Tested new thermostat and then put it in my 02 Taurus: Still no heat. The first new thermostat did not work, I tested it in boiling water after I took it out and sure enough it did not open. I tested the second new thermostat before I put it in: Still no heat. I had trouble with leaks and also broke the housing. I have repaired the housing with JB weld and I have no leaks. In the process I quit wasting coolant and used water to replace the little that spilled out each time. The reservoir is full of coolant. I am not sure how it works. Is it possible there is mostly water in the engine and it is just to cold outside at 12 degrees for the engine to warm the water enough to open the thermostat? I hate to change it again since I know it works and each time I need to buy a new tube of thermostat gasket sealer which is about 4 dollars. The heater core may have a very mild leak in it but no moisture on the floor and very little moisture on the windshield. Is it safe to drive the care if the thermostat is not working? Thanks in advance!!
Hello,it'spossible with just watr it wont throw heat and also possibl your heater core is going out.Jim
It's possibly that the heating c opil is clogged and you not circulating the water through the coil
I would tend to agree with John. Are you SURE that ,A. you replaced the heater hoses to correct tubes, B that the core is not plugged up. Whether you use water or coolant won't make a diff with this problem.
A long time ago on an old Ford I had a water pump whose vanes had worn down, this resulted in low heat. Might be worth checking.
If the original thermostat wasn't opening the engine would have been overheating. No cabin heat is rarely caused by a bad thermostat, yet it's the first thing every DIYer will change. There is usually a valve in one of the hoses that controls the water flow to the heater core. Then there is a door in the box with the heater core that directs the air flow through the A/C evaporator or the heater core. Both of these are controlled by vacuum. Look around under the hood for a broken, cracked or dislodged vacuum hose.
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