M18 Oil Pressure issue
 

Hello all. I just bought my first 1872 super. The M18 has an issue with oil pressure after it heats up to operating temperature. I'm running 30wt oil. When I first start the engine when it's cold my oil pressure at idle is 25 psi. When I begin to mow the pressure rises to 50 psi. As I continue to mow the pressure begins to drop to around 12 psi. When I idle the engine down the pressure drops to near zero and the pressure light flickers. I've mowed with it 3 times and the above has happened each time.

This deeply concerned me so I pulled the engine and removed the closure plate to inspect the oil pump. The oil pump appears to have no problems. The pump gears appear to have no wear and the shaft is tight and turns when I turn the crank.

The pressure relief ball and spring are in place. Has anyone ever experienced the spring loosing its spring tension over time allowing the ball to open and dump oil pressure. I considered stretching the spring to see if this would help the low pressure issue. I've heard of putting in a stronger spring to increase oil pressure in certain oil pumps in cars.

Anywhere else the engine could be dumping oil pressure? The sleeve bearings seam to be tight and there is no rod knock. I've read in another thread that talked about the pickup screen clogging, but wouldn't it have low oil pressure when it was cold as well?

Thanks for the help!

I assume it has fresh oil and filter?

Seems I had to pull the switch/sensor off of my m18 to clean some debris--probably stirred up during a ring job. Anyway, the idiot light has stayed off for a year now. Never hooked up a gauge to see the real pressure.

Yes.

Thanks

I had an intermittent oil light problem with my M18. I looked into the oil pump and relief spring but they looked fine. I was worried it needed a rebuild. Then I followed advice I received on this forum to check for a restriction in the oil lines. Remove the oil filter and blow air through both lines to see if it is restricted. Double check the filter number.

In my case someone had collapsed one of the oil lines with a hose clamp.

I also had a mag 18 with oil issues and it turned out to be a collapsed oil hose. When I took them off I blew air through them and one would barely let any air through.

I'll check my oil hoses and oil lines. Thanks so much!

if you look @ the oiling system diagram, the M-18 pressurizes the cam on the pto end and the crank, and rod journal.
it also pressurizes the hollow cam to lube the other end of the cam as well as feeds the other end of the crank & rod journal.(flywheel end)
A loss through excessive clearance in each & every journal will cause low pressure when the oil is hot.
They can run as high as #80 when cold with tight clearances.
#10 @ idle when hot is as low I'd want to see on a high hour machine.
But check your oil lines as mentioned.
I don't use cooling lines/remote filters, I use a block mounted filters, but some don't like them because they are messy when changing filters.
Now as far as a plugged screen, it is possible because you are restricting the flow (amount) of oil.
The pressure relief ball is just that, it relieves the pressure in the system that is in excess of the rated spring pressure.
If the flow is not there, you are not going to build pressure.
To make you feel better, a lot more engines are running without oil pressure gauges than are using them.
No gauge = no worry.
Ya I know I like a gauge also, but my main mower don't have one.
And it has a lot of hours on the rotating parts.
If it goes "boom", I just slip in a spare engine and fix the old one.

Thanks ol'George for your insight to my problem.

I'll share some history that I have discovered as I have progressed with my investigation of what's going on.

First of all I bought this super as a 2072 from a person I have known for over 40 years. He told me it had the M20 engine in it and I had no reason to doubt him. 20 years ago he had bought an 1872 and shortly after he bought it, a screw that holds the air filter assembly to the elbow on the carburetor came loose and got sucked into the # 1 cylinder. This screw got embedded into the top of the piston. He took the head off and found the screw and removed it. As of last summer, he was still using this engine in that same 1872, according to him.

When I pulled the engine out of this 2072, I discovered it had an M18 in it. I really didn't think much about it because a previous owner could have switched hoods or replaced the engine. The engine ran good with no smoke and no knocking.

While the engine was out I removed the heads and guess what I found on top of the number 1 piston? A nice dent left by a screw!

Moral to the story, Even someone whom you may trust, will still put the screw to you!

