Rear of Engine Oil Leak-- Rear Main Seal?

#1

Symptom: Increasingly LARGE oil puddles under the car, especially when parking after a longer trip. Entire center underside of car is now coated w/ oil, all the way to rear suspension. Top rear of engine (valve cover gasket/ head gasket areas) is dry. Last oil change (last month) I cleaned up the oil pan and adjacent engine block areas; oil continued to drip directly from the lower flange that connects to the torque converter inspection plate/transmission coverplate mounting gussets. There is a slight opening there in the center bottom between the sandwiched pieces where the oil drips from after wiping the surfaces clean.

My own guess is the crankshaft oil seal, rear main seal? If that is what it is, then the tranny has to come out. This is beyond my resources. FSM shows a largish round seal accessible from the rear exterior of the engine, and also "side seals" that look to be in or around the rear main crank bearing, accessible via dropping the oil pan. Not having much experience in this area I ask members for further troubleshooting tips and solution help.

CC oil changed every 3000 mi., 15w-40 ci rated, now cj is what the stores carry, EXCEPT late last winter ran Pennzoil synthetic 10w-30, don't know if I believe the old wives tale about synthetic causing leaks in older engines. Also recently installed a new (smallish) muffler, probably high restriction for the amount of air a diesel engine pushes. Could this cause higher blowby forcing cc oil out of the cc seals during extended highway cruising?

#2

If the oil isn't migrating to the rear via the oil pan rail (fairly common on other engines), then your guess that the source is the rear main seal is probably correct. The side seals probably aren't the source (and are a great deal harder to replace. NAPA/Fel-Pro's rear seal kit ($13) includes both.

The transmission has to come out, yes. But the pan does not have to come off.

Oil choice probably did not trigger nor exacerbate the seal's leakage.

If you want to do this job yourself, you can use my shop on a weekend. I have a transmission jack, which can make this job a bit easier. I generally replace the transmission's torque converter seal anytime I have an old trans out, because you always disturb it when you move the torque converter in/out during installation, and an old seal may not conform after that. So plan on two seals. You will do the work, I'll provide the space and tools and moral support.

#3

I can take another look underneath to verify again the source of the leak. The pan areas, while a bit crusty, were not as clearly wet as the lowest rearmost flange of the engine where I saw several active drips and seepage immediately after repeatedly wiping the area clean.

Your offer is a kind and generous one Al; I will contact you offline to see your schedule. You have seen my wrenching abilities-- how many hours would you estimate for this job, provided I don't break anything in the process? If possible, while I am there I would like to lend a hand to one of your projects, remember my back is in good shape and I don't mind working underneath the cars.

#4

Including cleanup, probably a solid day.

Car wash
jack up car, stands
disconnect battery
driveshaft
speedo cable
park brake cable?
shift lever rod
wire harness
starter
Exhaust manifold/headpipe
cooler lines
modulator line
trans jack
rear crossmember
lower torque converter shield
TC nuts
dipstick tube
bellhousing bolts
remove trans
flex plate
R&R crank seal
R&R TC seal
R&R extension housing seal?
"To reassemble, reverse above steps"

Or something like that. Yeah, that would take me a solid day. Figure five hours for you -- I work slow. But doing it inside with decent lighting and a concrete floor sure beats the alternative, BTDT.

#5

Since the RMS is a similar form factor as the gasser engine, I figured there would be more info on this on the Z-Car sites, sure enough turns out to be common enough that they had some recurring BTDT recommendations.

Foremost being to get the genuine Nissan part, as some had reported non-factory seals as being the wrong size-- too small to even fit over the end of the crankshaft.

Symptoms reported similar to mine: Small puddles after shorter trips, large pools after long trips, oily undercarriage back to rear suspension.

#6

You might round up the headpipe gasket too, just in case. It's cheap. The old one can usually be re-used, but not always.

I see that NAPA lists the same part Nos. for the L24e and LD28 for 1983, with one of the four seals offered having dimensions:

ID = 80mm
OD = 100mm
Width = 10mm

Does that tally with other info you've seen?

You might fire up Nissan FAST and try to get it to give you part Nos. for the LD28 and L24e RMS.

#7

Burien Nissan is expecting the RMS to arrive tomorrow, could not give dimensions but RMS P/N: 12279-R4611, around $22.

Also gave torque converter seal P/N: 31954-X6100

Looking at your list above, as long as I am touching the cooler lines (to/from radiator?) I will for sure want to replace them. Pretty sure they need to be rated for tranny fluid. Any ideas on the size?

