P38A Bleeding the coolant

Hi all
I have changed the coolant in the car and the steps say to blow through the bleed pipe that goes from the rad to expansion tank have tried doing this but does it mean with forced air from a hose or blowing cos If they mean with your mouth mine is blocked as I get nowhere fast

take the hose off and see if its blocked, also check the rad and expansion tank ends to see if they are clear.

Not something I have ever bothered with. Flow to the expansion tank is usually confirmed when I start the engine and run it for a few minutes.

Thanks I'll check both ends then

Moonfire said:

Not something I have ever bothered with. Flow to the expansion tank is usually confirmed when I start the engine and run it for a few minutes.

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Well you wont get flow if there is a blockage

You need to make sure the bleed pipe is clear, that is where the air from the top of the rad escapes through as coolant is added. If it is blocked you will have an air pocket at the top of the radiator.

Evening Alan.

Hi I know you have to clear the bleed pipe but what I mean is should I be able to clear by just blowing through with my mouth or do I need pressurised air as I have tried blowing down the pipe but nothing comes out no air or water which makes me think it's blocked
Thanks in advance

Baileyroverq said:

Hi I know you have to clear the bleed pipe but what I mean is should I be able to clear by just blowing through with my mouth or do I need pressurised air as I have tried blowing down the pipe but nothing comes out no air or water which makes me think it's blocked
Thanks in advance

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You should be able to clear it of coolant by blowing with your mouth. If you can't, remove it and find out why you can't.

The few I've seen where it's been blocked, it's been crud up at the coolant tank end - usually in the plastic connector on the tank itself. A thin bit of wire usually helps dig anything out which is clogging it up.

Changed my water pump not so long ago so been doing this to get the air out of mine and if you blow on it with your mouth, then if there is coolant in there it's a bit of a blow to get it to shift, but once it's pushed through then you should be able to hear the air coming out at the coolant tank end.

Thanks for all the advice sorry for delay got it cleared with a piece if wire all good and bled now

For future ref - easiest way i find is disconnecting both ends - into cup of water and blow, see bubbles you are happy!

Falk said:

For future ref - easiest way i find is disconnecting both ends - into cup of water and blow, see bubbles you are happy!

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The rubber pipe will very rarely if ever get blocked. It is the nipple on the header tank that blocks up.

wammers said:

The rubber pipe will very rarely if ever get blocked. It is the nipple on the header tank that blocks up.

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Yep, but blowing through the connected pipe to the nipple doesn't do much If it is blocked. run the engine (obviously not warm and at op temp.) then as you disconnect there should be some coolant coming out of the nipple. Test and repeat. Or just run the engine and see if colant is coming through into the exp tank.

Had to replace my rad because of knocking that plastic nipple, expensive battery change !

Falk said:

Yep, but blowing through the connected pipe to the nipple doesn't do much If it is blocked. run the engine (obviously not warm and at op temp.) then as you disconnect there should be some coolant coming out of the nipple. Test and repeat. Or just run the engine and see if colant is coming through into the exp tank.

Had to replace my rad because of knocking that plastic nipple, expensive battery change !

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It does 99 times out of an 100 indicate that the nipple is blocked, as i said the pipe very rarely if ever blocks. So no cup trick needed.

Well general fitting reminder then easier than " listening for air " haha.

I heard somewhere that if you rev really really hard the water pump will give extra pressure and clear blockages. Let's just hope the blockage gave out before his gasket !

Falk said:

Well general fitting reminder then easier than " listening for air " haha.

I heard somewhere that if you rev really really hard the water pump will give extra pressure and clear blockages. Let's just hope the blockage gave out before his gasket !

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You could always take the pipe off put your finger over one end and blow then remove your finger and blow and see if there is a difference. Much better to have the cup full of tea. Try the high revs method and let me know how you get on.