Losing water, coolant

[billysmart]

I am losing water/coolant at a very slow rate, i rebuilt the the unit due to an overheating problem 4 months ago, head skimmed, all new gaskets including P, new rad last year.

Loss has occured during the cold snap, the coolant ratio is as spec and i cannot see any obvious places for the leak, clips all tight and pipes all in order, no fouling in the oil, no smoke and no loss of power...

A long shot i know but is there anything obvious that i am missing?

Thanks

Paul

[JimAttrill]

How slow is it?

I top up my 300Tdi about once a month with antifreeze mix but only about a cupful.

If you have to top it up every day then you maybe have a problem. The favourite place on a Tdi is at the P gasket behind the alternator, though if that is leaking it is normally very easy to see.

[fozsug]

Core plug at the back of the head, or the core plug behind the belt tensioner?

[Tetsu0san]

Leaky header tank perhaps? Especially if the engine overheated.

Could also be the core plug at the back of the block and that is a right bugger to fix.

Try to get a pressure thingy (can't remember what it is actually called) to pressurise the water system without running the engine and see if there are any obvious leaks. If it is only a little bit of water leaking, then the heat of a running engine would evaporate the leaking water and you would have no idea where it is getting out.

[JimAttrill]

And if you have ANY suspicion that the coolant is getting into the cylinders, take the glow plugs out before turning it on the starter. I pressure tested a 300tdi and then bent a con rod trying to turn it on the starter (it didn't turn but bent the rod).

Or you can jack up one front wheel and turn the engine that way to see if it has hydraulicked.