My independent mechanic performed a valve job, replacing two carbon-encrusted valves. The Check Engine Light is still on. Went to Mini Dealer and requested diagnostic. Diagnostic codes: carbon buildup and spark plugs misfiring. Question. How could it be possible for the Head of the engine being sent to the machine shop could not have received a carbon cleaning ? Have been going around and around with the CEL on for the past two years!

 

The independant mechanic should have cleared the codes when he did the valves. The Engine Control Unit is remembering the old codes.

Bring the car back to the mechanic who did the job and have hime clear the codes, he should do it for free.

Dave

 

Hi Dave, thank you. My independent mechanic had reset the codes but the (it) returned back immediately. It is said that only Mini Dealers can reset codes adequately because they have the software specific to Minis to do the job and auto should be returned to Mini for resetting codes? This doesn't ring quite true to me. In any event, before the dealer returns the car to me they will reset the codes as part of the diagnosis charge.
Dave, is it at all possible that a machine shop would not have cleared the carbon from the head when they did the valve job. Mini dealer is trying to say that they (themselves) cannot know for sure unless they remove the manifold and physically check for, of course, yet another charge of $150 added on to the diagnosis for a total of $250.00 to do this. I'm somewhat at a loss as to how to proceed here.

 

Did the codes go away, then return, or was the independent mechanic unable to clear the codes?
The only way to tell if the carbon was removed is to remove the intake manifold and have a look at the intake valves. If they are clean, then clearing the codes should reset the check engine light and nothing more should have to be done.

If the valves are carboned up, have the dealer take photos, you would have a case against the independent mechanic.

He shouldn't be working on MINIs if he can't clear all the codes anyway, the tool isn't that expensive.

Dave

 

When the valve job was done 12/30/13, the codes were cleared and returned before I even left their lot. The CEL remained on continuously for the last 3 months, then last week the codes were reset and the check engine light returned after about a day.
The dealership did a Coking test (as well as reading the codes). If, after removing the intake manifold, they find that it is clean in the engine, then am I in my rights to request a refund for $150? Maybe I should take it back to my mechanic (whom I trust for his integrity) and have him take a look inside and give me some pictures. If it's clean then I would have saved money for mechanically looking. If it is not clean then my mechanic is liable under his one year warranty.

I might add that the valve cover vent hose was found to be broken last week when I took the car in because I was worried about the CEL being continuously on. Once they replaced that (and notified of an oil leak which am not doing anything about since it is not really dripping) the cel was then reset and took about a day to return.

 

I have to agree with Dave above. I had a carbon build-up issue when I first bought my car, so I had MINI do the walnut-blasting to clear all that gunk out and my CEL code immediately disappeared. Its been that way since it was done 6 months ago. If carbon build-up is the reason behind the CEL, then it being cleaning should have resolved the CEL after being reset.

If the $150 is a standard labor rate for the dealership to check everything out for you then no, a refund is not really an option even if they don't find anything. They're still performing the work to see if they can diagnose an issue for you, whether they find clean valves or not.

I guess the first thing you should find out from your mechanic is .. how did they clean the valves? I see your first post in this thread said they "replaced the two carbon encrusted valves" but I am not quite sure what you mean by replacing .. I mean .. you don't just simply "replace" the valves ..

 

I wonder what it is that the dealer calls a coking test? I have heard of a coking test that is done to lubricating oils to test their propensity to carbon up, but not something that is performed on an engine, other than taking parts off and physically looking.

If the dealer did the labor to check the valves for carbon, you would be on the hook for any work you authorised.

A head that has been to a machine shop for a valve job should look brand new when you get it back. I'm wondering why they would replace two valves if they were just carboned up, dirty valves can be cleaned easily, especially when they are already out of the engine. The only reasons I can think of to change out valves is if they were physically damaged or worn beyond tolerance. You mechanic wouldn't have put a head back on the car if it looked like it hadn't been cleaned.

Just a couple of other things, What are the actual codes that they are getting and what year and model MINI do you have?

Dave

 

This is a parallel question, not quite touching on the discussion here. When the independent mechanic reads codes P115C with P0301,02,03 and 04 (sub codes?) and then tells me (last week) that I had a High Pressure Fuel Pump issue, which turns out to be really a Carbon buildup issue along with spark plugs based on different codes that the dealership is using, then I should listen to the Mini dealer? Because, apparently, their sources of information regarding codes is totally different. It makes no sense then to take the car in for repairs to an independent if we're dealing with a major issue as CEL. How legitimate are the codes used by independents vs. what are used by Mini dealers?

