Rear of Engine Oil Leak-- Rear Main Seal?

[asavage]

I don't know that you have to stop driving, I don't think it will damage the crank. However, you can't rely on it to stay put forever. As long as you have the plastic splash pan in place, if it comes off you won't lose it, but it will foul the fan and make horrible noise and plastic shavings if it decides to fall off.

[Carimbo]

I could move it fore and aft w/ my fingers so it's quite loose. Should I try to pull it off?

A little disappointing because I know those balancers are rare; kind of offsets the good news about the engine and transmission not leaking anymore.

[asavage]

I removed the o-ring and it appears that it may originally have been round, though it's a flatter cross-section now, more like rectangular with rounded corners.

Shaft groove minor ID is .768" (19.5mm). Major dia. is .850" (21.6mm), width is .085" (2.16mm). All dimensions +-.002" .

This o-ring seals in a static application (no moving wear after installation).



It appears to be Ref "H" in the FAST illustration. No applicable part No. out of FAST though.

[Carimbo]

I don't know that you have to stop driving, I don't think it will damage the crank. However, you can't rely on it to stay put forever. As long as you have the plastic splash pan in place, if it comes off you won't lose it, but it will foul the fan and make horrible noise and plastic shavings if it decides to fall off.

That's not a pretty picture, not catastrophic yet damaging enough that I am not going to drive the car until I can fix it. Now that I know what it is. Also, the extra vibration could not be good for the engine.

I will open another thread on harmonic balancer (or does the FSM call it crankshaft damper?).

[asavage]

TC is not locking up like it used to (37MPH).

Back in this post from 23 Apr 2006, you said:

Others have said the lockup at 37MPH is noticeable. On mine it is definitely not noticeable. FSM states the shock is low and hard to determine and suggests using a tach to verify a 200-400 RPM decrease.

Can you guys really feel it when the lockup kicks in?

Did you determine, back then, that it was working?

[Carimbo]

Yes I was able to notice it. Took some practice, felt like a gear change lite (almost more of a sound change) right at 37 MPH indicated, more noticeable under harder acceleration.

[asavage]

And it's not present now?

[Carimbo]

No. Well, not much IS present now w/o a crank damper, but-- Have not been able to perceive any 37 MPH lockup "shift" recently. Previously, it was subtle yet noticeable, especially when accelerating hard past that speed point. I suppose a tach would really help to prove a lockup/no lockup condition.

The driving experience changed greatly after the tranny R/R.

At low speeds, there was a new fatiguing vibration/resonant drone just off idle, so stop-n-go traffic (encountered more often than not here in Seattle) is even more of a draining experience. Also during engine warmup, since the cold idle likes to hover more at the RPM that exhibits the vibration. We had attributed this to the new harder tranny mount but now I think it is mainly caused by a rapid deterioration of an already slowly deteriorating crankshaft damper (AC compressor engagement had been causing a "bearing noise" racket that was hard to pinpoint).

At high speeds there was a new louder exhaust pulse at just over 60 MPH. I used to cruise at 61 MPH indicated (closer to 64-65 MPH actual) because at 65 MPH (indicated) there was a roar that, while it was fun, seemed like a better idea to not dwell there for max engine life. Oil consumption also apparently rose measurably with sustained travel at that speed.

Now at 60 MPH I hear more of a what reminds me of the exhaust note of my old Yamaha 350 4-stroke enduro. Seems like it is coming more from the driver's side of the engine. Possibly also related to the failed crank damper? Stiffer tranny mount? We shall see.

Anyway, I realize that this is a what-- 26 year old car and some things are bound to break when fixing others. Mainly, rubber cracks, wires corrode, and plastic brittles.

Positive note: Look Ma-- No leaks!

[rlaggren]

> [noise at ~60...]

You might look at the exhaust system which is fairly simple, easy and cheap. Maybe something got strained when you did the tranny; it might be hard to locate in it's early stage unless you can get beneath the car easily to feel and listen to the whole system with the engine running.

