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Differential breather leak


steve91tt

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I recently changed the gasket on my differential and ever since I have had a leak from the vent. I removed the vent, cleaned and replaced it with the arrow pointing to the rear for the car. The Royal Purple 75W90 gear lube is level with the bottom of the filler plug with the car sitting on the ground.

There is definitely oil coming out the top of the vent after just a few miles of normal driving. Anyone else had this issue?

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Ya all the 240Z I own let some oil out the breather. Well the last one didn't till I found it under the road grime and cleaned it off, so it wasn't really a breather till I cleaned it I guess. It is made of two part the part the screws in and a cylinder shaped cap, you have the cap. Did you take pictures, maybe you have more spill out than expected???

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It is made of two part the part the screws in and a cylinder shaped cap, you have the cap. Did you take pictures, maybe you have more spill out than expected???

I have both the vent and cap and both look to be in good condition. I created a dime size oil spot on the floor after I drove it the first time. That seems like a lot.:ermm:

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There is a thread somewhere around here for a fix that goes into more detail but here is the basics. Take the inspection plate off. Take the breather off and tap the hole. Put a fitting in there that will thread in and hook a hose to the other side of the fitting. Run the hose up and zip tie it to something. On the end of the hose put a little filter that would normally go on a valve cover.

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Mine too is slowly covering the back of the differential housing with oil. Luckily, the dirt stops it from dripping on the garage floor. I wonder if a piece of sponge or cloth or maybe a plug of Scotchbrite might stop the splashing, but still let it breathe.

I've never had one off so don't know what's inside but have to assume that the leak is oil getting splashed up, probably in a fine mist form, in to the vent where it can then dribble out and down the differential housing.

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Isn't the arrow supposed to point towards the front of the car? That's how mine is on the diffy and the tranny. Filled correctly w/ RedLine 75-90 and no leaks. When I pulled my diify to replace it w/ a 4:11 R180 from a 200sx the vent was made of metal and the part inside the diffy was slanted towards the rear arrow to the front. Just my 2 cents.

Cheers, Mike

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The vent is symmetric back to front so the arrow pointing front is the same as it would be pointing back.

The top of the vent tube is, but the bottom that sits inside the diff/gearbox, is not. The arrow on the top cover is meant to line up with the "cut away" side that is in the diff/gearbox. If this is put in wrongly, it would not matter how the top was put on. Have you pulled the tube that goes into the diff out?

Cheers

Ian

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The minutiae is the most interesting stuff...

I think that there might be two different breather types. The text below is from the web link shown.

The breather on my car was pointing sideways. I think it may have "walked" its way around after a few million heat cycles.

http://www.carpartsmanual.com/datsunS30/PartNumberDetails/tabid/1848/Default.aspx?PartNo=38352-78600&SectionNo=088B&KeyNo=10

Section 88B Key# 10 Datsun 240Z/260Z/280Z Differential Gear, Pinion & Cover (R200)

38352-78600 BREATHER

Model code: C30-SUT

Newer part numbers:

Older part numbers: 38352-78500

Part No. Model Applied Date Qty Ica Superceded

From To N F

BREATHER

38352-78500 - 7510 1

38352-78600 7511 - 1 38352-78500

Edited by Zed Head
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Have you pulled the tube that goes into the diff out?

I did pull the tube and I thought that there was a hole on either side of the bottom of the tube that line up with either end of the arrow, if that makes sense.

I'll pull the tube when I get a chance this weekend and flip it around so that the arrow points the other way.

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Here is a picture of the breather vent from a 1976 R200. The screwdriver goes through the hole at the bottom. The stepped down portion is a press fit in to the breather hole.

Same effect, arrow pointing forward or backward. In general, I have found that arrows are usually meant to point forward.

There has to be some "breather vent install instructions" out there somewhere!

p.s. I crawled under my car and found that the arrow on that breather points sideways as noted above. I forgot to look at the one in this picture (it's a spare), I pried it out then noticed the arrow.

Bonus finding though - my fill plug could be tightened an extra turn and might have been contributing to the oily mess.

Edit - amusing coincidence - here's a 71 R180 with the arrow pointing forward, post #9 pictures (you might have to view it and blow it up to see it) - http://www.classiczcars.com/forums/showthread.php?threadid=40824

post-20342-14150813277463_thumb.jpg

Edited by Zed Head
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I checked a few R200 vents I have. The arrow points forward. My finned R200 cover has a metal vent which remains closed until the spring loaded valve is opened to relieve the excess pressure. I measured it if you are interested in swapping one of these in place of the plastic one. It is 14mm. Don't know the part number or availability off hand.

Edit - After removing and studying one of the plastic vents from a R200 cover, I can't see any reason why the arrow couldn't also point to the rear as long as the through holes in the case are oriented to the sides, which they would be either way.

Edited by geezer
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