Now i have air in coolant system!

**86mud** · 18th February 2014, 08:01 AM

As per previous thread, my Defender 300tdi has been sitting for 48 hours since I last drove it after installing new radiator, and new fans.

Today I go to start it and the low coolant alarm is screaming at me. So I pop the bonnet, and undo the sensor (which I have in the top of the radiator) The coolant is down slightly - just below the sensor level.

I top it up and off I go. Only a short trip but enough to get to operating temp. I get home pop the bonnet to check things and squeeze the top radiator hose to check pressure - nothing! No pressure at all in any hose.

Today I will order a new radiator cap and new expansion tank bleed hose. Even though these items are only just over 12 months ago.

Any other ideas? When I replaced the coolant I had the vehicle parked on a slight hill facing upwards and bled the system via the thermostat housing bung....maybe I didn't do it enough?

Thanks heaps

**Bazzle218** · 18th February 2014, 10:34 AM

My way. Open radiator top bung and thermostat bung. Fill through expansion tank till coolant runs out of radiator. put in radiator bung and put cap back on expansion tank. Now fill thermostat housing, till full and replace bung. open heater and go for drive. When you get back check water level. I also let it cool down and refill via the thermo bung to top up level. works for me with no issues.

**86mud** · 18th February 2014, 11:43 AM

Thanks for that...will give this a try this afternoon...assume on flat ground?

**Bazzle218** · 18th February 2014, 03:45 PM

yes, dont forget if you have drained the system turn the heater on to circulate any trapped air in that side of things. When I replaced heater hoses it took till the thermostat opened to purge any air. Baz

**uninformed** · 18th February 2014, 04:06 PM

We need to stop this myth regarding the heater in TDi defenders.

The water is circulating through them 100% of the time. There is no valve, tap, switch, solenoid or anything that controls water flow through it. The controls in the cab simply operate a flap the directs, or not, outside air over the heater core. The other two operate the electric fan and the direction for footwell or dash

Turning the heater "on" does nothing for bleeding the coolant system.

**rover-56** · 18th February 2014, 04:43 PM

My way is:
Set the vehicle so that the expansion tank cap is slightly above the thermostat bung and the radiator bung.
Then fill slowly with the bungs removed.
Wait, keep topping the expansion tank until coolant flows out of one or the other bung hole. Replace bung.
Keep filling, be patient, let the air bleed thru the thermostat bleed hole.
Eventually the coolant will exit the second bung hole, fit bung.
Forget the heater, there is no water valve.
Run engine to running temp with the expansion tank cap off.
Top up as necessary.
Fit cap.
No more problems

Terry

**Bazzle218** · 18th February 2014, 06:10 PM

I stand corrected uniformed and humble apologies for misinformation.

I stand corrected and bare my back for a flogging. Saying that air will be in the heater hoses as they are higher than the block if the system is fully drained.

**uninformed** · 18th February 2014, 07:32 PM

You are correct Baz, in that it is the highest point and a trap for air. Its a bit of a bugger but it comes out eventually.

You are not the first and wont be the last to say turn the heater on to circulate the water

**86mud** · 19th February 2014, 06:36 AM

Thanks heaps for this.

A new cap and expansion tank bleed hose should arrive today so will fit tonight and refill coolant.

Cheers

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