Pajero diesel 2800 radiator coolant overflows, engine temp. up

No just the coolant surge tank.

If the thermostat is not opening, the engine will keep getting hotter as you drive. You could be low on coolant and have air pockets in the system which would cause the temp gauge to not be accurate. Is the radiator fan coming on when the tank is boiling ?

YOU NEED BLEED AIR OUT THE COOLING SYSTEM.WAIT TO ENGINE COOL DOWN.YOUR VECHICLE YOU HAVE TO POUR COOLANT IN THE COOLANT OVERFLOW JUG UNTIL COOLANT LEVEL STAY AT THE FULL COLD MARK.THEN START ENGINE LET IT IDLE A FEW MINUTES WATCH COOLANT IN THE OVERFLOW JUG WHEN IT DROPS ADD MORE COOLANT UNTIL COOLANT LEVEL STAY AT FULL COLD MARK.WHEN COOLANT LEVEL STOP DROPPING IN OVERFLOW JUG.SCREW RADIATOR CAP BACK ON OVERFLOW JUG WATCH ENGINE COOLANT TEMPERATURE GAUGE AS COOLANT TEMPERATURE START CLIMBING TURN OFF ENGINE LET IT SET A WHILE KEEP FROM GETTING SCALDED.TAKE LARGE RAG PLACE OVER COOLANT OVERFLOW JUG CAP SLOWLY OPEN RADIATOR CAP A LITTLE AT A TIME UNTIL PRESSURE RELEASE.REMOVE OVER FLOW JUG CAP.ADD MORE COOLANT UNTIL COOLANT LEVEL AT THE FUL COLD MARK ON THE OVERFLOW JUG.THEN SCREW CAP BACK ON THE OVERFLOW JUG.START ENGINE LET IT IDLE AGAIN WATCH ENGINE COOLANT TEMPERATURE GAUGE WHEN TEMPERATURE GAUGE START CLIMBING.TURN OFF ENGINE WAIT A WHILE.CHECK COOLANT LEVEL IN THE OVER FLOW JUG.DO THIS PROCEDURE UNTIL THE COOLANT LEVEL IN THE COOLANT OVERFLOW JUG STOP DROPPING AND STAY AT FULL COLD MARK,WHEN THE TOP RADIATOR HOSE GET HOT THERMOSTAT OPENING AIR IS OUT THE COOLANT SYSTEM. WHEN ENGINE COOLS DOWN.CHECK COOLANT OVERFLOW JUG COOLANT MUST BE IN THE COOLANT OVER FLOW JUG AT THE FULL COLD MARK WHEN ENGINE COLD. DONT .DONT OVERFILL COOLANT OVERFLOW JUG.KEEP COOLANT IN THE OVERFLOW JUG IF YOU LET COOLANT OVERFLOW JUG RUN DRY AIR WILL BE DRAW IN COOLANT SYSTEM CAUSE ENGINE TO OVERHEAT.