On my wagon I found a weld behind the muffler cracked; something started to rattle , then the "background" noise slowly got louder over a period of several weeks. Apparently when Steve the PO had a new exhaust installed they didn't get it positioned right and the constant stress broke the weld. Took a while before it got bad enough for me to see where the problem was.

Or your pipe might have shifted into contact w/something. Did you (re)move any of the hangers or anything? Is it still sealed tight at the manifold? Anyway it's prolly worth a careful look b4 getting any more complicated about it.


Rufus

[Carimbo]

Had some free time this afternoon and some agreeable weather so was able to put the car on ramps and swapped in the old trans mount for the new one. E.T. about 1.5 hr., not including time spent degreasing the old mount or chasing to the HW store for ball bearings to replace those lost from one of the (mysteriously loosened) swivel casters on the jack.

Cursory examination showed the exhaust system to be intact.

Quite a different profile between the old & new mounts. Old one is on the left, w/ "F" cast into the rubber:


The old one is much more flexible; inner portion can easily be moved using hand strength. The new one is almost unmoveable.

This photo better shows the difference in resting height, the newer is 1/4" - 1/2" higher at rest:


Mounted in the car the difference is even greater but I had not thought to measure it.

The old mount seems to have relieved the heavy vibration off idle, more road testing will show if it helps at cruise.

Wonder if I can return the new one? It might be OK for a gasser but a diesel vibrates too much.

[rlaggren]

When I was under my wagon last week I did notice the rear mount was _very_ flexible - easily moved around by hand as you said. This looks like a critical part of the system for "domesticating" the diesel, along w/the various exhaust hangers etc.

Be nice to find some original types. When you looked for a replacement (and got the new one you tried) how and where did you look? Think more time spent could source a few? Seems like it'd have to be OEM, although I haven't ever tried to find mounts and maybe there are after market or jobbers who can make these things. Are there "rubber" parts that one could assemble (w/some metal fabrication) to create something that compliant? How about mounts from other diesel vehicles with similar flexibility that could be made to work? Again, I'm not very familiar with this area but there _are_ a number of diesel vehicles out there and some of them must have pretty good damping; MBZ jumps to mind.

The old one you showed (great photos) besides being somewhat "deflated" looks like one side is settled more than the other. Wonder if it was made that way; if it was not wonder if its new resting place shifts the tranny tail a little to one side. Might try "straightening" that by moving the mount toward the other side a little or shimming under it if there is still noise. Hmm.. maybe regain some height with a spacer block? That might straighten the drive train also, make it quieter; good for another 75K.

In working on my exhaust I noticed there are different thickness of donuts used in hanging exhausts; the FLAPS seems to have the skinny ones. There's another variable that's pretty easy to try.

Rufus

[Carimbo]

When you looked for a replacement (and got the new one you tried) how and where did you look?

FLAPS. I could try the Nissan dlr. where I sourced the rear main and torque converter seals. Had no problems w/ those items yet.

The old one you showed (great photos) besides being somewhat "deflated" looks like one side is settled more than the other. Wonder if it was made that way; if it was not wonder if its new resting place shifts the tranny tail a little to one side.

The photos are actually showing the side view, as mounted on car. Top of photo is up, left side is front of car. Bottom surface of Tranny extension mounts to large top surface, the inverted u-shape channel sits on top of the crossmember.

It is twisted, but not sideways. It is the angle of the tranny-- front is higher than rear relative to the crossmember. Parallax error in the photo doesn't allow us to see that the new mount actually has even more twist.

The old mount is not wasted; I had wanted to replace it during the RMS R/R because I figured it would be destroyed after the several months long continual oil bath it was subject to. As it is, it is way more preferable than the new one. Car is relatively quiet and posh now, relaxing to drive even.

[rlaggren]

Ah, that makes more sense. Somehow I just clicked into thinking I was looking at it from the rear. Heck, maybe the things are good for 500K. <g>

Rufus