The car stranded my wife out of town last week. Rented a U-Haul trailer and picked them up.

My independent mechanic, who I trust and who has maintained the car regularly since it went out of warranty, tells me that the exhaust valve for cylinder #3 'dropped' into the cylinder and has damaged the piston & cylinder wall. He says the most cost-effective repair is a replacement short block. He's still working on a cost estimate for this.

We had trouble with this car when it was ~three months old (about 8K miles), which Mini eventually diagnosed as a bad high pressure fuel pump and replaced under warranty. At about 40K miles, they also replaced the turbo under warranty--the dealer blamed oil starvation, but they had done all the oil changes under Mini's schedule.

Questions:

• should I go with the short block, or, not knowing the root cause and whether it's likely to happen to another cylinder, go for a more expensive long block?
• what is the likely root cause?
• Personally, I've never had an engine 'drop' a valve. I'm not a mechanic, but this suggests to me either that the valve stem broke, or whatever is intended to hold the valve in the head broke. At 130K miles, I think that's a design flaw. I doubt Mini will agree. Should I even try to get them to cover part of the repair cost, or is that just banging my head on a wall?

Thanks in advance.

 

Dropping a valve is usually caused by the valve failing in some way. The stem can stretch, the keeper grooves can wear, the keepers can let go, and other stuff can happen that causes that as well. The cases I am most familiar with are caused by the valves overheating and stretching, sometimes to the point where the head comes off the stem! (Not good for the rest of the engine, as you can imagine!)

I have experienced valve seats dropping in other motors; the hardened ring-shaped seat falls out of the softer aluminum head and wedges the valve open, which can lead to piston-to-valve contact and extensive damage.

It is arguable if it is a design flaw; MINI will no doubt claim that improper use or maintenance caused the problem. Your odds of getting anything from them (especially if they're not even doing the work!) are pretty low, IMHO...

 

The N14 is a great big design flaw, amazing that you made it to 130,000 miles! Have you ever had your intake valves walnut blasted before? Those intake valves get coated in oil and then the oil bakes itself onto the valve that can eventually end up burning the valve, in some cases I've seen pieces of the valve broken off like a cookie crumbling apart.

 

you mean like this:

burnt intake valves on my 2010 JCW

 

Peanut,

How many miles on ur JCW?
Any engine mods?
Regular maintenance?

 

That's exactly what I talking about, but I think it has more to do with the hardening process, if I'm not mistaken if you heat treat metal or steel to much it become to brittle. I don't know of many ways hardened steel can fall apart like an overcooked cookie, that's the way a cookie crumbles!

If it that was the result of a valve strike your valve would have been pulverized, bent and splintered, but clearly a chunk of your valves just fell off. In 28 years I have never seen most of the N14's troubles in any engine before it, the manufacturing process, design, execution and materials used are absolute poorest quality I have ever been witness to. Then again I have never owned a German car before either and never will again, its not for me.

 

That's not a "crumbled" valve--that's a burned valve. It has overheated badly, but I couldn't tell you why.

 

The only way I know of how to burn a valve is if it's still open and/or too much timing advance, but these Mini's start to pull timing do to the fact that they already run pretty lean.

Many have stated that with direct injection you can get away with that, but now I'm not so sure Mini knows what they think they know to be correct. Probably hot spots in the cylinder and/or coked oil deposits heating things up, but I'm just guessing at this point. I don't have much faith in German engineering any longer.