[N2 Tractors]

The engine has low compression on one cylinder and engine was said to be puking oil into the air cleaner. Wondering what are some things that would cause this?

 

[dave_r]

maybe do a leakdown test to find if the problem is through one of the valves or past the rings.

w oil getting on the air filter, I find that's normally with excessive crankcase pressure (generally via rings or perhaps blown head gasket), and the crankcase vent tube that goes back to the intake winds up blowing oil onto the air filter.

 

[Frogmore]

puking oil into the air cleaner.

The general reason is the engine needs a rebuild. The low compression in one cylinder basically confirms it.

My X534 was doing it when I got it and I was really worried. But, the leak down test indicated a near new engine. Turns out the leak down test was accurate. The problem was the breather valve and filter. There was an upgrade kit that fixed it, but did require removing the flywheel.

I have not heard your model engine having a similar issue and the low compression on one cylinder pretty much indicates it needs a rebuild.

 

[denverguy]

In addition to the other listed things, potentially a bad head gasket leaking compression into the crankcase which a single low compression cylinder is consistent with.

 

[Mike514]

My 445 is in the shop for this (more light misting into the filter housing), burning oil, in addition to a few other minor issues. I believed the rings and pistons needed replacement. Haven't heard back from the dealer since they started work, so I'm not sure if theres any other concerns identified. Someonelse here has a Cub with the same Kawi engine and has a similar experience with oil in the filter.
I'd suspect rings and pistons.

 

[rickyracer583]

Regarding the low compression, more than likely the rings are worn and need replacing. However the valve clearances should be checked as well because if the valves are too tight, it can contribute to low compression numbers. A quick check would be doing a dry then wet compression check. If the compression does not improve slightly when doing the wet test, it's likely the valves.
Regarding the oil in the air box, I'd check and replace the M76125 crankcase ventilation valve assembly as well as replacing the air filter. A dirty air filter can cause an excessive vacuum through the crankcase ventilation valve and draw oil into the air box.
The FD620 engine is a very cheap and easy engine to rebuild at home if it has normal wear.

 

[N2 Tractors]

Yeah I did the wet compression test and the numbers went up on that cylinder by about 40 psi.

Dry test

Wet test

 

[N2 Tractors]

The engine was rebuilt by Deere shortly before this with new pistons, rods, crank etc. it was low on oil as well.

Previous owner pulled the engine and filter housing and left it outside exposed to rain. So when I went to do the compression test the offending low side puked some orangerusty water out of the spark plug hole. Not a lot but enough to know it was sitting with water in that cylinder. I was thinking maybe the rings froze to the piston but even if they did, they would not shrink from being rusted onto the piston IMO.

So it’s time for a tear down inspection then?

My next test would be to test valve clearance. I need to pressure wash the engine before I open up the valve covers. Otherwise I’d have checked clearance already.

 

[rickyracer583]

The engine was rebuilt by Deere shortly before this with new pistons, rods, crank etc. it was low on oil as well.

Previous owner pulled the engine and filter housing and left it outside exposed to rain. So when I went to do the compression test the offending low side puked some orangerusty water out of the spark plug hole. Not a lot but enough to know it was sitting with water in that cylinder. I was thinking maybe the rings froze to the piston but even if they did, they would not shrink from being rusted onto the piston IMO.

So it’s time for a tear down inspection then?

My next test would be to test valve clearance. I need to pressure wash the engine before I open up the valve covers. Otherwise I’d have checked clearance already.

Your compression test indicates the problem is most likely the rings. The minimum compression for the FD620 is 170# dry. Rust will not cause the rings to shrink but it will negatively effect the seal between the rings and the cylinder wall. It sounds like a tear down is in your future but it sounds like most of the expensive parts have already been replaced. You can probably get away with some clean up, replacing the rings and run a ball hone through the cylinder bore. I like using a ball hone because it follows the contour of the bore if it has a bit of wear in it and it leaves a nice crosshatch finish.

 

[rickyracer583]

Is this engine out of a tractor? What are your plans for this? Do you have the tractor? If I was going through this engine either for my own use or for resale, I'd measure all of the bearing journals and bearing bores along with the cylinder bores to verify they are within spec and not damaged in any way. I would then install new rings and run the ball hone through the cylinder bores, replace all of the plastic gears (oil pump and governor gear) and replace the water pump (around $60 at Scrubber City) and replace the crank seals as well. Reseal it with new gaskets and you should be good to go.

