5.9 Cummins - what fluid is this leaking?

[wysiwyg]

Hi! Thanks for taking the time. Two years ago I bought a 93 ford Cummins diesel from a catholic school. 120k miles. Runs great. Drove it on a 100mile round trip over two hours at one time. No problems until I noticed a significant puddle of what I originally thought was oil from the blowby tube. Upon further inspection saw that it was actually coming from a few inches over where there is what looks like a 4”x6” panel with four bolts attached to what I think is the transmission. I checked the transmission fluid and it is low when it wasn’t just a few months ago. Can anybody help? Thanks again

 

[gs1949]

On mine there is an open hole there. When I first noticed it a couple of weeks after I got my bus I thought I might been vandalized, and all my transmission fluid would leak out if I put the transmission in gear. So I didn't put it in gear for a while.

Finally I contacted a retired Allison guy who now sells NOS parts for obsolete Allisons looking for a plug. He said there was no plug, and the threads inside were a BlueBird thing not an Allison thing. He wasn't sure what the threads would be for, but thought it was probably for something used to calibrate the tach.

There is nothing that comes out of that hole even when I put it in gear. By sticking my finger in the hole and feeling around, I can tell that it's only slightly oily in there.

I assume that your's leaks more and someone has put that patch on there to stop oil from leaking out of a bad crankshaft seal, but you'll have to get someone with real mechanical experience on a Cummins to confirm that. I'm moderately mechanical, but had never even seen a Cummins close up before I got this one.

Oh, just reread your post and want to say that my transmission fluid was never low, and if what's leaking out of there is very black, yours is not transmission fluid either.

 

[wysiwyg]

Thanks for the reply. I don’t fully understand. Are you saying that panel is a patch and not part of the original transmission? Im not even fully sure it IS the transmission housing. The fluid that leaks from that corner bolt is a really dark brown...? The oil level is still good. Also, unless you are talking about the blowby tube (that thick plastic/rubber tube in the vicinity), there’s no other hole I can stick my finger in.

 

[HazMatt-SKO]

The panel on the fotos is on the tranny, located as it is just behind the engine's bell housing.
My first thought was a blown main seal, but the mating surfaces look dry.
That sole drop on the bolt head doesn't look like it could contribute to a considerable puddle, but hard to tell from a distance.
In the first foto, it looks like the bolt may have backed out a little. I'd take a socket to the other 3 first, just to get a feel for the torque, then try tightening the oily one.
No offense, but was the tranny at operating temps when you checked it's level?
Finally, I'd give the puddle a nasal appraisal. Compare it's odor against the engine & tranny dipsticks.
If your engine oil isn't very old, it could still be brownish instead of black. And with a 6 or more gallon capacity, that little loss wouldn't register on the stick.
Brown tranny fluid, on the other hand, has been badly over-heated and needs replaced PDQ.

 

[gs1949]

No, that's not the transmission housing. That's the bellhousing. The transmission is on the other side, away from the oil pan. And I'm not sure that patch isn't original.

It may be what that retired Allison guy would call a Ford thing, but I'm sure there should not be much of anything coming from there.

What color is your oil? Has it been in there long enough to turn dark like it always does or is it still lighter?

Edit: I suppose it is possible that I am a little turned around because my BB is rear engine, but I don't think that patch, or whatever it is, is on the transmission. And I am very sure that mine just has a threaded hole there, which is just a little too large to take an oil pan plug and nothing comes out of it.

 

[Ronnie-SKO]

this is the housing that the torque converter is in. The "patch" is a factory access plate.

Looks pretty dry under there to me. Define significant puddle, a few feet in diameter? and few inchs?

Color and odor as suggested compare to engine oil on dipstick and also compare to transmission oil on its dipstick. From this location it could be either leaking and most likely is nothing to be worried about unless it really is a big puddle.

 

[gs1949]

After looking carefully at these photos again and crawling under mine, I don't think your leakage has anything to do with the transmission. It's too far away. There is no fluid in my torque converter housing, or bellhousing, whatever you want to call it. I am pretty confident that it will turn out to be engine oil. But, as I said I am not an expert, and I am still hoping a Cummins expert will sign on to this discussion

 

[EastCoastCB]

Looks like a rear main seal area to me.
Its REALLY common for the rear main to leak.

 

[gs1949]

Yeah, it looks too far from the transmission. In my REBB it's the front seal that leaks very slightly at 90,000 miles, but then it's almost 25 years old.

 

[EastCoastCB]

Yeah, mine leaks very slightly at 90,000 miles, but then it's almost 25 years old.

The bus I have right now is the only one I've owned that doesn't leak there.

 

[gs1949]

That one is a keeper then.

 

[wysiwyg]

Thanks everyone. To answer one question about the puddles. After having just pulled into my parents driveway, I noticed at least 10-15 silver dollar spots every couple yards. And once it was turned off the dripping continued for another five minutes or so until a 4” puddle formed. The panel and surrounding area looks dry because I wiped it off and that bolt with the drip in the photo is the corner where the fluid is leaking from. There’s no place above that I can tell where it flowing down to that corner.

