OK to run car on jackstands?
 

I have no idea what kind of coolant was in the car, so I'm flushing the system several times with water, and it's a real pain getting the car on and off the stands.

So I'd like to run it on the stands long enough to get the water up to temp before having to dump it each time.

Yes you can, as long as the jackstands are secure.
Are you using jackstands front and rear? If using only 2 stands (at the rear) chock the front wheels and you should be fine but DON'T get under the car with the engine running !!
Be aware that if you run the engine in gear on the jackstands, you may experience some vibration due to the rear wheels turning - something I would advise against.... Make sure you are at low revs and in neutral.

As long as you have a decent set of stands, and not those tinney cheap ones, I don't see any problem. We used to run our cars back in our hot rod days, all the time when on stands. But we had the heavy duty garage style ones, not the cheap auto parts store variety. I have seen them run AA fuel dragsters and funny cars in the pits on stands, so I wouldn't worry about running a Boxster on them. Just make sure you do it on level ground. I have seen some idiots jack up their cars on slanted driveways. I wondered if they had any common sense at all.

Yes, front and rear. I'm only trying to warm up the water in the cooling circuit, so I would only run it at idle and definitely not in gear.

Sounds like one of those perfectly good and innocent ideas until something goes wrong - and then its a YouTube video...

Those stands better be the equivalent of 40 mule team . :eek:

Would there be an alternate method of flushing the coolant system...perhaps a pressure bleed system that would avoid you having to do this?

Make sure the car is really on those stands before starting...vibrations can make things shift over time. Are you having it sit on rubber or? You might want to weld on some jack stand pads with locking pins for the jacking points.

There are some events in life that we will remember for all of our days..... But for the sake of the rest of us, please have video running so we can share in the experience, but not the cost, as the car slips off and you experience one of the worst days of your life.

Use 2X6s to construct some 4 wheel ramps maybe 3 or so boards high so you can do this work, plus oil changes etc without jack stands. I did a coolant change with such ramps. No problem and no worry.

There's no way I'd try running in on stands. Just too risky.

YouTube
 

+1 on the camera running! Be careful and good luck!!