow tank later (thanks Flute! ) and it stays full at all times. In terms of increasing reliability, this has to be the best mod you could do..

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Simon

The adventures of an owner builder in the Tallarook Ranges

tested the bag method, got no air, but ran the car til it was hot and revved it and it shot out of the overflow pipe so im assuming thats where its coming from, so i made a little overflow bottle and stuck it in there.. will it put the coolant back in? the pipe is in the water so it can pick it up..

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Potato

With a standard radiator cap, no -- you want a 'recovery' type. This is a normal pressure cap, but with a return valve in it which will allow fluid back in as the coolant cools and contracts. This works with a non-pressurised overflow bottle, as you're suggesting.

The type I have is a pressurised overflow -- the pressure cap lives on the overflow tank, and the radiator just has a flat cap which seals at the top lip, not the lip in the neck. This allows pressurised fluid to flow between the radiator overflow and the overflow tank.



This is true, but the reason isn't obvious. What an overflow tank does is ensure that your cooling system is full to the brim at all times, and has NO AIR. Air in the system encourages oxidisation and therefore corrosion, and an alloy radiator is the first thing in the system which will corrode.

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Simon

The adventures of an owner builder in the Tallarook Ranges

will i survive from sunbury to calder, calder to hanging rock, hanging rock to sunbury tomorrow then?

hope so

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Potato

Yeah, you'll be fine -- just take some coolant with you. If yours is like mine was, you only lose coolant when the engine stops and the coolant boils around the cylinder walls, increasing the system pressure beyond the 13psi the cap can withhold. Just top it up before you hit the road, you'll be right

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Simon

The adventures of an owner builder in the Tallarook Ranges

I am having similar issues with my coolant level dropping. I know the coolant is being blown out via the overflow. I drive my Mini to work daily (approx 30kms p/d) and generally have to top it up every four days as it will get below the core level in the radiator. Temp sits at 1/2 to 3/4 and bit higher in traffic and engine runs well with no problems and oil is clean.
When I bought the car it had an overflow reservoir fitted which I removed when I fitted new radiator, cap, thermostat and water pump. I have been thinking about refitting the overflow system and haven't due to a couple of concerns: a) I don't really understand how the coolant returns to the radiator - is it because of a "negative pressure" in the radiator when it cools or simply because the level in the overflow is greater than the radiator and it reverse flows. and b) is the position of the overflow important? I would like to fit it under the guard adjacent to the radiator to keep my engine bay simple and tidy.
Any advice or opinions appreciated.

Tim

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1971 Mini K