[CT_335D]

Is carbon buildup only common on diesel engines or is it also present on gasoline engines?

Is the main cause of carbon buildup due to direct injection and EGR valve?

[335D Alpha Pappa]

CBU happens in both engines. My stealership said is has cleaned hundreds of gassers and only a few diesels. If you go to the N54 section, you can find more topics on cbu. I also talked to a vw dealership and he stated that they have a cbu as well but for an extra price, vw is happy to sell you a policy to clean your engine. I should have kept the flier.

IMO, cbu is 100% related to the egr valve. That is the only device that allows hot exhaust gas to feed back to the intake. The buildup happens due to the much cooler temps of the intake causes the hot gasses to quickly condense and then stick to the surfaces. Much like creosote build up in a chimney. If you look at all of the pictures, all of the cbu happens after the egr. Never find any build up in the intercooler. Block the egr and you kill the feedback loop for cbu.

My anecdotal evidence is my 2001 duramax with DI. No egr, dpf, scr, and no cbu in over 400k miles. I will know more when I rebuild it in a few months.

[Lexx.md]

I read in other topic, the main issue is when EGR gases mixes with oil from PCV, This is when it has ability to create soot.

So you want to address both problem.

And i am reading this forum and it looks like meth\water system will wash it away, so it might be a solution.

[Lexx.md]

And there are probably 4-5-10 times more gasoline 3.5 engines on the road than diesels, so i believe diesels have more CBU than gasolines, but gasolines are more often for obvious reason.

[CT_335D]

Thanks for the info.

When I purchased the car, I thought the only reason I would get rid of it was if I got bored of it. I thought that diesel cars last forever.

Now I will have to get rid of it in 2017, granted I don't have any major issues with it. It was nice to have the CPO until 100k miles.

[glitdi]

Soot/ carbon buildup is a common occurrence on a variety of German motors seen it on gassers, and diesels, heavy duty diesels as well.. Been told it has to do with the crappy fuel on this side of the puddle. Don't know if its an excuse the Germans use for a poor design or not, either way its prevalent on most German brands to some extent. Seen it on Bmw, Volkswagen, Mercedes passenger, and heavy duty, and Liebherr..

[Hoooper]

The gassers dont have EGR so its not the cause of their CBU. The CBU on a gas car is also hugely different than the CBU that we get, they get hard deposits only on/around the intake valves. We get semi-soft deposits all through the intake, head, and intake valves. CBU on direct injection gas cars exists because gas no longer washes the valves off and prevents deposits, so anything that sticks to the valve just stays there and gets baked on.

[CT_335D]

Thanks for the info.

According to my service records and what BMW service told me, it seems like my 335d needs a carbon buildup cleaning every 40-50k miles. I purchased my car with 46k miles CPO. The service guy told me there was CBU cleaning performed at around 40k miles, then at 50k miles, they replaced the cylinder head, injectors and intake and outtake valves due to a leaky injector. Now they did another CBU cleaning at 100k miles.

Kind of makes me wonder why the original owner traded in the 335d. He probably didn't want the hassle of CBU, so he dumped the car. BMW certified it as CPO and I ended up buying it. The only thing that saved me after 11 times in for service, I only had to pay a $50 CPO co-pay. Otherwise I would be around $25,000 in the hole and I would have dumped my car a long time ago before I spent that kind of money on the car.

Won't be buying a diesel anytime soon. Not worth the hassle.

[Hoooper]

If you want to drive a diesel you have to be willing to give the middle finger to the EPA equipment on the car. There are quite a few people on here who have no emissions equipment problems and never will.

[montr]

Originally Posted by CT_335D

Thanks for the info.

According to my service records and what BMW service told me, it seems like my 335d needs a carbon buildup cleaning every 40-50k miles. I purchased my car with 46k miles CPO. The service guy told me there was CBU cleaning performed at around 40k miles, then at 50k miles, they replaced the cylinder head, injectors and intake and outtake valves due to a leaky injector. Now they did another CBU cleaning at 100k miles.

Kind of makes me wonder why the original owner traded in the 335d. He probably didn't want the hassle of CBU, so he dumped the car. BMW certified it as CPO and I ended up buying it. The only thing that saved me after 11 times in for service, I only had to pay a $50 CPO co-pay. Otherwise I would be around $25,000 in the hole and I would have dumped my car a long time ago before I spent that kind of money on the car.

Won't be buying a diesel anytime soon. Not worth the hassle.

I feel your pain. My experience with the 335d is similar. This is why the 335d is on the "Used cars to avoid list" in Consumer Reports.