The engine only has 75 psi of compression in each cylinder. Both pistons are loose in the cylinders. I'm convinced this engine is wore out and I'm just going to put it back together and use 40 or even 50 weight oil in it and run it till it runs no more. I will be looking for a command engine to put into my 72 series super this winter.

Thanks for the help!

Why not get a brand new vanguard from small engine warehouse? I plan to order one for the 782 come income tax time.

If both cyl's have #75 it sounds like it has higher hours on it, and is prolly pushing a bit of oil in the air cleaner, but not slobbering.
It's been my experience #95 is normal.
Sounds like the "screw" didn't do a lot of damage or it would of long since died.
If you are comfortable with not rebuilding it go ahead and use it.
I'd run #30W oil and continue not abusing it, and it just might live a long time.
A little oil usage is to be expected, just keep it full and not neglected.
It is obviously getting oil, just loosing pressure because it is worn.
I like those engines as most here know.
They got an undeserved rap because of the series 1 predecessors.
Truth be told, they will and have run longer than some of the later OHV designs, under the same conditions.
They are smooth and torquey,
I doubt a person uses 20 hp in a super
Enjoy it.

If you haven't been intimate with an M20, they look pretty similar to the 18s from the outside, but they have different tins that "bulge" around the heads to accommodate the engine's longer stroke. Once you've seen them side by side, it's easy to spot a 20.

If you're looking to rebuild, the 18 will be a lot easier to find parts for.

The KT17 S1 only had about 5 PSI of pressure and the same basic design as your M18 and they can last a long time, even without an oil filter. I just picked one up in an early MTD 782 the other day and it's one of the better running KTs I've had, though I'm not sure if it's been gone through or how recently.

For what it's worth, while most KT and Mag engines have that oil pressure port, up until the 1810/11/12, it wouldn't have been used on a Cub Cadet. That includes all of the 682s and 782s ever built by IH/CCC. Not saying that it's a good thing to have low pressure, but it's not 100% sure to kill the engine immediately or anything, and sometimes ignorance is bliss.

If you can swing it, move that engine on to someone who wants to rebuild it before it throws a chunk of rod out the side of the crankcase and swap in a CH20 or vanguard.

I've also grown to like these engines.

While the series 1 is the same basic design, the oiling system is where it lacks.
It does share the same oil pump as the series 2 and magnum, but does not have an oil pressure relief spring, thus the low pressure.
Also the crank is not cross drilled to pressurize the rod journals, they rely on 2 drilled holes in the hollow camshaft to squirt oil toward the rod journals every other crankshaft revolution ( camshaft turns 1/2 crank speed)
so, while many are still running, it is not as desirable a system, compared to the improvements that the series 2/mags have.
Also the 2 and mags, have more and heavier webbing in the block as well as the mags have a larger diameter crank at the oil seal area for flywheel support.
As the Kohler engines were used in many applications like skid steers etc. they felt a need to strengthen that area of the crank.
I would not consider a series 1 as a replacement engine, but a series 2 and magnum would be a nice bolt in.
Understand,
i have nothing against fellows going to modern OHV designs.

I guess I don't understand this statement.
Cub Cadet used the KT I in the 82 series, but the late 82's had the KTII which did have a pressure lube system. The Mag motors (Same as a KTII only with magneto ignition) was used until the 1811 series tractors which included the 1872. So... yes, CCC used the pressure lube engine. Actually, CCC only used the KTI for a short time before they moved on to the better engine.

And yes, low oil pressure in a pressure lube engine will kill it. The KTII and Mag engines (as George has explained well) used a completely different lube system, so you cannot compare the oil pressure in a KTI to the II or M motors. They are apples and oranges.


To the OP:
FWIW, a pressure drop once heated up, is not all that uncommon, but it shouldn't go that low. I would replace the oil filter lines and the pressure regulator valve and see if that fixes it.

George I know there are at least two different SII crankcase castings, one with oil filter and one without. Do you know if both of them have the additional webbing?

