Ford 640 - bad oil leak

[TC10284]

I have just reviewed this whole thread, and I don't see where you have responded to two requests about the drain hole at the bottom of the bell housing with the head of a cotter pin dangling from it.

Apologies...
The drain hole with cotter pin on the bottom of the bell housing is there. It was a little stiff at first but appears to be moving around mostly freely. I'm not sure how freely it's supposed to move but I don't really see any oil dripping from that area.

I can try to spray some carb cleaner in that hole or maybe push a wire up in there to help open it if I should.

Pics/video:
https://photos.app.goo.gl/4byVU2FzbxMsc3GQA

 

[showcrop]

Apologies...
The drain hole with cotter pin on the bottom of the bell housing is there. It was a little stiff at first but appears to be moving around mostly freely. I'm not sure how freely it's supposed to move but I don't really see any oil dripping from that area.

I can try to spray some carb cleaner in that hole or maybe push a wire up in there to help open it if I should.

Pics/video:
https://photos.app.goo.gl/4byVU2FzbxMsc3GQA

There is supposed to be nothing but air between where your starter mounts and that cotter pin, which tells me that the oil/mud dam is still holding despite the cotter pin moving "mostly freely"

 

[Sean in PA]

There is some oil visible on the cotter pin in those latest pictures, but nowhere near as much as there should be considering the amount of oil leaking farther forward in the earlier pictures. Try pushing an awl straight up into the hole beside the cotter pin ad far as it will go and then angling it as much as you can and spin it around to try to clear it some more.

 

[john in la]

First things first.
Spray degreaser over entire area and wash down with a water hose.
For hard to clean spots you can use brake cleaner.
You want clean dry metal to where any oil you see is a fresh leak.

Now there is the engine block.
Then a plate of metal between the engine and trans.
Then the trans.

What is the highest place you see fresh oil.
If the highest leak you can see is between the plate and the trans the rear main is leaking.
If the oil is running down on the engine side of the plate trace the oil to the source.
Is it leaking out between the block and plate.
Or is it running down the block onto the plate.

 

[showcrop]

First things first.
Spray degreaser over entire area and wash down with a water hose.
For hard to clean spots you can use brake cleaner.
You want clean dry metal to where any oil you see is a fresh leak.

Now there is the engine block.
Then a plate of metal between the engine and trans.
Then the trans.

What is the highest place you see fresh oil.
If the highest leak you can see is between the plate and the trans the rear main is leaking.
If the oil is running down on the engine side of the plate trace the oil to the source.
Is it leaking out between the block and plate.
Or is it running down the block onto the plate.

Did you see his video from the 17th?

 

[TC10284]

There is supposed to be nothing but air between where your starter mounts and that cotter pin, which tells me that the oil/mud dam is still holding despite the cotter pin moving "mostly freely"

Understood.

I took the starter off yesterday and used a light to look in there. There was some engine oil on the bottom. Maybe... 1/8 and an inch or less? I took pics but they don't really show anything.

I saw some oil on the flywheel.
I also noticed some on the opposite side of the bell housing on the outside below where it looks to be a hydraulic pump (sorry, I didn't get a pic tonight). I'm thinking it's leaking onto flywheel or enough is pooling and the flywheel is slinging it on both of the opposite sides of the housing.

I'm guessing I do actually have a rear main seal leak (?).

And to address your drain hole concern, I'll have to find a wire small enough I can run up in there because the cotter pin takes up most of the space. It's so tight I can't even fit a carb cleaner straw in there.

After cleaning up the valves and trying to make sure oil drains were clear, now it smokes some when I throttle up whereas it didn't before. Maybe it's just residual oil leftover? I didn't run it that long.
The oil pressure looks worse also. A little above 0 at idle until I throttle up and then maybe get 15 to right below 20psi max.
I didn't really do anything that I'd think would have affected either of those two things I thought.

Anyway, wanted to update on the status.

 

[TC10284]

There is some oil visible on the cotter pin in those latest pictures, but nowhere near as much as there should be considering the amount of oil leaking farther forward in the earlier pictures. Try pushing an awl straight up into the hole beside the cotter pin ad far as it will go and then angling it as much as you can and spin it around to try to clear it some more.

I will try this. Thanks

 

[TC10284]

First things first.
Spray degreaser over entire area and wash down with a water hose.
For hard to clean spots you can use brake cleaner.
You want clean dry metal to where any oil you see is a fresh leak.

Now there is the engine block.
Then a plate of metal between the engine and trans.
Then the trans.

What is the highest place you see fresh oil.
If the highest leak you can see is between the plate and the trans the rear main is leaking.
If the oil is running down on the engine side of the plate trace the oil to the source.
Is it leaking out between the block and plate.
Or is it running down the block onto the plate.

The highest place I see oil leaking currently is both sides of the housing - side of the starter where it mounts to the housing on the left side, and the opposite behind the hydraulic (?) pump on the right side. After redoing the oil pan gasket with a new one and torque to 18ft lbs, I don't see any oil leaks there anymore.

 

[showcrop]

It sounds like you found it with the oil on the flywheel as well as up the side. Oil being slung by the flywheel explains the presence of the oil as high as it is.

 

[Hobo,NC]

Understood.