[CT_335D]

Originally Posted by Hoooper

The gassers dont have EGR so its not the cause of their CBU. The CBU on a gas car is also hugely different than the CBU that we get, they get hard deposits only on/around the intake valves. We get semi-soft deposits all through the intake, head, and intake valves. CBU on direct injection gas cars exists because gas no longer washes the valves off and prevents deposits, so anything that sticks to the valve just stays there and gets baked on.

So only diesel engines have EGR valves? I thought all newer gasoline and diesel cars have EGR valves.

[dr_dirtg]

This is sad. Its too bad todays men aren`t mechanically capable.
The 335d is a torque machine, its for real men, the whiners can go buy a corolla and drive slow on the passing lane.

I have cbu and boost loss issues too, I fixed them up and I have my torque machine again. Its really not that big a deal.
And it provides a manly bond between my self and my car.

If you want a reliable car with this kind of power you need to buy a v8 at minimum.

And forget about the mpg in the v8.

The 335d has it all.

[Hoooper]

Originally Posted by CT_335D

So only diesel engines have EGR valves? I thought all newer gasoline and diesel cars have EGR valves.

New cars in the 90s and early 2000s pretty much all had EGRs. However, around the early 2000s car manufacturers realized that EGR is, in fact, the devil and began developing engines that dont need EGR to achieve emissions requirements. I have been told by one or two people that some new gas engines are getting EGR again, but I havent seen anything about that. As far as I know any new gas engine worth owning has no EGR.

[TDIwyse]

I think some of these newer engines, like my wife's GM 2.4 ecotec, use "internal EGR" via controlling valve overlap. This can effectively do EGR without routing exhaust all the way back through the intake system ...

[iaknown]

Originally Posted by TDIwyse

I think some of these newer engines, like my wife's GM 2.4 ecotec, use "internal EGR" via controlling valve overlap. This can effectively do EGR without routing exhaust all the way back through the intake system ...

That's some crazy stuff....great idea though


You guys should check out a company called Kenvo, they make carbon/EGR cleaner systems. My dad happens to be the rep in our area selling them and we have one sitting in the garage. He sells to a lot of the diesel performance shops for the trucks but it supposedly can connect to almost anything. Going to try the wife's tdi soon. They claim to clean the EGR, cooler, intake, dpf, etc with a special solution. Would love to put a 335d on there sometime too...

[Mik325tds]

Originally Posted by TDIwyse

I think some of these newer engines, like my wife's GM 2.4 ecotec, use "internal EGR" via controlling valve overlap. This can effectively do EGR without routing exhaust all the way back through the intake system ...

I thought that technique was already used in the E46 323i. At least I remember reading something about it.

[Hoooper]

I wonder how that's any different from valve overlap which has been a part of naturally aspirated engines forever. I guess with variable valve timing you could do a little more with it

[TDIwyse]

Originally Posted by Hoooper

I wonder how that's any different from valve overlap which has been a part of naturally appeared engines forever. I guess with variable valve timing you could do a little more with it

Yeah, I think the variable valve timing makes it tunable and more effective.

http://www.motor.com/article.asp?article_ID=1506

GM, however, phases exhaust cam*shafts for a different reason: internal exhaust gas recirculation (EGR). Internal EGR is accomplished by overlapping the exhaust cycle into the intake cycle. Think of the basic four cycles, then imagine if the exhaust valve delayed closing well into the downward stroke of the intake cycle. The opposite of cylinder scavenging would take place. The movement of fresh air and fuel being pulled down into the cylinder would create a draft to pull some of the exhaust gases back into the cylinder.

[Hoooper]

Well that's different from normal overlap so there's definitely a difference there. Late closing exhaust valve vs early opening intake valve. Pretty smart if you have to have EGR to keep it contained to the cylinder and exhaust rather than the intake.

[Puerto Rican 335d]

All Direct Injected engines will have CBU more so than previous generations

[Thecastle]

Originally Posted by Puerto Rican 335d

All Direct Injected engines will have CBU more so than previous generations

I wouldn't quite say all. Toyota who actually tries to make cars reliable hahaha, on most of their DI engines also has a port fuel injector as well, to improve efficiency and spray fuel in the intake tract to eliminate cbu.

Audi and vw have adopted the same thing in European versions of their ea888 gen 3 engines in Europe.

Cbu is a design flaw. It's an unfortunate side effect of direct injection and motors that don't compensate with with coatings on the intake and valve that prevent oily deposits from adhering, or adequate filtering of these elements.

Our 335ds problem is egr pre dpf, egr, and probably ccv (pcv) valves that are shoddy. Vw has had a lot of trouble with crappy pcv designs as well a.lowing to much oil into the intake leading to cbu.

[Puerto Rican 335d]

very true Castle our cars are screwed
Thanks for great insight