Thread: Video showing how the TD5 LR coolant fill method creates airlock

It’s not complicated. As Tombie says all you need to do is fill with the nose up, eg park on a significant hill. Fill, take car for a spin, check and top up if necessary.

I also thought that elevating the front and taking it for spin would work - not so.
Before I made these videos - which are for enquiring minds - I experienced this airlock when I first refilled the cooling system after a fitting a new radiator and backflushing everything, and yes I did actually have the nose of the car elevated on a rise and then carried out the recommended LR technique.
I took it for a spin - result was no flow through the heater and extremely hard hoses - so hard they could not be squeezed at all.
For the information of all, normally the internal coolant circuit pressure is 7 - 9 psi with no airlock and the hoses are easy to squeeze.
There was clearly an airlock so I decided to find out how that could occur - even after having elevated the nose of the vehicle.
Anyway, You can easily simulate raising the nose of the vehicle by
1. lowering the feed hose to the matrix - you would expect the airlock to break - it simply does not no matter how you manipulate the height of the matrix feed hose relative to the coolant bottle.
2. elevate the coolant bottle as high as you like which is the same as elevating the nose of the vehicle.
In the first video you can see that elevating the coolant as high as possible does not drive coolant into the matrix feed.
So the car up on ramps is not the remedy - in fact I tested this theory and observing the clear plastic tube I got the same result.
Everything in this cooling system is new so I dont believe the car is an outlier. When I get rid of the airlock the heater works immediately a few minutes after start and the cooling system pressure is rock steady at 7psi when coolant temp reaches its normal value- with airlock the internal pressure is double that.
I can observe this cooling system pressure by a gauge.
BTW - There are no combustion gases getting into the system - system pressure is steady plus or minus 1 psi at all times since I made these videos and removed the airlock as shown. Head gasket issues would cause continual high coolant system pressure
There are dozens of posts on D2 forums where people have done a coolant change and have reported no heater and an apparent airlock - the info I have posted is to simply explain why and help them out.

Originally Posted by peter51

2. elevate the coolant bottle as high as you like which is the same as elevating the nose of the vehicle.

You have clearly given this a lot of thought, and i thank you for your efforts. However, I don't believe the above statement to be correct. Elevating the nose of the vehicle is done to make the top of the radiator, and by extension the top hose, the highest part of the system, which it is not on level ground, at least on my car. That tube on the turbo side of the head is. Lifting the tank doesn't alter that relationship. Raising the front of the car and then lifting the tank is what I'd try.

I'm not saying you are wrong. It's a fascinating experiment which I'm sure we can all benefit from.

You know, I’m dealing with this on top of everything else right now too. I’m just gonna bypass the stupid heater core. Don’t need it here anyway, especially with moving to north QLD in the next week. Eliminate the airlock problem once and for all. Cap off the heater core so it doesn’t corrode out for if I ever decide I want to use it again.

park it or jack it so the header tank is at the high point, turn the heater on flat out, blanket the radiator and do the coke bottle trick in the header tank.

Done

I may be wrong here, but this is my take on it.

I have probably at least six to seven times since owning my D2 had to refill cooling system. I have just followed RAVE which says to remove coolant tank and raise.

Fill till coolant comes out bleed screw.

Now if it is not filling the heater core at this point, I am sure after a good drive the air in the system will eventually find its way out.

Which would explain why it often needs a small top up.

I have never had any overheating issues in 14 years of ownership, even towing a 20 foot caravan on 40 degree day and the heater works well

Originally Posted by Blknight.aus

park it or jack it so the header tank is at the high point, turn the heater on flat out, blanket the radiator and do the coke bottle trick in the header tank.

Done

What exactly is the “coke bottle trick,” that I’ve seen referenced here a few times?

I have used in the past the vacuum air process, it will remove all the air from the system and on new vehicles it works well. BUT for aged vehicles such as our D2 it puts all components especially the seals for the engine oil cooler etc under stress, on the other hand it exposes weakness that should be rectified before natural failure.

User beware...


What is a Vacuum Coolant Refiller, and why do You Need One? - YouTube