95 Dodge 2500 conversion high top van (5.9) that overheats at freeway speeds W/ the AC running. Had the radiator flushed. Runs great. Help!!!!!!!

Hi. Do you own an infrared thermometer? This is a great tool to have for this type of failure. Keep in mind that one of your new parts may be defective. Just because its new, doesn't mean its ok. Before you started replacing parts. How was the antifreeze? Was there any rust? Coolant should be flushed every 3-5 yrs. if not, passage ways can become restricted or clogged. Now a flush isn't good enough and the engine needs to be chemically descaled. How is the cabin heat (is the heater core working well)? If your engine runs cooler at night and the ambient temperature does affect your engine. I would start by looking at the A/C condenser. Is there something preventing air flow? You can feel and squeeze hoses. You are feeling for thin wall thickness. Hoses can fail internally, collapse and cause a restrictions. With an infrared thermometer you can point at different areas of the engine block, heads, and related cooling system components. While the engine is running, monitor coolant temperatures, thermostat and fan clutch functions and circulation through the engine, heater core and radiator. Your car has a fan clutch and an electric fan. The fan clutch is for the engine cooling system. The electric fan is for the A/C. If the electric fan is coming on as designed and it isn't helping to cool the radiator. You are probably going to find that you have a circulation problem. The fan clutch is not going to operate if the radiator doesn't get hot enough. Please write back with any questions. Good Luck.

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Hello! Can not tell from the question if your loosing coolant...But it sounds like an air bubble behind the thermostat is blocking the flow...Remove the thermostat...Replace housing...Buy a back flushing kit from an auto parts store...Back flush the cooling system...Make sure heat is on high...Replace thermostat and refill with 50/50...start the engine with radiator cap off...Let all the air bubble out, even after thermostat opens...Wait until upper hose gets hot then replace the cap...Top off in the recovery tank...Now, monitor temperature...If all is well back flushing and air bleeding cleared the fault...If engine overheats due to loss of coolant I'll address that next...If coolant is not being lost does the engine actually overheat? ie..bubbling into recovery tank...If not the temperature sending unit is defective...send a comment...Guru...saailer

I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

Hi Big Mike, Have you checked the timing? If you have a petrol engine it could be ignition or valve timing which has gone out. A stretched chain could do it. Like wise for diesel. If the pump has been ******** too much it will heat more at higher speeds. The overheating can also be caused by a cracked cylinder head. The symptoms are those which you've described! Regards John

If you didn't do a thorough cooling system flush with the radiator replacement last year, then i would say you may have excessive build up of rust, scale and other debris. This will certainly clog up a new radiator quickly. You may still have a restriction. I would do a good flushing, including REVERSE flushing until water runs clear. This should help... Good luck, my friend.

blocked radiator cores and or faulty fan

P1596 Speed Control Switch Always High,
you should take it to a chry dealer

ONE SUGGESTION COULD BE TO SWAP THE RELAY FOR ANOTHER TO SEE IF THIS FIXES THE PROBLEM. IF IT DOESN'T, THEN PERHAPS THE COMPRESSOR CLUTCH IS STUCK IN THE CLOSED POSITION. UNPLUG THE CLUTCH TO SEE IF THE COMPRESSOR STOPS. HOPE THIS HELPS. PLEASE KEEP ME POSTED. THANKS FOR USING FIX-YA AND FOR AN HONEST RATING. GOOD LUCK

Have someone flush cooling system & check condition of rad for debris in front of rad & blow or spray it out as necessary. Next time it runs hot, turn your heater temperature up high, blower fan on high, and see if gauge starts to come back down a little. If it does, my guess is your rad needs replacing, or at least consider trying a good reverse flushing of the system first, then rad.

those sensors could cause the issue, clean the MAF 1st, also clean the idle system using the following procedure, the IAC can cause cruise surge. I use this to cure these problems all the time.

Here is the most common cause of surges and stalls and low idle, it is the idle speed control air-bypass valve (IAC) and throttle valve, they get full of gunk over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.