If I don't use my Astra 1.4 Mark 3 (petrol) for some months, it loses coolant. It seems to be coming from the water pump, but after some use of the vehicle, the leak seals itself. This has happened on several occasions when I've laid up the car; it’s embarassing when you take it for its MoT test!
The mechanic says...
This sometimes happens when cars are laid up for a while; minor coolant or oil leaks appear and then tend to stop when the car is put back into use. The danger is that a leak like the one on your car might suddenly worsen while you are driving the vehicle, resulting in a major loss of coolant and overheating, with resulting engine damage likely.
You could try using one of the proprietary leak sealing products available from ‘do-it-yourself’ motor accessory shops/superstores; however these do tend to clog up tiny water passageways within radiators (etc.) as well as sealing external leaks.
Ultimately the answer is to renew the water pump, if this is the culprit. You should then have peace of mind that the coolant will stay in the engine, even when the car is laid up!
