Where Is This Leak?

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
OK, so I've long had a slow leak that I've really just ignored because it wasn't enough to worry about. But it's getting so that it drips every time I park.

I get motor oil coming off of the bolts that are on the bottom of the bell housing to engine. This is not a place that can leak on its own, so the oil is coming from up above someplace. It could be the vacuum pump, maybe the back side of the valve cover, or...? I do have seepage on these spots, but none of it is ever enough to make for what I see dripping off the very bottom. Any ideas?
 

Napalm00

Well-known member
It's most likely coming from the t seals on the rear bearing block or the rear main It's an engine out service to replace them .

Super common and shitty
 

Napalm00

Well-known member
Unfortunately age has really nothing to do with these rear main seals.

They are extremely sensitive for some reason.

It's more likely the t seals as they may be original and many don't replace them.


if you want a definitive answer where the stuff is coming from without any back and forth. Add UV dye that's made for air conditioning systems to your oil (available any auto parts store) , then power wash your engine and transmission or take it to the coin operated car wash and do the same, drive it for a day and then check it that night with a UV light. It'll be instantly obvious where the oil leak is coming from
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
I can see that a few of the bolts on the pan do seep, but not enough to drip. The problem with seeing where it is coming from is that other than some minor seepages, I can't see anything. There isn't any oil anywhere on the truck except for on those two bolts, mainly the right side. I'd be expecting those two bolts to glow, but that doesn't show me anything new. Sounds like it might be fun anyway, so I'll see about picking some up later today.
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
Let me expand a bit on this thread.

I usually spend a bit of time cleaning the underside of the engine once a week or two. I missed the last few weeks, and have noticed a few new leaks!

First, the drip from the bolts I described above might actually just be a culmination of a bit of a leak from here and there -- one from the back of the valve cover, one from the vacuum pump, and one from the back passenger side of the oil pan. None of these are too bad, I can easily clean the area of these leaks, and see right where they are coming from. But I think they are all adding up to the drips coming off that lower bolt. There doesn't seem to be any other place that it could be coming from. There are no seams on that side of the bell housing/engine/transmission. I hope the dye will help, but only if I am completely missing something. Like I said, it's easy to see where leaks are coming from because the engine is cleaned on a regular basis.

However! I just noticed a coolant leak that appears to be coming from right above the alternator. It could be the large hose right there. But it seems to be coming from the pump housing. Does this sound familiar to anyone?

I'll update once I get the dye running through in the next day or two and am able to use my new UV flashlight to check.
 
I had a horrific leak on my 300TDI that started about 50-100 miles after a full rebuild. I ended up pulling the pan, replacing the t-seals and rear main with a rear main from Turner. I didn't think it was worth my time to do the rear main and not the t-seals in-case I was wrong. I have put a couple thousand miles on her since and I have yet to see a drop of oil come out of the bell housing.

That being said, when I had my leak, the oil came out of the wading plug hole on the bell housing. I didn't have any oil coming from other spots. You might just have a combination of a few leaks from other places that just end up where you are describing.
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
UPDATE:
The coolant leak decided to go away. I'll keep an eye on it in case it decides to come back after a long drive or something.

I can't get the glowing oil to glow. No indication of the UV stuff anyplace. However, I've been checking the drips before, and after every drive, and I can see a few specific things. First, the main drip is from the vacuum pump. It could be also contributing to the drip that comes off the bolt on the lower part of the bell housing. Second, there is oil coming out of the hole on the front cover..... Third, I can't yet tell if oil is coming out of the bell housing. There SEEMED to be a bit coming out of the bottom seam of the bell housing, but none is coming out of the drain hole itself, so I'm not sure what to think yet.

I'm driving it for a good 20-30 miles after work today, so I'll definitely see new developments this evening.
 

NPT90

Well-known member
front cover is a concern, there are seals along the cam and crank that are pretty easy to replace just have to get in there and pull the crank gear and the cam gear. If you have oil coming form there its worth doing the timing belt and giving it a good cleanout.

The vaccum pump is just a paper gasket I am pretty sure, might be worth replacing if you think it might be on its way out, makes sense you would have an oil leak if the gasket is shot or it could be a simple case of not tight enough.
 