#8

8mm (5/16")

Standard stuff at your FLAPS -- as long as you specify for automatic transmission or power steering duty. It's about a buck a foot. You'll need three feet.

#9

Gathering my parts. Got the new RMS last week and TC seal yesterday from Bruce Titus Nissan in Oly. (I know Burien Nissan told me they could get the RMS "tomorrow" but when I called them back "tomorrow" they told me no way, would be weeks.) Doubting the TC seal is correct; it's a small o-ring barely large enough to slip onto a pencil. Does that seem right?

#10

NAPA NOS16489, $12

Attributes:
Features & Benefits:Rubber Covered OD
Spring Loaded
Auxiliary Lip
W/CW Helix from Air Side
Well Suited for Extreme Pressure (EP) Lubricants
Resists Oxidation and Ozone
Hi- Temps -40 to 300F
I.D.:1.6540"
O.D.:2.3680"
Width:0.2760"

NAPA ATP17691, $3

Attributes:
Features & Benefits:Duplicates Original Equipment in Fit & Function
I.D.:1.606"
O.D.:2.372"
Width:0.354"

Different IDs & Widths. Scary. But those are the approximate sizes of the seal you desire. I like to see orange in TC seals, because that usually indicates silicone (higher temp) rather than plain-ish nitrile.

You might get an extension housing seal too (the one that seals the driveshaft slip yoke at the transmission). It's cheap too.

The seal you want is Ref. "H" in this pic (seals kit):

And Ref. "31344" in this pic (Oil Pump):

The part No. appears to be 31344-X0101, $6.

#11

Photos of parts gathered so far:

Rear Main Seal, approx. 79mm id, 101mm od, 12mm width. Does the blue/gray color denote anything special?

My admittedly approximate measurements are similar to what Al listed above for the NAPA part. What could have been causing the problems the listers on the Z-car forums were having (aftermarket RMS i.d. too small and not fitting over the crankshaft end. Maybe that was old info and aftermarket now providing correct part)?

Trans mount. The one on-car has been living in an oil bath.

Sorry blurry image. This camera (Sony Cyber-shot 5.0 MP) has a mind of its own when focusing on a subject less than a few feet away. Macro feature does not have any perceptible effect on this.

The torque converter seal from Bruce Titus Nissan was definitely incorrect. I will try for the orange one from NAPA.

Remaining: Trans extension housing seal, trans fluid cooler hose, trans fluid. Getting hard to find something labled "Dexron" anymore.

#12

Carimbo wrote:This camera (Sony Cyber-shot 5.0 MP) has a mind of its own when focusing on a subject less than a few feet away. Macro feature does not have any perceptible effect on this.

One of my Olympus D550s was that way -- sold it off. Probably 70% of the photos I take are less than five feet from subject. Macro is of high importance to me. Wish I had better manual focus control on this Olympus SP-350, but Hey! It's a $200 8MP camera, what do I expect?

Getting hard to find something labled "Dexron" anymore.

While I run AMSOil ATF in everything, I will be flushing my '93 Aero's A4LD this weekend. I'm going to pick up a case of Chevron "Dexron III/Mercon" (which has morphed into Chevron "MD-3") at Costco, probably tomorrow night. I'm using it just as the flushing fluid, though we run it in our Dodge service vans, and I'm running it in the '82 Wagon because I didn't have any AMSOil ATF in stock at the time I did its flush three years ago.

#13

Couple of candidates for tranny ext. housing seal:

Here is what the local NAPA has in stock

12325 A/Trans Seal, Extension Housing (Metal Clad)(w/boot)

Another, NAPA special order

17692 A/Trans Seal, Extension Housing (Metal Clad)

Anybody ever have one of these apart? 1982 L3N71B AT 3-spd? Do I want the ext. housing seal w/ boot or w/o?

#14

I would not think that the booted one would work -- the front of the driveshaft's yoke covers the extension housing, so the boot isn't as useful as on, say, my Aeros (which came OEM with a boot).

I would choose unbooted for this app.

#15

Ordered the seals today at brick & mortar NAPA.

TC seal 1-7691, $2.96 plus $6.50 shipping from Portland-- first time they ever charged me for shipping a part.

Trans. extension housing seal 1-7692 $5.16, this one they had in a local warehouse.

Looks like they are both orange.

4 ft. of 5/16" trans. cooler hose.

NissanDiesel Forums

Rear of Engine Oil Leak-- Rear Main Seal?

Rear of Engine Oil Leak-- Rear Main Seal?

Who is online