Ford 640 - bad oil leak

[TC10284]

I have what I think is a 640 that has a bad oil leak and gets worse as it is used.

Am I correct in thinking this is a rear main seal issue or something else? I'm assuming it requires breaking it in half to replace, and that is probably beyond my ability without a proper garage to do it in.

Link to pic and videos:

5 new photos · Monday, May 4 📸

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[KCTractors]

I have what I think is a 640 that has a bad oil leak and gets worse as it is used.

Am I correct in thinking this is a rear main seal issue or something else? I'm assuming it requires breaking it in half to replace, and that is probably beyond my ability without a proper garage to do it in.

Link to pic and videos:

5 new photos · Monday, May 4 📸

Tap to view!

photos.app.goo.gl

Is the engine oil going down? Could also be a leaking camshaft cover leaking. Is the cotter pin that is under the bell housing loose so that any oil can leak out there?

 

[Ultradog MN]

I have what I think is a 640 that has a bad oil leak and gets worse as it is used.

Am I correct in thinking this is a rear main seal issue or something else? I'm assuming it requires breaking it in half to replace, and that is probably beyond my ability without a proper garage to do it in.

Link to pic and videos:

5 new photos · Monday, May 4 📸

Tap to view!

photos.app.goo.gl

Not going to install a google app to view your photos.

 

[TC10284]

Not going to install a google app to view your photos.

You shouldn't have to, but OK.

 

[TC10284]

Is the engine oil going down? Could also be a leaking camshaft cover leaking. Is the cotter pin that is under the bell housing loose so that any oil can leak out there?

Yes. Pretty bad. It lost a quart from maybe 45min or so of finish mowing. Around 1800 RPM I think.
The videos should show where it's leaking. On one side it is just behind the starter. Similar on the other side.

 

[pomester]

I think you have an NAA there, not a 640. Tip-off is the nuts on the rear axle. Also the hydraulic lines from the pump rather than a cast aluminum manifold. And the toolbox in the running board.

Oil is coming off rather high on the machine for it to be the rear main seal and the oil looks rather clear/clean for engine oil unless you just changed it. If you have a pressure washer, do a thorough cleaning of the oily area and then try to pinpoint exactly where the oil is coming from.

It's nice to have a concrete floor/pad to do a split, but there are threads here about doing it outside utilizing plywood.

 

[TC10284]

I think you have an NAA there, not a 640. Tip-off is the nuts on the rear axle. Also the hydraulic lines from the pump rather than a cast aluminum manifold. And the toolbox in the running board.

Oil is coming off rather high on the machine for it to be the rear main seal and the oil looks rather clear/clean for engine oil unless you just changed it. If you have a pressure washer, do a thorough cleaning of the oily area and then try to pinpoint exactly where the oil is coming from.

It's nice to have a concrete floor/pad to do a split, but there are threads here about doing it outside utilizing plywood.

I haven't really used it much other than starting it up to run every month or so, and I added about a quart of fresh oil just before using it today. It was a little over full mark when I started using it to finish mow. By the time I got done, I let it sit, off, for maybe 30min while I ate supper and oil was showing maybe a quarter inch from the Add mark on the stick.

 

[a49deere]

That's not a rear main seal leak, appears to be coming from above! Not familiar with these tractors, Is there an oil pressure line above?

 

[TC10284]

That's not a rear main seal leak, appears to be coming from above! Not familiar with these tractors, Is there an oil pressure line above?

That's an interesting thought, because when I first start the tractor I see oil Pressure for a bit on the gauge. But as I use it, it drops to zero. That may not be related, but thought I'd note it. I'll look again.

 

[john in la]

A rear main leaks from the hole in the bottom of the transmission bell housing.
This leak appears to be running down the back of the motor.

My guess is the oil return holes in the block are clogged so the valve cover is full of oil causing it to leak.
This would also explain low oil pressure after running for a few minutes.

 

[TC10284]

A rear main leaks from the hole in the bottom of the transmission bell housing.
This leak appears to be running down the back of the motor.

My guess is the oil return holes in the block are clogged so the valve cover is full of oil causing it to leak.
This would also explain low oil pressure after running for a few minutes.

Would adding some Seafoam or similar to the oil help clean this up or am I looking at removing the valve cover, or more?

