The heater in my y-reg punto is acting up. If I start my car up and turn the heaters on it continually blows cold air, if I leave it too long the engine overheat light comes on. (First thing I did was check my water level, it was fine). After letting engine cool I drove off, and the heaters started working, but after about twenty minutes they cooled down again ( not totally though) Last time I drove it the temperature warning lit up for a few seconds after about 30 mins driving (it may have came back on but I'd just got home!)

Any suggestions?

One other thing, when checking the water level, after the inevitable steam, there were a lot of big bubbles coming up through, maybe some sort of air-lock like in a central heating radiator?

Sounds like the head gasket has gone.

you could try bleeding the system and topping up the water level, but with the air bubbels coming up through the coollant resovoiur its unlikely to fix anything as the Head gasket looks to eb the culprit.

Chack under your oil cap, is there any mayo-like substance?

Its almost definately an air lock, this pushes the water level up in the rad making it appear to be ok when it isnt. You need to bleed the system using the bleed valves on the heater pipes and the radiator.

NumanR said:

Its almost definately an air lock, this pushes the water level up in the rad making it appear to be ok when it isnt. You need to bleed the system using the bleed valves on the heater pipes and the radiator.

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Yup I agree... same thing happened to me. Also check all hoses are connected properly so there are no leaks.

Thanks guys, I'll check in the morning!

This was happening to me...

Got someone to look at ittonite...

Trapped air - a ell of alot tho.

However - there seems to be a leak from somewhere - not 100% sure tho

pressure test the cooling system as this a determine where a leak is located

Throw in some Radweld!

Something similar happened on my Corsa (RIP) and it turned out the blades had come off the water pump.