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2004 LB7 oil leak---front of pan

26K views 17 replies 8 participants last post by  Ron Nielson 
#1 ·
I'm new to the duramax scene(I've owned the truck for about a month) and after a quick search, didn't find an exact answer to my problem. Just walked out from eating lunch and noticed I have a pretty serious oil leak(dripping every second or two) on my 2004 Silverado(LB7). It's a bone stock motor with 263,xxx miles. The drip is coming off of the front of the center of the oil pan(directly under the crank pulley). There is no oil above that. I am parked on somewhat of an incline with the nose down. What are the possibilities of what could be leaking? My guess is the crank seal but is there anything else I can check before I tear the front of the truck apart? I was able to take a pic and catch the drip. Any guidance would be greatly appreciated.
 

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#2 ·
I assume this is a Non-Emission non-Calif vehicle-- no vacuum pump or EGR.

First pull the oil dipstick, smell the oil- does it smell like diesel-?? Is it over full-?? Drop some oil on a paper towel-- the oil will make a spot, and the diesel-[if any] will make a halo around the oil spot. The LB7 engine can dump diesel in the crankcase if an injector is leaking.

Next to the crank balancer is a crankcase vent tube- if the oil is over full, it will blow oil out the tube and show leaks at the front of the oil pan. You need to check further.
 
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#3 ·
Thank you. There is no cat on the truck so I'm gonna assume it's a non-emission truck BUT I'm sure there are other things that I need to learn as far as it being emissions equipt or not. I will do a search and figure that out. I checked the bypass tube and it appears throughout the miles, there has been some oil come out of there but as for today, it looked like it was more centered(did not look like it was dripping on the wire loom and running down) on the oil pan. There's a black plastic cover in front of the oil pan that it looked like the oil was dripping from between that and the pan. I checked the oil. The level registered on the dipstick(a little low but still within range) and it did not smell like diesel fuel but I'll do the paper towel test tomorrow. Thanks for that trick. I'll research and check things and report back tomorrow. Thanks again.

Bo
 
#4 ·
Sorry for the extra post. I can't edit my previous post on my phone.

My truck is a non-emission, non-Cali, no egr and no vacuum pump. I parked the truck in the driveway with the nose slightly higher than the rear and it didn't leak nearly as bad but still dripped on a piece of cardboard from the back of the skid plate. I'm ready to get out there and try and figure this out tomorrow.
 
#5 ·
After a day of degreasing, it appears to be leaking from the crank seal. Yay! I get a new $200 tool. Just what I need. Haha. It doesn't appear to have any diesel mixed in the oil which is good. I'll do a search and figure out the best way to go about replacing that seal.
 
#6 ·
Update. After adding a quart of oil, it leaked right back out within 10 min. Weather finally allowed me to work on the truck. I got the front of the motor torn down and cleaned and now I'm not sure if it's leaking from the crank seal or the front of the oil pan. Is there an easy way to figure out the leak between the 2 or would adding another quart of oil be the way to go?
 
#8 ·
Thank you.

I must have fixed it because I can't get it to leak! Haha. I guess I'm gonna throw the harmonic balancer back on it and crank it up and see what I can see.

I've searched and can't really come up with a definitive answer but...If it is the front of the upper oil pan leaking (between the timing cover and upper oil pan), can I pull the timing cover and reseal just that area to save me from having to go through the trouble of dropping the upper pan?
 
#9 ·
Ok, I put the truck back together and took it for a drive. When I got back, oil was leaking out of the crank case vent tube. And nowhere else. It's possible that the truck was so dirty that the oil was coming from the tube all along and I just couldn't tell. I might have overfilled it today trying to get it to leak. But that doesn't explain why it leaked the quart I added earlier this week just sitting(not running). The oil that leaked today didn't smell like diesel and my injector rates read surprisingly good. I'm kinda stumped here. I guess a compression test comes next???
 
#12 ·
New findings. After adding a couple quarts to try to get the truck to leak with. no luck(still barely showing on the dipstick) I changed the oil. I drained a full 5 gallon bucket full of oil and I believe diesel out of my motor....it wasn't water. I'm glad i didn't run it with that much fluid in the motor.

I obviously have an injector issue. My question is...is there a way to figure out which injector(s) are bad? Using the torque app on my phone, I checked the balance rates on the injectors and *if* I have the correct readings, they are all reading well within the "ok" range. The worst was #1 that read 2.1. I'm guessing that changing all 8 injectors is probably what I'm going to have to do BUT I just had my first kid and $2500 for all injectors is a little out of my price range right now. So fixing only the faulty ones is what I'd rather do to get me by if possible. Thanks for any input.
 
#13 ·
The LB7 injectors are under the valve covers and are labor intensive to change, so most will replace all of them, or at least all on one side. If you change one or two and the others go bad you will have to tear into it again.
 
#14 ·
Thanks. In my searches, like you said, I'm finding that most people will just replace them all. My lil man had an extended stay in the hospital that used up all my truck money so if there's a way to just replace a couple, at this point, it might be what I do to get me by until I get my truck funds stocked back up. I'm not too worried about the labor portion of the job. Wrenching on stuff is like therapy for me which I'll need plenty of after spending $2500 on injectors, haha.
 
#15 ·
A faulty return line or CP3 pump can also put fuel in the crankcase. I would check it out good before I would just start throwing parts at it.
 
#18 ·
When you start your truck, does the engine turn over evenly, or part of the revolution is harder/slower than another part? Fuel in the cylinder, harder to compress than air, fuel leaks out of the cylinder to the crankcase. Pull the glow plugs, one at a time, see if you get a spray of fuel out of any of the cylinders. Maybe give it some time between each cylinder test for fuel time to leak into the cylinder. Probably better ways to check this, but this is no-cost, except for your time.
 
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