Hummer h2 limo occassionally overheats

[pteam]

Thank you good suggestions. I will add these to the lists.

The thing is we have 5 h2 , 4 are limos, and none of the others have problems. All have the stock radiators and tranny coolers and this is the only one to have a problem. So its something out of the ordinary.

We have replaced the thermostat like 5 times. Last time we put a fail safe in it, so if it does overheat (remember its a limo and it does alot of idling at wedding and when 25 people are getting out) the thermostat will stay OPEN. Its not the thermostat.

Would it be ok to completely take out the thermostat for the summer only and put one back in, in the winter? Would this help?

What we plan to do is complete coolant flush, then install extra aux fan in front of the radiator, and 2 aux fans behind the radiator blowing towards the engine.

We put a new radiator and fan on the h2 last year, cant remember if we did the water pump. Could the water pump cause it? Last year we thought it was a leaky head gasket and we ran some sealant in there, and it didnt overheat since then because it didnt overheat all winter, then bam it did it again today.

Thanks for your help guys! Trying to get as many ideas to check as possible.