Newbie post... I recently bought a 2000 4.6 Vogue, its a lovely car, with just 60,000 miles and 2 previous owners etc... I bought it knowing it had a slight overheating problem, its a strange one... i can drive round in the car for anywhere up to 30+ mins and it all runs sweet as a nut, then all of a sudden the heater blows cold air (even though its on the hot setting) and the temp guage shoots straight up into the red, literally within 5 seconds, i immediately pull over, and it cools within a few mins to crack the resevoir cap of, i then just top up the water and the car runs fine, and the heater returns to normal... One other probelm i've noticed is that sometimes when sitting on tick over the heater will start to blow much cooler air...
Any experience or advise would be much appreciated, thanks...

It would seem that you have an air lock in there. Topping up the water wont clear it, it just buys you a bit of time. As you look at the engine from the front, on the left hand side of the radiator is a small pipe that goes to the header tank. Pull the end off that goes to the rad and blow through it to clear any water from the pipe. Top up the header slowly making sure you dont spill any water down the hole for the small pipe. fill untill you get a trickle from the outlet on the rad and then re-connect the pipe.

Are you losing any water ? any signs of "mayo" under the filler cap ?

rewmer said:

It would seem that you have an air lock in there. Topping up the water wont clear it, it just buys you a bit of time. As you look at the engine from the front, on the left hand side of the radiator is a small pipe that goes to the header tank. Pull the end off that goes to the rad and blow through it to clear any water from the pipe. Top up the header slowly making sure you dont spill any water down the hole for the small pipe. fill untill you get a trickle from the outlet on the rad and then re-connect the pipe.

Are you losing any water ? any signs of "mayo" under the filler cap ?

Click to expand...

Thanks... I will try topping it up with the pipe removed, shall i run the engine whilst doing this? There's no sign of mayo, im gonna do a sniff test to be sure, but i can't see how it would be a head/block prob as it only happens occasionally...

Top up engine running, you need to get it up to tempreture to make sure the thermostat opens and you get a good circulation - the top hose should get warm when the stat opens. At this point switch off, and let it cool down, then top until you get to the level mark.