The transmission was checked after it idled about five minutes?

So this is a common leak? Is it oil? I seem to be getting different impressions. You guys really have helped so much with just this.

 

[HazMatt-SKO]

Clarification: Did you mean to say there were silver dollar-sized blots every couple yards, totalling 10-15, or there are clusters of that number at that spacing?
Cleanliness may be next to godliness, but "before" pix would have been more diagnostically helpful. Can you graphically indicate the limits of what wanted wiping down?
I may be wrong, but the tranny was probably too cold to give an accurate level.
I'm thinking rear main seal. Just for gits & shiggles, did you olfactorily compare the fluids' bouquets as suggested..?
By the way, if you populate ALL of the fields in your profile, it will remove many mysteries, and help us to help you more readily.

 

[Ronnie-SKO]

First and foremost what hazmatt said.

Checking tranny fluid, is often done with engine running and tranny in nuetral, for an automatic. You may be doing it this way, if so great.

I am also leaning towards rear main seal on the engine.

 

[cadillackid]

is the fluid reddish? or more brown/black?



transmission fluid should be a more red color(should match the color on your trans dipstick) and when you rub it between your fingers feels thinner and more watery..



engine oil is more brown / black. (should match the color of the engine oil on your dipstick.) and feels thicker / stickier esp after it cools..



you can get an idea also of the fluid by smell..



smell the fluid on the end of each dipstick (trans and engine).. and smell the fluid see if you have a match..


once thigns cool down a bit after driving you can touch the wet area with your finger to smell it.. ..


Allison 545 transmissions are notorious for front seal leaks esp if they have been Hot a few times.. ..



the other thing to do is take that bottom plate off and see if you have oil inside the housing... as others have mentioned.. that plate is the inspection plate.. its designed for inspecting the flywheel. any oil in there usually means a leak on the rear main engine seal or front trans seal..



sometimes oil can run down from above from a turbo pipe, valve cover, etc and fool you.



-Christopher

 

[wysiwyg]

There is no fluid accumulating from above that panel. It all starts above that bolt I pointed to in the pic. If I put decent pressure with my fingers, I can see the fluid swell around the seams of the panel a bit.

The fluid feels thinner than oil but it is VERY dark brown. The trans fluid on the dipstick is still cherry red though..I’m sorry, I tried using my olfactory senses and I guess I fail because I can’t tell the difference by smell and neither can some other family members...to me they smell too similar to determine the difference.

If I take that panel off, am I gonna get showered in one fluid or the other? The inside of that housing is SUPPOSED to be dry, correct? Just checking. And is the only way to loosen/tighten those bolts with a torque wrench? (Which I don’t have...)

 

[CMORGANSKOOL]

I would put a drain pan under it and remove the panel to investigate. There's not supposed to be any liquid in the bell housing to my knowledge.

 

[gs1949]

What I got from emailing that retired Allison guy who now sells NOS Allison parts was that Allison never plugged that hole. Mine is just open. It is threaded and about an eighth of an inch larger than an oil pan plug, apparently by BlueBird to attach something to calibrate the tach, but what the threads are for was a guess on his part. He admitted knowing basically nothing about Cummins or BlueBirds, but knows Allison transmissions inside out.

When I stick my finger in that hole, it feels slightly oily inside, but there's never been any evidence of anything dripping out. I think we need to find out if other Fords with Cummins have that plate over the hole.

 

[Rivetboy]

There is no fluid accumulating from above that panel. It all starts above that bolt I pointed to in the pic. If I put decent pressure with my fingers, I can see the fluid swell around the seams of the panel a bit.

The fluid feels thinner than oil but it is VERY dark brown. The trans fluid on the dipstick is still cherry red though..I’m sorry, I tried using my olfactory senses and I guess I fail because I can’t tell the difference by smell and neither can some other family members...to me they smell too similar to determine the difference.

If I take that panel off, am I gonna get showered in one fluid or the other? The inside of that housing is SUPPOSED to be dry, correct? Just checking. And is the only way to loosen/tighten those bolts with a torque wrench? (Which I don’t have...)

That panel is nothing more than a piece of sheet metal held on with 4 cap screws take off with reckless abandon; nothing there to hurt. You might have a little oil inside put some rags down After you get the cover off chock the wheels and set the brake and start the engined and peer up there with a flashlite and see if it is dripping out of the back of the engine. Another place the 5.9 likes to leak is under the cover on the drivers side of the engine. That is where mine leaked The bad news is to replace the rear main seal or the side tappet cover the engine needs to come out. You can try and replace it by just removing the transmission but it is a bear. When I repaired mine, I pulled the engine and transmission together and make sure you remove the passenger side rear engine mount. This is a big job that needs experience would not try this for my first rodeo. The engine alone weighs 1100 pounds and with the trans hanging off the back close to 1500 pounds. If you are still unsure what type of fluid it is rub some on a piece of typing paper and hold it up to the light. red trans fluid is readily apparent. PM me if you have more questions. Joe

 

[wysiwyg]

Oh boy.. thanks guys. RivetBoy, (or anyone), how detrimental is a leak from the rear seal?