ok the story,

built a new motor, block acid washed. new water pump, new 2 core radiator and cap. every this is in good order (heater not plumbed in yet). and yes i've got a corrosion inhibitor in there as well.
the car stays cool, doesn't use water or oil.
but it keeps making this ugly sludge, that floats on top of the water and sticks to the cap.
what you see here is only from 30 minutes running in city traffic, i cleaned it off yesterday before going for a lap.

cap and radiator top tank


better shot of the cap


sorry for the crap photo's camera phone

Looks like you might have a little oil seeping into the coolant, possibly from the head gasket. Do you have any emulsion under your oil filler cap as well?

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Simon

The adventures of an owner builder in the Tallarook Ranges

ditto im going with oil in the coolant... usually seeps from waterpump, mine was doing that for a while, replaced the head gasket and waterpump, problem solved!

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Here am I sitting in my tin can far above the Moon
Planet Earth is blue and there's nothing I can do...



“A turbo: exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster.” - Jeremy Clarkson

no more than the usual BMC light smear, it it hasn't been for a long drive.

the motor is well ventilated with three breathers, one on the tappet chest, one on the rocker cover and one on the flywheel housing. these go into a catch bottle, that has no trace of condensation or oil. but there was a mist emanating from the bottle last week when the car had been for a long drive.

i'll change the gasket anyway.

I'd say the head gasket also but it could just be condensation from the build.

If it running fine at the moment I would not change the gasket yet....What size motor and what head gasket did you use

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Stop Licking the Dog...I Don't Care Who Started It

Talking to my engine reconditioner awhile ago he told me not to anything in cooling system for about 500k so head gasket can seal up properly cause he saw the same thing

An ausmini member a while ago had that problem, it turned out the block had a crack somewhere.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

block is good, it's been crack tested.

the engine is 850 'ish (actually about 935cc), running about 9.5:1 CR

it's a 998 block bored +0.060 thou, with an 850 crank, custom thrust bearings ($$$) and some extras (lots of secret squirrel stuff).

just used a STD gasket, i've got a copper gasket here to go on.


Thanks everyone, i thought that it might be the gasket, just didn't want to believe it.

The copper gaskets these days are rubbish, for a small bore you're best bet is an ACL Monotorque one -- I have one here ready to go on my 1152 because it showed almost exactly the same symptoms as yours.. except the symptoms seem to have disappeared for the moment.

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Simon

The adventures of an owner builder in the Tallarook Ranges

where do you get one of these gaskets from?

edit, don't worry found it, google is your friend

I got mine from Karcraft, $30-ish for the kit including head, manifold, thermostat, rocker cover and other misc. gaskets.

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Simon

The adventures of an owner builder in the Tallarook Ranges

thanks found my usual supplier has them as well

mine is doing the same thing. i have had a mini mechanic take a look at it and he didn't seem to think it was a gasket. I have put a pressure tester on the radiator and there doesn't seem to be a leak either.
no sign of sludge in the oil, filler cap or rocker cover.
the verdict was just crap from inside.

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I'm running a copper gasket on my car BUT it's on there with Holmar, it's good stuff about $30 a can (I think)

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"In two years time your car will be like a lady's clothes, out of date, my car will still be in fashion when I am dead" - Sir Alec speaking to Pininfarina

I would be tempted to flush the coolant and recharge....run it a while and see what happens...

if it keeps on fouling new coolant after a day or so running....than it looks like you have a problem elsewhere (as discussed above) rather than just the normal amount of crud finding its way into the cooling system after a rebuild.

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"Show me the Mini!"