Is there a trick to installing the rear main seal on a 4.0L?

[fast_dave]

Get a Motorcraft rear main seal.

I have used a couple different brands on my 4.0L, and done this job 3 times on it. All 3 have failed. I thought I must have been installing it wrong, BUT.. I used the seal tool each time. I searched this problem out here, and found that you really should only replace with a Motorcraft seal. The seal lip is special, and differs then aftermarket brands. Lesson learned, and when I do this for the 4th time, I will use the Ford seal, and the seal tool.

@gmanpaint

Your post intrigued me enough to go back in my Ex's service records.

OK - to start, the FORD OHV Engine has a reputation for rear main seal leaks.

It may be an internet myth repeated over and over, but many say the reason is that crank snout was polished TOO fine, allowing oil to slip past.

Apparently, the sleeve isn't polished as fine as the crank snout - hence the reason for the sleeve.

I don't recall any posts saying the sleeve was included because of a circular ring being ground into the crank snout.

OK - back to my OHV Ex. In December 2007 @ 90,579 Miles I had a local mechanic replace the rear main seal in my OHV.
I don't have any note as to the brand of rear main seal he used, BUT I do know it was aftermarket due to both memory AND my next service entry.

Next service entry - March 2008 @ 93,958 Miles and I have a note that the rear main seal was leaking, and my mechanic replaced it again, this time with FORD Part Number F5TZ6701A. Even back then I remember him complaining that it was around $40.

It was a LONG time ago, BUT now that my brain juices are flowing I remember him saying that when he picked it up, the FORD parts guy said it had to be installed with a special tool to assure it being leak free. I imagine this is the same tool that is mentioned earlier in this thread. I remember this because my mechanic had to wait until the weekend to borrow it from a service guy buddy that worked at the local FORD dealership he bought the seal from. The guy that worked at FORD didn't want to give it up until he had the weekend off. This caused me to be without my Ex for a few days more than originally expected.

I ran a GOOGLE search with the parts number, and found a guy on EBAY that offers a 100% FORD 4.0 SOHC Timing Chain Kit, and he includes the same Rear Main Seal - FTZ6701A - this is a long way to say it'll fit an SOHC.

OK - hope this helps @koda2000 and good luck with your rebuild!

 

[koda2000]

@gmanpaint

Your post intrigued me enough to go back in my Ex's service records.

OK - to start, the FORD OHV Engine has a reputation for rear main seal leaks.

It may be an internet myth repeated over and over, but many say the reason is that crank snout was polished TOO fine, allowing oil to slip past.

Apparently, the sleeve isn't polished as fine as the crank snout - hence the reason for the sleeve.

I don't recall any posts saying the sleeve was included because of a circular ring being ground into the crank snout.

OK - back to my OHV Ex. In December 2007 @ 90,579 Miles I had a local mechanic replace the rear main seal in my OHV.
I don't have any note as to the brand of rear main seal he used, BUT I do know it was aftermarket due to both memory AND my next service entry.

Next service entry - March 2008 @ 93,958 Miles and I have a note that the rear main seal was leaking, and my mechanic replaced it again, this time with FORD Part Number F5TZ6701A. Even back then I remember him complaining that it was around $40.

It was a LONG time ago, BUT now that my brain juices are flowing I remember him saying that when he picked it up, the FORD parts guy said it had to be installed with a special tool to assure it being leak free. I imagine this is the same tool that is mentioned earlier in this thread. I remember this because my mechanic had to wait until the weekend to borrow it from a service guy buddy that worked at the local FORD dealership he bought the seal from. The guy that worked at FORD didn't want to give it up until he had the weekend off. This caused me to be without my Ex for a few days more than originally expected.

I ran a GOOGLE search with the parts number, and found a guy on EBAY that offers a 100% FORD 4.0 SOHC Timing Chain Kit, and he includes the same Rear Main Seal - FTZ6701A - this is a long way to say it'll fit an SOHC.

OK - hope this helps @koda2000 and good luck with your rebuild!

Yep that's the type of seal that came in my gasket kit with the removable metal ring/sleeve. If what you heard about the crankshaft being too polished is true, this would not be the only Ford vehicle to have this problem. IIRC there was a TSB on my daughter's Fusion V6 about the CV axle seals leaking for the same reason.

 

[RickOTR]

What's amazing is that I have ever had to replace the rear main seal on my Xplorer even though it has over 670K miles. Wonder if it has anything to do with using full synthetic and changing it every 3000 miles?