Napalm00

Well-known member
agree with above. if you do pull the vac pump note the orientation of the gear that drives it and reinstall in the same fashion, it beds into the cam over time
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
I’m not 100% sure which seals you are referring to because I’m not schooled enough yet. I know that before I had the engine installed the front and rear main seals, I think the t-seals, and the oil pan gasket were all changed. If this is something that happens every 10k miles, I can’t keep the truck. I’m not going to be removing the engine every year. There has got to be a better alternative.
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
BTW, the vacuum pump is leaking out the top cover, not the gasket on the block. I've heard tell of people drilling out the rivets, and replacing with new gasket (right stuff) and then using small bolts to really close it tight. Anyone done this?

I think this is where I will start because it is an obvious leak, and it is letting enough oil out that I think it may be causing some of the other drips I'm seeing, mixing the results, and not allowing me to nail down exactly where the other leaks are coming from.
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
So I tried a thing.

I've had the vacuum pump off before, and it isn't fun. So I looked at this thing for a bit, and decided I'd try to fix the leak without removing it. If you have a LHD vehicle, and if you remove the air filter, you might be able to pull it off. But some vehicles might have other things in the way.

Using an angle drill, a chisel, and a nail to punch left overs through, I was able to get each of the rivets out. I pulled the top off and found that the pump "looks" fine, and that someone had already been in there. The o-ring was already covered with black RVT type stuff. The fact that these were rivets put in by a DIY'er, and more than one of them was not really very tight, gave me hope. Maybe they never pulled the lid as tight as they could have.

I did my best to clean up the o-ring, but all along I'm thinking I'm going to rely more on the sealant than the rubber. I then realized that my Right Stuff was solid in the tube....... so I had to resort to some standard Permatex Black Silicone. Which is not bad stuff, it's just not Right Stuff. I smeared a bit on both surfaces, and made sure that the reused o-ring was well in it in its groove, then I used a set of #8, 3/4 inch screws and lock nuts to tighten down on the lid. I don't know how tight it should be, so I simply did my best to get them even, and to guess at how much would be enough. The nice thing is, if it does leak, I could at lest try to tighten it more now. And if that doesn't work, I'll go get some Right Stuff and try again.

I let it sit for 24 hours, then started the car and let it run, revved it a bit, then shut it off and checked for a leak. It is certainly better than it was. Nothing is coming out yet. But time will tell. I'll actually drive it tomorrow, and check a few more times before I'm sure it worked.

I should have gotten a different type of nut/bolt combo. Maybe an M5 or M6 by 20mm with nylock nuts and Allen heads would have been better. However, I was able to use a screw driver on each of the bolts from the outside, while holding the nut on the back side with a small spanner. A larger nut might not fit the space, but if you had Allen head bolts, you could put them in from the back, and bolt from the front.

Anyway, it may be that I fixed the leak. But I did prove that it can be done without that extra step of removing the replacing the pump itself, which should save some time and frustration.

If it does not leak, I should now be able to tell where my other leaks are coming from, and get a better sense of how bad they are. I'm sure this leak was the main culprit, and was contributing to the other drips in some way.
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
I’m going to claim that I fixed the vacuum pump leak. After 20 miles I hasn’t seeped a single drop.

Now on to trying to track the others. There is a noticeable lack of oil underneath already.
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
So fixing the vacuum pump has made a big difference in the amount of oil I'm seeing in my garage floor every night. However, it seems like the other leak that drips to the same area of the floor is getting worse, and I'm pretty sure this is the rear main.....

The oil seems to be coming from the seam between the engine and the piece that fits to the bell housing. I'm not sure how else to confirm this other than just looking.

If this is the case, what am I in for? Is this really a job that means I have to pull the engine on a yearly basis? Which brand of seal is going to get me the most miles?
 

Napalm00

Well-known member
If it's coming from the seam area it's not the rear main.

It's the t seals or the block to clutch housing gasket.

If it was the rear main it would leak into the clutch housing not behind it.

If you are doing the t seals only and have a 300tdi you can do it in the truck without removing it.

If you have a 200 or need to do block gasket/tseals or rear main on a 300 it's an engine out of the truck job.

Huge job

The right way to do it, no matter the engine or the symptoms is to pull the engine and do block gasket, t seals, rear main dowty type. Check the clutch and reassemble


Rubber type t seals coated in right stuff
Dowty rear main
Black and grey type block gasket with right stuff on horizontal seam
 
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