Cylinder head core plug.

Post Fri Sep 04, 2026 8:39 pm

Hi, pulled into my garage Sunday and coolant started pouring from the front of the engine. After a fruitless search with mirror, torch and endoscope I stripped down the cooling system looking for obvious hose splits. Had the radiator out filled it with water. No leaks, of course its not pressurised. So, I'm thinking the core plug on the front of the cylinder head is leaking. Is there anyway to check it visually without removing the cam wheel? I'd be grateful for any ideas and am I thinking in the right direction?

Post Mon Sep 07, 2026 3:53 pm

Well, I'll answer my own question

. You can get to see the lower part of the core plug. Remove the upper section of the cam cover and look to the lower right of the cam wheel. With a bit of a faff I got my mobile positioned and got a video. It was all made easier with the radiator and the kidney grill removed.

Post Mon Sep 07, 2026 6:15 pm

Post Mon Sep 07, 2026 8:43 pm

And... latest news! The core plug appears sound. No witness marks to indicate its been leaking. Reassembled everything and filled with water for now. Run at idle up to temperature. No leaks! Test drive to come when time permits and if all's well I'll refill with coolant. I don't know why it gushed out in the first place though. Maybe I said something that upset it on Sunday

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Post Sun Sep 13, 2026 5:20 pm

Pressure test at my local garage showed no pressure drop off, no leaks. Conclusion: I misinterpreted to drama at the front of the engine. It was likely the radiator cap releasing pressure and the overflow running into the undertray. Research on this site says that I should have a yellow indicator on the radiator cap. All's fine at the moment but I'm ordering a new radiator cap from BMW.