Rear Main Seal
10-31-2009, 12:05 AM
#1
Rear Main Seal I recently got a horrible oil leak, oddly when the cars on a slant the oil spot is quite big but on flat ground it is just a little spot
I'm guessing its from my rear main seal. I'm checking it this weekend. But assuming it is about how long doest it take to replace that on a M6 car...ill be using a lift, so I'm just wondering what im in for.
I'm guessing its from my rear main seal. I'm checking it this weekend. But assuming it is about how long doest it take to replace that on a M6 car...ill be using a lift, so I'm just wondering what im in for. 
10-31-2009, 10:12 AM
#3
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Changing the Rear Main Seal itself isn't very tough to at all, it's getting to the mail seal that's a pain. But if you choose to go through with it you've atleast got a lift, so it won't be a tough job, just time consuming.
First things first, just check and make sure you don't have an oil leak coming from the back of your intake manifold where it meets the engine block. That's commonly and easily confused for a rear main seal leak since the oil will run down the back of the block, usually under the bellhousing, and drip from the bottom of the bellhousing just like a rear main seal leak. You can usually reach around the back of the motor from above with your hand where the manifold meets the block and feel for oil. If there's nothing there than you've most likely got a rear main seal leak.
So since you're wondering what you're in for, it'll take about a full day depending on how much you work on cars and if you've got help.
I've also been workin on a brief write-up on how to do this so here it is-- (and you might wanna replace the clutch while youre in there if you think it might not have much life left on it):
Get the car up nice and high, somewhat level, drain the transmission fluid from the litte 3/8" square plug on the passenger side of the tranny tailhousing (just under 4 quarts).
unplug your electronics (VSS, skipshift solenoid, reverse lockup solenoid, reverse light connector)
unbolt your driveshaft (4-7/16" bolts at the yoke) and torque arm (1-15mm bolt at tranny, 2-21mm nuts/bolts at pumpkin) and remove them.
unbolt the 2-13mm nuts that hold your slave cylinder and housing on and remove them. Don't let the slave hang by the hydraulic line, hang it out of the way with some wire or something. Then disengage your clutchfork by pulling with your hand on the end of the fork outwards. It should kick a few inches out of the bellhousing and feel very loose while hanging there.
get in the car and remove you center console and unbolt your shifter and remove it.
support transmission with a tranny jack or somehting similar (it weights about 130lbs), unbolt the crossmember (4-15mm bolts and 1-9/16" nut).
unbolt the transmission-to-bellhousing bolts (8-15mm bolts) and carefully slide it straight back till the input shift clears the throwout bearing and then drop it down. You may need to lower the tail end of the transmission an inch or two to get to the 2 top bolts on the tranny. Make sure you've got some different length extensions and a universal joint for your ratchet for the two top bolts, they can be tricky to get to.
Unbolt the black inspection cover (4-10mm bolts) from the back of the bellhousing, and let it hang off the starter motor.
The rest is easy, unbolt the bolts that hold the bellhousing to the bock (6-9/16" bolts) and remove it.
Unbolt the clutch from the flywheel (6 bolts, can't remember if they were 14 or 15mm), be careful not to let the friction plate drop out and land on your foot.
unbolt the flywheel and remove it. (12-point socket socket needed for 6 bolts, I think they were 3/4")
drain your motor oil.
Now youre finally to the rear main. There's more than 1 way to change the seal, but in your case this method seems most logical and easy.
-pry out the old seal from the 3 prypoints around edges of it, and pull it off the crank. Then put some new clean motor oil on the inner lip of the new seal and gently slide it back onto the crank (make sure the crank is clean when you put the new seal on it). Use a block of wood and a hammer to carefully pound the new seal into place. Do this as evenly as possible and make sure the new seal goes to the same depth as the old one did.
Other ways to change the seal are more time consuming since they require the engine to be unbolted and lifted a few inches so that the oilpan can be unbolted and removed over the k-member. Then the whole real main housing containing the seal can be unbolted so that not only the rear main seal but the rear main housing gasket can be changed. But in your case, this is method is most likely unnecessary unless you discover you're also leaking from the oilpan and/or the rain main housing (like my car was).
At this point you're half done, everything goes together the same way it came apart. Here's a few pointers for when your puttin all back together:
-if possible, but a small amount of high temp RTV around the outside lip of the new rear main seal when youre ready to pound it into place. This will help it seal better to its housing, then wipe off any excess RTV.
-torque the 6 flywheel bolts to 75 ft/lbs, the 6 clutch bolts to 22 ft/lbs (using red thread lock!), the 8 transmission-to-bellhousing bolts to 30ft/lbs, and the slave cylinder housing nuts to 15 ft/lbs when puttin everything back together.
-use a clutch alignment tool ($8 at autozone) when reinstalling the clutch. Use it to hold the clutch disk and plate in place on the flywheel before AND while youre tightening the 6 clutch bolts. Don't pull it out till the clutch bolts are fully tightened.
-if you're re-using your old clutch, put marks with a sharpie somewhere on the side of the pressure plate and flywheel because its crucial that you put it back together exactly as it came apart. This will prevent chatter, slippage, and everything you don't want in a clutch.
-if you're installing a new clutch, have your flywheel resurfaced! Most local shops or tranny shops can do this for around $30. Also, the pressure plate doesn't need to be installed a certain position on the flywheel because they will be two brand new surfaces.
-be careful, gentle, and patient when sliding the transmission back into the clutch. It needs to be lined up PERFECTLY or it simpley won't go in, so don't force it. Also, when you get it in, don't let it hang by the input shaft. Keep the jack under it till you get the 8 tranny-to-bellhousing bolts in and the crossmember bolted up.
