Hot water system

[Pjj]

Is the header tank another name for the coolant tank?

Yes

 

[Mr B]

Yes

So do these systems have a pressure relief valve or does the coolant/water just expand in the header tank as it heats up?

 

[Pjj]

So do these systems have a pressure relief valve or does the coolant/water just expand in the header tank as it heats up?

The cap has a valve in it that acts as a pressure relief valve I found it didn’t work very well so drilled a hole in the cap and put a bit of hose up in the air from it

 

[Mr B]

The cap has a valve in it that acts as a pressure relief valve I found it didn’t work very well so drilled a hole in the cap and put a bit of hose up in the air from it

Thanks for the info. A quick easy fix.
I'm trying to get my head around how these hot water diesel systems work.