Quick question - situation is a '98 Volvo S90 with a broken thermostat in the "open" position- Okay, a thorough search of available resources seems to lend credence to a failed thermostat thht failed in the "open" position which leads to "over cooled" engine and needs to be replaced.... Need to know if driving the swedish iron for about 50 miles to get to a mechanic tomorrow will hurt the engine? If it was an overheat problem that would be an obvious NO, but in this condition, it would seem that there should be no long term bad effects from a relatively short, low speed drive... Any comments?

I would not worry.

We drove our '90 744 TI for almost 3 years with a thermostat that was doctored to stay open. Only after I found out that the electric fan was siezed and replaced it did I think to have the thermostat checked.

Aside from a small increase in mileage and much better heat, we noticed no difference after it was repaired.
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96 855R, 95 855,854, 90 744 Ti - 340,000 Volvo miles put on 7 bricks

no, it's not a big deal. many people drive with it in the open position for a VERY long time and don't even realize it until the winter comes along.

your car will run suboptimally, possibly consume a bit more gas, but i wouldn't worry about it.

50 miles for a mechanic is pretty far away, bummer that you have to make such a long trip. :(

happy holidays!
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'