Manual Transmission Missing Bolt/Oil Leak?

Zed

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I've been trying to locate this oil leak coming from the trans for a while now, and I believe I have come across a missing bolt. Can someone confirm for me? If not, any ideas as to where this oil is coming from?

Honda Civic 10th gen Manual Transmission Missing Bolt/Oil Leak? IMG_20200304_170322~2


Honda Civic 10th gen Manual Transmission Missing Bolt/Oil Leak? IMG_20200304_170341~2


Honda Civic 10th gen Manual Transmission Missing Bolt/Oil Leak? IMG_20200304_170330~2
 

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What year is your Civic?

As far as I know, on a Type R, the fill plug and check-fill bolt are on the opposite side (toward the front of the car beneath the air box assembly).

If possible, I recommend cleaning the area of the transmission free of any grease/oil, and then inspecting the area after a day to see exactly where oil is discharging. Right now, from the pictures, it seems hard to tell what is fresh and not fresh oil/grease.

Typically, the oil leaks are found on the drain plug (stripped, missing a washer, etc), or the gasket (poor seal after a repair). I’m not sure if these transmissions have external coolers, but if they do, you would have to follow the path of that external cooler and examine it for leaks.
 
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What year is your Civic?

As far as I know, on a Type R, the fill plug and check-fill bolt are on the opposite side (toward the front of the car beneath the air box assembly).

If possible, I recommend cleaning the area of the transmission free of any grease/oil, and then inspecting the area after a day to see exactly where oil is discharging. Right now, from the pictures, it seems hard to tell what is fresh and not fresh oil/grease.

Typically, the oil leaks are found on the drain plug (stripped, missing a washer, etc), or the gasket (poor seal after a repair). I’m not sure if these transmissions have external coolers, but if they do, you would have to follow the path of that external cooler and examine it for leaks.
It is a 2017 model year, but not a Type R. This trans is the same way, fill plug on the front side, check plug towards the rear, but neither of those seem to have residue around them.
 

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I don't believe there's a bolt missing there. Usually these are technological holes that are used for positioning the detail on the lathe table during machining process. Also, i can't see how the leak would end up being on top of the trans (against the gravity). Is there any chance motor oil has been spilled during the oil change? No leaks around the valve cover gasket?
 
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I don't believe there's a bolt missing there. Usually these are technological holes that are used for positioning the detail on the lathe table during machining process. Also, i can't see how the leak would end up being on top of the trans (against the gravity). Is there any chance motor oil has been spilled during the oil change? No leaks around the valve cover gasket?
I had the same thoughts aswell. No leaks around valve cover gasket, and haven't spilled motor oil when doing oil changes. I'm confident it wasn't a fluid spill on my end. It's hard to pinpoint where the leak is with all of the bolts, sensors, hoses, etc.

I cleaned the area off and will have to inspect in a day or two to see if the leak is still present.
 


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Update:
The leak has reappeared after driving a bit and seems to be centered around the shift lever assembly. In particular, the lever circled in red. Any ideas?

Honda Civic 10th gen Manual Transmission Missing Bolt/Oil Leak? IMG_20200308_185749~2


Honda Civic 10th gen Manual Transmission Missing Bolt/Oil Leak? IMG_20200308_185818


Honda Civic 10th gen Manual Transmission Missing Bolt/Oil Leak? IMG_20200308_185818~2
 

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When was the last time you performed maintenance on the transmission?

Oil dispersing from the selector seems odd. I would check the MTF level by removing the oil check bolt. I’m curious if the box is overfilled.
 
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Transmission was last drained and filled with new fluid at 30k. Car has 36k at the moment. I actually first noticed the leak when I went to service the transmission initially.

Good idea with the check bolt, I'll have to try that.
 

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What's right above that shift lever ? It might be leaking from above and dripping down.
 
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What's right above that shift lever ? It might be leaking from above and dripping down.
There's nothing directly above it other than the battery. Also, the top of the shift lever is totally dry which leads me to believe it could potentially be the seal right below it. I'm going to have to take it to the dealer if the box is not overfilled with fluid as suggested by blitz.
 


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Just removed the check bolt and no fluid came out indicating that the box is not overfilled. Its currently at the dealer now.
 
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The dealer called and said it's coming from a breather valve? Said its nothing to worry about. Not too sure what valve they are talking about.
 

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The dealer called and said it's coming from a breather valve? Said its nothing to worry about. Not too sure what valve they are talking about.
I'm not sure if that's the one they're talking about but there's a little tube sticking out on top of the transmission with a rubber cap on top of it. If you pull the rubber cap off you may discover some oil underneath it (that's what happened to me when I was poking around under the hood trying to figure out the clutch creaking). There was some oily film but not leaking all over for sure.

Edit: just looked at the picture again and if you go back to pick #1 it is right under your acuity bushing, little tube with a rubber cap on it
 

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I find the fault of the oil discharging from breather valve to be a result of too much oil in the case, or the incorrect type of MTF in the case. This is my assessment. One of the main purposes of this valve is to release excess pressure that accumulates in the box due to an increase in changing temperatures, and typically, the discharge is hot vapor, not oil.

Under normal, operating conditions, the MTF will not discharge through the breather valve unless conditions in the case are causing the oil to escape. If the breather is clogged, you will start seeing MTF leak through a seal, which is definitely not a good diagnosis.

I rarely hear of this issue occurring in cars, however, I see this issue of oil discharging from the breather valve in vehicles like Jeep Wranglers and similar vehicles with a live or dead axle, where owners overfill the differential.

Eventually, in your scenario, the seepage will stop when the amount of oil in the case returns to a normal level. I can reasonably understand that the MTF is escaping from the breather valve as a fine mist, and then collecting aft of the valve onto adjacent areas, as seen in your photos (ie discharge is occurring while in motion and moving rearward).

For the purpose of illustrating the location of the breather valve, here is a diagram:
Honda Civic 10th gen Manual Transmission Missing Bolt/Oil Leak? XC1OBIz


Honda Civic 10th gen Manual Transmission Missing Bolt/Oil Leak? A2yDZBE
 
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Update:
The leak has reappeared after driving a bit and seems to be centered around the shift lever assembly. In particular, the lever circled in red. Any ideas?
]
The shift select rods have seals that can wear/leak.
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