Overheated on track - now what?

[infernosg]

Originally Posted by Pete_89T2

Definitely replace the cap with a new Mazda cap then. If it's not sealing properly, it won't hold its rated pressure, and this in turn will make it more likely to boil over.

If it's not a Mazda T-stat, I'd just replace it. The Mazda T-stat & gasket for it is pretty cheap, like under $15

I'll take a picture of the tear and post, but you're right, might as well replace it as they're only like $10. It looks like regardless of the condition of the engine I'll be needing a new thermostat so might as well pick up one of those as well.

Originally Posted by Pete_89T2

Not that I can find in the FSM. What I do whenever I flush & fill the system is make sure the heater is set to full heat before starting, and after I do the initial filling of the radiator with coolant, I'll let it idle with the rad cap off. When the engine reaches operating temp and the upper hose is hot to the touch, I'll run the engine in neutral at a constant 2~3K RPMs for a couple of minutes, then I'll quickly rev the engine up past 5K & back down to idle a few times, still with the cap off. When the level in the radiator drops (it will as trapped air pockets escape), add more coolant till its full. While you're doing this drill, the coolant level buzzer will sound off from time to time - it's normal. I keep repeating this process until I can't add any more coolant to the radiator. Then I top off the overflow tank with coolant to the full line, put the radiator cap back on, and take it for a drive. Let it cool down fully, check the level in the overflow tank, add coolant if needed to get it back to the full mark.

That all makes sense, but the problem I'm having is with the car on and the radiator cap off I get a lot of coolant coming up and spilling out. Maybe there was just a large air bubble pushing it all out but the pessimist in me says this is the pressure from the combustion chamber. Maybe another picture will suffice...

[infernosg]

Originally Posted by Pete_89T2

Definitely replace the cap with a new Mazda cap then. If it's not sealing properly, it won't hold its rated pressure, and this in turn will make it more likely to boil over.

If it's not a Mazda T-stat, I'd just replace it. The Mazda T-stat & gasket for it is pretty cheap, like under $15

I'll take a picture of the tear and post, but you're right, might as well replace it as they're only like $10. It looks like regardless of the condition of the engine I'll be needing a new thermostat so might as well pick up one of those as well.

Originally Posted by Pete_89T2

Not that I can find in the FSM. What I do whenever I flush & fill the system is make sure the heater is set to full heat before starting, and after I do the initial filling of the radiator with coolant, I'll let it idle with the rad cap off. When the engine reaches operating temp and the upper hose is hot to the touch, I'll run the engine in neutral at a constant 2~3K RPMs for a couple of minutes, then I'll quickly rev the engine up past 5K & back down to idle a few times, still with the cap off. When the level in the radiator drops (it will as trapped air pockets escape), add more coolant till its full. While you're doing this drill, the coolant level buzzer will sound off from time to time - it's normal. I keep repeating this process until I can't add any more coolant to the radiator. Then I top off the overflow tank with coolant to the full line, put the radiator cap back on, and take it for a drive. Let it cool down fully, check the level in the overflow tank, add coolant if needed to get it back to the full mark.

That all makes sense, but the problem I'm having is with the car on and the radiator cap off I get a lot of coolant coming up and spilling out. Maybe there was just a large air bubble pushing it all out but the pessimist in me says this is the pressure from the combustion chamber. Maybe another picture will suffice...