Are you blowing out the corners of the radiator in between the shroud? That is a known problem on smaller units causing overheat. Worth a look.

i already replaced head cylinder gasket

I would do a carbon monoxide test in the radiator to be absolutely certain there is no combustion gases getting in there. Once even a little bit start leaking into the cooling system there is a overheating problem. Some of the Toyotas I service are run in a plastics extrusion plant at 100f air temperature and they seem to hang in there ok but as soon as a slight head gasket leak starts they can't.

Contact your Toyota dealer, If they do not have a solution for the overheat problem you might want to look at a larger unit. Less strain on the system. Toyota had overheat issues at a customer of mine and they stayed with it until the problem was fully resolved.

@zeeshan_k

One more time:

"model number & serial number would be very helpful as you seek a solution Toyota has built many different designs of a 2 ton forklift over the decades"

You haven't provided this info yet - it is key information to help resolve your issue

I wouldn't try "re-engineering" the cooling fan system. Let the manufacturer /local distributor try to help your situation. Remember an auto cooling system is a the front of the car and the fan *** air through the radiator and air volume is aid by the speed of the vehicle. The fan on the forklift engine pushes the air thru the radiator.

I would have suggested a coolant additive called 'enginkool' you might want to try along with using dexcool instead of the normal type coolant. This stuff is made by a company called crc industries here in the states. It's the best stuff i've ever seen for extreme heat conditions but unfortunately crc has discontinued making it.
They have apparently replaced it with something called 'revitacool'.
I can only assume this is an improved version of the old 'enginkool'.

just google crcindustries and it should come up on the first hit.

The only other suggestion is to try and improve your air flow through the engine compartment by adding some vents in the front of the kickpanel of the engine compartment/hood?
You may wind up using both ideas to achieve your goal.
At external temps you are experiencing there it's going to take a miracle to keep it from running hot.
I believe my idea by adding coolant additive might be your best bet.

check on it and see.

The idea about putting a high speed pulley on the fan might or might not work, and keep in mind it will make the truck alot louder at high rpm's with excessive fan noise. You will probably have to change the fan as well, it will be turning alot faster and could fly apart if it is not made well. ;o)

I DID EVERY THING YOU ARE TELLING AND I ALSO PUT ELECTRICAL FAN AS SAME AS IN CAR RADIATOR IT WORKS BUT ONLY 20% IMPROVEMENT
THE ONLY PROBLEM IS WEATHER OUT SIDE AIR ITS ALREADY HAS HIGH TEMPERATURE HOW ITS DISSIPATE THE HEAT FROM RADIATOR COOLANT.
IF YOU HAVE ANY IDEA TO COOL DOWN THIS AIR COMING FROM OUTSIDE PLEASE TELL ME.
THANKS FOR YOUR SUGGESTIONS SOME ARE VERY HELPFUL LIKE REDUCE THE PULLEY DIA TO INCREASE THE SPEED I WILL TRY THIS THANKS

Toyota at one time had overheating issues here in parts of texas, they ended up replacing the counterweights with a different opening for the airflow to the radiator. They stuck with it until the problem was cured

1. did you install an OEM radiator? or a less expensive after market (aka will fit) radiator.
2. did you install the proper (recommended) coolant when you replaced the radiator?
Been away from the lift truck industry for 12+ years (retired) but when I went to flush my cooling system on my 2011 automobile I discovered that various car manufacturers have a special coolant "cocktail" for their anti freeze & you don't want to mix them up or you can have a big problem. Maybe lift truck companies have done the same - just a SWAG - scientific wild azz guess on my part.
3. did you properly flush the coolant system when you did the radiator job?
4. you might want to check to see if Toyota has any suggestions for improving air flow thru the radiator - like a higher speed fan pulley or venting of the engine compartment hood to draw air in from the outside.
5. is it possible the transmission & cooling system is causing extra heat to transfer into the engine cooling system? Some times this happens when the operators - keep using that left foot brake - better known as an inching pedal or if they "rest' their left foot on the inching pedal - operators do strange things at times
Just food for thought -
PS: model number & serial number would be very helpful as you seek a solution Toyota has built many different designs of a 2 ton forklift over the decades they have been building forklifts and have been known to use different engine sizes in the same chassis design. The model and s/n will tell.

no i am not tried yet but i will try after i tell you the condition.
thanks

Whatever you do don't run this engine without the thermostat installed. The cooling system is designed to run with the stat in place and you'll definitely blow the head gasket if you run without one. Have you tried a new thermostat as a sticking stat even if it's stuck open will cause the engine to overheat