1990 Bluebird Bus converted to motorhome. All bone stock on the 12v Cummins. 193k miles. Noticed 4 bolt connection from exhaust manifold to turbo was wet around it, and a little run of black oil or diesel trickling back down the exhuast manifold. Thought for sure it was the turbo, and rebuilt it. Turbo had nothing unusual wrong inside, and rebuilt it anyways. Upon fire up, after 5 mins or so idleing, same wetness came back. Unbolted turbo, and noticed front half of exhaust manifold was wet. Took off the exhaust manifold, and cylinder #2 exhaust port is "wet". Smooth and slippery like oil, but much thinner. Very hard to tell if it's oil or diesel. Removed #2 injector, dismantled and cleaned in SeaFoam. Put it all back together and same issue. And I didn't get it pop tested while it was off...DOH!! Valve guide seals are seated well and didn't see any oil residue on exhaust valve when manifold was off. After driving, residue burns off, and it never gets wet again until the next startup and idle. I'm lost on what to do next? Ideas?? How can I tell if it's oil or diesel....someone told me that diesel that far through the system will not smell like diesel anymore.......... Also, anything I can pour in the cylinder if I have a stuck ring?

 

3 things I can tell you to try. 1, move the injector to a different cylinder and see if the problem follows. 2, do a bore scope and see what it looks like inside that cylinder. And 3, do a differential compression test on that cylinder and see if and where it is leaking. Did the injector look like it was getting oil on it before you cleaned it? There is the possibility of a cracked head or a broken/stuck ring.

 

Cougar,

When I removed #2 injector, it didn't appear abnormal at all, no caked oil residue, no wet oil residue, just a tad bit of carbon deposits on the tip. Last time I had the exhaust manifold off, all cylinders exhaust ports had a nice sooty appearance to them, except #2. It was clean as heck, which makes me think it could be a bad injector washing the cylinder..... I guess I will try a cylinder to cylinder injector swap. Could my wet exhaust port symptoms be fixed by a valve adjustment? I took off most of the valve covers, and valve adjustment seems excessively sloppy. Plan to do it anyways, but I can't think how that would fix my issue unless someone knows otherwise.

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Oh,

Also, I tried the "tea kettle" trick with the oil cap, and also went to the breather tube to see if I had excessive blowby. Everything appeared normal. Also, after removing the injector, I peered down the injector hole and could see the top of the piston. Looked normal and slightly sooty. It was also dry, but it was after sitting for days. Possibly the excess diesel being dumped by the injector evaporated and that's why it appeared dry? Fluid ring at turby manifold dries also after shutdown. I'm hoping it's just a leaky injector........ Anybody know the cost of a Pop Test?

 

Where in AK are you, if your close enough I'd like to take a look at it. There is a Bosch dealer in Anchorage near Merrill Field, can't remember their name off hand that can pop test it. One more thing to try is when the engine is up to temp and idling, crack each injector line and listen for a change in how the engine is running. You should have a fairly consistent change in sound and RPM with each injector.

 

I'm bettin it's the injector

 

With this issue seemingly not causing any driveability issues, how long before I should address this? Is it ok to drive out on a roadtrip, should I do it ASAP, how long before I "wash" the cylinder and damage it? Anybody have any issues with Napa Injectors? Found a brand new one in stock for $88. Is it ok to replace just the one, or should I be doing all 6 since they are probably original......

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Cougar,

I'm in Butte, outside of Palmer. Advanced Diesel Service is I believe close to Merrill Field. I work in Anchorage, so I was going to bring the injector in with me one of these days. Gonna try the cylinder to cylinder injector swap first to see if it follows. If not, I guess I'm doing valve guides or paying someone to check the compression for ring issues.

 

I would at least ID the cause before doing a "road trip". Doesn't take long before cylinder washing does damage. It also dilutes your oil which is not good either. Replacing just 1 injector is kind of precarious in that it will not match the others in pop pressure and flow. It would be better if you either replaced or rebuilt them all. Yes, Advanced is who I was thinking of.
Actually I am in the process of moving to Butte, near the Green Store. I also work in Anchorage, at Merrill Field. Small world, ain't it.