The Classic Machinery Network

Hello to you all. I am the proud owner of a 1978 3C Mk 2 which runs really well, including brakes. but insists on blowing its water out of the radiator overflow after about 15 minutes of use. There is no expansion bottle on the machine which has a Leyland 4/98 engine, also new thermostat and rad cap. The water temperature gauge which appears to work rises to just under mid point in its scale. Any ideas/experience of possible probable cause.
Thank you

Hi and welcome to CMN have you checked that the radiator core is clean and not restricted? Try that first if that is not the problem my best guess would be a blown head gasket.

Jeremy

I wonder if this is any good or similar? https://www.ebay.co.uk/itm/BT-3-BLOCK-C ... SwLEtYi8Gi

I´m wondering if you may be overfilling the radiator? These older engines without expansion bottles generally require a bit of air at the top of the radiator, to allow the water to expand. Of course, the water should at least cover the top of the radiator pipes when cold.

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Regards, Kari.

Thank you all for your input, I like the idea of not overfilling the rad - cheapest option to try and I don't have a lot of time to lift the head. I have been making sure the rad is topped up to the top before using the machine so that could be it. I will also try and flush the rad and clean the fins but the drain plug is not budging.

Last head gasket I changed was on a Mini in 1968 - seems like yesterday!

Ordered the test kit too essexpete will let you know how I get on.

Used the test kit mentioned by essexpete which showed gasket blown. Used K-seal in the cleaned up radiator and it seems to have cured the problem. Didn't really think liquid sealer would work but it seems to have done the trick and saved hours of work - I hope. Worked using the back hoe for about an hour and all good