Welcome, Guest

Transmission Oil Leak
(1 viewing) (1) Guest
  • Page:
  • 1
  • 2

TOPIC: Transmission Oil Leak

Transmission Oil Leak 4 years, 6 months ago #48293

  • Randy87is
  • ( User )
  • OFFLINE
  • Posts: 91
  • Karma: 0
I am dripping a lot of transmission oil out of the slot (weep hole?) at the bottom of the bell housing where the trans meets the engine. I'm sure it it transmission oil because it is red (MTL) and my engine oil is green (Brad Penn). Plus, the engine oil isn't low, but the transmission is losing oil at an alarming rate. I checked the transmission oil level before going to the track this weekend and it was WAY down. I checked it again Sunday morning and had to add a fair amount of oil after just one day.

It apparently comes out more when driving, which makes sense, but also drips slightly when the car is parked, which doesn't (if the input shaft opening is higher than the oil level).

I pulled the engine and trans and I replaced all the seals on both after buying the car. Due to unclear instructions in the Bentley manual, I may have buggered up the housing that the input shaft seal fits into. I tried to sand off any rough spots I caused, but may not have done it well enough. I suppose it is also possible that I didn't get the seal installed correctly. Either way, I'm afraid I will need to drop the transmission and try to reinstall the seal.

Before I do that, I thought I'd see if anybody knows whether there is another source the trans oil could be coming from? As far as I recall, the input shaft is the only opening in the front of the transmission. But, the fact that it was leaking there before I replaced the seals makes me wonder if there might be something else going on.

Any ideas?

Re:Transmission Oil Leak 4 years, 6 months ago #48296

  • poppy
  • ( User )
  • OFFLINE
  • Posts: 492
  • Karma: 0
Are you sure it's not coming from the vent tube on the top of the trans, mine was so I put a tube on it and router it to a catch tank in the engine compartment.
Bennett McMicking
#17 NorCal SpecE30
2011 NorCal GTS1 Champion
2013 NorCal SpecE30 5th Place

Re:Transmission Oil Leak 4 years, 6 months ago #48300

  • jlevie
  • ( User )
  • OFFLINE
  • Posts: 1840
  • Karma: 3
+1, the leak is either from inside the bell housing or from the vent. If the sides of the transmission are dry, the input seal is the likely cause.

FYI: if the input seal is bad oil will continue to drip out of the bell housing for quite a while after the car is parked. I've also seen cracked transmission casings and seal failure where the blind plugs are.
Jim Levie, #38
MidSouth Spec E30 Series Director

Re:Transmission Oil Leak 4 years, 6 months ago #48303

winduck wrote:
Are you sure it's not coming from the vent tube on the top of the trans, mine was so I put a tube on it and router it to a catch tank in the engine compartment.


Where you able to get the hose on w/o dropping the tranny? I neglected to put hose/catch tank on mine before install.
Kevin Butler
Mobetta Autosport #612

Re:Transmission Oil Leak 4 years, 6 months ago #48309

  • poppy
  • ( User )
  • OFFLINE
  • Posts: 492
  • Karma: 0
Nope, had to drop the tranny!
Bennett McMicking
#17 NorCal SpecE30
2011 NorCal GTS1 Champion
2013 NorCal SpecE30 5th Place
Brought to you by MAD Motorsports - providing top notch SpecE30 rentals in the Southeast

Re:Transmission Oil Leak 4 years, 6 months ago #48312

  • Randy87is
  • ( User )
  • OFFLINE
  • Posts: 91
  • Karma: 0
Thanks for the suggestions.

I was looking at the Bentley manual again this morning. The manual shows a bearing shell for the lay shaft pressed into the casing just below the input shaft. I guess that could be the problem, but sure hope not. Same for a cracked casing.

I didn't notice any oil coming down the sides of the trans, so I don't think it is leaking around the vent.

The manual says that before assuming the oil seals are bad to check that the vent is moving freely. If the vent is clogged, it will cause high internal pressure that can force oil past the seals. I didn't see anything in the manual about how to check the vent, other to make sure it moves up and down freely, or how to fix it if it does not.

Anybody know how you fix a stuck vent? Can you do that without dropping the trans?

If not, I guess I'll have to bite the bullet and drop the trans. If I do that, I guess I'll first check the the casing for cracks and the bearing shell for signs of leaks. Assuming they are good, I'll either fix the vent or install a hose and catch can. I guess I'll go ahead and install a new input shaft seal and housing "while I'm in there." I sure wouldn't want to fix the vent and then find out the oil seal/housing were also bad and have to drop the trans again.

