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Radiator Cap Issue


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I'm not sure where to post this since the issue is with a 2008 and a 2012; both H6 cars.

My son complained of "getting warm" on a 73° day, pulled the radiator cap and found the negative pressure valve parts missing. I did recover the spring just sitting on the coils in the upper tank. So, we ordered 2 caps from Subaru. When they arrived, we replaced the caps in both cars, and yes, I had to recover the spring in my car as well. WTF!

1) Where are the other parts?

2) Are they wreaking havoc some place in the motor and where?

3) How to retrieve said parts?

4) What to replace the caps with that operate properly AND don't fall apart?


The search for anything related to Subaru Radiator caps BOTH on the WEB and within several forums is overwhelming, yet no one mentions this particular issue.

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I've had this happen to me with old OEM and not so old aftermarket radiator caps in several previous vehicles. Disclaimer: this is my first Subaru and I haven't had this happen to it yet. Without the internal parts the cap will leak some. You may smell evaporated coolant but never see a drip. My last acura ate the internals of 2 or 3 radiator caps (during my ownership). I never recovered all the parts of any of the caps. I figure the parts are too large to ever escape the narrow spaces inside a radiator core, and there is enough space around wherever the parts lodge for coolant to still flow around. That acura radiator kept going with all those cap parts in it and finally started leaking at a crimp point at ~235K. I believe it was the original, and over 15 years old.

So... recover what parts you can, replace the caps, don't panic unless the vehicle continues to overheat after you've topped off and burped the coolant system.

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Well, unless these little parts block a coolant passage. I believe these systems return coolant to the motor via the top hoses, in which case, these get into the block someplace, just where?
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