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A4 Heater blows cold unless the car is driven or revved


happychappy
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Hi Maersk,

The head was removed and pressure tested pressuming it was cracked. There was no sign of it being skimmed before. Regards the cold start smoke, i thought as things got hotter the leak would get worse due to expanse. Car going back in tomorrow to check that it's not over fuelling when it's cold. Strange thing occured to me tonight driving home, as the temp gauge started moving up from 50 the heaters where getting nice and warm, then as if the water pressure dropped (at around 80degrees) the heater temp dropped. I know vw's used to suffer from the expansion cap failing, does anybody know if this is still the case?

Regards

Stuart

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Good morning,

Just read on another forum that the turbo is oil/water cooled and if the seal goes it would cause white smoke and coolant loss. Can anyone tell me if this is the case?

Thank you.

Regards

Stuart

That is possible, as water/coolant would then be in the intake ready to be burnt.

A new cap is cheap enough though. Worth running it up to temp and opening the cap a bit. If it makes a noise, then you are sealed. Any holes in the pipes will be like a fountain!

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Cheers Cruiser,

We've eliminated the cap. Next test is the EGR cooler. One of the mechanics said my turbo only uses oil cooling method which rules out the possability that water could be leaking through the turbo! Funny thing this morning, switched the ignition on then checked my water level before turning the car over. Had to top the water up but on start up and 10 mins of driving smoke was as little as i've seen it since buying the car?!

Thanks for the replies.

Stuart.

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There's light at the end of the tunnel!

Replaeced the EGR cooler yesterday and took the car for a run today (20-30 mile) and as of yet no sign of smoke and more importantly no coolant loss. However (there had to be!) the internal heater is getting nothing more than luke warm. I've had the return hose from the heater matrix off whilst the car was idling and it was nothing more than trickling out. All the other pipes are getting hot (top and bottom rad, inlet to the matrix etc). I bled the matrix as described then replaced the hose. This increased the heat slightly but then dropped again after 5 mins. Pulled back the bleed hose to the matrix again to find no water coming out of the hole. I pressume the water system should pressurise when it's running yet all the hoses remain squeezably soft. I'd expect water to gush out of the bleed hole but nothing. Any ideas please?

Regards

Stuart.

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Partially blocked heater matrix. Remove both hoses from the matrix and back flush using a garden hose - the pressure should be high enough - make sure you identify which way the coolant is circulated normally and make sure you do it the other way round.

You will of course lose your new coolant inhibitor!!!

Probably the reason for the blockage is a lack of inhibitor from your (not you personally) first head gasket change. Ally heads are very fussy about their coolant additives.

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Once again, thanks.

My only arguement against that theory though is that the flow rate alters with engine speed. If there was a blockage then i'd pressume the flow of coolant woud be constantly poor? With the engine at 2000rpm, after a minute the coolant comes squirting from the matrix hose and maintains it once i've dropped the revs to idle. Only after 5 mins of replacing the hose and clip does it seem to drop again!

I've also noticed that my engine temp doesn't get higher than 90 and my fan never kicks in. Got back from a run today with engine temp at 90 and opened the bonnet, left the engine running for another 20 mins but the temp didn't raise nor did the fan kick in. Maybe it's just the ambient temperature thats helping to keep the engine cool!?

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My appologies,

back flushed the matrix this morning and was amazed at the crap that came out. Heaters now working at 70%. Going to try filling the matrix up with coolant flush/hot water and see if it removes any more.

Feel like i'm about to close this chapter.

Thanks for all your help.

Stuart.

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