I took the starter off yesterday and used a light to look in there. There was some engine oil on the bottom. Maybe... 1/8 and an inch or less? I took pics but they don't really show anything.

I saw some oil on the flywheel.
I also noticed some on the opposite side of the bell housing on the outside below where it looks to be a hydraulic pump (sorry, I didn't get a pic tonight). I'm thinking it's leaking onto flywheel or enough is pooling and the flywheel is slinging it on both of the opposite sides of the housing.

I'm guessing I do actually have a rear main seal leak (?).

And to address your drain hole concern, I'll have to find a wire small enough I can run up in there because the cotter pin takes up most of the space. It's so tight I can't even fit a carb cleaner straw in there.

After cleaning up the valves and trying to make sure oil drains were clear, now it smokes some when I throttle up whereas it didn't before. Maybe it's just residual oil leftover? I didn't run it that long.
The oil pressure looks worse also. A little above 0 at idle until I throttle up and then maybe get 15 to right below 20psi max.
I didn't really do anything that I'd think would have affected either of those two things I thought.

Anyway, wanted to update on the status.

If it is the rear main seal with those oil pressure numbers you will never stop the leak by just replacing the rear main seal. To have any luck the crank would have to come out and be machined.

Another overlooked issue is excessive crankcase pressure.

 

[pomester]

I feel like something is being missed here, but I'm not certain what it is. If the rear main seal is leaking, oil should be dripping out the cotter key hole, apparently it's not. The videos are difficult to interpret, but it looks like a pressurized oil leak. I've never seen anything like it except for hydraulic O-ring leaks, but I don't know how this could be that.

 

[TC10284]

I feel like something is being missed here, but I'm not certain what it is. If the rear main seal is leaking, oil should be dripping out the cotter key hole, apparently it's not. The videos are difficult to interpret, but it looks like a pressurized oil leak. I've never seen anything like it except for hydraulic O-ring leaks, but I don't know how this could be that.

If there are any videos I can take that would help, I am glad to try.
At this point I am feeling like it's a rear main seal. I band-aided the leak in the starter side with some black rtv and that helped but of course now it's coming from the other side even more and will pool up in the housing. But I guess at least it won't cause a fire possibly by dripping on the hot exhaust.

I did take a few more videos to try to help you guys see what I see.

6 new videos · Saturday, May 23 🎬

Tap to view!

photos.app.goo.gl

 

[John Harry]

Instead of fussing with the cotter key, just take the darn plate off. Only 4 5/16/bolts and its off.. Then you can reach up in the bell housing and feel around ,and /or stick a bore scope in and look around. If you are careful, you can do that while running. just don't let it get caught in the clutch. I have done that to verify a hydraulic tube leak.

 

[showcrop]

Instead of fussing with the cotter key, just take the darn plate off. Only 4 5/16/bolts and its off.. Then you can reach up in the bell housing and feel around ,and /or stick a bore scope in and look around. If you are careful, you can do that while running. just don't let it get caught in the clutch. I have done that to verify a hydraulic tube leak.

No you haven't because the tubes don't get leaks in the bell housing. It doesn't hold water or get water. They rust in the transmission because water sits in it.

 

[pomester]

If there are any videos I can take that would help, I am glad to try.
At this point I am feeling like it's a rear main seal. I band-aided the leak in the starter side with some black rtv and that helped but of course now it's coming from the other side even more and will pool up in the housing. But I guess at least it won't cause a fire possibly by dripping on the hot exhaust.

I did take a few more videos to try to help you guys see what I see.

6 new videos · Saturday, May 23 🎬

Tap to view!

photos.app.goo.gl

Here is a youtube of a fellow pulling the clutch and rear cover and rear camshaft cover off a Ford NAA. As I pointed out earlier, you have a NAA, not a 640. The engines are similar between those models but the stuff behind the clutch is quite different.

At about the 3 minute mark the plate is removed exposing the rear of the engine proper and the cover at the rear of the camshaft which accesses the gear which drives your hydraulic pump. It appears to me that that cover is where your oil leak is.

Your oil pressure is marginal at best. I think that is a separate problem from your oil leak tho.

 

[TC10284]

Instead of fussing with the cotter key, just take the darn plate off. Only 4 5/16/bolts and its off.. Then you can reach up in the bell housing and feel around ,and /or stick a bore scope in and look around. If you are careful, you can do that while running. just don't let it get caught in the clutch. I have done that to verify a hydraulic tube leak.

Which plate are you referring to?

2 new photos · Sunday, May 24 📸

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photos.app.goo.gl

 

[John Harry]

Which plate are you referring to?

2 new photos · Sunday, May 24 📸

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photos.app.goo.gl

Sorry, my mistake. On the 800 series there is a rectangle plate, under the bell housing, maybe 4"x5" that carries the cotter key. Remove the plate and you can see up into the clutch area. Also gives you access to muck out the bottom of the bell housing. I just looked at the transmission diagrams on Messicks site and unfortunately, the NAA or the 600 series do not have the plate. The cotter key is the initial indicator of an oil leak and by removing the plate you can see if it is from the transmission oil seals or engine. But I agree with the general consensus of the cam plate leaking which has a gasket behind it or the rear main seal. Neighbor has an 840 leaking just like yours. Planning to split it. Only way to really know and to fix it.