12.7 Detroit leaking oil from blow by tube

You can see the blow-by. Don’t know why you need a test . It’s not losing much oil or burning it cause you haven’t had to add oil.Save your money change oil run a sample test.They get excessive blow by usually made worse from excessive idling. Probably have some upper cylinder glazing.If it has a lot of miles.Id be more worried about fuel in oil causing the leaks.Old compressor can cause it . And turbo especially if idled at low RPM. The tube itself may be plugged. Causing the blockage and oil leak. The blow by gets bad and they do drip oil.Mines been doing it for years . Changed comp and turbo still does it.You don’t state how many miles or if you let it idle excessively. You can change oil and run it hard sometimes to help seal up rings but Detroit’s are plagued with blow-by.Sometimes mine looks worse I believe it has to do with the outside weather atmosphere as to how it visually appears worse. High humidity it shows up thick. Just my theory. I ran a tube out the back out of sight out of mind.

 

If you have a crankcase pressure problem the oil pressure gauge will show high. Probably just old gaskets. Have you tried to snug valve cover up tight. Either way I would save money for overhaul.If it’s still got power run it.Im sure when they overhaul mine they will find at least 1 cracked ring.Doesnt mean it won’t still run

 

Good luck! Mine has a lot of blowby too. But not leaking. Have about 300,000 since I frame.

 

Heve a 1993 fld120 with a 1992 12.7 Detroit Deisel 60 series DDEC1,,, I have oil coming out of my blowby tube what would be the cause of this ,,, when i idle it doesnt leak but when i start driving it leaks why is that ??? Any help Mechanixs

 

This was my question I was gonna ask. Ill just revive an old thread instead. Its not a real bother, problem is it slings bits of oil backwards and onto my passenger side fuel tank(not a lot its just annoying)

 

Also, ive never changed the crankcase breather filter......DO I even have one????

 

The filter is inside the valve cover, right where the hose connects. It’s just a metal mesh screen. You can blow through the hose, going into the valve cover, to see if it’s plugged. If it’s plugged it will increase oil pressure, and have less blow by out of the tube. I doubt it’s plugged. Large mesh screen. I see a lot of 12.7s with the hose almost to the ground. That’s why, to keep it off the tanks, etc. I had mine freeze up once, in a bad snow/ice storm. when I had it ran back by the Drives. Once blocked, it bled from every seal. Lost 6 gallons idling in a dock. Unbelievable how badly it leaked, and how fast. Barely made it a mile to buy oil. 10 below, all I had was a gallon of Lucas. Got 1/2 gal in it. Just enough to keep it from shutting down. Pulling a hill, it died just as I topped it. It was that low. Thought it was toast. Topped it off, 6 gallons, disconnect the blow by tuba at the valve cover, till I got to warmer weather. You can’t kill a serous 60. I tried a few times. Lol

 

Im gonna go ahead and get my turbo and compressor changed this weekend. I just got back from running the truck to the shop down the road here.....

Ill have then clean/change the crankcase filter when I get my valves adjusted at the end of the month. Ive developed an oil leak at the back of my oil pan and front driver side of engine which annoys me. Just giving an update on my situation here..... @Rideandrepair you ever think about getting like a catch can that attaches to the end of blow by tube to catch any oil? On my other 12.7's, the majority of the tube is rubber and can move it from place to place. The one on here is metal....

 

Oh yeah, thought of everything. I still have a 2” pvc one piece plumbing p trap, for a sink. It has a drain cap on the bottom. Plan was to cap it with a rubber plumbers test cap, cut a hole for the tube, and draining the trap as needed. Lol. It wasn’t a bad idea. I never did it though. Since then Pittsburgh Diesel has developed a steel box, for any engine. Basically the same idea. Just costs Hundreds of dollars. The tune up might help. I have mine on an angle now, the steel pipe, with hose. Dumps out near the bell housing. Some mud flaps, on the front of side boxes would help. For now, it barely has any blowby at 77k on inframe. I’m hoping it quits for a while at least. But I know it’ll be back eventually as it wears.