The only problem with the stop leak products in cooling systems is where you have a very low level of coolant, causing foam at the water pump as it incorporates air.

These products react to air, which is why they can stop a leak. If there is no air incorporated into the system, they can't solidify.

BTW, if you need it and don't have it, stop at a nearby farm and beg or borrow an egg. Let the engine cool a little and add the egg white with the water you add. The egg white will seal the leak so that you can get back to town.

onetim.. that is scary story.. thanks for sharing.. bc

A friend of mine worked for Ford in Wixom MI assembling late 80’s Lincoln Town cars, every one got two large brown pellets of stop leak right on the line.

white smoke is indicative of a bad head gasket.  I'd replace that before anything else.
and never use the stuff that seals a leaking cooling system.  It will clog the heater core in short time and then you'll need to replace that.

Several very good comments, especially from Dan (in between some weird stuff).

Brown coolant can be oil mixture, old coolant, coolant added to a rusted system, or mixtures of coolants. Use a liquid flush agent as per its instructions (don't use powdered stuff because it often does not completely dissolve and ends up in the pump housing.

Then fill it with water and change the oil. Drive it around, let it heat up, cool down, etc. a time or two. Check the oil for water and the water for oil. When cold, there is more oil pressure than water, when hot, but shut off, there is more water pressure than oil pressure.

If nothing mixes, put in a good HOAT coolant, replace your turbo, etc.

If things mix, it is probably your head gasket that needs replacing.

Don't get too hung up on the coolant sealers. Some work very well. Someone gave me one in 85 when I was driving to Alaska. I carried it with me until the year 2000 when my truck sprung a leak in the radiator. I tried it and ended up leaving it about 5 years since it fixed the problem and I forgot about it. I remembered it when changing the coolant and the new stuff spurted out. 

well.. dan.  I just sent my youngest skunk.. Josephine. a text . she said NO comment..  as she has MARKED a few MINI tyres in her days.. in the wild.. later bc

I've never used (and would never use) anything like that... sounds like it wouldn't work any better than skunk poop.

I second what a previous poster said about NOT installing the new turbo on there until you get ahold of whats going on.Drain the oil and examine that as well as the coolant.Poor oil quality or water entering the oil can/will ruin a turbo in short order.Id venture to say if the turbo is bad,that it was related to a motor issue (oil/coolant).Are those turbos water cooled as well? Do a compression test.

If you have smoke out of the exhaust, does it smell like coolant or burnt oil?

I am concerned about your intention to simply replace the turbo.  With smoke coming out of the exhaust, the catalytic converter is probably contaminated and is probably causing some back pressure. This back pressure will damage any new turbo that you install - not 'if' but 'when'. You should have the cat either refurbished or replaced if you want your new turbo to last. You should also replace the oil supply line (read any of our turbo product pages which contains a lot of useful information.) I would be concerned about 'why' the turbo failed.

On another note, Dan listed some very wise steps to take. I would recommend you follow them.

Seems like low boost? How do you know? Low power of course could be from low boost, but blown head gasket and low compression would do that too. Add white smoke and it sounds even more like head gasket. Do the compression test like already suggested and it may tell you the answer . Maybe you do not need that turbo replacement. No amount of bad turbo or good turbo will matter if your problem is head gasket

yes... head gaskets are problem..

Thanks for all the info Dan. I actually drove the car home it seams to have low boost and white smoke out of the exhaust. I tore the whole front clip off to replace the turbo along with the huge oil leaks coming from the oil housing. Definitly seams someone added bars or some type of stop leak in the cooling system. The turbo gets here friday so my plans are to put it back together, flush the coolant and see how she runs. It has 138K on it, are head gasket issues common with these models? 2008 mini s  

Once again thanks for all the info everyone!

dan.. you know it sounds like some dumped some the BARRS stop leak.. it is ugly brown and chunkie..  later bc

First, welcome to the board.
Second, yes, we do have some curmudgeons here - it would be dull without them/us.
Third, as Elpez says, you did admit to buying a mechanic special. According to what you wrote, it had a claimed bad turbo. Perhaps the bad turbo is the cause of the bad coolant, OR the bad turbo is a result of something else contaminating the coolant and causing the turbo to fail.

I suspect you're going to need an engine transplant or rebuild. Before throwing too much time and money into this one, I'd start with some simple diagnostics.
- check the plugs to see if they look in reasonable condition or if here are signs oil or other fouling. If you can scope the bores so much the better.
- check the oil for contaminants such as water or fuel.
- do a cold compression check to see how healthy the engine is.
- drain and flush the cooing system several times to see if you can get it clear.
- with the cooling system clean and full, try starting the engine. I would try this with the rad cap off so you can monitor the coolant. It should be able to run even with a bad turbo. It may be in "limp-in" mode but you should be able to get it up to operating temperature. Watch carefully for overheating - some passages may be blocked. Look everywhere for leaks. Check the coolant for oil or other contaminants - it will probably discolour as the running engine flushes the "skunk crap" out of the system. Watch also for steam bubbles or excessive steaming - if cooling passages in the engine are blocked, localized overheating/boiling may occur, indicating an internal problem.

Doing these steps will not solve your problems - just diagnose the condition of the engine and whether it is worth fixing. That's where your cheque-book comes into play. Some "bargain cars" aren't bargains in the long run. If you have the tools and skills to rebuild or replace an engine, it may work out, but if you need to employ a garage it may be costly. If you need to resort to a dealer, it WILL be costly.

Personally, I like some of the new BMW MINIS but would never own one - just too expensive to maintain and repair. On the other hand, a classic Mini would probably cost the same to buy as a used BINI, parts are a whole lot cheaper and I can do just about all the work on it.

Sounds like you may have oil in the coolant - I would also check to see if you have coolant in your oil?

Is the car running? 
When you say a 'bad turbo', did it have a catastrophic failure or is it simply burning oil?

If someone used a block sealer, I would be concerned as they tend to block small passages in potentially critical areas (including the turbo )...

You could have googled, brown crap in  the radiator and gotten your answer, it's a mechanic special, did you get a mechanic to look at it before you bought it?  Are you tearing into it and don't have a clue as to what the brown, milky substance with particles in the coolant may be?  Did you take the radiator cap off before you bought it?  I also see the humor on this as does bc, those dammed skunks are at it again!

BTW, you call this bashing???? Stick around for a while!  Really sorry about the state of your MINI, hope you get it running and are able to enjoy it.

yes..  I really like doing the bashing to BMW mini owners..  

Your really on this forum to only bash people? get a life!

danm,,  guess my oldest skunk has got out AGAIN. and pooped your BMW mini.. shame on her.. later  bc  

I also found the coolant resevoir had some nasty stuff inside, looks and feels like bbq sauce. I poured the coolant out of the bucket and found particles that inside. To me it either seams like rust or maybe someone added block sealer?