Was in heavy traffic, bumper to bumper last week. Temp gauge went into the red zone. This not the first time this has occured. Coolant boiled so hot in reservoir, it cracked the cap and coolant was everywhere. Does the 940 have a overheating problem when behind running vehicles in traffic? If so, what can I do to correct this problem.

The car will only have an overheat problem when mafunctioning, not when beind vehicles in traffic. Has the ambient temperature been hot on those occassions? Any other information than being behind traffic...? Any noises or other warning signs?

The system is reatively simple compared to other parts of the car. Something is blocking either air flow to the radiator or water circulation in the system, assuming it's holding coolant. So, you could have a failing water pump, sticky thermostat, a blocked radiator, or a mass of debris blocking air to the radiator.

If you're not seeping coolant at the pump or there is little play in the pump mountings (trying moving it from side to side), then I'd thoroughly clean and flush the system, replacing the thermostat and even the hoses, depending on when that last change may have been done. If you feel comfortable about removing the radiator, have it flushed and cleaned professionally or do it yourself. Water should flow freely through the system. If you're losing coolant, then I'd suspect the radiator, hoses or waterpump, but not necessarily in that order.

Did I forget anything BBsters?
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John Shatzer, '97 V90 @ 94K

I think you hit every possibility under the hood, shatz, except for one last thing, the electric fan, not cycling on properly.
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Tom F

ARUGH! Of course, the cursed electric fan! I tend to forget about these new fangled components...thanks for the reminder. Add that to the list Chudar!
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John Shatzer, '97 V90 @ 94K

Thanks John. I will check the fan next.