Also, do you know if the later SII (with bypass/oil filter provision) casting is identical to the M18 casting aside from being drilled for the points?

I know they were making KTs up until the 90s, and I can't imagine they would be making both engines with two different crankcase castings when they are identical.

I was talking about the oil pressure port. IH/CCC used horizontal twin KT engines without oil pressure sensors, so you would never have known what kind of oil pressure you had unless you put a gauge on it, which it didn't come with. I'm sure a lot of engines died from low/no oil pressure over the years, which is for sure one of the main reasons for the oil sentry in later engines, but I'm sure a good deal of them have oil pressure issues that ran for a good long time before they blew.

They all had the pressure port. They just didn't all have a pressure sending unit/oil light. None of them had a sentry system, as CCC didn't use a low pressure shut down on any of their machines. As I recall, the light didn't come on until pressure was below 5 psi.

Kohler referred to the sending unit and wiring (3rd wire on the harness) as "oil sentry". The system on the 1800 series is also referred to as "oil sentry" even though it doesn't shut down the engine. It was up to the manufacturer what to do with the low oil pressure sensor. CCC just decided to put a light on the dash instead of putting in a circuit to kill the engine.

On my 682 M18 swap, I wired in a 10s time delay relay to kill the engine if the oil sentry switch senses low oil pressure (~3.5 PSI per the service manual) since I wanted to keep the dash factory stock but still have some protection from low oil pressure.

Yes, I understand what the books call the oil pressure switch system. But just like the part books call the magneto an "ignition module" there is nothing about that part that is a "module". It is still a magneto no matter what the book calls it.

I can't tell you if the last Kt blocks were the same as mag blocks as I don't have a late kt block to compare to a mag block.
I do know they eliminated gaskets and went to RTV sealant,and caution that if the pto cover had a gasket, to reinstall with one.
That would indicate the .020 or so gasket thickness, was taken care of in the cover, not the block.
I personally don't think it is critical as far as the cover with or without a gasket.
I think the series 2 had the thick webbing but can't swear to it.
Don't disrespect a series 2 block without an oil filter provision.
Production went to many manufactures that didn't request/require it so it was not provided by Kohler.

The jugs on the late mags went to a *30 valve & seat angle.
Also the right & left jugs were different in at least 2 ways.
One for a magneto mounting, also a hardened valve seat for the exhaust valve.
So while the jugs will bolt on, they would not have the correct valve seats and the mounting holes for magneto mounting.
IIRR also the camshaft has a different part number for the *30 valves
it is covered in the service manual.
But again I don't see why either cam will not work in either magnum block.
other than the mag cam has no lobe for ignition point activation if installed in a kt block.





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Currently sitting on about 10 complete KT17s. 2 series 1s and 8 series IIs.

I have about 50/50 oil filter blocks and non-oil-filter blocks for the series IIs.

I just snagged a KT a couple weeks back that has a 1997 serial number on it (oil filter block), so they must have made both the M18 and KT17 at the same time for quite a while. It doesn't look any different than my other KT SII oil filter blocks, but I'm not going to tear it down to find out since it allegedly runs really well. Just seems like it would be a waste of resources to keep two different castings around if you're making basically the same engine.

I seem to recall in the M18 service manual that the jugs were swappable until the 30* valve change. The bosses are on even the KT jugs for the magneto mount, but they'd need to be drilled and tapped obviously .

Thanks so much for the interesting discussion on the KT series and magnum series engines.

After a closer examination for crankshaft side play, I discovered that both sleeve bearings have excessive play in them. This is most likely where most of the oil pressure is escaping from.

If I had only had a low oil pressure light I most likely would have never have discovered the low oil pressure at idle because the light barely flickers. Thus I'm wondering how many other high time engines keep going, going, and going with low oil pressure.

Here is a couple of pictures of the screw dent on top of the piston and on the head. I thought you all might be interested seeing this

That’s pretty crazy.

There are different sized thrust washers you can get to take out the end play. There is usually very little wear on those bearings though. There were .010 and .020 bearings available but I don’t know how hard they would be to find.

