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NC280z

L28 Oil Pan Sealing

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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!

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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?

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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. 

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One last thing.... check your transmission oil level. Front seal may be wet. It would run down hill and forward to above and behind the oil pan.

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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. 

 

l2R0QCE.jpg

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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. 

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That L shaped strap does not look flat. Looks high at the middle two bolts.

 

The L20B only comes with one corner strap so I used a second one that I trimmed so both corners are clamped..

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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. 

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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.

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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. 

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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.

HoleFix.JPG

 

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.

FlatCheck1.JPG

 

Another picture, checking the side of the oil pan.

FlatCheck2.JPG

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.

Painted1.JPG

 

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Awesome pictures and tips on repairing the L series oil pan, thank you! I'll hopefully be able to knock out this project on Saturday.

 

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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

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The gasket I used was a mixture of rubber and cork. Maybe 1/8" thick no more.

 

So it was leaking at the rear and now the front?

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It was leaking at the rear previously, but now it's only the front, starting at the pan bolts located just under the alternator. 

 

Do you recall the brand gasket you used?

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