Irrigate my passages

[Peetee]

With the water pump off I can see the state of the water channel in the block. It's in a poor way with a huge ridge of rusty scale marking the waterline.

What would you recommend to clean it out with the engine in-situ? Likewise, what can I dip the cylinder head in to sort out the gunge in that?

[d_harris]

Coca cola....

[MarkyB]

The water line?
Is your engine tidal?
Drain cleaner has been suggested before.

[PSL184]

Rad flush which is some kind of caustic soda I think.....

[bmcecosse]

Don't worry about it too much -scrape away anything obvious - and when it's back together run some drain cleaner through it - but don't leave it in for more than one 'heat cycle' - then drain and flush with a hose pipe. Then refill with anti-freeze of course!!

[Peetee]

The tide line doesn't worry me but the almost complete crusty masking of all the water channnels visible on the face of the cylinder head does.

[bmcecosse]

Just clear them out with a drill bit held in the hand.