Hi, I am new to the forum, and have had my 06 Cooper S for about a year and have loved every minute of it. I was driving home yesterday and the car started misfiring pretty bad. I was able to make it a short distance to an off ramp and park it. I pulled the codes and got a P0304 for cylinder #4 misfire. I swapped plugs and coil pack with no change. Today I did a compression check and got 0 psi. I used my bore scope suspecting a possible hole in the piston but it looks good. I pulled the valve cover and it seems that the valves are all moving as they should. I have a Bentley manual on the way, but I am looking for some guidance from people who have more experience with these cars than I do. I made my living as a mechanic for a long time, so I am comfortable doing the work. I am suspecting a burnt valve or valve seat, any chance this is common. The car has 95k miles on it, I have owned it since 78k miles. And help is greatly appreciated.

 

1st welcome aboard. 0 PSI is not a good sign. It most likely is a failure in head or piston. Either way next step is to pull the head IMO.

 

I am headed that direction, just wanted to get as much testing done before pulling it apart. I am going to do a leak down test next. I am debating just pulling the entire motor and rebuilding it completely.

 

The number 4 in my 2003 S just had a piston/ piston ring failure that gashed the cylinder wall bad enough that a new motor is on its way. It was the original motor with 101K miles on it - at least 30K of those were track miles.

And the only code thrown was a P304...

My mechanic said he had seen several cracked pistons in R50/R53s.

 

If it was a valve like this it would have sounded like a suburu. If it sounds like an STI and it's not a suburu you got problems. The bottom end on these motors is rare to fail. It is usually the top end that goes. Squirt oil in the cylinder then do compression check if it comes up it's most likely the lower end (rings) if it does not then the top(valve).

 

So, it turned out to be a broken intake valve spring on the #4 cylinder. I pulled the head and had the valves checked. I am replacing all the springs along with the stem seals and have the head planed. I have already put in the new water pump while it was apart, the flange was leaking at the motor. I am wondering what people recommend to use for getting the MLS gasket cleaned off the block. The Bentley says to not use a metal scraper as it may gouge the block and not seal correctly.

 

To remove a gasket other then scraping I have always used one of these products by Permetex http://www.permatex.com/products/pro...asket-removers

 

Did you see that before or after you pulled the head?

///Rich