Ren
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Registered: 16th Oct 04
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My Audi (the A4 that is) has had a slow coolant leak for the past couple of months. Every couple of weeks I would have to refill the tank completely, and I located the leak to be from a metal pipe at the back - which subsequently leaked all over my speedo sensor causing it to die on me. Well for two months, I left it as I literally needed the car every day but now I've developed a problem. Instead of putting in the usual G20 coolant I normally do, I started using regular water as the G20 stuff is expensive. Since I filled up the car every couple of weeks, the last month I stopped putting in anti-freeze (costly too) and now there's some thick grey sludge in the coolant tank. I'm not sure what it is, but it feels very spongey and stinks too.
I've already done a compression check, and the headgasket is fine. It's a 1998 1.9 derv, and I read online that sometimes the oil cooler leaks oil into the coolant tank causing the sludge... but surely it would be brown right?  What else could the grey sludge be? I'm just a bit worried because I've searched online and there're a few articles saying the engine can rust without anti-freeze but others saying it doesn't, so does anyone actually know 
[Edited on 05-04-2009 by Ren]
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mattk
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Registered: 27th Feb 06
Location: St. Helens
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it would freeze in the winter
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Ren
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Registered: 16th Oct 04
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Adam_B
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Registered: 13th Dec 00
Location: Lancashire
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Ive seen cars rust and fuck up with no antifreeze in.
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tom_simes
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Organiser: South Wales
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Registered: 12th Jan 05
Location: Undy, Newport Drives: Skoda Octavia vRS estate
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Yea, it can rust up extremely badly, leading to very bad corrosion in the engine block and may be even blocked waterways.
It also reduces the boiling point, as water boils at a lower temperature than the coolant.
btw, I've just finished writing a dissertation on engine coolants
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Ren
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Registered: 16th Oct 04
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Any idea what the grey sludge would be tom?
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DizzyRebel
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Registered: 2nd Jan 09
Location: Lincoln
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It raises the boiling point and lowers the freezing point of the coolant/water mix. In really cold weather the water in the block can freeze and actually crack the engine block. core plugs are designed to prevent this but its not always the case.
Also coolant has anti corrosive properties, if you have an alloy block/head then chances are the water will erode away at the coolant system eventually fucking things up.
An engine will run for a while on just water, but if you actually care about it just get a new rad fitted and bung some coolant in it.
Grey sludge will be aluminium oxide, or alloy 'rust'
[Edited on 05-04-2009 by DizzyRebel]
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Ren
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Registered: 16th Oct 04
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Shit 
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tom_simes
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Organiser: South Wales
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Registered: 12th Jan 05
Location: Undy, Newport Drives: Skoda Octavia vRS estate
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As dizzy says, most likely to be the corrosion of aluminium components, which could be engine block, cylinder head, water pump etc. - or if you're lucky, just the radiator.
Out of interest, what metal part had snapped originally?
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sand-eel
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Registered: 15th Mar 07
Location: carluke/braidwood--IRNBRULAND
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Just put in some radweld and it will be fine, sometimes new cars have it anyway to stop small leaks under warrenty.
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Ren
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Registered: 16th Oct 04
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Used radweild already but didnt work. A day after, I got brown slude funny enough. Now its turned grey
Tom its some sort of T-junction behind the engine and its made from metal.
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Leighton
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Registered: 21st Feb 01
Location: Liverpool
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Sell it 
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Ellis
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Registered: 11th Sep 07
Location: Aberdeenshire
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So using screenwash for anti freeze is not a good idea then?
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DaveyLC
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Registered: 8th Oct 08
Location: Berkshire
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Without a decent coolant addative any iron/steel components in the cooling system will start corroding, very quickly!
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Ren
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Registered: 16th Oct 04
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I just assumed engine internals were rust proof. Added 50% antifreeze now anyway  Lets hope theres not much damage. Anyone want to buy an Audi
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alan-g-w
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Registered: 9th Nov 07
Location: Glasgow
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I had no anti freeze in the corsa due to it overheating and boiling it all the time. Came out on hogmany to go down the shops, turned the key and the starter sounded like the battery was flat. I bumped it, then found out the water in the engine was frozen, including the water pump impeller. So cue 16 bent valves and 2 months of the car off the road. Only reason I knew it was cos it had frozen was because a core plug on the back of the head had been burst out the way.
Keep anti freeze topped up now though.
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Edd
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Registered: 8th Nov 04
Location: Glasgow
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its amazing because it will obviously fuck up eventually but i ran a ford ka over the winter months about six years back with just water in the coolant tank
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crazybrightman
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Registered: 30th Mar 09
Location: leicestershire
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the main reason for antifreeze is not to stop freezing but corrosion. especialy when alloy and metal are used as they react to each other! its only changed every 2 years or so because its anti corrosion properties wear off.
how ever running water for a short amount of time wont make that much differance.
as for sludge check the other half hasn't topped the oil up lately....
seen it many a time!
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Graham88
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Registered: 16th Apr 07
Location: South East Kent Drives: E46 M3
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My mate cracked his head on his xr2i cause he had a leaking rad and was only putting water in, then the cold weather came in one night.
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Edd
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Registered: 8th Nov 04
Location: Glasgow
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quote:
Originally posted by Graham88
My mate cracked his head on his xr2i cause he had a leaking rad and was only putting water in, then the cold weather came in one night.
what happened did he slip?
im here all week
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Graham88
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Registered: 16th Apr 07
Location: South East Kent Drives: E46 M3
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FFS
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Baskey
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Registered: 31st May 06
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Had a spare nova back in the day. Ran it for about a year with only water in. It all went brown and slugey but still worked fine.
Wouldn't dream of doin that to a decent car though
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