Pressurised header tank?

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Joined: 24 Jul 2020, 05:04
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Location: Lincoln

Pressurised header tank?

Post by OldSmithy »

So a couple of weeks ago as I set off on holiday my van 1990 1.9DG lost its coolant and started to overheat. I limped it home and traced the leak to the core plug at the bottom of the engine. This seems perfectly ok now I have replaced it and refilled the system. I’ve had to quarantine for 14 days after getting back from holiday so today was my first drive except for revving it on the driveway.

I went out for about an hour with speeds of up to 65mph and also through some villages at 30mph. Temperature gauge held steady, heater worked, fan kicked in and out. I have a couple of very minor water marks on the water jacket seal once it cooled down and one droplet of water (not a constant drip). The expansion tank did not fill (or at least overfill) and hasn’t gone down so nothing major sucked back into the header tank as it cooled. Hence, everything appears fine.

I’ve just undone the header tank cap to check it is brimmed still and all is ok and about half a litre of water was pushed out. There was no air just water which clearly was under some pressure still. I did top up the header tank whilst revving the engine (which reduced coolant levels in the tank slightly) and put the cap back on under revs as part of the bleed process so as I wasn’t revving it this time that may be expected. I think I left it to cool long enough so my question is if the tank once cold should still hold the water under some pressure such that it would push a little out or should it depressurise as it cools too? I can check it later by going for another drive.

I know that the droplet may mean I need to sort something in future regarding the water jacket but I’m trying to gauge just how big an issue the pressurisation may be or if it is normal.


1990 Komet Autohomes 1.9 DG 5 Speed

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