Rear main seal

[scubscout53]

Hey guys, I’m leaking oil in my 96 Bronco 351. I must have had two leaks as the drain plug was leaking but it’s clean now . It’s oily between the transmission and the engine. (See picture). There is also a bit of coolant present. This could be due to the plastic coolant reservoir brackets being broken and not sitting properly but not sure.
I read that if it’s rear main seal it would steady drip when running. Is that true?
There’s minor oil around the valve covered in the back. Don’t think that’s the issue. None around the oil pan. I’m going to Jack it up and clean away what I can and try to look further. Also read a post about using dye which I’ll try if I can’t spot it after cleaning. My skills and tools are limited so if it’s serious I’ll be taking it to a mechanic.
Any idea what typical cost is to replace rear main seal?

 

[miesk5]

Yo scubscout53,
Following from 1996 Bronco/F Series Workshop Manual partial @ http://www.diesel-dave.com/vehic/manual/stj/stjleft.htm

Section 03-01B: Engine, 5.0L and 5.8L MFI

1996 F-150, F-250, F-350 and Bronco Vehicles Equipped with 5.0L or 5.8L MFI Engines Workshop Manual​

IN-VEHICLE SERVICE

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Crankshaft Rear Oil Seal — 5.8L​

SPECIAL SERVICE TOOL(S) REQUIRED

Description​	Tool Number​
Rear Oil Seal Replacer​	T65P-6701-A​

Removal

1. Remove the transmission (7003) as outlined in Group 07.

1. If equipped with manual transmission, remove clutch assembly as outlined in Section 08-01.

1. Remove flywheel attaching bolts and remove rear cap (main bearing) and flywheel (6375).

1. CAUTION: Use caution throughout this procedure to avoid scratching or otherwise damaging the crankshaft oil seal surface.
   Use an awl to punch two holes in the crankshaft rear oil seal (6701). Punch the holes on opposite sides of the crankshaft (6303) and just above the bearing cap-to-cylinder block split line. Install a sheet metal ***** in each hole. Use two large screwdrivers or small pry bars and pry against both screws at the same time to remove the crankshaft rear oil seal. It may be necessary to place small blocks of wood against the cylinder block (6010) to provide a fulcrum point for the pry bars.

1. Clean the oil seal recess in the cylinder block and main bearing cap. Inspect and clean the oil seal contact surface on the crankshaft.

Installation

1. Coat the oil seal-to-cylinder block surfaces of the crankshaft rear oil seal with oil XO-5W30-QSP or -DSP or equivalent meeting Ford specification ESE-M2C153-E. Coat the seal contact surface of the crankshaft rear oil seal and crankshaft with heavy SG engine oil. Place crankshaft rear oil seal on Rear Oil Seal Replacer T65P-6701-A and, using hammer, tap into place until tool contacts face of cylinder block or bearing cap.
   
   

   Item​	Part Number​	Description​
   1​	T65P-6701-A​	Rear Oil Seal Replacer​
   2​	6701​	Crankshaft Rear Oil Seal​

   oat the threads of the flywheel attaching bolts with oil resistant sealer. Install the bolts and tighten in an opposing pattern, to 102-115 Nm (75-85 lb-ft).

1. Install flywheel.

1. If equipped, install clutch.

1. Install transmission.

1. Check engine oil level and refill as required.

1. Start engine and check for leaks.

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Section 03-00: Engine, Service

1996 All F-150, F-250, F-350, F-Super Duty and Bronco Vehicles Equipped with 4.9L, 5.0L, 5.8L or 7.5L Gasoline Engines, and 7.3L Diesel Engines Workshop Manual​

SERVICE PROCEDURES

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Engine Oil Leaks​

When diagnosing engine oil leaks, the source and location of the leak must be identified prior to service.

Fluorescent Oil Additive Method

1. Add Rotunda Gas Engine Dye 164-R3705 or equivalent to the engine oil. Use 29.6 ml (1 ounce) of fluorescent additive in all engines.
2. Clean engine with a suitable solvent to remove all traces of oil.
3. Run engine for 15 minutes.
4. Stop the engine and inspect all seal, gasket and galley plug areas for leaks using Rotunda Oil Leak Detector 164-R0756 or equivalent. A clear bright yellow or orange area will identify leak. For extremely small leaks, several hours may be required for the leak to appear.
5. NOTE: For minor gasket leaks tightening the retaining bolts may resolve the problem.
   Service all leaks as required.

