Leak from rear main seal

[Notmikeb]

While I have not 100% confirmed it yet, it looks like I may have a small rear main seal leak. It's not bad but I do end up with a small 2" wide puddle of oil underneath where the tranny meets the engine after sitting somewhere for a few hours.

Assuming I don't find it leaking from somewhere else, I am not going to fix this anytime soon. It's just not losing enough oil to justify the effort.... Yet.

When the time does come, which do people find to be the easier option?

1. Pull the engine and fix from a bench
2. Drop the transmission and fix in place

It seems to me that it might be easier to pull the engine but that may potentially create a bunch of other problems.

Is dropping the automatic transmission any more complicated than the manual? I've seen some walkthroughs on this site for the manual but not the auto.

Alternatively, has anyone had any luck with any particular brand of those "seal rejuvenating wünderoils"?

[Ridlbox]

Yes it's six to one half dozen the other I myself prefer to pull the transmission out to do the rear main seal pulling the engine requires vacuum lines and remembering where they go

[Notmikeb]

Vacuum lines wouldn't be a problem. With the non functional distributor advance and the weber, I'm down to 3!

[marlinh]

Make sure it isn't coming from the valve cover. There is a half moon seal at the back of the head. It could be leaking and hard to see. Or the distributor o-ring.

If it is the rear main, people have different opinions on whether to pull the engine or the trans.

[Notmikeb]

Both of those have been replaced recently. And that section of the block is clean. Oil shows up from about midpoint down (starter height).

[xirdneh]

I have only had one tercel out of many that ever leaked at the rear seal
the oil has to come over the top of the diferential housing
i made sure by wiping it clean and checking after driving
its a lot of work for nothing if thats not where its coming from
in my case it was not the rear main seal but the gasket between the aluminum main seal holder and the block
be carefull seperating the engine from the auto tranny
its easy to bend the big starter gear and/or torque converter
find out how to do it right before you start
i have done it twice and messed them up both times
but it did not matter cause i was getting rid of the autotran's anyway

[Petros]

If you have oil "from the midpoint down" on the outside of the block, that does not seem like a rear main seal. the seal is behind the metal backing plate on the front of the trans/back of the engine, and a leak tends to leak straight down internally and leak out the bottom only. It is possible that it gets sprayed out the sides, when the crank is turning, but that would put oil everywhere, and I have never seen that happen (it always leaks straight down). Beside, typically when a rear seal is really shot, it leaks like a sieve. I messed up a seal installation in a honda CRX (tiny 1.5 L aluminum engine), it leaked a quart of new oil all over the garage floor in about two mins of running (the seal was not pushed in all the way and matting part in the trans crewed it up, it had that little clearance, one of the annoying things I found about Hondas, and why I drive Toyotas now).

Look carefully for a leak at the back of the valve cover (even if new, it may have been squished in such a way that it is pinched and leaking, I have done it), check the rear plug under the valve cover gasket, the distributor itself or the o-ring on it, and the gasket against the plastic isolater on the fuel pump. all of these tend to leak oil and it will drip all over and make it hard to see where it is coming from. Carefully check all of these places before you pull the trans.

If you do go for the rear seal, I have always found it easier to drop the trans, even with the extra work the 4wd trans requires. I have done it both ways, it is only worth pulling the engine if there is other work you need to do to the engine like replacing bearings or oil pump, motor mounts, etc., its is much easier if the engine is out.

I do not think I have ever seen a Tercel rear seal leaking either (I have had it happen on a corolla with the 4afe engine, with 375,000 miles on it. excessive ring wear pressuried the crank case and actually damaged and blew out a stiff cracked old rear main seal-leaked like a screen door on a submarine). But not on a Tercel, of which I have owned about 14, rebuilt many others and worked on or examined perhaps 30 or more different ones belonging to others.

Before I pull the trans however, and once I know for certain it is the rear seal, I would try the stop leak/seal conditioner. These work by softening and swelling the seal, when seals get very old they get hard like plastic, and worn. by softening and swelling it with chemicals, it often will stop the seal from leaking. I would not do that to a good seal, but if it needs to be replaced anyway, it is worth a try. Sometimes it actually does work. It will give you more time if nothing else to plan on replacing the rear seal when doing other heavy maintenance.

[marlinh]

Check to make sure oil isn't leaking through the distributor. I had that happen recently.

[irowiki]

He has a FWD, so it'd be easier than a 4WD to drop the transmission.

[Petros]

With the FWD trans, than if a new rear seal is necessary, it would most certainly be easier to drop the trans, rather than pull the engine.

[Notmikeb]

Upon closer inspection, it seems the leak could indeed be coming from the fuel pump gasket. I just changed it but didn't use any sealant on the very thin paper gaskets. I just did a good scrub and clean on that side of the block so I'll see if it comes back. There doesn't seem to be enough oily residue below the fuel pump to explain the amount of oil I get on the ground though. I'll put the car up on jack stands tomorrow and dig into this a little further. Seems like pretty much anything other than the rear main should be a relatively easy fix.

[ARCHINSTL]

Tape a rolled paper towel around the fuel pump.
Tom M.