The most obvious valid reason for replacing a water pump would be an overheating incident due to actual or suspected water pump failure .

Further to my last post, the bubbling coolant has continued but in all honesty I am not too fussed as long as the car can last me another 3-4 months. My main concern is that if I drive it without the internal fan on to accommodate for some of the extra heat, the temperature of the engine (on the dashboard, at least) begins to very slowly climb above 90 degrees. It remains on 90 if I keep the fan on, but the engine fan creates a hell of a noise (not that it matters if it is working). Now it is getting towards summer I am starting to get fed up of absolutely roasting in my car every time I go to/from work so am looking for an answer, however, given my problems with previous mechanics and the fact that I have already paid out a few hundred pounds on this issue I wanted to ask the advice of you guys before having a paid mechanic come and look again. I have a couple of fridge compressors that I could try, but I'm getting used to the boiling method so I probably won't bother..I suppose you could “tune” it with a blanking plate with a hole in it, to provide less but still some restriction. Never remove the coolant reservoir cap when the engine is running or still hot. Let it cool down first. If the coolant level is low, add the correct coolant to the reservoir (not the radiator itself). You can use diluted coolant by itself or a 50/50 mixture of concentrated coolant and distilled water. Coolant circulates through the engine and absorbs heat, helping keep the engine at the right operating temperature.

Roll up or remove loose clothing, and keep your arms away from the cooling fan(s). Fans can turn on automatically, even when the engine is off.I try and be as cynical about garages as the next man, (though/so/because I have hardly ever used them apart from MOT's) BUT I think the innocent-until-serious-grounds-for-suspicion principle ought to be applied. You can buy products in Halfords to seal leaks. There is no need to drain the coolant, just remove enough from the filler tank and add and follow the instructions. There is a lot of pressure in the cylinder head so how effective a seal you could get here is debateable, You can sometimes score extra cooling using the aircon fan (I ran my Sierra using the aircon fan only for a while) but I assume if you had one you would already be using it The OP is unlikely to want to bother with that though, especially as he already has some blowing from the coolant reservoir so couldn’t easily detect any local boiling due to modification.

The mechanic I used took another look at it today and has returned it to me stating that it is in fact a problem with the head, stating he ran some tests and found gas to be escaping and entering the coolant system. He has now offered a short term solution by saying he can apply some sort of leak repair stuff which requires the coolant system to be flushed then the additive put in with new coolant. Does anybody have any experience with this and if so, how long is it likely to withhold? My car is due to have it's MOT in February, how likely is it to pass this?The reservoir has a fill range marked on the side. If your engine is cold, the coolant level should be up to the cold fill line.

renewed on my diesel car last year and found the reservoir empty when I got home - the techy just hadn't run the engine enough for the thermostat to open fully.Only reasonably practical desperate improvisation I can think of would be removing the thermostat. This will potentially increase circulation in the cooling circuit, allowing it to remove more heat. I wouldn't do that, and I probably wouldn't buy the kit they use, but it should be possible to adapt another form of pump. You can of course improve your personal cooling a bit with various supplementary fan and evaporative solutions. Look up “swamp cooler” if interested, though I doubt you want to get quite that elaborate. Make sure your engine is off and cool, the vehicle is in Park or Neutral, and the parking brake is set.