 

My mechanic did a valve job (meaning they removed the head and sent it to a machine shop and I quote from their work order, " Resurfaced head, valve job, pressure test, replaced two damaged valves". In this scenario I assumed that this major repair had cleaned out all the carbon. Maybe I'm wrong...

 

I could ask the dealer next week when I pick up my car as to what he is talking about with reference to a coking test.
Right, that's what I thought that it should look brand new, and when I asked my mechanic he looked incredulous, like how could one even think that after a valve job it wouldn't look spanking clean, but there you are, the dealership is looking at their codes and coming up with carbon buildup.

My work order indicated that one of the valves was "burnt" and the other had a hole in it. I went from 82 mph down to 57 mph while driving on the freeway when this happened.
My car is a 2007 Cooper S with 120,000 miles on it now. The codes that came up for my mechanic were: P115C followed by P0301,02,03 and 04 and his interpretation of these codes were that I had a HP Fuel Pump issue. He noted that there was an extension of the warranty on the HPFP, and I noted that I had replaced this HPFP back in 2009 (and will get re-reimbursed for it since the dealership found nothing wrong with it as of yesterday).

 

P115C, air mass or volume too low, can be a dirty MAF sensor, do you have an aftermarket oil type air filter that you oiled just before the code came up? It probably has nothing to do with carboned up valves.

The other four are spark plug misfires, which could be caused by a lot of things.

Are these the codes that you are having now? What did the dealer get for codes?

Dave

 

Dave, the P115C code was thrown in 2011, reset code only and CEL remained off for a year.
In 2012 (P115C) CEL came on 9/12 and has been on ever since until the present day. MAFS was replaced in 9/12
In 2013 (P115C) CEL MAFS replaced (on warranty) and replaced spark plugs
In 2013 Dealership. diagnosis. NOT MAFS - valve cover leaking and carbon buildup was indicated. Replaced Valve cover by independent.
In 2013 Valve job in December.
In 2014. Still reading P115C as of today. I didn't get a chance to ask dealer what codes they were getting, but last week my mechanic was throwing the P115C along with the (4) P0301,02,03, 04.

 

I think that if you had the valves done last December, you don't have a carbon build up problem.

Your problems started right after the valve job, I would start there. Maybe the camshafts are out of time, it is real easy to do on a MINI engine, when taking the head off and putting it back on or maybe it is something as simple as a pinched wire to the MAF sensor.

Dave

 

'
Very much appreciating that you can zero in past the history of P115C and point to problem starting after the valve job. I will take note and bring back to my mechanic. If there's anything else relative to taking the head off and putting it back on that you can think of, I would be grateful for you posting it here, because I will take due note of all and pass on to him.

 

Hello Dave, to update you and also thank you for your input. Last week the problem with the CEL being on for the last 1 1/2 years has been resolved. Mini Cooper Experts in Glendora, CA read the codes (which have been the same since at least 6/13) as P115C and 2B5C. This latter code is related to "Mass Airflow Plausibility". From his experience this code points to a bad Throttle and not a bad MAFS. Indeed, once changed out, my CEL disappeared! Letting you know and anyone else out there have issues with an unresolved CEL issue.

 

Dunno if y'all are still taking census on the carbon build up problem but it just showed up in my 2010 MCS at about 55k miles. Dealer recommended the walnut blast but I'd never heard of this issue or repair so I told them I'd pass (since it sounded like BS to me). Came home to do research and, well, turns out it's not BS. Thank goodness for this thread!

For what it's worth, I live in SoCal, the weather is warming up, and most of my driving is 80 mph on the freeway. And I've put nothing but Top Tier 91 in her since the day she was born (although I understand that isn't related; but it sure was satisfying to retort with that fact when the dealer suggested bad gas was the problem. GRR.)