Re:Transmission Oil Leak 4 years, 6 months ago #48316

  • jlevie
  • ( User )
  • OFFLINE
  • Posts: 1840
  • Karma: 3
The easy way to check the vent, or to install a tube and catch tank is to cut a hole in floor pan just above the vent. Though if you remove the transmission cross member and allow the transmission to drop you can, just barely, get to the vent from under the car.

In this case I'm more suspicious of the input shaft seal. So it may make more sense to just pull the transmission.
Jim Levie, #38
MidSouth Spec E30 Series Director

Re:Transmission Oil Leak 4 years, 6 months ago #48321

jlevie wrote:
The easy way to check the vent, or to install a tube and catch tank is to cut a hole in floor pan just above the vent.


I've been wondering about that. I bet if I had the defrost/air handler box still installed, it would need to be removed for access?
Kevin Butler
Mobetta Autosport #612

Re:Transmission Oil Leak 4 years, 6 months ago #48322

  • cwbaader
  • ( User )
  • NOW ONLINE
  • Posts: 890
  • Karma: 0
There is a plug under the input shaft that often leaks. It is not available. So, the fix: Pull transmission. Stand transmission on output shaft flange. Get can of carb and choke cleaner, the nasty stuff with Methylethylkeytone. Get small wire brush...brass works great. Clean plug with whole can of spray while brushing the plug and surrounding area. Get tube of Permatex grey RTV and, when all is dry (blow it off with high pressure compressed air), liberally coat the plug to case interface. You cannot press enough in the area so make sure you have plenty on the interface and make a nice bead over the area. Let sit 24 hours....Must let sit 24 hours to fully cure. Should fix problem...fixed mine. CB

Re:Transmission Oil Leak 3 years, 10 months ago #54572

  • Randy87is
  • ( User )
  • OFFLINE
  • Posts: 91
  • Karma: 0
I'm reviving this thread because I finally got around to pulling the transmission out of my car to find the cause of the oil leak.

When I pulled the trans, I inspected the inside of the bell housing. It was pretty evenly covered with black oil residue, but there were no "trails" of oil to show where the leak came from.

I tried pressurizing the trans by applying light air pressure to the trans breather opening to see if it would push out some oil. Air whistled out through the hole in the shifter shaft seal (I knew about the hole), and also around cover on the shift detent balls near the shifter shaft, but no oil came out the front which is where the major leak is.

I raised the rear of the trans and let it sit for a couple of days while I was out of town and checked it when I returned. Still no leaks at the front, not even a drop.

After replacing the shifter shaft seal and applying anerobic gasket sealer to the shift ball detent cover plate, I applied low pressure air again. The cover plate didn't seal and is apparently warped (not unusual I understand), but still no oil out the front of the trans.

At that point, I was convinced the leak would only occur if the car was running. I spun the output flange by hand and saw maybe a slight film of oil where the oil seal met the input shaft, but nothing that would create even a drop of oil. So, I chucked the tip of the input shaft in my drill driver and spun the shaft for a few minutes. Sure enough, oil began to flow from around the input shaft at the oil seal.

Good news is I found the leak and it apparently is not due to me buggering up the seal housing the first time I replaced the seal. The seal is just not sealing around the shaft. Hopefully a new seal will fix it. I'll pull the seal, inspect the housing and input shaft and then install a new seal and test it again with the drill driver before re-installing the trans. If the housing is really buggered, I have another I sourced from the Rev. Al, but it is a one-piece unit (oil seal housing and sleeve for throw out bearing) and mine has the two piece housing/sleeve.

After all that, I have two questions:

1) The one-piece housing/sleeve has two bolt holes at the bottom where it mates to the transmission, and my two-piece unit has only one hole there. Otherwise it appears the one-piece unit will work. Anybody know if they are interchangeable?

2) Any tips on how to make sure the oil seal and shaft properly mate? (I guess I could try romantic music and candles. ) I understand it is sometimes necessary to install a new seal so it doesn't ride in a groove left by the old seal. Any other suggestions?
  • Page:
  • 1
  • 2
Brought to you by MAD Motorsports - providing top notch SpecE30 rentals in the Southeast
Time to create page: 0.58 seconds