Thread: 300tdi cooling system question

remove the thermostat plug open the expansion tank fill from the expansion tank till it runs out the thermostat. replug the thermostat.

turn the heater on flat out,start engine and maintain 1200-1500rpm, and if the level in the expansion tank drops top it up.

once the engine has warmed up fill the expansion tank to just over the correct level and then cap the tank.

that should have you sorted.

Why turn the heater on?

Because the coolant system incorporates the heater - there are hoses running to the heater unit when you have a look under the bonnet.

I could write an essay on this but I won't

The Engine saver instruction sheet says:-

Radiator Sensor Installation
Carefully remove the black plastic or brass bleed screw from the top of the radiator..
Keep it in the glove box in case you want to remove the Engine Saver when you sell the vehicle.
Lubricate the O ring on the new Sensor Plug with washing up liquid and screw it in taking care not to cross thread it.


The thermostat is higher than the level of the coolant in the header tank.
How do I know?
During testing a laser level was run through the engine bay of a 300 TDi.

locating the sensor in the thermostat housing will give maximum sensitivity at the cost of false alarms when the engine is at rest due to the natural air pocket which most engines seem to develop at rest.

This is also why we say to connect the alarm to a power supply which switches on and of with the ignition, as Landy Andy discovered on a recent camping trip
with his alarm connected to the auxilliary circuit
His alarm went of due to an air pocket after running his gear without the engine on.



Hope this helps

Davy

when you drop the coolant it usually picks up an air pocket there, if the valves for the heater flow are closed it cant purge out.

if its gone dry it takes about 1l to fill it as well as the pipes that feed it and thats more than is in the expansion tank when filled to the nominal full point.

once the expansion tank is empty it can cause an air feed to circulate in the engine the water pump churns this into froth and then you get all sorts of fun problems if you havent picked it up. On some older low water sensors the froth is enough to stop the sensor sounding but is about as usefull as porridge for cooling your engine.

No point in turning the heater on as water flows through the core all the time in a 300Tdi, there isn't a valve that regulates water flow as heater temperature is regulated by air flow, not water.

someones been bad then, Ive seen a few with bypasses fitted....

without bothering to do more research I assumed that the heater unit had a change point in a year model.

Originally Posted by Blknight.aus

once the expansion tank is empty it can cause an air feed to circulate in the engine the water pump churns this into froth and then you get all sorts of fun problems if you havent picked it up. On some older low water sensors the froth is enough to stop the sensor sounding but is about as usefull as porridge for cooling your engine.

This is what is happening with mine when I look inside the thermostat once the engine has stopped. So ill try your suggestion Blknight and fill the expansion tank to get rid of the air.

I will also move the sensor to the radiator as per instructions.

Thanks all.