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Heater wont get hot

(1994 Mazda B3000)
in Hutchinson, KS on December 19, 2010
If I drive it around and let it idle for about an hour it gets a little warm, I changed the thermostat and took heater core out to change it but it looks as if it was recently replaced so I hooked it up under hood to look for leaks and see how hot it got after 30 minutes running and jst got warm enuf not to touch nt very hot though how and if I rev the engine u can just watch the temp gauge cool off everytime hlp plz I'm lost
Displaying 1 answers & 11 comments
Popular Answer
on December 19, 2010
Do you have hot hoses going in and coming out of the heater core? And you say they are not scalding hot, but "warm enough"?

Since you changed the thermostat and accessed the heater core, have you made sure there is no air pocket in the cooling system now?
on December 20, 2010
Yes I tried burping the system some times it will gt kinda warm but I dnt think it pressures up unless I rev the engine cause heater hoses are never tight they completely squeeze closed if u pinch with ur fingers. I took 1 hose off at heater core and fluid barely runs out don't matter which hose either and it dont have an inline valve could this possibly b a water pump problem I mean rev the engine with radiator cap off and can see the fluid bein pulled down pretty good but I don't understand the temp gauge never really gets to normal and whn sitting or driving and are accelerating the temp drops like how an oil gauge would move
on December 20, 2010
You could theoretically have a water pump problem, but it's not terribly common.

Make sure your thermostat is hot enough. An original equipment Mazda (Ford) unit is preferable. Aftermarket ones are rated at various temperatures, and you might get one that is too "cold" for the truck.
on December 22, 2010
Ok its a 195 degree thermostat i just changed it again because last nite i was in the truck and i had a continuous popping in the upper hose i think thermostat wasnt opening I tested the new one b4 I installed it. It opened at like 198 degrees but after running about 45 mins still temp gauge never got to normal running temp and still no hot air radiator was cold engine was at a good warm temp and the heater hose coming from the water pump was warm not hot but the other heater hose from intake below thermostat was hot what is causing this please help as to I dnt have much money for trial and error
on December 22, 2010
Is your fan running full speed all the time? Your cooling fan clutch might be an issue. I have concerns about the flow of your cooling system too, as all the hoses as they go through the engine should be about the same temperature -- very hot.

Make sure again the air is purged out of your cooling system after the latest thermostat change.
on December 22, 2010
Even if there was air in a line normally that would cause steam and would be pressuring the system and i should get a little more heat than I do i knw when the engine is off I can spin the fan a little over half way around with a decent amount of force to do so, i don't know what to do I'm freezing everyday driving it now
on December 22, 2010
No; air pockets cause cool air to be blown. The heater core doesn't do a thing with "steam".

I'm pretty darn sure that the fan should be freely spinning and only lock up when desired... if it is locked on all the time, you will never get to operating temperature.
on December 23, 2010
What's the best way to make sure I get all the air out of the system and to check how hard the fan spins
on December 24, 2010
Watch the fan while the engine runs. It should be fairly slow until the engine gets hot. You should be able to "stop" it with a tool, as it should not be firmly engaged.

The air - get the engine hot, open the cooling system pressurized cap, allow air (and some coolant) to escape; top off, get hot again, same thing... Just use extra care not to burn yourself.
on December 30, 2010
Ok I flushed system out and checked all ports and hoses for blockage and isn't any but did see rust residue in heater hose coming from intake under the thermostat I removed this hose while it was running and it took a good minute or more to see fluid pump out but I replaced the coolant and went thru cycle several times to releave air temp gauge now stays at normal but heater is still barely warm
on December 30, 2010
Make sure the inlet and outlet hoses at the heater core are both very hot.

At this point, you could have a temperature blend door issue in the dash. When you turn the knob to cold, does it get cold? Does it get warm again when turning it back?
on January 26, 2011
The flap is working and still no heat anybody want a truck its Hutchinson ks $600 I give up
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