335i with a N54 with carbon build up,,,,car ran ok,,,,but you could notice a rough idle,,,,which was caused by to much carbon build up on the intake valves,,,,,when removing the intake manifold,,,,remember to also remove the manifold studs,,,,removing the stud helps out a lot when removing the manifold.
Here you can see the build up on the intake valves.
We use walnut shells to clean the valves,,,,using walnut shells is nice,,,but it leaves a big mess and its a lot of work,,,,I have done this repair at home for some friend,,,,I have used some good intake valve cleaners and I would turn the motor over until the valves are closed,,,,then pour the cleaning solvent inside the intake and soak the valves,,,once done soaking,,,,I would use a long pick to chip off the carbon,,,,,some of the picks I use look like dentist tools,,,,it takes some time but you can do this job at home.
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bmwtechnician 
Is there any additive you can add to the gas to prevent this? If so, how often? Concerning ethanol and non ethanol gas which one of these gases will leave less carbon build up?
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No there really nothing you can do,,,,it just the way the engine is designed,,,,other car company’s have the same problem with direct fuel injection,,,,no fuel to wash down the intake valves
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If no fuel is passing the intake valves what than, just air? How/what is making them so dirty? In your opinion what gas would be best to burn in the car, gas with ethanol or gas without ethanol?
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In California we have very hard fuel laws,,,,we have premium fuel,,,,yes the main thing is just air going past the intake valve,,,,but with the turbos,,,,there might be some oil blow by with turbo,,,,which then pumps some air and some oil into the intake valves.
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My son tackled this project on a 335i exactly as you described. About 80,000 miles. The job was done as a preventive measure more than anything else, but yah, MESSY, MESSY.
On a related note, F01….possible to do at home too?
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Very cool,,,I’m glad he was able to do it at home,,,,on a F01,,,,,no you can’t do it at home,,,,the whole engine and trans with subframe has to be dropped out of the car to remove the intake manifolds,,,,,remember the intake manifolds are on the outside of the V ,,,,,so the intake manifold are up against the sides of the engine compartment.
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I had my n54 Walnut blast couple of weeks later I hear this clunking noise coming from underneath the hood hard to pinpoint sounds like it was coming from underneath the valve cover but then when I lift my head up sounds like it’s on the driver side in the back Smh….. Damm thing a Money Pit! Lol…. but I love driving it.
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Lol,,, I understand,,,it’s hard to say what the clunking noise is coming from.
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Ok thank you…. order new valve,cover so I’ll be changing that soon see if there’s something under there thats not right
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Good afternoon mr. BMW Tech I had a coolant leak problem when I got in my car this morning not sure where it’s coming from but when I did get under the car I noticed that the coolant leak into the water pump electrical connection…. on that note
mechanic put in 3 months ago put the wrong water pump in because the connector will not clip into the water pump I’ve been having problems with codes to the water pump not working…. like I got today a code…my question is because coolant got into electrical connection would it fry the water pump? I’m afraid to try to plug it back in and caused a major problem when I start it up
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No ,,,coolant into the connector will not fry the water pump,,,,you could disconnect it and spray brake cleaner or carb spray or electrical cleaner and then reconnect the waterpump,,,,I don’t understand how the mechanic put the wrong waterpump in the car with the wrong connector,,,,there is only 1 type of waterpump and they all have the same connector,,,,have someone look at the connector to make sure it is not damaged in anyway or corroded
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It’s all aluminum water pump bought from AutoZone the connector….. will not fit over the little notch on the pump seal it in there. I looked on the web haven’t seen any water pumps that looks like that. Fit my 135i
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Sounds like you should get the correct waterpump.,,,,autozone should be able to take it back and get you the correct one for your car.
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Unfortunately I’m screwed there because the mechanic went out of business I just have the receipt from the work he did thank you!for your help I’m going to go out there and try to clean the connector and see if I can get it to clip to the water pump
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