Ok..... so I'm going to call BS on this. An engine bearing has about .002"-.003" running clearance. If it is loose enough that you can literally rattle the crank in it.... the seal would be leaking and you would likely not have any oil reaching the rear bearing. It would have to have a horrific amount of clearance for you to be able to "feel" it. My bet is when you jerked on it, you felt the crank end play, which is normal. If the main bearings were wore enough that you could actually feel the movement in them, you better be looking for another engine because that one may run a couple more hours.


Hopefully you still have the head off. A dent like that will cause hot spots on the piston and the head. You need to take a die grinder or a dremel with a grinding wheel on it and smooth out the dents. Don't make them any deeper, but wider is fine. No sharp/thin spots. Nice smooth sides into the crater. That will keep them from making hot spots and causing pre-detonation. It will be fine with the divets but they need smoothed out.

On another note, It appears someone has used scotch brite pad on the head.
Not what I like to see for a good seal for the head gasket.
Be sure to use sandpaper on a surface plate or flat glass to restore it flat.
I will not use a scotch brite pad on any machined surface,
I've seen a few surfaces ruined.

Yes, the crank seals were leaking and leaking really bad. I do see severe SIDE play on this crank on both bearings. It's not end play that I'm seeing. This engine is shot. You yourself J-Mech have said in several other posts that magnum engines are not worth overhauling because of the extreme cost of the parts. You have said that they are a disposable engine. I considered buying .010 over pistons from baktforkids on Epay, but when I found the play in the sleeve bearings, I decided no more! You're right, this engine is on it's last leg and may only last a couple more hours. That's why I'm putting it back together and not spending anymore money on this engine.

It's time to lick my wounds and move forward. I got taken on this engine. It was always my intent to find a super and put a command engine in it with the CV joint drive-line. I guess I'll be doing that sooner than expected. In the meantime I'm going to find out how much more this engine can take. If it goes boom, then I still have my 3000 series with a 60" deck to fall back on.

I used a wire brush on a bench grinder and also a rotary wire brush on a drill. I'll keep this in mind for future reference. I've always cleaned with wire brushes and haven't had any ill effects from doing so, so far.

I sure thank you for the advice!

I wanted to post a follow up to my oil pressure problem.

I had a low time MV14 engine that I had robbed the cylinders off of. I decided to check the sleeve bearings on this engine and found them to be in good shape. I cracked the case on my M18 and found the crank in good shape.
So I replaced the sleeve bearings and checked the rest of the engine. I found the cam in good shape. The governor gear had some play in it so I replaced it as well as the rotor set in the oil pump.

I put it back together and ran it today. When hot I now have 50 psi high speed and 25 psi at idle. Major improvement from almost zero!

We'll see how it holds up over time. Thanks so much for all the help!

Excellent news. If I recall, there is a slight difference between the jugs on an MV and an M. I can't remember exactly what it is, but I'm sure someone else on here knows.

Also, there is a TSB to "pin" the governor stub shaft. Don't know if you're worried about that or not, but it's something I like to do on my M/KTs.

The vertical jugs have an oil drain back hole drilled in the spigot, or mounting base if you prefer.
Since the horizontal block is not drilled for a matching hole, there will be no problem.
But if horizontal jugs are used on a vertical engine,(no hole)
the drain back holes will need be drilled in the spigot, or the oil will pool in the valve spring chamber causing too much lube oil remaining in there.

Good info George, but if I understand him correctly..... he pulled the used bearings out of the MV14 and put them into the M18. Swears the crank was good. :ScrewLoose:

I love the H motors.... but I hate to fix them. Such a poor design.

If his main bearings were worn, and the inner and outer rotor of the oil pump
was found with a lot of clearance,
I can see the low pressure condition.
Those cranks are hardened, been my experience they are pretty tough.
The main bearings are costly, but I think they are still available.
I'm optimistic, if he assembled it properly.