Anyway, from what I've read here I'm surprised the problem didn't show up sooner. Maybe it's because I'm a spirited driver?? Kinda wish it had cropped up before the warranty expired, though. Instead, I get to go shopping for someone who will do the walnut blast for less than $600... plus, apparently, an oil catch-can and PCV delete kit. Oh boy... let the post-warranty repair bills commence. :/

 

You'll be amazed after your valves are cleaned, night and day difference for me. Strange thing is they weren't as bad as most here on NAM. Don't forget that if you have carbon in your intake valves, you also have carbon build up in your combustion chambers. The most effect treatment for that is a few bottles of BG 44k, you won't find it in a shop but can get it online.

After my carbon cleaning (walnut blast) my Mini was still knocking, after 5 bottles of BG 44k knocking all gone. I checked every cylinder after each bottle, started out black ended up silver in the end. The walnut blast is the most effective way to remove carbon even if your head was off the car.

 

I have no knock or ping (yet, knock on wood, har har) but plenty of hesitation. Since that's the case, think I'll still need the BG 44k after the walnut blast? Or are you suggesting I do the BG44k instead of the walnut blast? I also don't own a scope or any equipment, really, so any cylinder checking I wanted to do would have to be at the shop.

 

Most people get the walnut blasting as it's the most effect cleaning procedure, but you need to understand these Cooper S models have direct injection which means the fuel is injected into the cylinder. Port injected cars don't have direct injection, they spray gas behind the valve so when you add BG 44K it sprays on the valve before it enters the engine. I bet if you remove your spark plugs you'll see black instead of silver. How much oil does your MCS go through when checking your oil levels? Since you're already at 55k and you aren't pinging yet that suggests you don't burn much oil.

 

She's been pretty awesome on the oil levels, actually. (As an aside, I am tempted to attribute that to how I handled her from the beginning: thanks to an education from NAM, I got her an immediate oil change the day of purchase to make sure no metal shavings from the factory were floating around her veins and then adopted driving patterns to make sure the rings were well-seated.)

Anyway, it sounds like I really should get the walnut blast. Further research seems to indicate I should have Motoring Magic do the work. I can ask them to show me how bad it is (and how black my plugs are).

 

I cannot believe that here we are in the 21st Century, and a modern (BMW engineered MINI) engine has carbon build-up problems! My 2010 Cooper S has this problem after 65K, and the local dealer wants over $1000 to media blast my inlet ports. So I said no thanks, and picked up the car tonight. My last car was a VW VR6 that was tuned, and gave me 150,000 miles phenomenal performance from new. Track days included. Sold it to a friend who put another 50k (with more track time!) and still no mechanical issues. Don't get me wrong, I love my MINI, but this should be a recall service. An obvious design flaw, as we are not living in the 50's when 'decoking' was commonplace. I do understand that turbos burn oil however, and that contributes to the problem we are seeing.

 

There are many car marques, not just MINI, with direct injection that suffer from carbon build up on the intake valves. It is caused by oil vapor from the Positive Crankcase Ventilation system, not getting washed off the valves, as it is on an engine with port injection. Part of the reason for the redesign of the cylinder head on the N18 engine was to reduce carbon build up on the valves.

Adding an Oil Catch Can and/or methanol injection, can help prevent carbon build up on your intake valves.

Dave

 

I had the same issue with carbon buildup. I let it go because the dealer wanted $700 for the blasting with walnut shells. Since then (6 months later) I had to have a valve job done (no doubt because I didn't attend to the carbon buildup). To the point: I have found a totally reliable and very knowledgeable mechanic "Mini Cooper Experts" in Glendora, CA. They suggested for a carbon buildup issue to do a different type of cleanup. Cost is much less at around $300. I totally trust these guys because they found the source of my Check Engine Light issue, which codes indicated a Mass Air Flow Plausibility issue (and many thousands of dollars later was NOT a MAFS issue) but was in fact a Throttle gone bad. They knew this from experience. Voila, problem solved!

 

It is not a flaw. It is a result of the decision to use direct injection. I'd suggest re-orienting your frame of reference to see carbon cleaning as a routine maintenance item. I'd also suggest finding a different source for walnut blasting that can do it much cheaper than what your dealer is proposing.

 

Direct Injection itself isn't the problem, it's the design of the PCV system that's lacking which was greatly improved upon in the N18 engine. A well designed PCV system that returns oil to the pan rather than throwing it at the intake valves is what makes the difference. There are a few DI engines out there that don't have any issues with their DI cars.