Jump to content

L28 Side Oil Seals


Recommended Posts

Good evening all,


I'm fighting an oil pan leak that's been a constant issue with my '75 280z for the past few years. Last weekend I dropped the pan, cleaned the pan and block mating surface, checked the pan for dimples (none found) and re-installed a Fel-Pro gasket. Today I noticed that the passenger side gasket corner near the rear of the block is weeping a very small amount of oil. I'm using the pan reinforcing strips and torqued the bolts to 7 ft-lbs in a star pattern to avoid dimpling the pan, and the only sealant I used was Permatex gasket tack to mount the gasket to the pan, the surface mounting to the block was left dry. Oil pressure is at the normal rating idle/driving, and PCV system components have all been replaced so I don't think the oil system is being over-pressurized. 


I've always had a small drip from this corner, and previously thought it was a rear main seal. I installed a new Nissan rear main seal about 3 years ago, and the side seals were replaced around 5 years ago when I rebuilt the engine. Does anyone have tips/advice for getting this thing to seal? Right now the front of my car is raised and the gasket will weep oil, so I'm guessing this is strictly a gasket issue. Would side seals or the rear main leak without the engine running? The drip is not a large amount of oil, but I'd like to not have any leakage if possible. Any advice will be greatly appreciated!

Link to comment
  • Replies 27
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

If the block is clean and the pan flat, a new gasket must seal or one of these three must have a fault.



Just how high is the front because it would have to be extremely high for the oil level to over top the pan/block surface.


Is it possible it's seeping elsewhere and running down to this location? Oil pressure sender? Dip stick? There is an oil gallery (from the oil filter and under pressure) running from front to back on the right side the feed all the crank mains and even up to the head. The ends are plugged but if the rear plug were leaking it would seem like a rear main or curtain seal. Any chance the valve cover is leaking down the back of the head and down the right side? maybe getting between the transmission and block?

Link to comment

I'll check the valve cover tonight and see if that's the issue. The front of the car isn't raised too high, but I imagined that the 5 quarts of oil the manual calls for would be more than enough to send oil to the pan/block surface if the front was raised sufficiently. The block still has the stock galley plugs on both ends, though I haven't thought to check the rear plug for leaks. 

Link to comment

So I've removed the starter and checked the inside of the bellhousing, and both the bellhousing and rear face of the flywheel are clean and dry. Looking at the pan, it would seem that the leak would have to be gasket-related, since it also weeps oil up to the 3rd bolt running along the passenger side of the engine. The plate between the transmission and engine is dry where the rear main cap meets the shield, so it would seem that the leak is likely either the oil pan gasket or side seals. I've torqued the pan bolts to 7 ft-lbs, is it possible that this isn't enough torque with the reinforcing strips in place? Just looking for advice on how to seal this damn thing, because I've had this drip for as long as I can remember. 



Link to comment

You can try tightening the bolt a little bit, but if that does not work, it needs more attention.  Over tightening the oil pan bolts distorts the bolt holes under the bolt head, and crushes the gasket, sometimes making the leak worse.


If this really bothers you, the solution it do remove the oil pan, and using the ball end of a small ball pien hammer, place the ball end on each dimpled bolt hole, and then hit the face of the ball pien hammer lightly, just enough to remove the dimple around the bolt hole. Then you need to place the pan upside down on a flat surface, and work the gasket surface around the pan until is is flat to the surface.  Flat within .025 to .040 of an inch is probably good.


When you reinstall the flattened pan, use a 10 MM nut driver to install all the bolts, and get them all snug with just the nut driver.  Then tighten the oil pan bolts to torque, 4.3 to 6.5 Ft/Lbs. 

  • Like 1
Link to comment

I'll see if I can fab up some flat steel reinforcing strips using the old ones as templates. Since the gasket has wept oil, will I need to replace it, or could I try replacing the reinforcing strips and not drop the pan? I'm not certain if oil would continue to leak due to some sort of capillary action. 

Link to comment

Still say that one is not flat. Tale it off and check. Hammer flat or make new ones. Put on and see if that works first and replace the gasket if it doesn't.


It can only leak if the pan is not flat. Tightening those strips should press it into contact. 


Like Daniel said 6.5 Ft.Lbs max, those are small bolts.

Link to comment

I managed to sneak an inspection camera between the flywheel and engine by removing the starter, and the rear main and side-seal joints appear to be dry. Looking more closely at the pan gasket, I realize that I did not correctly apply sealant at the rear of the block covering the joints of the rear main cap. This being said, the pan gasket is brand new, so would there be any issues dropping the pan, sealing the joints, and then re-installing the pan using the same gasket? It's a Fel-Pro gasket with maybe 10 minutes of exposure to the engine running. 

Link to comment

This shows some work I did on a junkyard L-16 oil pan.

The next step was to fix the damage on the pan.  It was glued really well, on the bottom of the engine in the junkyard, and I bent it, prying it off the engine.  One that was done, I reworked the bolt holes on the pan.  They get distorted, and bent up from tightening the bolts too much, so the pan does not seal very good.  This is how you bend distorted bolt holes back down.  Place the ball end of a ball pien hammer on the bolt hole, and gently hit the face of the ball pien hammer with another hammer.



The next step is to check if the pan is bent, or twisted.  I really had to use a lot of force to pry this pan off the engine, and I bend the pan a little.  This is how you check if the pan is flat.  I used the bottom of an engine, on a engine stand.



