Originally Posted by Aretoo
First thing to do is try replacing your cap. Over time the caps can weaken and not hold the right amount of pressure causing them to leak. Personally I would only use an OEM replacement cap as there is some question about the quality of some of the aftermarket caps.
If you replace the cap and still have puking issues then you need to look at doing a pressure test. Look at this thread for making a coolant test gauge and what to look for.
Homemade coolant pressure gauge
I and several other members here have the stant cap and haven't had any problems with it, I just wish it clicked when tightened.
Also to the OP if you need a pressure testing gauge I'd be willing to let you borrow mine.
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