Burnt valve

ok I just love stuff like this,,,,this X5 with a N55 engine has been already at 3 different dealers for misfire on cylinder 1,,,,each dealer would replace ignition coils,,,spark plugs or fuel injector and they would ship the car saying it was fixed,,,,so my dealer gives me the car and tells me to find out what the problem is,,,,I knew 3 different set of spark plugs and ignition coils and injector did not fix the problem,,,,so I decided to check compression test,,,found 80lbs on cylinder 1,,,performed cylinder leakage test we had 80 percent leakage on cylinder 1,,,,I checked the intake no air leakage,,,checked the exhaust and found air coming out,,,ok now we know we have a problem internally with the engine,,,I installed a borescope to check out the valves but was unable to see anything,,,,so I had to remove the cylinder head and this is what I found,,,problem found,,,,happy customer

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39 Responses to Burnt valve

  1. Musti says:

    Ooh man, stories like this. The satisfaction. Keep posting this man. Any ideas how the valve get burnt like that? Because of my main work, I can’t work on cars often, but reading your experiences are keeping me alive. I had valvetronic issues with my N55 and you helped me sort it out months ago, thanks again for that. Happy follower from Belgium.


  2. JC says:

    Wow. That’s a first for me. Was there a lot of carbon in the combustion chamber?


  3. Sam G says:

    Good job đź‘Ź!!!


  4. F30ed says:

    Is it defective valve or is it burnt by using wrong fuel? What is the reason?


  5. Bart Bixler says:

    Disappointing that the other so called qualified BMW dealers tech’s could not find the problem, nobody is teaching basic troubleshooting anymore.


    • Don’t get me started on this subject,,,lol,,,,this is a major problem with the newer and younger BMW techs,,,,they just know how to replace parts it’s a very sad issue in this business.


      • Alan says:

        Just blindly replacing parts makes more money mate!

        Your kind will be run out of town if you keep looking after the customer like that!!

        Bloody good work mate. Keep it up.

        Your blogs are always a great read man.


  6. Lee says:

    Ha- the others made it ez for you. Had one years ago- replaced the coil and plug but not the boot connector (was the earlier two part coil/boot).
    Worked for a while. Then went to the dealer. They finished what I started by replacing the boot. Some spark plug insulators come loose and allow hot exhaust gas to escape up and when everything is cold and damp from humidity it will blow moisture under the boot and cause carbon tracking/arching = random misfire. When BMW started using the one piece coil the problems missed by trying to save a customer money by reusing boots went away.
    While a bit off course it’s the same subject but my point being a smart tech reviews whats been done and moves forward.
    My question is: how many miles?
    My experience is that it’s possible a bad injector could cause this (lean = too hot) but a new injector won’t fix it but a new injector should be used or risk a repeat- unless stats prove a bad batch of valves which BMW may or may not share info.
    Keep up the good werk and thanks for sharing!

    Liked by 1 person

  7. JC says:

    Morning Andreas!

    Quick question, How are the B-series engines holding up? Any issues unique to these particular engines?


  8. Will says:

    Hey, How’s it going. I have an “issue” I would love to pick your brain about. I have a 2011 BMW 335I Xdrive Build date of 04/10, it has a spun rod bearing. So with the help of some e90post members, I found a mechanic who is a BMW master tech with his own shop. Per his advise I bought an N55 engine with all the bits with it, It is a “New to Me lol” N55 from a 2013 335I that has a build date of 2012-07-09. Come to find out a lot of parts attached to the block have changed from my N55. Is there a way to compare what parts will be different and what will need to be swapped and what CAN’T be swapped?


    • No there is no way to compare on which parts are different,,,besides you are best to swap over your part from your engine to the new engine,,,,lol,,,because you know your parts are good on your engine,,,,I have seen people not swap over parts and they find out the intake manifold is cracked or something else is bad.


  9. Sandiego says:

    Thanks for the very good posting. I was told N55 is one of the most reliable engines on these days BMW. However, the more I see the issues here, the more I think I should be away from BMW. 🙂 My 550i is super nice to drive until it drives but so many issues are killing me. Not only the issues related to the engine but also all the basic issues.


  10. Robin says:

    Good afternoon!

