MM G1000 Vista Rear Engine Oil Leak

Jeremy L

Member
Recently we decided to turbocharge our 1967 MM G1000 Vista (diesel). In order to provide a sufficient oil return line for the turbocharger we removed the oil pan and drilled and tapped the side of the crankcase so that the oil draining from the turbo would enter the engine above the oil level in the pan. Everything with respect to the turbocharging setup went relatively smoothly but ever since we removed the oil pan and did this work a leak has started somewhere in the bellhousing and we cannot get it stopped. We originally did not gasket glue the new oil pan gasket and assumed that the oil was coming out just below the crankshaft rear engine seal retainer as it seems to be recessed (set up) about 0.050? higher than the bottom of the crankcase. Considering this, we removed the oil pan and made a new piece of gasket to fill the gap below the crankshaft seal retainer and then we gasket glued both side of the new gasket. I felt very confident that we finally solved the oil leak issue but just the other day when we put everything back together and tried running the tractor the leak started again!!!

A couple key things I should note are, 1) we did plug the positive crankcase ventilation tubes on each cylinder head just as the tech manual suggested was to be done for all turbo installations. 2) The oil leak does not occur instantly. It takes about 15min of running before it starts and when it does it is a constant stream of oil that comes out of the inspection plate at the bottom of the bellhousing. 3) Upon our first attempt at start-up after we installed the turbo, we did notice that the oil pressure was running up about 55-60psi where it was supposed to be set to about 40-45psi when running wide open and warm. We did not run it wide open but the pressure was running high until we set it back after a few minutes of running the engine. Lastly 4) we did not have any issues with leaking oil in this area prior to the turbo work and oil pan removal other than a bit of seepage in the bellhousing which seems to be typical of most engines this age. I should also note that this engine was completely overhauled/rebuilt from top to bottom by a reputable engine machine shop approximately 10 years ago and we might have put about 100hrs a year on it since then.

I am not sure if the rear of the oil pan is the cause OR if it is the rear engine seal (if so what would have caused it to all of a sudden give trouble) OR, I have been told that it could be the camshaft plug but again what would cause this to occur? Any assistance at all would be greatly appreciated.
 
Seems weird because what you did wouldn't affect the rear main seal. Are you sure its not hydraulic fluid? Mine leaks bad only when warmed up. Also a turbocharged vista but it is hyd fluid. Not caused by the turbo
 
Your crankcase needs to vent somewhere. If it is not out the top, it may well be pushing oil past the rear main seal if there is pressure build up in the crank case.
 
The crankcase vents out the breather on top of the center valve cover. I checked it and the oil fill tube and there was no pressure coming out of the crankcase when running and as I previously mentioned, we made sure we propertly plugged the crankcase positive ventilation holes in each cylinder head to keep the turbo from pressurizing the crankcase so that is why I am confused and find it hard to believe that the rear engine seal is now all of a sudden the problem. I am not saying this isn't the issue but I am skeptical thats all.
 
I can't say for certain whether it is hydraulic fluid or not but I do know that it is coming from the front of the bellhousing between the flywheel and the engine somewhere. Either way, I can't figure out what would cause the hydraulic fluid leak either if that is in fact the case.
 
I'm pretty sure its not a crankcase ventilation problem. The dipstick does not seal that tightly. How do I know, you ask? Well, when I first put a turbo on my g1000 I didn't realize about the vent tubes under the valve cover. Didn't plug them. Took it up the road for a test drive. Going up a decent grade in 5th low, crammed into the throttle, and shifted to high. When the boost came up it shot the dipstick out a good 20 feet or so! Funny now but made me feel kinda stupid!
 
In the original setup, the crankcase is under a slight vacuum. Now its under a slight pressure. Doesn't take much pressure to make the rear seal leak if its old. Also that gasket area under the seal retainer, I use rtv and not shy with it.
 
Yes that makes sense to me. Thank you all for your replies. The assistance is greatly appreciated.

We are going to attempt to replace the rear engine seal as discussed as most seem to think that is the issue. My question now is, do I need to loosen the crank or will the upper seal go in with the proper tool/puller and some silicon lube?

Also, based on my interpretation of the tech book, it sounds like I am supposed to add enough shims/gaskets between the retainer and the crankcase to have the retainer stick out below/lower than the surface where the oil pan gasket is. Basically the retainer should be shimmed so it is 0.005" lower than the crankcase at the bottom. Does that makes sense?
 
I loosen the main caps, but it's still not an easy task. Use the puller/Installer from napa. Take your time, and go easy when you pull the new seal around the top half. I would put the seal retainer below (shallower) the bottom of the crankcase. Lay a strait piece across and check it. I use rtv across this and the side corks, also at all the gasket joints to hold things in place. The seal needs to stick out at the edges enough to compress it when you tighten the retainer down. Good Luck!
 
I received the rear engine seal kit (which was very expensive to my surprise considering what is in it). Are they typically an expensive item?

We installed the seal and in reading through the instructions it mentions that when you remove the bottom seal retainer there should be 2 wires/rods in with the side seals but ours did not have any of them in it. The kit mentions that once you have the rear seal retainer in place you then soak the side seals in diesel for 3 minutes and then slide them up into place along with the wires/rods. Are these wires/rods necessary? Is there anything special about them or are they just a normal gauge wire cut to a certain length? What is the purpose of them?

See the attached sheet for details related to the wires/rods (Part # 20-000 7249)
 
I am trying to upload the photo but not having much luck.
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