UK Car Repair: Heater Problems, heater control valve, radiator cap

Question
Hello Christian,

I have a 1997 ford Ka and it refuses to be warm! After purchasing it I noticed it had no heating, on both hot and cold it gave out cold air. I did a little research and listened to a lot of advice (the advice mostly telling me to buy a new thermostat) but in the end went for buying a heater control valve (apparently a common problem in this car type) After installing it successfully just before Christmas I drove around and got the pleasure of heat. This lasted until the end of January when I failed the MOT and due to insufficient funds had the car unused for around a month. Upon getting back on the road the car developed a new heating fault. Now when I turn the heater on I get a refreshing blast of hot air which slowly fades to warm then cold. If I turn it off and wait then put it back on, again I get  blast of hot air which slowly fades to warm, and then cold.

A little research suggests it might be a blockage is this possible? The only non internet advice I am getting is to change the thermostat, but considering this is what they told me to do before I hardly trust this judgement.

Do you think perhaps a blockage occurred due to non usage? Personally I think it may be blocked (though I am very new to this area so my personal beliefs are hardly worth the time to hear them out). The reason for this theory is that I also got told on my MOT I have a leak. I have been suspect of a leak for some time but the strange thing is I can fill my water and drive about 4 or 5 miles and need to refill my water again, then after the refill can drive 140 miles at 28 miles per day over 5 days and only have a tiny water drop.

If it is a blockage (sorry for the cyclic blockage referrals it could be something completely different) what is the best cause of action? I hear of using a hosepipe, is this correct? Strange thing about the Ka is I do not believe it has a radiator cap which I think I read is the most used point to flush the system.

Anyway I thank you in advance for any help you may have to offer.

Kind Regards

Answer
Radiator flushing fluid is ok, especially for reduced flow like this (fully stopped flow is rarely solved with flushing fluid) .

Try Holts Rad-Flush, at about £4-7 a bottle.

Add it to the coolant as indicated on the bottle.

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To manually flush the system - search my old answers for RADIATOR :I have a detailed rundown of how to do it in very simple terms.