Thread: Bleeding TD5 cooling system

I'll bow to those with greater knowledge but simply not putting enough coolant wont cause a "loss" of coolant. There would need to be a leak.

However if you were to under fill significantly then my understanding is you would get less cooling therefore higher engine temp and also "air" in the cooling galleries would/could cause damage to block by the uneven cooling.

Air doesn't transfer heat as well as coolant hence where air (bubbles) contacts the metal inside the engine it causes little hot spots which then come in contact with the coolant and can cause metal to "flake" (small) in teh galleries. (Something like that).

When I do my coolant (distilled water with redline) I give the vehicle a good run and check the coolant level every day for the next week to see any air was trapped during the change over. When doing long trips I check every day and usually when filling up?

if you have air trapped in the cooling system........after you take it for a drive.......
when the thermostat opens and the coolant starts to flow through the system.....the air may be pushed out by
the water pressure/flow.........this will find its way to the highest point in the cooling system.......
which should be the reservior........
which will cause the level in the reservior to drop........


there is a bleeder screw on the top hose on a td5........and also one to drain with on the bottom hose.......

and when doing a coolant flush.........make sure the heater is turned on.......
so that gets flushed out and bled as well.......

and thats the nice version... heres the nasty...

that pocket of air gets super hot as does the metal under it..

when fresh coolant hits it it boils instantly and blows coolant out of the system via overpressurisation..

Assuming you have enough coolant to cool the hot metal (and that in the process of doing that you dont frell the head) you have, at a guess, now lost anything up to about 2l of coolant.