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

83,145

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

Add photo

Related Questions

Search Mazda MAZDA3 Questions

UK Questions

Are you a UK consumer? CarGurus now has a discussion forum in the UK.

Mazda MAZDA3 Experts

#1 Tom Demyan
Tom Demyan
Reputation 340
#2 Richard Boettger
Richard Boettger
Reputation 230
#3 FordNut
FordNut
Reputation 190
View All

Related Models For Sale

Used Mazda MAZDA6
198 Great Deals out of 15,478 listings starting at $2,400
Used Honda Civic
817 Great Deals out of 69,478 listings starting at $1,200
Used Toyota Corolla
989 Great Deals out of 66,021 listings starting at $1,595
Used Honda Accord
988 Great Deals out of 74,848 listings starting at $899
Used Ford Focus
867 Great Deals out of 58,281 listings starting at $800
Used Toyota Camry
1,181 Great Deals out of 95,093 listings starting at $1,250
Used Mazda MAZDASPEED3
34 Great Deals out of 380 listings starting at $3,500
Used Hyundai Elantra
664 Great Deals out of 51,952 listings starting at $895
Used Nissan Altima
1,049 Great Deals out of 82,898 listings starting at $670
Used Volkswagen Jetta
510 Great Deals out of 31,465 listings starting at $1,000
Used Subaru Impreza
153 Great Deals out of 10,709 listings starting at $1,295
Used Mazda MAZDA5
43 Great Deals out of 1,537 listings starting at $3,400
Used BMW 3 Series
1,501 Great Deals out of 38,748 listings starting at $1,495

Used Cars For Sale

2017 Mazda MAZDA3 For Sale
14,653 listings starting at $16,460
2016 Mazda MAZDA3 For Sale
21 Great Deals out of 4,254 listings starting at $10,999
2015 Mazda MAZDA3 For Sale
63 Great Deals out of 1,336 listings starting at $9,980
2014 Mazda MAZDA3 For Sale
60 Great Deals out of 1,301 listings starting at $8,923
2013 Mazda MAZDA3 For Sale
82 Great Deals out of 1,505 listings starting at $5,995