<span style="font-family:Arial">My D47U, SE# 10164, is leaking diesel fuel into the crankcase.

A few months ago, the diesel in the fuel tank leaked into the crankcase. At that time I took off the transfer pump, replaced the seals and made certain the drain line was open. I only used the Cat once since then before today but when I checked the oil today before starting it smelled like fuel in the oil but the level was not excessively high. I had shut off the fuel at the tank after using it the last time.

Today when I started the beast, I had to bleed the injectors to get it started. The fuel pressure from the transfer pump at the filters came right up to the max. It ran fine but after about 3 hours I noticed that when I throttled down the oil pressure gage came off the peg and it always stays pegged unless it is really hot outside even at a low idle. I really wasn't pushing the Cat very hard as I was only dozing part of a pole barn into a pile and smoothing up a part of the corral.

About thirty minutes later I noticed there was "oil" leaking onto the ground and so I checked the oil level and it was about 3" too high so i headed the Cat to the yard. The oil pressure at idle was a little over half the gage so I didn't think it would hurt it to drive to the yard. At half throttle the oil gage was about 3/4.

In the 4 hours or so today I used twice the amount of fuel that I should have and obviously half of it it is now in the crankcase again.

How in the heck can diesel fuel be getting into the crankcase? I am positive the line from the injector pump is also clear and I have seen no drips from either pipe. Any suggestions are welcome.

My first task is to drain out the mixture and start again with clean oil.

Thanks in advance for your help.</span>

There is a o-ring seal between the injection pump and the fuel filter housing. This is above the pump drive. It must be rotted away. Remove the injection pump and governor to replace.

When I restored my 5U D2, I found that there are actually two o-rings that seal that passage in the injection pump. There's the one between the pump and the filter housing, and another between the pump and governor housing. The parts book for the D2 shows the same part number for both o-rings, the one on the governor end of the pump is on a plug that seals the end of the fuel passage. I figured I'd mention this because your 7U might be a similar design, and if you already have the pump off to do the one, it's not much more work to get both of them taken care of.

Rome, Thanks for the help. Looks like getting the bolts out of the back side of the injector housing will be the hardest part. Caterpillar in their infinite wisdom made some impossible circumstances. Looks like it is a line to line fit to get it out past the pony clutch.

Do you think there is a need to replace the lower seal on the drive shaft while I have it out? Looks like that just keeps oil in the pump housing and I never have to add oil.

There appears to be two seal numbers so will have to wait til Monday to talk to Cat to see what they are.

Only one seal number....the one with the black triangle in front of the number is for shipping only.

Thanks Toby,
I think this is probably the seal you mean on the governor side. (see photo)

How in the heck did you get to the bolts on the back of the injector?

I havent started taking anything apart but it looks like the bolts are pretty well hidden away!!

Thanks OM about the seals and the meaning of the black triangle!!

Yes, that's the other o-ring I was talking about. If one is deteriorated to the point of leaking, then the other is likely in the same condition.

I just use a ratchet, some extensions, and a 9/16" swivel socket to remove the injection pump nuts between the housing and engine block, its not bad at all.

you might want to change the metal sleeve the o'ring fits over. it fits tight in the filter housing but comes right out with a couple of twist with water pump pliers it is still available at cat and now is a good time to replace it. I have found them badly pitted and pin holed from rust do to moister from lots of years of sitting. its cheap and easy wants your there and then everything is new and you have know worries.

The studs behind the pump housing usually come out with the nut. Sometimes you get lucky and just the nut comes off. When you are ready to go back together, install the studs with locktite sealer and give them time to set up.

The replacement camshaft seal (1H5959) is about as strong as a beer can. If you get in a hurry and drive it in with something that is smaller in circumference than the seal, it will warp and become garbage. Use a seal driver that is the same O.D. and it won't bend. Seal is cheap from Cat; $15-17. Must be used in many other applications.

Whatever you do, don't turn the crank on the Main when the pump housing is off or you'll loose your timing. The back of the pump housing is probably filled with fuel and dirt; cleaning it out is the worst part of the job.

Rome already told you about removing the governor first. If you attempt to remove everything as one assembly the governor will run into the pony motor clutch. If you remove the clutch you'll have unbolt the pony motor and lift it up which is going to increase your workload 4x.

I've never removed a governor on a 7U so maybe someone else can tell you if there are any traps for the unwary.

It looks like I can remove the top two bolts in the end of the pony clutch to clear the governor and pump. If my tape is correct it will give me a whole 1/4" clearance past the end of the studs unless there is something else that gets in the way!!

Might be a couple days until I get to it as my elderly mother fell and broke her hip yesterday.

Thanks again for all the help.