How can I re-lock the radiator locks on top of engine frame?

For the heating blowing cold
Air Lock
Low Coolant Level
Blend Door Actuators not working
Water valve not opening, some are electrically operated (fuse?).

For overheating
Low Coolant level
Air lock
New thermostat faulty
Radiator blocked
Cooling fan not running

When you put in a new thermostat, and refill the system, you have to burp the air out of it. There are videos online, but you fill the system by the radiator (are opposed to the filler bottle) and turn the heater on full to fully open the valve. Then you run the engine and keep topping it up, occasionally squeezing the bottom radiator hose. When the cooling fan kicks in, you know it is up to full running temperature. Rev the engine a few times, and turn off. Then top up one last time and put the radiator filler cap back on. Then top up the coolant reservoir to the line and put the top back on that. All done!

Question edited for typos.

You really need to just replace the temperature sensor. It is likely that the coolant system has air locks. You need to burp the system of air. Open the heater control to maximum heat, raise the front is possible. Take the top of the radiator and keep topping up until the cooking fan kicks in. Squeezing the radiator hoses, and revving the engine also helps. Turn off the engine, top up one last time, replace the radiator cap and then top up the expansion tank.

https://www.google.com/search?q=1983+toyota+hiace+burp+cooling+system

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- Remove battery and tray (12mm bolts x 8, 10mm battery and ground. maybe 13mm for tray if some previous guy got confused).
- Remove fan from thermo (4x12mm) and shroud from radiator (2x12mm).
- Remove top small hose with pliers
- Remove bottom large hose with pliers
- Remove top large hose with pliers
- Remove two trans line hoses, and snake them up high so they don't leak anymore fluid
- Remove lower bolts near frame (13mm gear wrench) on DS ONLY
- Remove top side bolts from DS ONLY radiator frame (2 x 13mm).
- Remove PS center bushing horizontal bolt thru the front of the grill (12mm - 8in extension with wobbly and 12mm socket while vice grip the bolt on the engine side)
- Remove 12mm long vertical bolt from PS only (you are going to leave the DS frame in the truck and pull the PS frame out with the rad). Move the PS frame toward the rear of the truck, and remove/install.

Engine Chip

Permanent air lock means your system has leak sum were or your reserve tank and radiator cup not function propebly full radiator fit cup Rev engine up to 1500to 2000 few times stop engine and top up sum time take 10 times.

Sounds like it's air locked. Too much air trapped in system. You could try opening the heater hose connection or any point that is highest, with engine OFF. Top up as much as possible in radiator (not overflow bottle) then close the connection. Leave rad cap off and start engine, allow to warm up. (put heat on full, fan on 1,) gently rev up engine, 2,000 rpm, and note drop of fluid level in radiator, keep revs up while topping off radiator as much as possible, close rad cap before allowing to idle. Hopefully this should do it, otherwise youll need a vacuum pump to do it properly. That would be very unusual for a standard production car.
Good luck.

Did you recheck the water level at the radiator filler cap after the engine was at normal temperature (ie after about 15 mins idling with heater control on full and fan on Low) because it sounds like there is an air lock in the system. Air lock should clear after thermostat starts to open. This is indicated by the top radiator hose becoming hot to touch.

check that the radiator is full to the top... sometimes there is a small air lock in the top of the radiator, take off the radiator cap slowly and fill it up till it overflows a little and replace the cap letting as little air as possible into the system, hopefully the light will go out. Otherwise it could be an airlock elsewhere in the system, squeeze all the pipes while the engine idles and move the water around by squeezing in a rhythm, you will feel the difference between an air filled pipe and a coolant filled pipe, check every bit of pipe is full of water with no air locks in bends or twists.

This is very vague and hard to diagnose without more detail. I have a hunch the the brakes "locking up" is a different problem than the engine overheating. To check the engine: Remove the radiator cap from the cold radiator. Be sure the radiator in almost topped off with 50/50 antifreeze & water. Start the car and let it idle until either you can turbulence in the radiator, or the engine is getting really hot. Is the water temp gauge working? You can keep an eye on it during the process. If you see turbulence then the thermostat is opening, and the water pump is pumping. The thermostat is fairly easy to replace. The water pump is lots of work. Usually the timing belt, tentioner, pulley, and accessory belt is changed at the same time as the water pump, because the labor costs more than the parts. Hopefully nobody ever put straight water into the radiator. It causes corrosion, and lots of related problems.

check the condition of the reserve tank and the hose from the reserve tank to the radiator for leaks if no leaks there have the Radiator cap presure tested . also this could be a air lock in the engine if the radiator is new with the engine running and the heater on hot observe the fluid level in the radiator with the cap off if it drops as it warms add more coolant this will purge the air .

it could be air lock , very common on those engines, more likley is a slight headgasket leak