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●

Section 03-00: Engine, Service

1996 All F-150, F-250, F-350, F-Super Duty and Bronco Vehicles Equipped with 4.9L, 5.0L, 5.8L or 7.5L Gasoline Engines, and 7.3L Diesel Engines Workshop Manual​

SERVICE PROCEDURES

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Leakage Points​

Examine the following areas for oil leakage.
Underhood

• Valve cover gaskets (6584)
• Intake manifold gaskets (9439)
• Head gaskets (6051)
• Oil bypass filter (6714)
• Distributor O-ring
• Oil level indicator (dipstick) tube connection
• Oil pressure sensor (9278)
• Cup plugs and/or pipe plugs at end of oil passages

Under Engine, with Vehicle on Hoist

• Oil pan gasket (6710)
• Oil pan front and rear end seals
• Crankshaft front seal (6700)
• Crankshaft rear oil seal (6701)
• Engine damper keyway (damper to damper bolt/washer interface)

 

[L\Bronco]

Hey guys, I’m leaking oil in my 96 Bronco 351. I must have had two leaks as the drain plug was leaking but it’s clean now . It’s oily between the transmission and the engine. (See picture). There is also a bit of coolant present. This could be due to the plastic coolant reservoir brackets being broken and not sitting properly but not sure.
I read that if it’s rear main seal it would steady drip when running. Is that true?
There’s minor oil around the valve covered in the back. Don’t think that’s the issue. None around the oil pan. I’m going to Jack it up and clean away what I can and try to look further. Also read a post about using dye which I’ll try if I can’t spot it after cleaning. My skills and tools are limited so if it’s serious I’ll be taking it to a mechanic.
Any idea what typical cost is to replace rear main seal?

Hey scubscout53,
looking at the pict, it could be a rear main seal, but based solely on the streaks and volume, plus the hint of coolant there, I'd look very closely at the rear of the lower intake manifold. there are coolant passages one either side between the heads and intake, plus a long seal between them sealing the manifold to the block (Oil), it's a common point to leak, and it runs down and exits at the bellhousing much like what you have there. look at the back of the engine from the top, (you might need a mirror) there is a small well in the block between the intake and the bellhousing where oil will usually pool when the leak is present. You can run your fingers around the back of the intake if you can get in there and see if they come out oily. I did way more intake gaskets back in the day than rear mains. (Mind you, that was back in the day!)
Hope that helps
Cheers

 

[Motech]

Also read a post about using dye which I’ll try if I can’t spot it after cleaning.

UV dye is the absolute best way to pinpoint oil leaks, and it does not require any cleanup. Leaks will appear clearly over the top of any residual that's already there.

This Tracer brand product is the most common you'll find at local auto parts stores:



You will need a decent UV inspection light. I use this one from Coast, a good deal at just twenty bucks:




It also comes in real handy for finding scorpions in your dark basement. Just beware about flashing it around your bathroom or bedroom!

LINK

Any idea what typical cost is to replace rear main seal?

It is pretty pricey. Consider the transmission has to come out, which often includes the transfer case. At minimum, depending on your local labor rates, you would be looking at a $600.00 to $800.00 repair. That is a lot chasing an oil leak, and I'm certain that's why @L\Bronco posted his very good reply.

The thing is, when there is a rear main seal oil leak, there is usually a reason. Primarily, main bearings out of tolerance, excess crankshaft ****** (t.h.r.u.s.t) or even bent shaft causing a little bit of crankshaft wobble. As you can imagine, a new seal will not last too long, and there is no joy for anyone in that outcome.

It is precisely for that reason that I will not reseal a rear main without first doing a complete and thorough UV dye inspection to rule out all other sources. Even then, if I find it is primarily the rear crank seal leaking, I might just clean up the residual and change the oil to some high mileage blend of a slightly thicker viscosity to slow it down.

 

[Motech]

I read that if it’s rear main seal it would steady drip when running. Is that true?

Yes. Whether a steady drip or not, as that crank seal is above the oil level in the pan, it will not leak with the engine off.

But it may very well drip with the engine off as all the residual that collects inside the bellhousing needs a place to go even after it is shut off.

