2007 Mazda 3 Replaced Thermostat Now Cool Air on Idle

Asked by Jan 18, 2016 at 12:18 PM about the 2007 Mazda MAZDA3 GS

Question type: Maintenance & Repair

2007 Mazda 3 - Threw a CEL - (P0128 - Coolant
Thermostat (Coolant Temp Below Thermostat Regulating
Temperature)

Fixed CEL by Replacing Thermostat -

I Flushed Coolant and Replaced Thermostat -


                   New Problem -
-After replacing thermostat and adding new coolant -
Heater blows cool air when at idle even when temp is
engine temp is normal. When car engine reaches 2,500+
RPM it blows hot air. As soon as I come to a stop it blows
cool air (slightly warm). (This was not an issue prior to
replacing thermostat & coolant)

                       Things I’ve attempted -
-Iv’e attempted to "belch" the coolant lines - I’m not sure
if I’ve done it properly but it appears to fixed it about
25%-50%

-Also checked to make sure that the coolant level was at
the correct level, while the engine was both cold and
warm.

Thing’s i’ve checked & I don’t know if it could be
indication of whats going on)
-The Coolant reservoir appears to be reaching
temperature and creating pressure. - I’ve unscrewed cap
after car has warmed up and pressure has released.

-At one point I had Coolant reservoir cap off while car was
idling and coolant overflowed (Not sure if it’s supposed to
do that)

-After car is warmed up - I noticed only one of the two
hoses coming from the thermostat feels warm to the
touch.

-Replacing the OEM thermostat, looked slightly different
from the new one I put on. The difference appeared to be
a hole on the side of it (Possibly for burping the coolant?)

-Iv’e seen no signs of leaks, or anything like that as of
right now.

2 Answers

100,385

The hole is to help getting the air out of the system, a good thermostat will either have the hole or a jiggle pin in the body, it sounds like you still have air in the system. Sometimes you have to raise the front of the vehicles front up about 6 to 8 inches and slowly add coolant until it stops. There us another problem I should mention, if the cooling system is making pressure in a very short time when started cold it could be a blown head gasket or cracked head.

Okay, must still be air in the system. Pressure occurs in the coolant reservoir only after the vehicle is warmed up (15-20mins)- would a bad coolant sensor show these symtoms ?

Your Answer

Mazda MAZDA3 Experts

  • #1
    Tom Demyan
    Reputation
    400
  • #2
    Richard Boettger
    Reputation
    240
  • #3
    Tracy Hooks
    Reputation
    150
View All

Related Models For Sale

Used Mazda MAZDA6
166 Great Deals out of 11,258 listings starting at $1,599
Used Honda Civic
814 Great Deals out of 73,912 listings starting at $1,400
Used Toyota Corolla
916 Great Deals out of 57,791 listings starting at $1,488
Used Honda Accord
1,136 Great Deals out of 62,431 listings starting at $1,199
Used Ford Focus
750 Great Deals out of 53,163 listings starting at $999
Used Toyota Camry
1,076 Great Deals out of 73,749 listings starting at $295
Used Mazda MAZDASPEED3
12 Great Deals out of 359 listings starting at $4,995
Used Hyundai Elantra
506 Great Deals out of 42,811 listings starting at $2,295
Used Nissan Altima
1,014 Great Deals out of 75,761 listings starting at $1,627
Used Volkswagen Jetta
597 Great Deals out of 36,423 listings starting at $1,100
Used Subaru Impreza
182 Great Deals out of 19,845 listings starting at $2,200
Used Mazda MAZDA5
49 Great Deals out of 1,213 listings starting at $2,700

Used Cars For Sale

2017 Mazda MAZDA3 For Sale
8 Great Deals out of 7,508 listings starting at $12,999
2016 Mazda MAZDA3 For Sale
38 Great Deals out of 2,250 listings starting at $9,995
2015 Mazda MAZDA3 For Sale
49 Great Deals out of 1,207 listings starting at $7,980
2014 Mazda MAZDA3 For Sale
102 Great Deals out of 2,213 listings starting at $8,100
2013 Mazda MAZDA3 For Sale
27 Great Deals out of 825 listings starting at $4,995

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.