Another picture, checking the side of the oil pan.


I used a .018 feeler gauge.  It should not go between the block, or front cover anywhere.  Not even close to the bolt holes.  The pan is bolted to the block with two bolts, one in front and one in the back of the block, no gasket


In the two pictures above, you can see some surface rust on the pan.  I sanded most of it off, then scrubbed the pan with phosphoric acid metal conditioner, and then wirebrushed that, twice.  Next, I cleaned the outside of the pan with Dawn dishwashing detergent and water, and sanded the pan again.  The pan was dried, and sprayed with two thin layers of Dupont (now Alasta) Centari 99A pitch black.

This is right after painting the pan.



Link to comment
  • 2 weeks later...

Well, I've un-dimpled the one or two bolt holes that needed it, checked everything with a straightedge, and resealed the pan using the "competition" gasket that MSA sells. I warmed the engine up to operating temp and it seems that the gasket is weeping slightly, starting at the passenger side front of the pan. It's not a significant amount of oil, but it is still very frustrating. I've applied black RTV to the areas noted in the FSM, used gasket tack only on the pan side of the gasket, and torqued the bolts in a star pattern to 7 ft-lb. I'm at a complete loss on how to seal this damn thing.


Anyone have gasket recommendations, such as brand/material (cork vs paper)?

Edited by NC280z
Link to comment
  • 2 months later...

Sorry to revive an old thread, I've flattened the pan using the methods described above and I'm going to reinstall the pan this week. I know to use RTV at the joints for the front cover and the rear main cap, but I'm debating on whether or not to use gasket tack on the pan side of the gasket. The gasket I ordered from MSA is the cork/rubber type, does anyone have any recommendations regarding gasket tack and cork gaskets? It's this brand of tack:



Link to comment

I guess it works. Holds the gasket in place but a bitch to scrape off in the future. I've used this stuff and it's like tar when dry. If used on both sides of a part you can't get them apart. If you did a good job flattening the pan you won't need it.


The block will be smooth but if I had to use something I would smear the slightest thin amount of RTV on the pan side with your finger. 

Link to comment
  • 2 weeks later...

So I've used DanielC's tips and was able to fix the large leak from the front of the pan. I used a hefty brass drift and a set of feeler gauges to flatten and check the bolt holes around the perimeter of the pan. Unfortunately, I've got an extremely small amount of droplets coming from one of the rear main joints, and it looks to be coming from the block side of the gasket. I applied a thin bead of RTV as the manual specifies and I'm using one of the cork/rubber gaskets that datzenmike recommended. My guess is that either the bolt hole needs more work, or my application of RTV was insufficient. Everything's torqued down in a star pattern to just under 6ft-lb. I ran some UV dye through the oil and it's not a rear main seal or side seal leak (thankfully!). 


It's not enough of a drip to worry about yet, I'll probably readdress this at a later time. I appreciate everyone's help in this matter, and if anyone has any recommendations for sealing the joints at the front and rear of the block, please let me know. 

  • Like 2
Link to comment

I'll look into "the right stuff" gasket maker, all the threads that I've read on other forums have indicated excellent results. Could I use the right stuff to seal the front cover and rear main joints at the points indicated in the FSM and use a gasket as well? 


I ended up putting my car on stands and used my UV light to check for leaks last night, and it looks like both joints for the rear main have a slight leak, possibly due to the RTV not sealing up well enough. One quick question on side-seals, the "how to rebuild" book recommends leaving around 1/16th of the side-seal sticking out above the block, however, both of my side-seals are slightly recessed into the block, could this be an issue? I have new side-seals on hand, but I'd have to replace them with the engine in the car, which I'm sure is a PITA. The seals in currently in the block and the new ones I have on hand are the type which have the nail built into the seal, so it should make removing/installing them a bit easier. 

Edited by NC280z
Link to comment

*FINALLY* figured out what was causing my leak. The side-seals were not sealing correctly and were allowing oil to pool up in the seal's registers and then leak down through the oil pan gasket. This also explains why my leak would continue even with the engine off and the car on a level surface. The registers for the seals were basically acting like little reservoirs of oil that would continue to leak until the next startup, where they'd refill and then continue the cycle after shutting the car off. Both of the old seals were completely soaked with oil when I removed them, and not all of the oil had the UV dye in it so I'm guessing it was a very slow and gradual leak that compromised the side-seals. I've compared the old side-seals to the replacements and found that the old seals are significantly smaller, I expected some shrinkage with age and heat cycles, but they're as much as 1mm smaller in both width and height.


Now my question is how to seal the side-seals. The "how to rebuild your l-series" book and the FSM call for a ~1 inch strip of RTV on the groove in the cap, but I'm doing this replacement with the engine in the car and I don't have a nozzle small enough to reach into the groove to fill it with RTV. Has anyone here replaced side-seals with the engine in the car, and if so, how did you seal them? The how-to book also recommends coating the seals in oil prior to tapping them in place which seems counterproductive, since oil would likely prevent the RTV in the groove from curing properly. I followed the how-to book's guidance when I changed the seals last time and I think that this is why they did not seal correctly. My Chilton's book recommends coating the seals in RTV and then tapping them in place, which I may end up doing instead. 

Edited by NC280z
Link to comment
  • NC280z changed the title to L28 Side Oil Seals

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.