Diesel engine blow by???

[mlb4e]

I just finished reading a thread about someone having to replace the engine in their motorhome because of blow by or internal failure. I was surprised to find out it only had 66K miles. I wonder what is blow by and how can I keep something like that from happening to my engine. I did not hear any of the usual talk about a diesel going at least 500K miles. I was always told that a diesel is just getting broken in at 100K. Is this just bad luck? Engines being built with Chinese metals(like my 2015 Jeep Grand Cherokee Hemi which needed a new motor at 130K miles due to crankshaft failure from Chinese metal). Poor maintenance? Any thoughts and prayers for my engine would be appreciated.

[jacwjames]

Blow by can come from the cylinder wall and ring clearances letting pressure into the crankcase.

Biggest culprit could be from dirt getting into the air intake system.



I just got back from a +8K mile trip, when I was checking oil I noticed the filter minder was showing a little red. Meaning the air filter was pulling more of a vacuum. So I decided to change the filter, it was about 3 years old anyway and had on on the shelf. My filter has the disposable housing, costs +$200. While it was off I remove the metal cross over pipe that the filter attaches to, the pipe goes to the CAC, turbo, and engine. I gave the pipe the white glove test (paper towel actually), and it was essentially clean. I then took the filter outside, turned it upside down and pounded it down on the ground and quite a bit of dirt/dust came out of it.
Not surprised since I traveled ~+10 miles of dry dirt roads and my cooling fan pulls air in the side so the dust boils.

I wanted to make sure all was good. I will send an oil sample in and make sure oil is good, they check for silica (dirt).



Come from mining background, I've seen dusted engines, usually caused by air intake failure.

[Jzack]

Excessive blowby at 66K isn't normal. Did the OP find out why? Cracked rings, or maybe a leaking intake system dusting the motor? Was it an older coach that sat a long time?

Just keep up on regular maintenance and keep your intake system tight, you'll be fine.

[RVfixit]

Originally Posted by mlb4e

I just finished reading a thread about someone having to replace the engine in their motorhome because of blow by or internal failure. I was surprised to find out it only had 66K miles. I wonder what is blow by and how can I keep something like that from happening to my engine. I did not hear any of the usual talk about a diesel going at least 500K miles. I was always told that a diesel is just getting broken in at 100K. Is this just bad luck? Engines being built with Chinese metals(like my 2015 Jeep Grand Cherokee Hemi which needed a new motor at 130K miles due to crankshaft failure from Chinese metal). Poor maintenance? Any thoughts and prayers for my engine would be appreciated.

Hi mlb4e- So "blow by" refers to exhaust fumes leaking into the crankcase from the pistons/ piston rings and is normal to a certain extent. The "blow by" is vented to prevent premature seal failure due to crankcase pressure buildup. Excessive combustion exhaust in the crankcase due to failing or failed piston rings will cause engine oil leaks and short lived oil changes.

Diesels exhaust the excess "blow by" through a vent tube system into the atmosphere and sometimes into the air cleaner housing but if excessive, it plugs the air filter or can be seen coming out of the tube when running as faint smoke.

Since I don't know what engine year or make your talking about I can only generalize that for the most part, RV owners buy RVs with diesels because they can handle heavier loads and are generally more reliable and longer lasting. Semi trucks can go 1 million miles plus on a properly maintained diesel engine. I hope that answers your questions!

Safe travels!

[SafariBen]

Yes, air filter or intake leaking is the most common cause of blowby. Oil failure could contribute, or just random mechanical failure can happen at any point. 500,000 miles is virtually unheard of in RVs, as most have fallen apart long before that. Or some serious travelers trade in regularly. Mines 100k and will probably never reach 150.



Blowby is the air that bypasses the rings mostly, and goes out the "breather tube" on older engines, or is recirculated into the intake to be burned on newer engines. An open breather tube will start to drip oil, or even splatter oil when there is too much blowby. RVs often come with poorly calibrated dipsticks and lead to oil being overfilled and splattering also, that's different than a worn out engine blowby. Blowby quantity is hard to judge, a cold engine in cold air will often appear to have lots of blowby because of moisture condensing.

[jacwjames]

In the mines I managed we'd track hours on each piece of equipment and scheduled maintenance based on the hours. We would also track hours by component. Engines would get ~10,000 hours, some more, some less. Oil changes 150-200 hrs with sampling. We'd track $/hour and when we saw costs going up make a decision to pull and rebuild or scrap and engine. If a rebuild approach a % of a new engine we'd scrap it.

I had one engine in a loader that out lasted any other motor we had. I actually decided to let it run until it failed and didn't rebuild it. I got some flake from upper management but when I explained my reasoning they agreed. Got 14,000 hours on the engine without a major component change before it failed, by far one the cheapest $/hour we had. !4K miles is approcahing 700k miles on an RV at average speed. PLUS mining is a very harsh environment.

[FIRE UP]

Originally Posted by mlb4e

I just finished reading a thread about someone having to replace the engine in their motorhome because of blow by or internal failure. I was surprised to find out it only had 66K miles. I wonder what is blow by and how can I keep something like that from happening to my engine. I did not hear any of the usual talk about a diesel going at least 500K miles. I was always told that a diesel is just getting broken in at 100K. Is this just bad luck? Engines being built with Chinese metals(like my 2015 Jeep Grand Cherokee Hemi which needed a new motor at 130K miles due to crankshaft failure from Chinese metal). Poor maintenance? Any thoughts and prayers for my engine would be appreciated.

mlb4e,
You've been given some good info. I'll just add a tad of detail here. "Blowby" or otherwise known as Crank case pressure, is created with basic engine operations. As a piston travels up the cylinder, the fit between the piston and cylinder is about as tight as a engine manufacturer can make it without it being so tight that it seizes. To take up the small space between the piston and cylider walls, there's rings around the pistons that are spring loaded to expand and ride against the cylinder walls.