Never seen a crank that wasn't hardened. Never seen a crank so loose you could wiggle it in the bearings that was still good. By the time they get that loose.... everything is done. If it ran low on oil that much, it had to hurt the rods. I give it less than 50 hours. I would never go to the trouble of tearing down a split block and putting it back together with used parts. Talk about a waste of time.

I'd like to say something J-Mech. I have no reason to lie about anything I post here. You can believe me or not. I am a disabled person who lives life from a wheelchair. I spent my last dime on getting this super and saved to buy one for quite a while. I not a dumb-ass as you seem to be implying. I have to be frugal with my money. I broke every rule of engine rebuilding by using used bearings. I didn't have $140 for a pair of new bearings but I had these from a low time vertical Magnum engine I had robbed the jugs off of. I must have done something right to get the oil pressure back up to 25 psi at hot idle from almost zero.

Before I opened the case I checked the cam to see if I could wobble it though the opening under the closure plate. It was tight. I opened the case and checked the crank. It did not have scratch one. PERIOD! I removed the old worn sleeve bearings and put on the used bearings. Hmmm! No play in them. Checked rods. No play. Reassembled engine. Ran it 3 hours today. 47 to go.

I can't explain it. From the side play I had on these bearings you would think the engine was shot and I expected it to be shot. Both bearings were extremely worn. There was no indication that these bearing had ever been starved for oil. They were just worn out! I can't explain it.

I will take a picture of the hour gauge tomorrow. I doubt I'll be able to put 50 hours on it the remainder of this season, but like I said before, 3 down 47 to go.

I've seen so many cranks that "didn't have a scratch" on them that were wore beyond spec I can't count. Unless an engine had a catastrophic failure, that's usually how they wear. Evenly. I'm sure a set of used bearings and oil pump did tighten it up. No doubt in my mind. You say you couldn't "feel" any play in the rods. Great. You understand that the rod should only have like .003" clearance right? (Likely more like .002", but I'm not going to go look up the spec.) Even if they had twice that you wouldn't be able to "feel" it. Unless you used a mic on the main journals of the crank, took the rods off and mic'd the journals, inspected the rod bearing area, then plasti-gauged them to see what the clearance was, you have no clue on earth how much wear there was on any of those parts. So.... after all the time you spent doing that work, let's say it runs 40 hours and let's go. Now what? Now you are time and money behind when you could have checked those parts while you had it apart, saved your pennies and fixed it right. Then you might get 500 hours out of it instead of 50. Even if you do get more than 50, you are only running on luck and hope. Neither of which is a good plan. How do I know you didn't just mistake the end play as side play? Did you put a dial indicator on the flywheel or PTO and measure it??) Unless you did the checks that I listed, you are only guessing. Unless you have a whole lot of mechanical experience, and even if you do, guessing is never accurate. Grabbing internal parts like rods and jerking them around to see if they have play is not "checking" them. Looking at parts and running your fingers across them is not a good indicator of wear. I don't want anyone reading this for the first time and wanting to do a rebuild on an engine thinking this is how you do it.... that's why I make these posts.
Good luck with your engine. That's really all I can say.

I agree with everything you said. I want to thank you for all your help and the help from others in this forum. Thank You!

I just wanted to wish you good luck on your low cost repair job. When the money is low and you have the time to do the labor there is nothing wrong with a patch job with used parts. I hope it runs for a good long time for you. Back when I was first married and money was tight I was able to buy very cheap three KT-17 warranty engines from a local JD dealer who replaced them when they threw a rod. I was working at a parts store with a machine shop and the machinist and I straightened the best crank, he turned it down just enough to get the rod journals round and then took the two best rods and cut the caps and honed the bores to fit the crank. We honed the cylinders, used the best two pistons and main bearings from the three engines ground the valves and seats surfaced the heads and re rung it. The only new parts I had to buy were two sets of rings and a gasket set. This patched up KT-17 ran for many years mowing and when I traded off the 109 I had installed it in I traded engines with my brother who had a tired Kt-17 in his Simplicity and he used it for another six years before it finally gave up. So you never know your engine may last 50 hrs or could go 500. Good luck.