Passat temp issues

The ac fan only comes on when the ac is on , the engine fan comes on at engine operating temp . few things to check , the radiator core fins are free from rubbish leave or plastic bags , the thermostat is fully open , radiator tubes are blocked with gunk have it flow tested .

Could be.. is the system FULL? Air in it can cause some odd things. When engine and coolant are COLD (as in after sitting over night), open the radiator cap. Top off the overflow res with a 50/50 antifreeze / water mixture to HOT mark. Start engine, turn heat to hot and fan to high. Top off RADIATOR with same 50/50 mixture slowly & gradually. As the coolant circulates, it should bring any AIR trapped in the system (from heater core & engine block) to the radiator where you can replace it with the 50/50 mix. Once the coolant is HOT and stays level - about an inch under the opening, close the radiator. Monitor the overflow res and add as needed. Good luck!

If it is a manual system--sounds like coolant low ie: air bubble in system. If it is ATC system, Check Codes, if no failure codes, coolant may be low--air bubble in system--most Durango's have air bleeders in system.

Have you checked your cooling fan to see if it is working propely? Let the car idle and get warm and listen for the fan to kick in (if they are electric) or just watch to see if the fan starts to spin faster if it is the old school type with a clutch. Have you replaced the thermostat? A bad one will let the temp rise since it opens too late and then the temp will drop off. But it won't due this only at a light and it will do it infrequently.

your temp mark will also depends on your thermostat range anywhere between say 90 and say 180 if your temp goes in the red then you should be concern

CHECK COOLANT FAN FUSES AND RELAYS. CHECK COOLANT LEVEL.MAKE SURE ITS NOT TOO LOW BECAUSE IF COOLANT TOO LOW . BY NO COOLANT AROUND OR COOLANT SENSOR NOT SUBMERGED IN COOLANT COOLING FANS WONT TURN ON.MAKE SURE YOU HAVE 50/50 ANTIFREEZE AND WATER. CHECK FOR CLAPSE RADIATOR HOSES.CHECK RADIATOR HOSE AT WATER PUMP.IF HOSE LOOK CLAPSE REPLACE IT AND BLEED COOLANT SYSTEM.IF EVERY THING HAS BEEN DONE YOU NEED ENGINE BLOCK FLUSHED OUT.HEATER CORE ALSO COULD BE STOPPED UP.A VERY HIGH MILEAGE ENGINE WILL OVER HEAT.OLD ENGINE LOSES COMPRESSION AND HORSE POWER.PUTTING MORE LOAD ON THE OLD ENGINE WILL MAKE IT OVER HEAT.IF COOLANT LEVEL IS LOW.BLEED COOLANT SYSTEM.START THE ENGINE LET IT IDLE FEW MINUTES WATCH THE COOLANT TEMPERATURE GAUGE.WHEN TEMPERATURE START RISING.TURN OFF THE ENGINE LET IT SET FOR 20 MINUTES.TAKE A LARGE RAG PLACE OVER RADIATOR CAP ON COOLANT EXPANSION TANK SLOWLY OPEN RADIATOR CAP JUST A LITTLE TO RELEASE A LITTLE PRESSURE AT A TIME.DONT OPEN CAP RAPIDLY OR YOU WILL GET SCALDED.ONCE THE RADIATOR CAP REMOVED.IF COOLANT LOW ADD MORE COOLANT IN THE THE COOLANT EXPANSION UNTIL YOU GET TO THE COLD MARK.REPEAT THIS PROCEDURE START ENGINE LET IT RUN UNTIL TEMP GAUGE START CLIMBING A BIT DONT LET CAR RUN TO OVER HEAT JUST IDLE UNTIL TEMP JUST START TO RISE.THEN YOU TURN OFF ENGINE. WAIT 20 MINUTES.THEN USE LARGE RAG OPEN RADIATOR CAP LITTLE AT A TIME. DO THIS PROCEDURE UNTIL THE COOLANT IN THE EXPANSION TANK STOP DROPPING. THEN ALL THE AIR IS BLEED OUT THE COOLANT.WHEN COOLANT LEVEL STOP DROPPING, WHEN YOU DRIVE CAR AROUND.AND TURN OFF ENGINE.WHEN ENGINE OFF CAR SET FOR A WHILE KEEP CHECK ON THE COOLANT LEVEL IN COOLANT EXPANSION TANK. THE COOLANT LEVEL SHOULD BE AT THE COLD MARK IN THE EXPANSION TANK.MAKE SURE COOLANT IS IN THE EXPANSION TANK.IF NOT AIR WILL DRAW IN COOLANT SYSTEM. CAUSING ENGINE TO OVER HEAT.IF BLEEDING AIR OUT THE COOLANT SYSTEM DONT HELP AND COOLANT FANS DONT TURN ON YOU HAVE PCM PROBLEMS.

hi the temp gauge should sit in the lower quarter of the gauge, it has to be a faulty water temp sensor as anything else would cause it to over heat badly

100 degrees is the normal operating temperature for the motor. If it goes higher than that, the thermostate needs to be replaced. The temperature will be higher on the highway because the engine is producing more heat energy due to the higher load on the motor. Diesels idle cooler and the engine will cool down at idle or lower speeds. That is why it is best not to idle your car for long periods of time because this will cause deposits in the engine and glaze the cylinders. The engine is working normal from what you described and there is no reason to worry. I hope this helped.

The thermostat controls the temp of the engine. The temp sensor tells the gauge what temp to display. If the heater is still putting out a lot of heat then it may be a false reading temp gauge. If however the temp is noticibly cooler then replace the thermostat. A stuck open thermostat would also cause the engine to warm up slowly. check for a loose/dirty connection at the plug on the temp sensor.

they are designed not to fluctuate with engine temp and are kept stable once operating temp is reached. only if the temp exceeds a set mark will the needle rise to indicate overheating,