 

[donalds]

670k that's almost hard to believe wow

 

[410Fortune]

I think rear mail seal leaks have a lot to do with the location of the catalytic converters on these trucks......heat chambers right below the rms and the torque converter
I have replaced RMS on 4.0 ohv and 5.0 several times.... my repairs generally do not come back with a leak. Seepage (wetness) is pretty normal but a drip drip leak no.
This job and any seal job must be done clean clean
The new seal MUST be lubed, I have seen alot of people install seals DRY....the first time the crank spins it is going to wear out the seal, dry on dry.... you need to use some assembly lube, vaseline, something on both sealing surfaces EVERY TIME
Go through all the trouble to remove the trans and then try to do the seal job quickly so you can put the trans back in??? Makes no sense to me.
Spend some time on it
Make sure it is clean
make sure the new seal is prepped properly
Make sure it gets seated properly
Same goes for the sleeve....if you have to use one

The fingernail trick is only if your crank (or axleshaft or whatever we are sealing) saw excessive wear at the seal area and there is now a groove. A sleeve would be the best fix for this, if a sleeve kit is not avail then you need to re locate the seal outward slightly (thin washer/ spacer can do this)

I like that Ford seal!!!!!!

 

[RickOTR]

670k that's almost hard to believe wow

I know Explorer owners out there that have over 400K miles on the original engine. Other than the timing chain issues and week lash adjusters, I feel the SOHC engine can last a long time if taken care of. Did a compression test on mine last year and still gotta a lot of life left in it.

 

[masospaghetti]

I did the rear main seal three times on my truck. The first two times I messed up and installed the sleeve backwards (it wasn't obvious to me at the time which way the sleeve went -- but if its installed in the wrong direction, it will tear the seal as soon as you start the engine). The third time I just took the sleeve off and installed the seal by itself.

Yes, my truck weeps oil from the rear main, but slowly - slow enough that's its OK with me. In my case it's probably because the crank got scratched from installing and removing the sleeve.

Be aware there are two types of seals, a rubber "viton" seal (the typical brown ones) that should be lubricated when installed, or a teflon seal that must be installed dry. If the teflon seal is not installed dry apparently it never will seal correctly.

 

[410Fortune]

good info! thanks
Teflon seal gets installed dry, interesting!

yes 4.0 SOHC has a BULLETPROOF bottom end and rotating assembly....if you can keep the chains together they will last 500K miles!!!! VERY TOUGH engines.... but Im still not happy with them, 5 chains and a jackshaft dealio = bad taste

 

[koda2000]

good info! thanks
Teflon seal gets installed dry, interesting!

yes 4.0 SOHC has a BULLETPROOF bottom end and rotating assembly....if you can keep the chains together they will last 500K miles!!!! VERY TOUGH engines.... but Im still not happy with them, 5 chains and a jackshaft dealio = bad taste

Yep, more moving parts = more problems.

 

[donalds]

I'll jump that train^^^^^

 

[Deleted member 352605]

just to confirm, to do the rear main seal, you have to remove the transmission right? no tricks or other ways as far as i know... thanks!

 

[koda2000]

just to confirm, to do the rear main seal, you have to remove the transmission right? no tricks or other ways as far as i know... thanks!

Well, you always have to remove the transmission (or the engine) in order to replace a one-piece rear main seal. The special installation press tool, or something like it, is required to set the seal evenly, straightly and to the required depth. There is also the concern of preventing damage to the seal when pushing it over the crank shaft stub. Apparently there are two different types of rear main seals available from Fel Pro. The one I got in my complete engine gasket/seal set is one that comes with a removable metal repair sleeve which gives the "brown" seal a new surface to run on. This is helpful if your crankshaft has a groove worn in it and I've also heard that the finish on the sleeve promotes better sealing than the finish on the crankshaft stub, which may be too smooth. Fel Pro also offers a Teflon rear main seal, which is presumably of higher quality. This Teflon seal comes with a plastic installation tool to aid in installing the seal. IDK if it also comes with a metal repair sleeve.

If the rear main seal is not installed correctly it will leak. A video I watched showed a damaged seal which had rubbed on the flexplate/flywheel because it was installed crookedly, perhaps not fully seated or perhaps damaged during installation. As replacing this seal is very labor intensive, it's not the kind of job you want to have to go back and repeat.

Though I've always installed oil seals with just a hammer and a block of wood, a large socket, and sometimes even a seal driver, I wanted to make sure I did this job the correct way by using the recommended installation tool. No one responded to this thread saying the installation tool was not recommended/needed. As with all oil seals, they should always be lubricated during installation to prevent them from burning up the first time their corresponding shaft is spun. I lubed mine with Vaseline, though I've also used oil or grease. To my recollection I've never had to go back and replace a seal a second time.