    I am looking into purchasing either a 2016-18 CPO X5 30d diesel or 35i petrol model. In your honest opinion, which would be more reliable? I am planning to keep it 3+ years and most likely do my own scheduled maintenance. With that being said, would it be wise to purchase a 3+ year authorized BMW Platinum extended warranty service? Thank you for putting the time in to provide such helpful examples of BMW mechanics!


    • I would go with the 35i petrol engine,,,getting the extended warranty wouldn’t be a bad idea….stay away from the diesel


      • Robin says:

        Much appreciated for replying so promptly and with honesty! I wish there were more professionals like yourself. Keep up the good work and wish you get paid top dollar for your services. Kindest regards!


  11. BMW NW says:

    Hello BMW Tech. Is everything going well? Haven’t seen you post since July 31st. Would love it if you can post regularly. I love learning about the day to day life of a BMW technician and all the work that you do. Thanks for giving all of us good content. Keep up the hard work!


    • Thanks for checking in on me,,,yea life is getting a little tuff but we will get through it,,,we haven’t had anything exciting at work lately,,,,we have just had a lot of recall programming lately.


  12. alex_m135i says:

    Hi BMWTech,
    my name is Alex and im from Germany. I really appreciate all the great work you do with your Website. I think so many People can find a lot of helpful Information on here.
    Right now i´m experiencing lots of issues with my M135i with the N55 from 03/2013. After like 5 minutes of driving from Cold start i get Rough idles an loud backfires when i accelerate in low RPMs. Code is Always P0172 running too rich. Sometimes i get a CEL and the codes are misfires on ceveral cylinders and also on cylinder 3 and 4. Under higher RPMs and under some load the car runs smoothly. I took it to a technician who used to work for BMW. After we swapped Coils and plugs with other cylinders the misfires where still on 3 and 4. So we changed those two injectors. After that we experienced the same Problem. The car also doesnt seem to have any vacuum leaks and it has full compression on all cylinders. The technician said that the valves dont look like they needed cleaning, we also chenged the MAF without success. So Right now we dont really know what to do. Could it be a Problem with the valvetronic? I also experienced a loud wastegate rattle. Could this cause the issues? Interesting is the fact that when i turn the car off for like 30 minutes and then start it again, all Problems are gone. Only after the next Cold start it starts over again. The Cold start itself is smooth. Thank you already for reading. I would greatly appreciate every tip that you might have, since me and my technician are pretty desperate right now.
    Keep up the great work!

    Liked by 1 person

    • Ok,,,if the problem is still on cylinder 3 and 4 and we swapped coils and plugs and changed injectors and compression is good,,,we need perform a leak down on all the cylinders,,,,we need to see if there is any leakage inside each cylinders,,,the best way to check the intake valve is to pull back the intake manifold and make sure there isn’t to much carbon build up could be your problem,,,,if leakage test is good,,,carbon build up good,,, compression good,,,injector and spark plugs good,,,,the next thing would be engine harness or DME problem,,,I would first perform leakage test then check intake carbon build up on the intake valves.


    • I don’t think the problem is the valvetronic because the problem is only cylinder 3 and 4,,,,and the wastegate rattle is not the problem either,,,that would cause a boost issue,,,it wouldn’t cause a misfire issue.


  13. Jason says:

    Nice work! How much would this have cost if the car was out of warranty? Also, what would cause this highly uncommon problem? Defective part or did you suspect customer installed a boost mod?


  14. Dan FitzGerald says:

    Surprised bmw would fix an n55 rather than replace it.


  15. Paul Williams says:

    Hi I have a bmw m2 with the n55 engine I am experiencing engine hesitation at low rpm on cylinder 4 the car has had new coils, plugs and o2 sensor we have swapped the injectors but the problem is still on cylinder 4. There is no codes being thrown. The problem does get worse after we swap the injectors but it does not misfire on full throttle do you have any ideas


    • Question why do you think there is a problem with cylinder 4 when you said no codes being thrown,,,,ok that being said you have replaced coils,spark plug and swapped injectors,,,now we need to dig further,,,you need to check compression on all cylinders the you need to perform cylinder leak down test on every cylinder,,,if that is ok then you need to check engine harness and DME v


  16. Paul Williams says:

    Thanks for replying I have a data logger and it shows the misfires on cylinder 4. I had the engine compression tested and all was good cylinder 4 was one of the higher but they were all in tolerance. I will try your other methods do you think there is a possibility it could be an injector


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