Those rings, along with a very, very slight film of engine oil, provide an almost air tight seal as the piston moves up and down the cylinders. But, during what's called the compression stroke, when the piston is traveling up, there's only so much sealing those rings and oil can do before SOME of that compression is forced by the rings. That minute amount of pressure slips by the rings in between them and the cylinder walls and then travels down into the crank case.

Now, if you have anywhere from 2-4-6-8 cylinders, all contributing at least a small amount of this "blow by", you're filling that crank case with the pressure that was developed above the rings. If you have a completely sealed crank case, there's no where for that pressure to go other than the weakest point possible which, in most cases, would be a *seal* someplace, like the crankshaft and dampener seals.

So, the engine manufacturers developed a *crank case breather* in various forums to allow for that pressure to escape without damaging any engine components like seals etc. Blowby, in and of itself, is not harmful. It's merely pressure trying to escape. But, it's not CLEAN. It's mixed with exhaust, oil fumes and all that. Soooo, the smog gods frown on that stuff so, they've made engine manufacturers develop components to handle that pressure while still allowing the engines to run properly.

In the early days of our diesel motorhomes, the "blow by" was simply routed from the engines, down a tube to an open end and exhausted into the atmosphere. Over the years, those open ended tubes, gave way to components that contained and treated it. You won't see or experience ANY Blowby on any newer diesel (or gas ) engines that have been produced in the last, oh, about 18-20 years or so. Hope this helps some in clearing things up.
Scott

[mlb4e]

Thank you all for your replies. If I am understanding correctly the main thing I can do is make sure the intake air is clean, which I can control by having a clean air filter. Add in regular oil changes and keep my fingers crossed!

[Bimmerbob]

Originally Posted by mlb4e

I just finished reading a thread about someone having to replace the engine in their motorhome because of blow by or internal failure. I was surprised to find out it only had 66K miles. I wonder what is blow by and how can I keep something like that from happening to my engine. I did not hear any of the usual talk about a diesel going at least 500K miles. I was always told that a diesel is just getting broken in at 100K. Is this just bad luck? Engines being built with Chinese metals(like my 2015 Jeep Grand Cherokee Hemi which needed a new motor at 130K miles due to crankshaft failure from Chinese metal). Poor maintenance? Any thoughts and prayers for my engine would be appreciated.

Apparently in my case, It was a piece of the turbo that went through the engine and took out the injector in number one cylinder, which over fueled the cylinder and put a hole in the piston which caused the massive blow by.

I don’t know how I could’ve prevented it. When the engine failed all the temperatures and pressures were fine, within 30 seconds it was gone. Never had any blow by before that or any problems that would’ve warned me of what happened.

It was a Cat C7 2006

Rob

[desertdd]

Sometime ago I witnessed a fellow at a Cummins dealership who had excessive blow by on a low miles 400 hp. He thought it was going to fixed under warranty but they discovered he had installed one of those aftermarket high performance air filters and were going to deny the claim. I don't know how it turned out but lesson learned don't fall for the propaganda that these aftermarket filter people tell you. Make sure you a good OEM air filters.

[Dutch Star Don]

A couple of notes.....yes, air filter issues are one of the biggest contributors to "dusting" an engine......getting dirt in it.

If your coach is like many of the Monacos of that era, they had a removable filter element, not a cartridge. Often some will pull that cartridge out, bang it on the ground to knock the dust/dirt out to get a little longer life out of the filter.

Doing the above to a filter is a TERRIBLE idea/practice. That dirt goes back into the air filter on the wrong side and then gets pulled into the engine. Don't remove that element unless you intend to replace it.

On other coaches like mine (Freightliner), it has a horizontal filter cartridge that lays atop the engine. It has a 90-degree bend on the engine side and uses a rubber hose to connect to the turbo. Since the air cleaner end goes downward into the rubber hose, dirt can collect around the edges. When you "wrestle" that huge/tight filter out, you can dislodge dirt along the lip of the hose and drop it directly into the turbo.

When I change mine, I first wash off the area. Then I disconnect the clamp at the turbo side of the rubber hose and remove the air filter cartridge with the hose attached. Once off, I install the hose on the new filter and reinstall. This greatly lessens the chance that dirt can get in the turbo.

[jacwjames]

On my last trip I did travel ~10 miles on dry dirt roads with the dust boiling behind the coach. I also noticed the filter minder showing some red.



So when I got home I decided to change the filter, it was on for 3 years anyway and it was due. I had a new one on the shelf.


Mine is the disposable canister type, costs +$200. It lays horizontal above the engine on passenger side. Large flexible hose connecting the the water separator box. Large metal crossover tube going toward the turbo.


I pretty much have to remove the cross over tube to get the housing out. After removing the filter I did take it and turn it upside down and pounded it down on the ground several times and got a good pile of dirt/dust out. see picture



I also too the tube and checked for dirt on the inside using a piece of paper towel, there was not any measurable amount. I then cleaned it good with brake cleaner and then wiped it down before reinstalling.



I will pull an oil sample and send in, I keep them on the shelf.

[Beemermcrs]

Had that happen on a marine diesel: turbo blew parts through the motor. I paid for a new turbo, insurance paid for the engine. Was about 24 years ago, but might apply today. FYI.