Air lock

I now own a 2.5 TDI ES and done the head gasket today but cant get the air out of the system I have been reading a few posts on here but tried a few with no luck so i guess this is a common problem with these cars. Is there a propper way to do this or is it just pot luck ? I tried removing pipes until it ran water and at first it worked untill i was on my way home and it lost the heater again and temp went up but it then got hot again and then fell. I am really starting to think about buying a big jacket and removing the thermo just to keep it right.


Any sugestions are very welcome

Did u fill up the water via the 2 bleed screws on the head/radiator? I had this problem with mine but undoing the 2 big nut things fixed it!

I don't have probs with my disco but years ago with my RRC I had to ether park facing up a slope or jack the front up so the header tank/top of rad was the highest point and bleed the system like that, even just running the engine and letting the coolent circulate worked for some, as we know air will rise to the highest point and it works.

i just had the exact same problem, keep topping the system up from the bleed screw on the top of the thermostat housing, worked for me you have to fill it from yhe highest point on your engine untill it is squirting out a little,

Yu HAVE replaced those ****ty plastic bungs with household radiator bleed valves - havent you? If not, do that first. Best £3 yu will spend (apart from the penny trick).

Is it 300% better then the penny trick or 300% worse???

bigjohn1 said:

I now own a 2.5 TDI ES and done the head gasket today but cant get the air out of the system I have been reading a few posts on here but tried a few with no luck so i guess this is a common problem with these cars. Is there a propper way to do this or is it just pot luck ? I tried removing pipes until it ran water and at first it worked untill i was on my way home and it lost the heater again and temp went up but it then got hot again and then fell. I am really starting to think about buying a big jacket and removing the thermo just to keep it right.


Any sugestions are very welcome

Click to expand...

I find the best way to fill the system on a 300tdi is by the heater flow pipe.
This is the one that rises off the top of the head near the back not the metal horizontal pipe. Undo the clip, pull the pipe off the connection, get someone to hold a finger over the metal pipe connection, hold the rubber heater pipe vertically and fill with coolant. When overflowing quickly push the pipe back on the connection and tighten clip. Usually works.

the way I would do it is the 'coke bottle method'

undo all bleed screws

use a small long bit of pipe to blow through the header tank using your hand to make it air tight

now a friend would be useful - whilst blowing through the pipe water will run out of first bleed screw - still blowing tighten that up.

continue the process til all bleed screws are complete, do not stop blowing. now run engine and top up as needed- then replace cap

job done

When I did my head (slightly different from just coolant change etc as the whole system get's much emptier) I didn't put the heater feed pipe onto the head until water was coming out of it, as soon as it pours from this you know the block and head have a fair bit of water in them, then keep filling for a while and start the engine.

Keep the little pipe off the thermostat housing (the one that goes to the tank) and watch for air bubbles etc, when it's fairly clear you can stick it back on.

Watch the tank and the level will drop, keep topping it up, as the engine comes up to temp and starts to feed the radiator it will drop again. Check the heater pipes are hot on both sides - this means there is water flowing.

Once it settles a bit go for a drive. It may take a few checks and top ups until it is spot on. But it's easier to just top up after 50miles or so.

There are all sorts of ways to do it in one go, like jacking the front end up so the heater pipes are now lower than the rad, then you can undo the filler cap and top up from here. But I have found it's not really worth it.

Thanks for all the reply's guys and i got it sorted with all your help. I stuck the front end on a 4 poster ramp at work and filled the rad from plastic bleed screw and then on thermo. Left it there for 10 mins running and heaters got hot so went for a drive and its mint now. I have been a mechanic for 20+yrs now and this has to be the worst car i have ever had to sort.... lol


Thanks again guys :5bparty:

did yu replace that crap plastic bleed screw with a proper bleed valve?

Not yet mate but a trip to B&Q is planned for sat then it should be all sorted and sunday is a trip out to the beach to get some mud on it....lol