Main Seal ?

[terryb]

Gang,

My son has a 2000 XLT 4.0 with 49,000 gentle miles. Just like our other 2000 4.0 the head gasket blew at 48K! I had the valves done and replaced the head gasket but now the truck is leaking oil that looks EXACTLY like it is coming from the rear main. At first I thought it was the intake manifold but I reset that twice and it is still leaking. There was no leak prior to my replacing the head gasket and I don't believe in coincidences so I assumed it was related to the work I did, but the back of the motor is dry and the oil leak is manifesting itself between the standard trany and the motor.... I'm wondering if perhaps the rear main seal was damaged by antifreeze in the oil?

I'd appreciate any thoughts and if anyone has ever tried a rear main seal treatment product like Blue Devil?

 

[RonD]

No, coolant/water in the oil wouldn't hurt seals, it can hurt bearings because it "dries" them out when it turns to vapor(steam) from the high heat on bearing surfaces, displaces the oil coating, "dries them out"

Very odd for this to happen just after head gasket replacement
Only oil passage in a 4.0l OHV head is in its center, feeds the center rocker arm assembly leg
So only oil at rear of engine at the top would be valve cover gasket leak, or lower intake at the rear, by Cam synchronizer, but this oil would run down the outside of bell housing, none inside

How long did engine sit, unused, while heads were repaired?
It would have to sit for quite a few months for main seal to dry out enough to stick to crank surface and tear on startup, it can happen just a long shot

 

[terryb]

No, coolant/water in the oil wouldn't hurt seals, it can hurt bearings because it "dries" them out when it turns to vapor(steam) from the high heat on bearing surfaces, displaces the oil coating, "dries them out"

Very odd for this to happen just after head gasket replacement
Only oil passage in a 4.0l OHV head is in its center, feeds the center rocker arm assembly leg
So only oil at rear of engine at the top would be valve cover gasket leak, or lower intake at the rear, by Cam synchronizer, but this oil would run down the outside of bell housing, none inside

How long did engine sit, unused, while heads were repaired?
It would have to sit for quite a few months for main seal to dry out enough to stick to crank surface and tear on startup, it can happen just a long shot

Not long at all. WHat are your thoughts on a seal treatment product?

 

[RonD]

If its the front or rear main seal then the treatments won't work well

The treatments swell gaskets and "rubber" parts to help them seal better
Problem with front or rear main seals is that these are "Pressure Leaks", the front and rear main bearings are adjacent to these seals, rear more so than the front, so oil coming out of rear main bearing journal is forced against the seal before it can drain back to the pan
Which is why they leak a lot of oil once they no longer have a good seal to spinning crankshaft

It won't hurt anything to try it..........................just don't expect much

 

[mikkelstuff]

I believe the rear main seal can be replaced without dismantling the engine, at least so with my 2002 3.0L engine. Just have to remove the transmission and flywheel (as though that was nothing).