I have a 99 ram 1500 sport with 5.9 automatic 4x4 . I have changed the thermostat,water pump,clutch fan, flushed the radiator and heater core have a 195 degree thermostat in it and can only get it to warm up to about 150 to 170 degrees it will warm up and open the thermostat at first warm up then it drops back to 150-170 and stay there only way I can get it to warm up again is to block radiator 3/4 or better with cardboard thermostat has been changed 2 times does anyone have any ideas what would cause this? I used a hand held thermometer to check the temp and it reads the same as the guage. thanks for any help.

 

Sounds like you either have air still trapped in the system or a blockage in the heater core. Have you checked the temperature of the incoming and outgoing heater hoses at the heater core with a laser temperature probe? If both hoses are near the same temperature, also check the blend door to ensure its working properly. There is a common issue with it that is fixed with this offering:

https://heatertreater.net/dodge-ram-95-02/

 

Where do you live and how cold is it outside?

 

checked the heater hoses there is only 10-15 degrees difference also checked the blend door and it is working parked it with nose pointed up on a pretty steep bank and burped it ran it an hour or better figured that would take care of any air in the system it still don't get to operating temp.

 

live in Kingwood West Virginia right now it is 30 degrees was only 22 this morning.

 

If it gets up to 195 once, and then wont get there again, and STAY there, your thermostat is bad.

 

this is the third thermostat that I have changed in it in about a month I thought the same thing but they all do the same thing wouldn't think all three would be bad.

 

What brand are you getting? Not a safety stat is it???

Get a stant super-stat. I have had good luck with those.

 

couldn't run fast enough to give me a failsafe all have been stant never got a bad stant but I guess there is always a chance but like I said not likely to get 3 in a row.

 

Not so very long ago.... I used to buy three thermostats at a time for my Volkswagen, that just gave me a reasonable chance of having ONE that worked right.

I will grant you, three bad ones does seem rather unlikely, but, the thermostat is the ONLY thing that controls the temp of the coolant. It is sticking open for some reason.... it simply isn't cold enough for simple air flow to cool the engine that much.