My 1991 240 started over heating the other day on a short drive to the gas station. After slowly limping home with out over heating the engine I replaced the water pump and thermostat with Duralast parts from autozone. I tried to get all the air bubble out of the system but the upper and lower hose don't feel like their pressurized or at least as much as they should be car is still overheating within 10-15 min idle time. Not sure if there is an air bubble in the system or the water pumps non functional. I did test the thermostat before installing in boiling water. Did think it's worth mentioning the original volvo thermostat has a small hole in the side possibly to let air out I'm not sure but the replacement did not. Also upper hose gets
hot and lower hose stays cool. Any advice would be great this is my first time doing a job like this.

 

Do you have a functioning heater? You should make sure that there is no air pocket in the cooling system now but I doubt there was the original problem, and you say the overheating still persists. I'd do a pressure test to eliminate a head gasket issue. You may have a blocked radiator. See if it gets uniformly warm all over once the motor is warm. The hoses not being equally warm is a good sign of radiator blockage.

 

I do have a functional heater. It was not blowing warm when the car began to over heat as I was testing the new parts. Which did confuse me a bit considering the top hose that goes from the radiator to thermostat was very hot as well as the top off the valve cover. I'll take the radiator itself out and see if it's clogged up. I just didn't expect it to be because the colant that leaked out when I installed the water pump was very clean. At least compared to my previous experience doing radiator flushes on my past vehicles.

 

You don't have to take the radiator out. Just feel around it for cold spots.

 

You may need a new radiator or a heater core. Buy off of rock auto & use the 2 day shipping. Radiator starts at $59 to 119.00. Replace upper & lower hoses with new clamps and coolant cap

the heater core is $60

thankfully as you know the VOLVO is on ash to work on. I looked at video for heater core and that was not that bad as well. Sorry about the repairs.