School me on Rear Main seals

[JoshT]

My dad and I just finished rebuilding the 4.0L in my 99 Ranger. The engine had 180K miles prior to rebuild and didn't really need a rebuild, but the block was torn down for other reasons. Prior to removal the only thing leaking oil on the bottom end was the oil filter adapter to block seal.

Machine shop inspected the crank, and the surfaces looked good, only thing needed as polishing on the journals which they did. Rear main sealing surface was smooth no grooves or scratches. Due to surface condition of crank we got a regular rear main seal instead of using the seal and ready sleeve included in the gasket set. The only types of rear main seals tha were available local were the FelPro Rubber seal W/wear sleeve and the FelPro PTFE seal. Obviously I got the latter, and installed it per instructions included in box. Main thing it said different was that due to being a telon seal it should be installed with no lube on the crank sealing surface, further digging revealed that it builds up a teflon area on the crank surface and creates a teflon to teflon seal. Supposedly lubing the surface can interfere with this proess.

The engine now has about 300 miles on it and I have a leak at the back of the block dripping from the bottom of the bellhousing. Looking I can see that it is not running down the block but coming from inside the belhousing. This seems to leave two possibilities. Either the oil pan is not sealing good at the rear main cap or the rear main seal is leaking. I'm planning to have stuff to fix both on hand when we get the time to fix it.

My questions:

1) Is it possible that the PTFE seal takes time to seat and the leak will go away once it does?

2) Which type should I use and which brand is better? Loking on rock auto I see Timken brand Viton or PTFE heavy duty, National brand Viton or PTFE, and I see Fel-Pro brand rubber (guessing Viton) w/ sleeve or PTFE. It lso looks like the Fel-Pro rubber is oversized to use with the sleeve and I can't tell that I need it.

3) Since I've used a PTFE seal am I stuck using PTFE seals?

4) If I need to use a seal with repair sleeve, how does it get installed? I have the one included with the gasket set, but my books don't cover the sleeve and no instructions for it included with the set. It also looks like that seal is too loose of a fit without the sleeve.


Sorry about the long post, wanting to get this done right. Once it's back together this time I don't want to be touching the bottom end for a long time.

 

[RonD]

No, it doesn't take time to seal.

Maybe you scratched the crank when installing seal, IF it is the rear main that's leaking.

Many like the Teflon seals, others don't like or dislike them, they use stock seals if they have lasted a long time because they work fine and are less expensive.

Main seals are pressure seals, so unlike valve covers and oil pan gaskets, oil is be forced thru behind them, and small scratch will start to tear the seals and it will leak.

Sleeve seals come with a sleeve that is installed on the crank and a slightly larger opening on the seal part to accommodate the now larger crank dimension.
You use these if crank gets scratches, the sleeve covers the scratches and seal has smooth surface to ride on.

 

[veefer800canuck]

Viton is a great material for seals, it's resistant to almost anything, chemical wise.

 

[kimcrwbr1]

Are you sure it is not leaking from the intake manifold or the distributor? Did you put a new o-ring on the distributor and when you installed the intake manifold did you put sealant in the valleys between the head and the block?

 

[JoshT]

It is possible that it isn't even the rear main. It's entirely possible that it is the pan gasket at the main cap or something else in the area. I'm hopeful that that is the case, but either way the engine basically has to come out to fix it so I want to be prepared for either.

Maybe you scratched the crank when installing seal, IF it is the rear main that's leaking.

It's highly doubtful that the crank was scratched, but is possible that the seal itself got scratched. I'm hopeful that is isn't the rear main, but I know my luck.

You use these if crank gets scratches, the sleeve covers the scratches and seal has smooth surface to ride on.

I know what they are, and what they are for. I've never used one so if I need to go that route I'm clueless on the actual install procedure. The only locally available rubber Rear Main was a repair sleeve kit.

Are you sure it is not leaking from the intake manifold or the distributor? Did you put a new o-ring on the distributor and when you installed the intake manifold did you put sealant in the valleys between the head and the block?

Yes, I am positive that it is not leaking from the intake manifold or distributor (this engine doesn't have one). A new o-ring was installed on the cam position sensor before it was reinstalled and the lower intake manifold was sealed where required before torquing. I can look at the leak and tell that it is coming from the lower potion of the block at the back. Only possibilities in that area are Rear Main Seal, Oil Pan Gasket, or a slim chance of it being the rear main cap itself. Won't know for sure until I have more time to get under the truck and look better or we pull the engine.

 

[PlumCrazy]

Main seals are pressure seals, so unlike valve covers and oil pan gaskets, oil is be forced thru behind them

All the seals/gaskets you mentioned see the same pressure

I would also check you PCV valve to ensure that the crankcase isn't building to much pressure. And also make sure you don't have a blow by issue from worn rings causing excessive pressure.

 

[RonD]

Yes, same internal pressure as the rest of the engine but the location next to the front and rear crank journals causes a higher pressure of oil behind these seals because of limited space for oil to drain back to the oil pan, making for a higher rate of oil leaking even from a small breach.

Quite a few sleeve install videos available, I installed one years ago on an old ford motor, it came with an install tool but you don't really need one.
Installing a sleeve assumes crank has a scratch or groove in it, and these imperfections hold the sleeve in place, once installed the sleeve's friction hold on the crank is greater than the friction of the seal, so sleeve rotates at crank speed, it can't slip, so no it doesn't need to be sealed or "glued" into place.

One thing I remember about rear seals is that you shouldn't use an impact gun when tightening flywheel or flexplate, use a torque wrench, over torquing can deform the crank slightly where the seal rides, and it will leak.

 

[JoshT]

I would also check you PCV valve to ensure that the crankcase isn't building to much pressure. And also make sure you don't have a blow by issue from worn rings causing excessive pressure.

My dad and I just finished rebuilding the 4.0L in my 99 Ranger.

That means new rings, bearings and seals. If they had been needed it would have also meant new pistons, rods, and reman crank. Fortunately none of the latter was necessary which helped my wallet out a lot. Would have also installed a new PVC valve and had one on hand to install, but it wasn't needed. Guessing that I changed it when I replaced the heads.

Quite a few sleeve install videos available

If it comes to using that set-up I'll find one of those videos and watch it.

One thing I remember about rear seals is that you shouldn't use an impact gun when tightening flywheel or flexplate, use a torque wrench, over torquing can deform the crank slightly where the seal rides, and it will leak.

Since I bought this truck 100K miles ago, no impact guns have ever been used on this truck. Okay, not quite true the tire shop uses them when I take it in for rotation and balance, but even they do the final torque with wrench.

While I have both pneumatic ratchets and impacts as well as electric impacts, none of those were used. Everything was done with hand tools. All dissassembly of the motor was done with wrenches, ratchets, and breaker bars. All reassembly and installation of the motor was done with wrenches, ratchets, and torque wrenches. If there was a torque spec on the item final tightening was done with torque wrench, with the exception of the bolts which use a torque degree as final step.

 

[cp2295]

Just to let you know i rebuilt my 3.0 and it leaked out the back. I thought it was the RMS and it turned out to be the Oil pan. If you have to pull the motor again, that sucks, but at least this time itll be easier! Sorry to hear that man.

Fel pro sells sleeve and seal kits to take care of any scarring on the crank seals.

 

[JoshT]

Oil pan would be nice, but due to clearance on a 4x4 the engine practically has to be removed to fix it.

 

[cp2295]

Oil pan would be nice, but due to clearance on a 4x4 the engine practically has to be removed to fix it.

Yeah that's the issue I had unfortunately