 

[N2 Tractors]

Regarding the low compression, more than likely the rings are worn and need replacing. However the valve clearances should be checked as well because if the valves are too tight, it can contribute to low compression numbers. A quick check would be doing a dry then wet compression check. If the compression does not improve slightly when doing the wet test, it's likely the valves.
Regarding the oil in the air box, I'd check and replace the M76125 crankcase ventilation valve assembly as well as replacing the air filter. A dirty air filter can cause an excessive vacuum through the crankcase ventilation valve and draw oil into the air box.
The FD620 engine is a very cheap and easy engine to rebuild at home if it has normal wear.

I’m going to look at the rebuild parts list to see if that valve was replaced. Looks very small and cheap too. Looks like it is part number 3 in the pic below.

 

[Just Jeff]

Compression tests are good, but not that informative. I'd do as suggested, and do an actual leak down test. With this, you can tell WHERE you're losing your compression, and determine how involved your rebuild needs to be.

 

[N2 Tractors]

Is this engine out of a tractor? What are your plans for this? Do you have the tractor? If I was going through this engine either for my own use or for resale, I'd measure all of the bearing journals and bearing bores along with the cylinder bores to verify they are within spec and not damaged in any way. I would then install new rings and run the ball hone through the cylinder bores, replace all of the plastic gears (oil pump and governor gear) and replace the water pump (around $60 at Scrubber City) and replace the crank seals as well. Reseal it with new gaskets and you should be good to go.

Yes I acquired this tractor with the engine already pulled out of it. It does not look like that valve M76125 was replaced.

 

[N2 Tractors]

Compression tests are good, but not that informative. I'd do as suggested, and do an actual leak down test. With this, you can tell WHERE you're losing your compression, and determine how involved your rebuild needs to be.

I can put compressed air into the cylinder using a modified spark plug and air fitting I welded together. Any idea how much air pressure I should use on this engine for the test? TDC on compression stroke?

 

[rickyracer583]

Wow!! The previous owner dumped a lot of money into it. Why was the engine pulled out of the tractor?

 

[rickyracer583]

I can put compressed air into the cylinder using a modified spark plug and air fitting I welded together. Any idea how much air pressure I should use on this engine for the test? TDC on compression stroke?

If you are going to put compressed air into the cylinders, I'd suggest you put a regulator in the line and start near zero psi and slowly work up, listening for any air leaking from the exhaust (leaking exhaust valve) carburetor (leaking intake valve) or crankcase ventilation valve (leaking piston rings) checked at the hose #1 on the parts breakdown picture you posted. I'd put the piston at the bottom of it's stroke so the compressed air doesn't push it down there for you.

 

[N2 Tractors]

PO pulled the engine and had deere rebuild it after their claim of not being able to get a new engine. This is why no hour meter was recorded on the rebuild sheet. He took it back for same blow by issue and valves were most likely too tight. The work order just says out of spec. Hour meter during this valve adjustment was 774.

 

[Just Jeff]

I can put compressed air into the cylinder using a modified spark plug and air fitting I welded together. Any idea how much air pressure I should use on this engine for the test? TDC on compression stroke?

I'm NOT an authority, but I believe 100PSI is the norm. I'm sure someone else will chime in and correct me if I'm wrong. And in normal situations, for a good operating engine, you should have no more than about a 10% difference. But we already know that your engine has issues, so the point of that is moot. I would just want to find out WHERE the compression is being lost, hence the leak down test.

 

[N2 Tractors]

Wow!! The previous owner dumped a lot of money into it. Why was the engine pulled out of the tractor?

I believe he wanted to repower it with a new engine. But did not want to drive to Nevada to get the engine. He is going to be getting a slightly bigger used diesel tractor with a loader on it from some one he knows. He does not seem too mechanically savy IMO but that's just my observation. He was able to get the motor in and out. So he know how to turn a wrench for the most part but I’m thinking he might not have a grasp of all the inner working of the internal combustion engine or knowledge and ability to do the research for causes of the problem. Very nice guy by the way. I’m in no way attemping to knock him and his abilities. I could not help but feel bad for him on the loss of his investment.

 

[denverguy]

Previous owner pulled the engine and filter housing and left it outside exposed to rain. So when I went to do the compression test the offending low side puked some orangerusty water out of the spark plug hole. Not a lot but enough to know it was sitting with water in that cylinder. I was thinking maybe the rings froze to the piston but even if they did, they would not shrink from being rusted onto the piston IMO.

Ah, the rest of the story. The compression differential all makes sense now - likely sticking rings in that cylinder.

You're probably headed for a teardown but you won't hurt anything by putting some hours on and seeing if it improves.

And based on the info you provided, I personally don't see a point in doing a leak-down test.