Engine overheating

Driving home today, after about 10 minutes on the road in stop and go traffic, display read Engine Temperature High, or something to that effect. The temperature gauge was pinned to the high side. I was fortunately a few minutes from home. When I opened the hood the coolant reservoir was full and leaking from the cap. I let it cool down and then restarted and let it idle for a while, the cooling fan did come on eventually so I don't think thats the problem. Could this be due to the thermostat being stuck closed? I am thinking that the temperature sensor is OK since it was reading high.

Should I replace the thermostat as a first step? Thank you!

Don't continue to drive it until you find the issue.
YEAR?
MILEAGE?
How would we know what to tell you with a nothing posted?:confused:

2001 xc70 (see my sig?)

about 75000 miles.

Thermostat at 75K sounds like a good place to start
Change the coolant temp sensor too.

Having at car posted in your signature means nothing, you could be talking about any Volvo you may have, but no mileage means no help!
(for the future)

Replacing the thermostat and coolant temperature sensor seems to have fixed the problem.

Interestingly, the one I removed is a 90 degree C. FCP lists the replacement for my 2001 xc70 turbo as 87 degree. I couldn't get FCP to actually deliver the part, so had to go to my local auto parts store. They gave me a 92 degree vernet, so far works fine. Will have to replace with the 90 degree wahler that IPD sells if I have any issues with this one.