 

[masospaghetti]

Though I've always installed oil seals with just a hammer and a block of wood, a large socket, and sometimes even a seal driver, I wanted to make sure I did this job the correct way by using the recommended installation tool. No one responded to this thread saying the installation tool was not recommended/needed. As with all oil seals, they should always be lubricated during installation to prevent them from burning up the first time their corresponding shaft is spun. I lubed mine with Vaseline, though I've also used oil or grease. To my recollection I've never had to go back and replace a seal a second time.

I had a buddy fab a makeshift seal installation tool, basically just a round plate with two holes for bolts to thread into the flywheel. It worked fine.

Fel-pro is very specific about not using oil or grease when installing the Teflon seals.

 

[fast_dave]

just to confirm, to do the rear main seal, you have to remove the transmission right? no tricks or other ways as far as i know... thanks!

@ExplorerGuy2007

You'll need to split the engine from transmission & remove the flywheel/flexplate from the crankshaft (so you'll need an impact gun).

 

[koda2000]

@ExplorerGuy2007

You'll need to split the engine from transmission & remove the flywheel/flexplate from the crankshaft (so you'll need an impact gun).

If we're also talking tools, in addition to an impact gun you'll need a torque wrench and some blue loc-tite to reinstall the flexplate/flywheel, the torque specs and tightening sequence. If you have a manual trans the flywheel bolts may need to be replaced (not sure) because they may be TTY (torque to yield one time use). A long 1/2" breaker bar and 3/4"-19mm deep socket to hold the crankshaft would also be helpful. Unless you have a fairly severe rear main seal leak (valve cover gasket leaks can look like a rear main seal leak, but are much easier to replace) I won't dive into replacing the rear main seal "just cause". It's a pretty big job and if you don't do it correctly you may end up with a worse leak than what you started with.

@masospaghetti I once watched a video on someone making a rear main seal installation tool from parts from the Home Depot. It seemed to work okay. For what the recommenced special tool is it's quite expensive.

@boominXplorer I should have the tool you lent me on its way back to you this week. Thanks again.

 

[Deleted member 352605]

If we're also talking tools, in addition to an impact gun you'll need a torque wrench and some blue loc-tite to reinstall the flexplate/flywheel, the torque specs and tightening sequence. If you have a manual trans the flywheel bolts may need to be replaced (not sure) because they may be TTY (torque to yield one time use). A long 1/2" breaker bar and 3/4"-19mm deep socket to hold the crankshaft would also be helpful. Unless you have a fairly severe rear main seal leak (valve cover gasket leaks can look like a rear main seal leak, but are much easier to replace) I won't dive into replacing the rear main seal "just cause". It's a pretty big job and if you don't do it correctly you may end up with a worse leak than what you started with.

@koda2000 and fast_dave

thanks! i never thought of checking the valve cover gasket! I'll have to take a peek... is there a way to tell? i have the tools, and it's a very small leak... should i try one of those oil additives or will that gum up the rest of the engine as well... hoping to do the timing guides and some other misc. fixes

 

[fast_dave]

@ExplorerGuy2007

No prob-

Look at the bottom of the back of the valve cover - nearest to the firewall on BOTH valve covers.

While you're at it, you can also look at the oil filter "mounting plate" (aka Adapter) that the Oil Filter mounts to.

Oil is like water - follow the flow

If all is well in those areas, and it does turn out to be your Rear Main Seal, you'll also have to think about getting your Ex pretty high up in the air and supporting it on all four corners, as well as some sort of hydraulic jack that will securely hold the transmission when you perform the split (and thus not fall off or worse hurt you).

Having a pretty strong buddy on hand that will work for free beer would also be a great help

HTH -

 

[Deleted member 352605]

Thanks! Going to check that later when i go to pick up some stuff to deliver to a friend...

 

[masospaghetti]

@ExplorerGuy2007

No prob-

Look at the bottom of the back of the valve cover - nearest to the firewall on BOTH valve covers.

While you're at it, you can also look at the oil filter "mounting plate" (aka Adapter) that the Oil Filter mounts to.

Oil is like water - follow the flow

At first glance, oil leaks can be deceiving in their origin - everything eventually collects at the bottom of the bellhousing. Clean the bottom and sides of the motor really well so you can figure out where fresh oil is coming from. I think you can also use UV tracer dye for this although I haven't done it.

Valve cover seals are a common leak point and will appear similar to a rear main seal leak. Same goes for the oil filter adapter fast_dave mentioned, and a leaking lower intake manifold gasket.

 

[C420sailor]

Also, the flywheel bolts are external torx, NOT 12pt socket.