 

[showcrop]

As others are posting, it is probably nowhere near as bad as you fear because it is coming from too high. All of your pictures and video are of too low on the tractor for them to be of help to identify it. Removing the valve cover is easy. Just two nuts, and it just rolls out to the right side. If you need more room, you can always slack off the right rear, and front gas tank mounts. Most likely it is easy, cheap valve cover gasket or as John in LA posted a blocked oil return or two. Forget miracle cures and pick up your 9/16 combination wrench.

 

[TC10284]

As others are posting, it is probably nowhere near as bad as you fear because it is coming from too high. All of your pictures and video are of too low on the tractor for them to be of help to identify it. Removing the valve cover is easy. Just two nuts, and it just rolls out to the right side. If you need more room, you can always slack off the right rear, and front gas tank mounts. Most likely it is easy, cheap valve cover gasket or as John in LA posted a blocked oil return or two. Forget miracle cures and pick up your 9/16 combination wrench.

Thanks for that info. I've actually had the valve cover off before to replace the fuel shut off. But the oil leak was the same prior to removing the valve cover. I've had the valve cover (up top) and the valve adjustment cover(s) off of a different Ford tractor to replace the fuel shut off. I'm not afraid to do that, I just would want to have some pointers on where to look for those oil returns that may be blocked. I'm kind of new to tractors. My day job is IT, I can work on my cars (to a certain point) and my hobbies are small engines (single or twin - like 80-90s model Wheel Horse), so I'm not totally green to it all, but not well versed in certain things also.

Also, I will check again, but I don't recall seeing any leaks higher up than what my video shows, which is why I focused on that area. When I watch the oil drip, it forms a drip and looks to come from those areas that I focused on. Like watching a water drop form.

But I'll look again. Thanks again.

 

[TC10284]

I looked at it again briefly without running it, and I see where oil could potentially be pooling inside the valve adjustment cover area because I see fresher oil under/above the valve adjustment covers, but I don't see any evidence higher up. I am going to take those off and the valve cover on top of the engine and see if I can see anything going on there and try to clean oil drain passages with maybe a metal clothes hanger or a rag and some lighter air pressure.

 

[showcrop]

I looked at it again briefly without running it, and I see where oil could potentially be pooling inside the valve adjustment cover area because I see fresher oil under/above the valve adjustment covers, but I don't see any evidence higher up. I am going to take those off and the valve cover on top of the engine and see if I can see anything going on there and try to clean oil drain passages with maybe a metal clothes hanger or a rag and some lighter air pressure.

The "valve adjustment cover" is the highest point on your 640 engine.

 

[TC10284]

The "valve adjustment cover" is the highest point on your 640 engine.

Thanks! I've been working on a flathead 8n also lately, and learning the differences. Definitely appreciate the understanding there.

 

[cushman]

Thanks! I've been working on a flathead 8n also lately, and learning the differences. Definitely appreciate the understanding there.

You do not need to split it to change the rear engine seal,it is not easy but I changed one on an 860 about a year ago.It helps is you raise the tractor several inches with jack stands.

 

[TC10284]

An update:
I spent some of the weekend removing the valve cover, the push rod cover, the oil pan, replacing the oil pan gasket, cleaning up some oil sludge, I sprayed carb cleaner in all oil drain/passages I could find and all appeared to drain fine. There was some pooled oil in the valve area near the front left (it was leaning downhill that direction a little). Along with some sludge. Also replaced the oil filter and it was falling apart basically. I'm wondering if that was blocking some oil flow and causing the pressure to drop after a few minutes. I put in 5qts fresh oil with some MMO as extra.

Gave it a quick test. It started up and I immediately started seeing oil flowing from behind the starter. 100% flowing from behind the starter. So far I don't see oil flowing anywhere else but I didn't let it run long as I didn't want to waste my fresh oil.

The video isn't the best but you'll see what I'm seeing in the beginning.

Video:

New video · Sunday, May 17 🎬

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Where do I need to look now?

 

[TC10284]

Oh and the push rod cover bolts (not sure what else to call if it's not that) were fairly loose so that could have been causing some of the leaks on that side. The cork gasket under it was still intact.

 

[showcrop]

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.