CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Mini Cooper S carbon build up EXPENSIVE PROBLEM

Shortly out of warranty, my 2006 Mini Cooper S began to lose power, limp, and pop both “Service Engine Soon” code and the tire pressure warning light. This resulted in $3800 of work due to “excessive carbon build up” that “rotted out” the cylinder 1 valve guide & seat and was eating the rest of the cylinders, too. Four hundred miles later the car is belching huge clouds of white smoke at start up and now has “excessive carbon build up” on the “intake side”. The mechanic is fixing the car at no labor cost, but the materials and machining cost $800, I understand (car is still in the shop). Evidently, I need to do something regularly with water to keep this from happening. The car has less than 70,000 miles on it. I don’t feel like I can sell this car to someone without telling them the story, so it won’t be easy to sell. I like to drive it when it’s not popping codes (!), but prefer a less expensive option. Oh, and surely the clutch will need replacement soon, which will cost a bundle, no doubt. What the heck should I do with this dang car?

Well thanks for the heads up on MiniCoopers. Most engines dont act like this. When well maintained they run for well over 200k before the carbon and valve guide seals become a problem. 800 bucks for “machining” involves just what? Head warp, valve grinding, what?
White smoke is oil for sure, and the cause most likely is worn out valve guide seals. I dont know this particular engine, but that usually means pulling the head. As long as it is out, cleaning the carbon from the valves might as well be done. but 3800 seems like a lot of money. you could be a good used truck for that much.

According to the Mini forums this is a “chronic problem”. Aaaack! Should have bought a Honda, but it was the beginning of my mid-life crisis. Yes, the head has now been pulled TWICE!

It’s difficult to say what exactly is going on here without knowing all of the exact details but a lot of this does not add up. Rotting out valve guides and eating the rest of the cylinders is very incorrect terminology so this means the shop is feeding you a line of BS or you are misinterpreting what was said.

If excessive carbon buildup is the cause of whatever the problem was or is then the cause of that should be determined rather than continuing to remove this stuff. Carbon buildup is due an engine performance problem or oil consumption.

According to the machine shop, it seems to be a feature of the super charged models and my mechanic wonders why there hasn’t been a class action lawsuit against the manufacturer. A forum discussion presented a shop ticket from the local dealer that used “Seafoam” to clean out the carbon. I haven’t heard anyone with a suggestion for remedying the performance problem, which seems to stymy the mechanic and machine shop. Lots of head scratching. Some talk of “catch pan” or somesuch and some other high performance addition that burns out the carbon.

How often were oil changes?
Further than 7500 miles?
Longer than 6 months?

All maintenance and gas, etc., per the manufacturer’s recommendations. The Mini computer says when the oil should be changed, which is a minimum of 7500 miles. Sometimes I changed the oil more frequently.

Does it burn oil? “Carbon buildup rotted out a cylinder??” That’s BS…Carbon buildup in fuel injected unleaded fuel engines is almost unheard of. Show me the carbon…Most engine deposits result from high oil consumption…Sounds more like “These engines are junk but we have to make up some sort of excuse why they failed”…

Based on the terminology used, both with the original problem and the latest, I think this is all BS.
I’m having a near impossible time seeing how anything even remotely like this could happen on a less than 70k miles vehicle.

To raise the red flag a bit higher, you state that 400 miles later it was “belching huge clouds of white smoke upon startup”. This is generally a sign of coolant entering the combustion chambers; either through a head gasket leak, intake manifold leak, etc.
This falls back on the person who removed the cylinder head in the first place and did not inspect things carefully and/or did not reassemble it correctly.

Personally, I don’t think the car is the problem so much as it is the person you have working on this car. My gut feeling is that you have been played, either due to outight fraud or sheer, unadulterated incompetence and the original running problem was likely something very simple. In a nutshell, someone made an expensive mountain out of a cheap molehill.

I buy your story. I am sorry my friend this is a manufacturing problem straight from BMW into your garage. My mom"s car (A 2007 Mini Cooper) has the same problem. Her"s isnt an S though I heard its particularly bad in those S’s. My mom"s valves had to be cleaned too, and hers had only 30,000K but it was done under warranty. Personally I once drove a car up to 327,000 kms and the valves didnt carbonate…

The real root of the problem is the engine doesn’t get enough oxygen. The intake manifold is too small and BMW doesnt offer a fix. Best of luck…and sorry to say…this will happen again to your car in another 70K.

If the areas in the intake valve pockets were heavily sludged up for whatever reason I could see possibly a slight loss in engine performance, slightly rough idle, etc, etc.
This will not cause a sudden loss of power and limp mode, or a tire pressure light.

The OP spent 3800 DOLLARS for cylinder head work and we’re supposed to believe this head has “excessive carbon buildup on the intake side” after a paltry 400 miles?
And what does that have to do with white smoke belching out, which is most often burning coolant?

The shop is allegedly doing this repair labor free and only charging 800 bucks for materials and machining. I still ain’t buyin’ it.

That 800 will easily cover a head gasket, surfacing the head (maybe something that was omitted and should have been done and which could be the cause of the white smoke) the first time around, and still leave a lot of wiggle cash as part of a CYA (cover your axx) operation.
A head gasket set is about a 100 bucks and surfacing a head runs about 50 at the machine shop. Heck, double those amounts and do the math.