REPLACE THERMOSTAT IF TOP COOLANT COOLANT HOSE GOING TO RADIATOR IS HOT TO TOUCH THERMOSTAT OPEN. TO BLEED COOLANT SYSTEM FIRST YOU NEED TO ADD COOLANT TO THE COOLANT OVER FLOW JUG UNTIL COOLANT LEVEL STOP DROPPING AND STAY AT FULL COLD MARK.WAIT 3 MINUTES IF COOLANT DROPS ADD MORE COOLANT UNTIL COOLANT STAY AT FULL COLD MARK.WITH RADIATOR OVER CAP OFF CRANK ENGINE FOR MINUTE WATCH COOLANT LEVEL AT OVERFLOW JUG.IF COOLANT DROPS ADD MORE COOLANT IN THE OVERFLOW JUG.WHEN COOLANT LEVEL STOP DROPPING IN OVERFLOW JUG.SCREW BACK ON THE RADIATOR CAP TO OVERFLOW JUG.WHILE ENGINE IDLING WATCH TEMPERATURE GAUGE WHEN TEMPERATURE START CLIMBING TURN OFF ENGINE WAIT A WHILE KEEP FROM GETTING SCALDED.WHEN COOLANT COOL DOWN SOME. PLACE A LARGE RAG OVER THE COOLANT OVERFLOW JUG OPEN CAP LITTLE AT A TIME UNTIL PRESSURE RELEASED, THEN REMOVE CAP ADD MORE COOLANT IN THE OVERFLOW JUG TO THE FULL COLD MARK.THEN REPEAT THE PROCESS SCREW BACK ON THE COOLANT OVERFLOW RADIATOR PRESSURE CAP.THEN START ENGINE WATCH TEMPERATURE GAUGE WATCH COOLANT TEMPERATURE GAUGE WHEN COOLANT TEMPERATURE START RISING TURN OFF ENGINE AGAIN WAIT UNTIL ENGINE COOL DOWN ENOUGH TO KEEP FROM GETTING SCALDED TAKE PLACE LARGE RAG OVER RADIATOR CAP WHICH IS THE COOLANT OVERFLOW JUG CAP OPEN CAP LITTLE AT A TIME UNTIL PRESSURE RELEASED ADD COOLANT UNTIL AT FULL COLD MARK. WHEN YOUR COOLANT LEVEL STOP DROPPING.AND TOP RADIATOR HOSE VERY HOT THERMOSTAT OPEN AND AIR IS OUT THE COOLANT SYSTEM. MAKE SURE YOUR COOLANT OVERFLOW JUG HAS COOLANT IN IT,WHEN ENGINE COOL DOWN CHECK COOLANT OVERFLOW JUG KEEP COOLANT LEVEL AT FULL COLD MARK.BECAUSE IF OVERFLOW JUG IS EMPTY THATS A SIGN RADIATOR COOLANT LEVEL LOW.WHEN OVERFLOW JUG EMPTY IT WILL ALLOW AIR GET IN THE COOLANT SYSTEM AND CAUSE CAR TO OVERHEAT.WHEN REPLACING THERMOSTAT ALSO REPLACE THE RADIATOR CAP ON THE COOLANT OVERFLOW JUG.

In a properly working system, the coolant expands as the coolant temp rises. The excess coolant flows into the overflow container by the hose that runs from the bottom of the overflow to the top of the radiator, under the radiator cap. When the coolant begins to cool down, it contracts,drawing fluid back into the radiator from the overflow. The water pump has a "weep" hole located near the bottom of the pump housing that will leak coolant if the pump is going bad. In some engines, the 3.0, the water pump is located under the camshaft timing belt cover, and is a BEAR to deal with. However, the coolant should be pulled into the radiator when the engine cools, so check that the hose from the top of the radiator is attached to the bottom of the overflow and that it is not blocked or pinched. Have the system pressure tested to verify that it has no leaks. Hope this helps. Dano

These vehicles, when equipped with the 3.1L engine are very prone to head gasket failure. A local garage should be able to preform a block check to tell wether combustion gasses are entering the coolant. Because you said the coolant pushed out the overflow this is definately where i would start. The normal operation of that vehicle is for the fans to turn on around 106 degrees celcius. If you can, take a temperature reading of the coolant to ensure they are coming on at the right temp. Other possibilities are an inefficient radiator, coolant temp switch/sensor causing inproper fan on temperature,

Means you need to add coolant to either the radiater or the overflow tank on your vehicle. If the engine is hot add to the overflow tank while engine is running in case it is low so it draws it into the engine. DO NOT open the radiator when it is hot as you could get burned by hot steam. If cool, take off the radiator cap and poor into radiator, then run for a while and then recheck the overflow tank to see it is between the MIN and MAX lines on the tank.

Have a look at the thermostat.
If it's blocked shut, there won't be the circulation through the rad.
You may need to invest in some 'radweld' type treatment too.
Good luck with that.
Don't forget to rate, thanks ;)

You may need to ask AAA to put a radiator pressure tester on the resevoir bottle and pump it up to operating pressure(Pressure cap rating) and see if it over pressurises while it is running at operating temp,rev engine up and down and watch what the testers pressure readings do,it should move up and down in sync with the water pump.If the pressure keeps building i would have to believe that combustion chamber gases are over pressurising your cooling system.Also test the pressure cap is functioning within factory specs.