Because of that, slight rear main seal leakage might appear much worse after it is all collected inside the bell housing and begins to drain out from there. It's possible it's a much smaller leak, and you clean it up real well, you might not see it dripping in your driveway again for a few months.

 

[scubscout53]

I believe it’s my water pump and it’s washing some Old oil down with it. I can see coolant pooled at the water pump.

 

[Tiha]

That is tough to tell, but that doesn't look like a rear main to me.

Spend more time cleaning it up. Sounds like you are headed the right direction. And don't dismiss the valve covers so easily.

 

[L\Bronco]

I believe it’s my water pump and it’s washing some Old oil down with it. I can see coolant pooled at the water pump.

Is the coolant pooled in the wells between the block and Timing cover\water pump?
That can come from the gasket between the water pump and timing cover (There is an unused bolt hole in there that likes to weep when the gasket breaks down.) or it can also be the end of the intake manifold.
Did you get a chance to check the rear of the intake for that oil leak?
Cheers

 

[scubscout53]

Is the coolant pooled in the wells between the block and Timing cover\water pump?View attachment 31163
That can come from the gasket between the water pump and timing cover (There is an unused bolt hole in there that likes to weep when the gasket breaks down.) or it can also be the end of the intake manifold.
Did you get a chance to check the rear of the intake for that oil leak?

Is the coolant pooled in the wells between the block and Timing cover\water pump?View attachment 31163
That can come from the gasket between the water pump and timing cover (There is an unused bolt hole in there that likes to weep when the gasket breaks down.) or it can also be the end of the intake manifold.
Did you get a chance to check the rear of the intake for that oil leak?
Cheers

I didn’t see oil at the rear intake and minimal coolant at any of the suspicious locations.
I’m embarrassed to admit this but I inadvertently added a small amount of oil to the coolant reservoir before realizing it was old oil I’d captured. I also overfilled the reservoir. So now I’m hoping this overflow washed coolant and oil to the lower engine area. I’ve cleaned all the areas I could get to of any oil residue.
I drove several miles and looked under the truck with the engine running and saw no leak. Turned the engine off and after several hours still no leak.

 

[L\Bronco]

I didn’t see oil at the rear intake and minimal coolant at any of the suspicious locations.
I’m embarrassed to admit this but I inadvertently added a small amount of oil to the coolant reservoir before realizing it was old oil I’d captured. I also overfilled the reservoir. So now I’m hoping this overflow washed coolant and oil to the lower engine area. I’ve cleaned all the areas I could get to of any oil residue.
I drove several miles and looked under the truck with the engine running and saw no leak. Turned the engine off and after several hours still no leak.

Fair enough, Just watch it or a while then and you are likely ok.
Make sure you get all of the oil out of the reservoir as the cooling system uses natural rubber hoses and O rings and oil will cause them to swell and fall apart.
Cheers

 

[Motech]

Focus on and fix that coolant leak first, then blow it all dry and get some UV dye and light. You'll be a hero.

 

[scubscout53]

I didn’t see oil at the rear intake and minimal coolant at any of the suspicious locations.
I’m embarrassed to admit this but I inadvertently added a small amount of oil to the coolant reservoir before realizing it was old oil I’d captured. I also overfilled the reservoir. So now I’m hoping this overflow washed coolant and oil to the lower engine area. I’ve cleaned all the areas I could get to of any oil residue.
I drove several miles and looked under the truck with the engine running and saw no leak. Turned the engine off and after several hours still no leak.

Well I’m back to it being the water pump. I drove it to the golf course and back yesterday and for a long time I saw nothing under the truck. This morning I got up and there were several coolant drips. I’m thinking that it didn’t drip when it was warm as things had expanded, but when it cooled off it began to leak. There was no dripping from the weep hole. The drips are further back near where the transmission and engine meet but there is also coolant just below the water pump. So I’m assuming it is running down and around to the back of the engine.

 

[Motech]

Well I’m back to it being the water pump.

when it cooled off it began to leak. There was no dripping from the weep hole. The drips are further back near where the transmission and engine meet

Can you read any logic into those two statements?

Now do you see where that rear leak is coming from? Or is that just the general area you are seeing the puddles on the ground?

If so, it may be flowing back along the engine or chassis from up front...

but there is also coolant just below the water pump

If not water pump, then timing cover.

Go find yourself one of these Stant pressure test kits at your local used tool store and eliminate all this guesswork.