Overheating

[Imagin3]

Year/Make/Model: 2007 Mazdaspeed 6
Mileage: 140500
Location:
Concern: Overheating
DTC's: None
Modifications: None
ECU/Tuning Software:
Tuner: Cobb Accessport V3
Is the concern intermittent? No
Can you duplicate the concern? Yes
Recent Repairs: Heads Machined, Head Gasket, Water Pump, Radiator, Thermostat
Correction:

Need some help dealing with an overheating issue. First started about 8k miles ago, had the thermostat replaced first then did compression leak test, determined the head gasket needed to be replaced and heads machined. Radiator then sprung a leak and had that replaced. A few thousand miles later, started overheating again randomly. Replaced water pump to no avail. Had shop look it over and found no leaks in coolant system or combustion leak into coolant. Car will idle all day long and never overheat. Can rev the car and it will never overheat, only when driving is it randomly creating an air pocket. Need another place to look before I give up.

 

[Awafrican]

did the shop replace the thermostat after each overheat or only the first time? should be replaced each time. I'd wager your lower rad return hose to the thermostat is old and collapsing under heat. happened to me in my old BMW. inspect all your rubber hoses it being an ms6 it's not unreasonable that the rubber might be shot by now after 20 yrs

 

[jsmith]

Have you replaced the cap on the overflow tank?

 

[Imagin3]

did the shop replace the thermostat after each overheat or only the first time? should be replaced each time. I'd wager your lower rad return hose to the thermostat is old and collapsing under heat. happened to me in my old BMW. inspect all your rubber hoses it being an ms6 it's not unreasonable that the rubber might be shot by now after 20 yrs

Naw, I've only ever replaced the thermo once. I thought about going after that again but decided not to given I had just did all that work to replace the waterpump. Definitely worth a shot though given its inexpensive.

Have you replaced the cap on the overflow tank?

Would the plastic cap on the overflow really be an issue? I thought only the radiator cap would be an issue and that's new.

Does anyone know if the turbo itself could be the issue? Not sure if it's oil or water-cooled but wondering if a failing turbo could introduce air into the coolant.

 

[Awafrican]

yes the cap on the overflow would be an issue that also pressurizes the system. it's probably not the turbo.
which thermostat went into the car? not all are created equal and some non oem ones are known to cause issues.
how to check hoses:

Template public:_media_site_embed_youtube not found. Try rebuilding or reinstalling the s9e/MediaSites add-on.

 

[jsmith]

Would the plastic cap on the overflow really be an issue? I thought only the radiator cap would be an issue and that's new.

Looks like you are right. MS6 has one on the radiator, not the overflow tank.

 

[Imagin3]

yes the cap on the overflow would be an issue that also pressurizes the system. it's probably not the turbo.
which thermostat went into the car? not all are created equal and some non oem ones are known to cause issues.
how to check hoses:

Template public:_media_site_embed_youtube not found. Try rebuilding or reinstalling the s9e/MediaSites add-on.

Not sure which thermo was installed. Hoping it was OEM and for a Speed6. I have seen elsewhere on this site that there are different thermo's that fit but may not function correctly so I will be getting an OEM from Mazda or at least match the part numbers when I replace again. Thanks for the video on checking the hoses, I've done this a few times on the upper hose, not to the lower.