I found some engine oil leak right after engine oil pan. People at Autozone told me probably a bad real main oil seal. He told me it's hard for me to DIY. Because I probably need to remove the transmission. If I have enough time, I want to give it try. I don't think it's a serious problem. Just a bit annoying. Not hurt driving. Just few drops of oil on the ground every week. Hope you guru people can give me some input on this. Thanks! You can see the oil drops on the photo.
Engine oil leak probably from rear main oil seal
- Thread starter skarland
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search for pan arch. plenty to read. Get fact. manual. Stray from autozone.
This is very common. AutoRx treatments slowed mine down. 15W-40 stopped it (vs 5W-30) but the fuel economy hit wasn't worth it.
I get a drop or two on the bellhousing after shut-down and the wind blows it off when I drive again.
I am going to guess the majority of 80s past 80-100k have this same drip.
I get a drop or two on the bellhousing after shut-down and the wind blows it off when I drive again.
I am going to guess the majority of 80s past 80-100k have this same drip.
- Thread starter
- #4
Thank you all for your replies!
I probably just leave it as is. Seems too much work need to do.
Also I noticed a funny thing that I never met before. The oil pressure meter shows only 1/4 of overall when in idle. If I press the gas pedal in normal driving, the reading raises to be 3/4 of overall. When I starts the truck, the oil pressure meter just raises slowly instead of prompt jump. Is this just a normal toyota design like this?
Thanks!
I probably just leave it as is. Seems too much work need to do.
Also I noticed a funny thing that I never met before. The oil pressure meter shows only 1/4 of overall when in idle. If I press the gas pedal in normal driving, the reading raises to be 3/4 of overall. When I starts the truck, the oil pressure meter just raises slowly instead of prompt jump. Is this just a normal toyota design like this?
Thanks!
It's not an oil leak, it's an on board "underbody coating system". Mines been working great! 
skarland said:
Normal.
I'd suggest cleaning and wiping the whole area down with brake cleaner and keep an eye on it to see where the leak is coming from. I'm not convinced by the photo that you've got the typical pan arch/rear main leak, which does drip out in the area where that big drop is in your second photo, but when mine was leaking, I didn't have all that fresh oil up on the under side of the upper oil pan (just beside your lower oil pan in photo #2). Yours might be a leak in the lower oil pan gasket, which is cake to repair.
Rookie2
Rookie2
- Thread starter
- #9
Hi Rookie,Rookie2 said:
Do you mean the oil drain plug in the underneath the oil pan? It is really clean as I can see. But the edges around oil pan is a little bit messy with oil. But does not have apparent driping. Thank you for your input.
I think he means clean up all the oil on the pan and bellhousing, to aid in identifying where it is coming from.
Perhaps you need to very gently tighten your oil pan bolts.
I wipe that area down roughly monthly myself.
Perhaps you need to very gently tighten your oil pan bolts.
I wipe that area down roughly monthly myself.
skarland said:
Yes, clean the whole area. The pan with the oil drain plug in it is the lower oil pan. The lower oil pan bolts to the bottom of the upper oil pan (the one I'm saying has a lot of oil on it). It may be that the seal between your lower and upper pan is leaking. You will know pretty quick after you clean it and run it, if the leak is coming from the lower pan seal.
Rookie2
I had a the exact same drip when I purchased my 97. Before knowing about the upper arch seal (before I started coming to mud) I replaced the rear main seal. Turned out to be the upper arch after all. From what it appears, the upper arch seal is a spot that regularly leaks. I am not saying that this is the case with yours, but it looks very familiar to what happened with mine.
Farley said:
The drip is at the same location, but did you also have all that fresh grease up on the underbelly of the upper oil pan?
Farley said:
Correct. Something for anyone that is doing this job or having it done: If you're going in to have the rear main replaced, be sure you make them remove the retainer arch and reseal it to the oil pan while they're there. As you discovered, more times than not it has been the pan arch that is leaking, not the rear main.
Rookie2
- Thread starter
- #14
Hi Rookie,Rookie2 said:Correct. Something for anyone that is doing this job or having it done: If you're going in to have the rear main replaced, be sure you make them remove the retainer arch and reseal it to the oil pan while they're there. As you discovered, more times than not it has been the pan arch that is leaking, not the rear main.
Rookie2
Is the (retainer arch) a kind of ruber seal (or something similar) over the oil pan?
Thanks!
I also have a leak at the back of the motor, I at least have a rear main leak as I see radial streaks on the fly wheel when I remove the inspection plate. I may also have a pan arch leak, I to have heard (from Dan?) that the pan arch is more common, no matter witch of mine are leaking as long as mine stay at this level of leakge they are going to stay until time for an engine overhaul.
the rear main and the upper pan arch are are right next to eachother burried between the engine and transmission and dificult to get an eyeball on and diagnose, but unfortunalty they are very diffrent methods of repair, for the rear main the transmission, transfer case and flywheel have to come out, for the upper pan arch the transmission stays but you remove the lower oil pan (stamped steel pan painted black) and then lift the enine out of it mounts to get the upper oil pan out (bare cast aluminum structure on the bottom of the block)
if your leak is between at the lower (steel) and upper (aluminum) oil pan you have lucked out as the lower oil pan is quite possibly the easied oil pan ever to remove,
when I bought my truck the entire bottom of the enigne was covered in oil, as were most others I looked at, especially the left side, I cleaned it and turns out most of it was from oil change places not cleaning up after the oil filter barfing on the side of the block. I havew several seaps in the front and the leak at the rear. none winds up on the driveway, I guess it all falls off wile driving.
