Hello All,

I am finally working on my sister-in-laws 2013 Mini Cooper S. Automatic 78,000 miles. STOCK

It stop running on the highway in January. It shot oil all over the engine bay. It went to a mechanic who diagnosed it as needing timing chain and valves due to slipped timing/pistons hitting valves/no compression. Not sold on their willingness to even borescope the engine to confirm these thoughts, I recovered the car, and let it sit while we sourced and engine and found time to work on it. Anyway, we are now replacing the engine and I had a chance to tear down the old engine. The true cause of the problem was pistons #1 and #2 melted. The engine coolant passages are filled with burnt crap too. The coolant tubes and hoses are filled with less burnt, but smelly thick sludge. The new engine is low miles (12k) but we re-using the turbocharger. I have just ordered a new radiator based on the sludge found in the rest of the cooling system.

So questions:

• Are burnt/melted pistons common?
• Should I be digging deeper for a smoking gun on the cause of the heat problem?
  • I am at a lost for where to start searching. Might there be common issues to check for that could have lead to this?
  • Clearly everything got hot. Valve cover had melt internally too. But did an overheat/poor cooling cause piston melt or did a lean condition melt the pistons and cause the overheat (Chicken or the egg paradox)
  • I don't want to shortly smoke the new engine for a vehicle side problem.

Thanks in advance for any insights. Pictures included to show piston damage, nasty coolant passages, and sludge found in other coolant piping

 

Yikes!

I think the only time I've seen sludge like that in a cooling system was after an additive for stopping cooling leaks was used. Too much of that and instant gunk and clogging. Not sure if that the case here or not.

My guess would be an overheat event (or multiples) took place, and caused the pistons to get overheated.

 

I am thinking the same with regards to a potential additive being used. This car was used when they got it. So we have no history on what might have been put in. But based on the amount and hardness of the build up in the engine coolant passages, I think it is a longer and on going issue. Not just a single event at the time of the engine failure. I think overheating happened due to reduced coolant flow and thus pistons melted. Not pistons melted and caused burned things to get into the coolant and build up.

Turbo shaft is very tight. I was also thinking that could be a crossover point for oil and burned material to enter the coolant. But I don't think that is the cause based on the condition of the turbocharger.

 

That looks like the head gasket failed and oil got into the coolant. Oil would act like an insulator and prevent heat transfer. Did you drain the engine oil? Take a sample and send it to a lab to see if it has coolant. That will confirm if you had a head gasket failure.

The turbo should spin like a pinwheel; sounds like you need a rebuild.

Oh yea! You're going to need to flush the cooing system; all the hoses probably need to be replaced too ... and maybe the radiator. I just flushed a Ram 1500; the oil cooler failed and dumped a bunch of oil in the cooling system. After 6 flushes, I said forget it, and replaced the radiator and hoses. the oil really sticks to the insides of those components.

 

I was thinking headgasket could also be an option but I saw not clear signs of it when I pulled the head. Didn't save any oil from when we drained it. It did look a little milky but not the worst I have seen. I fully expect there was something in it just wasn't sure what.

When I said the turbo is tight, I meant axially and side to side shaft play. It spins very freely.

Flushed the trans cooler, heater core, and hoses. I was able to bottle brush hoses too. I also borescoped one just to check and was happy with how they cleaned up. New engine came a new t stat housing, water pump, aux water pump, and some hoses too. Ordered a new radiator. So I think the cooling system is decently refreshed.

Thanks for all input!