Coolant question

[d2dave]

I have noticed when filling my 300 TDI that the thermostat housing is higher than the full level in the expansion tank. When filling through the thermostat housing as the book says, it slowly runs to the expansion tank and will ultimately over fill it.

So can anyone explain how this works.

Dave.

[PAT303]

Because the thermostat is closed,you'll find that after running it for 5mins the tank will be empty as the coolant runs throughout the block so keep a close eye on it and fill the tank full again and run it a second time up to full operating temp and check the level. Pat

[bee utey]

Gravity?

[wrinklearthur]

Its a uphill battle.
.

[d2dave]

Gravity?

That's my point. What keeps the coolant in the head.

Dave

[bee utey]

That's my point. What keeps the coolant in the head.

Dave

In your OP you state

I have noticed when filling my 300 TDI that the thermostat housing is higher than the full level in the expansion tank. When filling through the thermostat housing as the book says, it slowly runs to the expansion tank and will ultimately over fill it.
That's the way water flows, down hill, did you mean something else? The thermostat housing is connected to the expansion tank via the branch from the bottom radiator hose, and the bleed hose that runs under the a/c compressor. Check the bleed hose is not blocked up at the plastic tee piece thingy. Many people replace these with a brass tee piece.

What keeps water in the head is that you reinstall the plug when its full, and the bleed hose purges the thermostat housing of small bubbles when the water pump is turning, ie the engine is running.

[eddy]

I have just flushed my Disco's radiator and fitted some new hose clamps,where there were a few leaks.I found removing the brass plugs and filling through the expansion tank until they overflowed, ie very slow, was successful.When it came to the thermostat housing,I unbolted the expansion tank[3x10mm] and raised it as high as possible.When coolant came out of the housing, squeezed the heater hoses to remove air,when no more bubbles replaced brass plug.
All appears good,no gurgling,low coolant alarm silent.

[d2dave]

The way my book tells me to fill the cooling system is to remove the plug at the top of the thermostat housing and pour in coolant until full. I can not do this as the expansion tank is lower and the coolant just flows out the top.
So how do others do it?

Dave.

[bee utey]

The way my book tells me to fill the cooling system is to remove the plug at the top of the thermostat housing and pour in coolant until full. I can not do this as the expansion tank is lower and the coolant just flows out the top.
So how do others do it?

Dave.

Put the cap back on the expansion tank first! Fill thermo housing, fit plug, fill tank afterwards to correct level, test drive, let cool, check level again...

[Blknight.aus]

or leave the plug in place and use the coke bottle fill method.

[bigcarle]

the way i do my 300TDI is park my disco rear end down my fairly steep driveway, open both heater taps/switches and fill from the expansion tank until full then fill, cap then from the thermostat housing until over flowing install plug and then run. it sorts itself all out then :D