the rear main and the upper pan arch are are right next to eachother burried between the engine and transmission and dificult to get an eyeball on and diagnose, but unfortunalty they are very diffrent methods of repair, for the rear main the transmission, transfer case and flywheel have to come out, for the upper pan arch the transmission stays but you remove the lower oil pan (stamped steel pan painted black) and then lift the enine out of it mounts to get the upper oil pan out (bare cast aluminum structure on the bottom of the block)
if your leak is between at the lower (steel) and upper (aluminum) oil pan you have lucked out as the lower oil pan is quite possibly the easied oil pan ever to remove,
when I bought my truck the entire bottom of the enigne was covered in oil, as were most others I looked at, especially the left side, I cleaned it and turns out most of it was from oil change places not cleaning up after the oil filter barfing on the side of the block. I havew several seaps in the front and the leak at the rear. none winds up on the driveway, I guess it all falls off wile driving.
RavenTai said:
Hey RT,
Just wanted to make sure you are aware that you can repair the pan arch seal from the transmission side. The retainer arch bolts to the engine block. So once the tranny is out, you can unbolt the retainer arch, clean the surface between the arch and upper oil pan and then reseal it. So if you suspect a rear main leak then the best course is to pull the tranny, replace the rear main and redo the pan arch seal from that side. Having said that... totally not worth it if you've got a small leak.
Rookie2
no I did not know that you could do the pan arch with only the transmission removed, I thught the upper pan had to come out for the pan arch regardless of weather the transmission was out or not. is the pan arch seal nto part of the upper oil pan seal? beign able to do both does make the transmission pull the better route for an undefined back of engine oil leak.
good to know. disregaurd my post above.
and I am still not fixig mine unless it gets worse.
good to know. disregaurd my post above.
and I am still not fixig mine unless it gets worse.
Rookie , RT can you tell me what the pan arch look like? I know the rear main seal but not the pan arch.Pic maybe?
Thanks
Thanks
Jerry,
I don't have a picture per say, but I'll try to explain it as best I can and reference pages in the FSM (I have the 97 LC FSM but I imagine the 96 and the 97 are the same). If you reference the exploded engine diagram on EG-75, you'll see the "Rear oil seal retainer" tagged. The "Crankshaft Rear Oil Seal" (commonly referred to as "Rear Main Seal") seats inside this retainer (also shown on page EG-93). It's a circular shaped steel plate that has an arched shaped flange around the top 180 degrees of the circle. This retainer is sandwiched between the transmission and the rear of the engine block. The top flange portion bolts directly into the back side of the engine block and the bottom circular portion of the retainer mates to a curved surface on the upper oil pan. This curved portion of the oil pan is typically referred to here as the "pan arch". This is where the leak normally develops. The FIPG seal between retainer and pan arch becomes comprimised and oil seeps out from the upper oil pan into the bell housing and oil appears on the outside bottom seam where the transmission bell housing mates to the upper oil pan (see big drip in picture above). Since the pan arch and rear main seal are within a mere 1/2" of each other, the leak is commonly misdiagnosed as a rear main seal leak. As Raven mentions, if the probable diagnosis is a rear main seal leak, the best approach is probably to remove the transmission and repair both from that side. But it seems the majority of the time it is in fact a leak in the pan arch seal.
If you decide to tackle a pan arch leak (3 bannana job IMHO), make sure you read up some. There's a thread a couple years back where I described how the engine and suspension need to be configured in order to get the pan out. I found this to be the biggest headache of the job and spent the better part of 6 hours trying to get everything raise and lower, and the right parts removed so the pan would come out. With this info. it's probably a day and half job.
Rookie2
I don't have a picture per say, but I'll try to explain it as best I can and reference pages in the FSM (I have the 97 LC FSM but I imagine the 96 and the 97 are the same). If you reference the exploded engine diagram on EG-75, you'll see the "Rear oil seal retainer" tagged. The "Crankshaft Rear Oil Seal" (commonly referred to as "Rear Main Seal") seats inside this retainer (also shown on page EG-93). It's a circular shaped steel plate that has an arched shaped flange around the top 180 degrees of the circle. This retainer is sandwiched between the transmission and the rear of the engine block. The top flange portion bolts directly into the back side of the engine block and the bottom circular portion of the retainer mates to a curved surface on the upper oil pan. This curved portion of the oil pan is typically referred to here as the "pan arch". This is where the leak normally develops. The FIPG seal between retainer and pan arch becomes comprimised and oil seeps out from the upper oil pan into the bell housing and oil appears on the outside bottom seam where the transmission bell housing mates to the upper oil pan (see big drip in picture above). Since the pan arch and rear main seal are within a mere 1/2" of each other, the leak is commonly misdiagnosed as a rear main seal leak. As Raven mentions, if the probable diagnosis is a rear main seal leak, the best approach is probably to remove the transmission and repair both from that side. But it seems the majority of the time it is in fact a leak in the pan arch seal.
If you decide to tackle a pan arch leak (3 bannana job IMHO), make sure you read up some. There's a thread a couple years back where I described how the engine and suspension need to be configured in order to get the pan out. I found this to be the biggest headache of the job and spent the better part of 6 hours trying to get everything raise and lower, and the right parts removed so the pan would come out. With this info. it's probably a day and half job.
Rookie2
scottm
SILVER Star
Both my '97s had the rear main seal replaced. Last one was $300, not worth a couple days under the truck plus parts.