-before you bolt the slave cylinder and its housing back on, make sure you fully engage the clutchfork onto the throwout bearing. This can be tricky to push back in, but you'll know when its in completely when the round indent on the end of the fork lines up exactly betwen the 2 studs sticking out of the bellhousing. If the clutch fork isnt fully engaged and you push pedal, ugly, expensive, and messy things will happen to your hydraulic system, so make sure its fully engaged.
Hope that helps, and good luck.
First things first, just check and make sure you don't have an oil leak coming from the back of your intake manifold where it meets the engine block. That's commonly and easily confused for a rear main seal leak since the oil will run down the back of the block, usually under the bellhousing, and drip from the bottom of the bellhousing just like a rear main seal leak. You can usually reach around the back of the motor from above with your hand where the manifold meets the block and feel for oil. If there's nothing there than you've most likely got a rear main seal leak.
So since you're wondering what you're in for, it'll take about a full day depending on how much you work on cars and if you've got help.
I've also been workin on a brief write-up on how to do this so here it is-- (and you might wanna replace the clutch while youre in there if you think it might not have much life left on it):
Get the car up nice and high, somewhat level, drain the transmission fluid from the litte 3/8" square plug on the passenger side of the tranny tailhousing (just under 4 quarts).
unplug your electronics (VSS, skipshift solenoid, reverse lockup solenoid, reverse light connector)
unbolt your driveshaft (4-7/16" bolts at the yoke) and torque arm (1-15mm bolt at tranny, 2-21mm nuts/bolts at pumpkin) and remove them.
unbolt the 2-13mm nuts that hold your slave cylinder and housing on and remove them. Don't let the slave hang by the hydraulic line, hang it out of the way with some wire or something. Then disengage your clutchfork by pulling with your hand on the end of the fork outwards. It should kick a few inches out of the bellhousing and feel very loose while hanging there.
get in the car and remove you center console and unbolt your shifter and remove it.
support transmission with a tranny jack or somehting similar (it weights about 130lbs), unbolt the crossmember (4-15mm bolts and 1-9/16" nut).
unbolt the transmission-to-bellhousing bolts (8-15mm bolts) and carefully slide it straight back till the input shift clears the throwout bearing and then drop it down. You may need to lower the tail end of the transmission an inch or two to get to the 2 top bolts on the tranny. Make sure you've got some different length extensions and a universal joint for your ratchet for the two top bolts, they can be tricky to get to.
Unbolt the black inspection cover (4-10mm bolts) from the back of the bellhousing, and let it hang off the starter motor.
The rest is easy, unbolt the bolts that hold the bellhousing to the bock (6-9/16" bolts) and remove it.
Unbolt the clutch from the flywheel (6 bolts, can't remember if they were 14 or 15mm), be careful not to let the friction plate drop out and land on your foot.
unbolt the flywheel and remove it. (12-point socket socket needed for 6 bolts, I think they were 3/4")
drain your motor oil.
Now youre finally to the rear main. There's more than 1 way to change the seal, but in your case this method seems most logical and easy.
-pry out the old seal from the 3 prypoints around edges of it, and pull it off the crank. Then put some new clean motor oil on the inner lip of the new seal and gently slide it back onto the crank (make sure the crank is clean when you put the new seal on it). Use a block of wood and a hammer to carefully pound the new seal into place. Do this as evenly as possible and make sure the new seal goes to the same depth as the old one did.
Other ways to change the seal are more time consuming since they require the engine to be unbolted and lifted a few inches so that the oilpan can be unbolted and removed over the k-member. Then the whole real main housing containing the seal can be unbolted so that not only the rear main seal but the rear main housing gasket can be changed. But in your case, this is method is most likely unnecessary unless you discover you're also leaking from the oilpan and/or the rain main housing (like my car was).
At this point you're half done, everything goes together the same way it came apart. Here's a few pointers for when your puttin all back together:
-if possible, but a small amount of high temp RTV around the outside lip of the new rear main seal when youre ready to pound it into place. This will help it seal better to its housing, then wipe off any excess RTV.
-torque the 6 flywheel bolts to 75 ft/lbs, the 6 clutch bolts to 22 ft/lbs (using red thread lock!), the 8 transmission-to-bellhousing bolts to 30ft/lbs, and the slave cylinder housing nuts to 15 ft/lbs when puttin everything back together.
-use a clutch alignment tool ($8 at autozone) when reinstalling the clutch. Use it to hold the clutch disk and plate in place on the flywheel before AND while youre tightening the 6 clutch bolts. Don't pull it out till the clutch bolts are fully tightened.
-if you're re-using your old clutch, put marks with a sharpie somewhere on the side of the pressure plate and flywheel because its crucial that you put it back together exactly as it came apart. This will prevent chatter, slippage, and everything you don't want in a clutch.
-if you're installing a new clutch, have your flywheel resurfaced! Most local shops or tranny shops can do this for around $30. Also, the pressure plate doesn't need to be installed a certain position on the flywheel because they will be two brand new surfaces.
-be careful, gentle, and patient when sliding the transmission back into the clutch. It needs to be lined up PERFECTLY or it simpley won't go in, so don't force it. Also, when you get it in, don't let it hang by the input shaft. Keep the jack under it till you get the 8 tranny-to-bellhousing bolts in and the crossmember bolted up.
-before you bolt the slave cylinder and its housing back on, make sure you fully engage the clutchfork onto the throwout bearing. This can be tricky to push back in, but you'll know when its in completely when the round indent on the end of the fork lines up exactly betwen the 2 studs sticking out of the bellhousing. If the clutch fork isnt fully engaged and you push pedal, ugly, expensive, and messy things will happen to your hydraulic system, so make sure its fully engaged.
Hope that helps, and good luck.
