Page last updated 5th January 2016
A topic of many an owner, especially for those of you with this engine. The
(original) radiator on the M Series is a very short but wide/deep one, due
to the spare wheel lying flat above it at the front of the engine bay. The
depth and width makes up for the low height, but when stuck in traffic on
any day warmer than about 14ºC, you may start to worry about the temperature!
The signs of overheating are firstly that (if working at all) the electric fan cuts in when in traffic or stationary, but doesn't stop again until you start to move. It ideally should only come on after about 5 minutes when stopped, and cut in & out every 2 minutes minimum or so. Basically, the engine being a "V" is one great hot lump of metal, and combined with the lack of ventilation in some models' bonnets, and the struggling radiator, it's not perhaps surprising that something needs to be done to improve this. In the near future, I hope to show you what can be done to alleviate this problem, allowing you to enjoy the car more (even when sat in a traffic jam!).
The first thing to do is to make sure your block & radiator are flushed out - any sediment allowed to build up will impair cooling efficiency.
Secondly, I have found that you need at least 2 electric 8" diameter fans to prevent overheating in summer temperatures while stationary. Fitting them to the front of the radiator (pushing air through it) was found to be less effective than fitting them behind it towards the radiator (pulling air through it). Also, make sure you fit an 82ºC thermostat or lower, don't opt. for the 88ºC one as you'll already be raising the engine temperature to 88ºC before the radiator circuit opens up! Never remove the thermostat unless you fit a special insert to mimic a thermostat's flow - without it you can find the correct water flow is effected - possibly causing hot spots in the engine/cylinder heads.
Water Wetter - the liquid you add to the cooling system to reduce overall temperature. I tried this and found that it works enough to visibly lower the coolant reading on an electric gauge. The only downside is that this works better if you use less antifreeze.