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Jerry, Master Mechanic
Category: Mazda
Satisfied Customers: 17217
Experience:  ASE Master certified, 30 years experience. Auto troubleshooting, electrical , ABS, SRS, EFI system
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It quit producing heat. Had a radiator plug failure last

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It quit producing heat. Had a radiator plug failure last week when the fan didn't turn on and coolant got hot. The plastic plug is approximately 2" outboard of the lower coolant hose. Removed the radiator, replaced the plug, reinstalled, and serviced with anti-freeze. System took approximately 1.5 gal total. Since then, no heat. Fan blows cold air. Apparently a blockage in the line to or from the heater core of some kind or maybe a clogged core. Was told to jack up front of car then run it to clear a possible air blockage. Ran car for over an hour with front raised 18". All that happened was coolant got hot again with on fan coming on and STILL no hot air in car. I'm guessing you'll tell me to change the temp sensor, but that still doesn't seem to address the lack of hot coolant getting to the heater core. Help.
JA: Have you checked the connectors on the sensor itself? It's important that they not be loose or corroded. What is the model/year of your Mazda?
Customer: It's a '91. Where is the connector and associated sensor? The fan will run when engine is warm occasionally. It did once last week post radiator reinstall. Is there another sensor for the heating system?
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: I'm fixing it myself. Told you both all that's transpired with it since last Monday pm when the plug failed.
JA: Anything else you want the mechanic to know before I connect you?
Customer: Can't think of anything else to share that's related. 274,000 on it.

Hello and welcome. My name is ***** ***** you for visiting the site, I am reviewing your question and will reply shortly, thanks.

1991 Mazda what?

How is the thermostat?

Customer: replied 3 months ago.
That seems to be working fine. Local trips plus a 120 mile round trip showed normal temp indications.
Customer: replied 3 months ago.
39;91 mx6.

I see, thanks. Do both of the heater hoses feel hot after running for a while?

Customer: replied 3 months ago.
Customer: replied 3 months ago.
Maybe not hot, but warm.

Sometimes it hard to tell if the temp door actuator is working. Does it seem to change any when going from hot to cold? (like get colder)

Customer: replied 3 months ago.
No, always cold or at best garage temp.

That could just be a bad actuator for the temp door but you may want to try flushing the heater core with a garden hose and blow some shop air through it first. It's more common for the heater core to become plugged up after the system has been opened up.

Customer: replied 3 months ago.
Will give that a shot. Thanks. Are they easy to get at or a pain?

The actuator is on top center of the heater box, about 3 hours book time. There is a test for it but you have to get at it to test, thanks.

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