I have a 96 850 and my heater isnt working, the blower blows cold air but wont heat up. even at running temps. i had a leak in my radiator and almost overheated the motor and used some radiator stopleak to fix it and everyday the heat gets less and less. I dont even know were to start.

 

With the engine warm, get down on the drivers side by the gas pedal. I cant remember but you may have to pull the under panel out to do this, anyway, pull the carpet back to reveal the supply and return line for the heater core. If you have flow through the heater core both lines will be warm. If one is warm and the other not....blocked. If you have warm on both then the core is ok and you need to look at your vent system.

***Caution, could be hot

 

is your rad full of coolant?

 

Replace your thermostat first if you haven't done so. Next comes checking for signs symptomatic of a clogged heater core. You can check by running the engine til it reaches normal operating temperature. Turn heater on full blast and let run for five minutes. Under the hood the heater hoses run thru the firewall on the drivers side of the vehicle. Reach down carefully and grasp each heater hose by the rubber and see if both are HOT. If the return is not as hot as the intake then the core is clogged up. You can try blowing out by connecting a compressed air source to the heater hose by unclamping hose from the coolant pipe and clamping compressed airline inside the heater hose. Remove the other heater hose from the firewall coupling and see what blows out. You can also try a garden hose but the water pressure probably won't be enough to unclog the blockage. CAUTION: You do run the risk of damaging the heater core with too much air pressure but if its blocked its going to need replacement anyway.

 

Any update on what fixed the problem? I have the same problem with my 95 855.

 

i flushed the heater core independent of the block, wasnt that bad, pain in the but but could be worse. i got a lil more heat. but just. going to run some solvents through it again and flush out the radiator one more time.

 

So what was the final solution?

 

I'd definitely look into changing the thermostat if you havent already. Mine was original in my 94 when i changed it 2 months ago.