Cooling system airlock on a Mk4 Polo!, Any ideas?

I have an airlock on a MK4 Polo

I recently replaced a faulty thermostat, which cured the overheating problem. Now the heater just blows cold air and I must have introduced air into the system.

I have flushed the system through (3 times now), and it does not make any difference. Thought the matrix might me blocked, so I put a hose down it and wached the water flow through the other hose. Even poured boiling water into the matrix and got hot air in the cabin, so I know it is not blocked. Problem is that the matrix is the highest part of the system, and that's where the air hides. Someone suggested bleeding the matrix, but I can't even see a bleed screw in the Haynes book. Another post claimed it took 10 hours to remove the dash and gain access to the matrix, so I'd rather not try!

At running temp (+ - 90 degrees), the hoses to the matrix, which have to climb up 3 inches, are hot at the bottom and cool at the top, so I suspect that there is no water circulating the matrix.

Must be an airlock. Any ideas on how to get rid of it? What do the dealers do? They must have a method?

Has anyone got any pearls of wisdom?

Thanks

You can get it vacuum filled, it's what I do with tricky airlocks, I think some of the quick fit outfits can do it when they change your coolant. Which is probably cheaper than asking the dealer.

Duncan

Thanks for the post.

Is there a special tool for the job. I'm guesssing that you have a device which fits on the expansion tank cap and produces a vacuum. Any idea where I could buy this?

Mark

Yes, but they're expensive.

You may get away with slackening the clip on the return hose when it's =

cold.

Sounds like the valve isn't fully open, turned to hot, or it's seized in the closed position, check the valve is operating when the control is operated. And a good blast with it turned to hot wouldn't hurt.

Steve

Is it like the MK2 & 3 polo that have a bleed valve at the highest point of the coolant system where the two heater hoses go into the fan unit? Follow the heater pipes to the area under the removable plastic panel between the bulkhead and wipers, it's a white tap there.

Alan.