[QUOTE=cooljess76;331730]M42's are just as prone to overheating due to cooling system failures as M44's are. Both engines have plastic components that fatigue and being an M42(older) is all the more reason you'd want to replace everything. Sure the M42 has an aluminum thermostat housing, but it's the actual thermostat that usually fails. Water pumps fail on both engines as do the radiators which are the same on both engines. While the M42 doesn't have the plastic "Y" connector on the back of the cylinder head, it still has the plastic "octopus" fitting on the side of the engine block. The radiators typically crack and leak between the side of the radiator core and the expansion tank. Hoses weaken and rupture etc.
For someone that's new to these cars, I think it's important to know the dangers of driving one with 100k miles on the cooling system. If any of those components fail, mark my word THEY WILL, your engine will overheat. Every second that the engine temerature rises above normal operating temp, you're putting significant fatigue on the head gasket. Who knows what was done to the car prior to you owning it. You said an old lady owned it for 50k miles. Well guess what women do when they notice the temp needle rising... A) They don't notice because they hardly ever pay attention to those things, or B) Nothing, they continue driving to their destination or until the engine blows up. Just sayin, people buy these 17 year old cars thinking they're cool and bulletproof, then a month later they're driving down the road and notice the temp needle pegged, next thing you know steams coming from under the hood and they now have to fork out 2 grand because their headgasket failed and their head is warped or cracked. An M42/M44 w/100k miles on the cooling system is a ticking timebomb. Not tryin to scare you, but yeah... Watch that needle like a hawk.
And also note that any time you open the cooling system loop ie; replace a component or simply top off the coolant, make sure to PROPERLY BLEED THE COOLING SYSTEM
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What Jess says is all true, but let me add one suggestion for your consideration. I installed an Engine Watchdog temperature warning system from Australian Signals for $149 US. You can set the temperature at which you wish the gizmo to light up and sound an alarm. It also gives you a digital read out of the engine temp in real time. For me the price has been worth the peace of mind.