Cylinder head removal CH18S

[Steve G]

Hello everyone.

Cub has started smoking a bit of late and I am going to do a leak-down test soon when I get a break in the action 'round here. Engine is a Kohler Command CH18S. I suspect the head gasket on number 1 (and perhaps number 2 as well) needs replacement. I'll know after I do the test of course. Likely it is that or a valve issue, either way requiring removal of one or both heads. Never been down that road, and seems straightforward, but one issue is bugging me and I would like to get clear on that before diving in.

I've watched many a video but remain unclear on the intake manifold disconnection. Does the full intake manifold, carb etc. have to be removed to get the head off, or can I just disconnect it at the entry to the head? Appears removal of the entire thing would mean removing an additional shroud and dealing with some hard-to-get-to bolts. Hoping to keep things simple here, removing as little as possible. Normally I would just take it to the shop, but hate to be without it for six weeks or thereabouts at the beginning of summer with sevral acres to keep mowed, plus I would have to haul it over there and bring it back, and it would have it sit out in the weather awaiting its turn in the shop.
Can anyone provide clarification?


Thanks, Steve

 

[oldnslo]

Not sure if 18 and 20 are he same but on the CH20 I had to remove the intake to get the heads off. Do not remember if was because studs holding intake on or metal to metal interference though.

 

[Steve G]

That's helpful and much appreciated.

 

[tomplum]

Getting oil fowling on the plug? If you go that route, best to do gasket sets on both sides, breather gasket and be sure to check or replace the reed.

 

[RandyT]

Not sure if 18 and 20 are he same but on the CH20 I had to remove the intake to get the heads off. Do not remember if was because studs holding intake on or metal to metal interference though.

The 18-20-22 hp used the same block. The 18 uses a throttle plate limiter screw in the carb which isn't used on the 20. And the 22 uses spark advance.

 

[Steve G]

I do have oil fouling. Good point on replacing breather gasket and reed, and both head gaskets while I'm in there.

Having checked the service manual at this point, pretty clear intake manifold would have to be removed. Not an issue really provided (2) I can access all bolts with a socket (on the one video I have seen that shows the manifold removal process there was a very tight clearance on one of the bolts to the no. 2 cylinder head, such that a socket wouldn't even fit over the bolt), and (2) no bolts are seized so bad I can't loosen them after using penetrating oil as needed. Those are my biggest reservations. Plus removing the shroud is a pain - some screws are very hard to get to on my machine and my old body rebels against laying on the floor and contorting to reach some of them. Done it before, though, when I replaced the coils a couple of years ago. Not planning to pull the engine.

May post more questions when I get around to doing this (assuming I do it myself). All input much appreciated.

I'll do what's necessary at any rate. These old machines are far superior to anything new out there of comparable size I have seen. They are just old and out of warranty, like me, and need attention on occasion.

 

[5030]

Far as I'm concerned, Kohler hasn't made a good engine since the K series. Have one on my gas welder and it's flawless and I love the sound it makes when it is ticking over.

 

[tomplum]

Far as I'm concerned, Kohler hasn't made a good engine since the K series. Have one on my gas welder and it's flawless and I love the sound it makes when it is ticking over.

When engines were knarly and sounded like power. True. Lots of love for the Commands though. A bit over engineered at times...

 

[Steve G]

I ordered gaskets kits today. Unfortunately, the new-design beefed up gasket (24 841-04-S) apparently is intended to fit only the 25HP and larger commands. No beefier gasket available for the CH-18S.

Have any of you tried using the new-design gasket on a CH-18 (or a CV-18) Command? Looks like it would fit anyway. Just wondering. Could be worth a shot if passages and bolt holes are the same and it's just a matter of trimming the outside edge.

 

[tomplum]

The bore is 6 mm larger on the 25. I work on a lot more CV's than CH's. Less head gaskets every year as there are less around, but every CV or CH that I've done had the fire ring in the last decade or whenever they changed.
The nice thing with the Kohler kits is everything that you need including the torque instructions should be in there. The breather covers gaskets I change because 1) I'm there and 2) they have been revised many times.

 

[Steve G]

I ordered the specified gasket kit for the 18HP (24-841-01-S) and it's on the way. Guess I need to stick with that, and hopefully those have improved over time. I gather you are saying the new design would not work on the 18HP. Just hoping I might be able to avoid future blown gaskets best I can, on an engine known for blowing gaskets.

 

[Steve G]

I ordered the specified gasket kit (OEM) for the 18HP (24-841-01-S) and it's on the way. Guess I need to stick with that, and hopefully Kohler has improved those significantly over time. Just hoping to avoid future blown gaskets best I can, on an engine known for blowing gaskets. Wish they made one of those nice beefed-up gaskets for the 18HP.

 

[tomplum]

You would have to have them both there to know I suppose. They blow between the cylinder and oil return holes. The stock gaskets seem to have enough area there.

 

[Steve G]

Well, I had both head gaskets replaced, all valves lapped and new valve seals installed, and replaced breather reed and gasket. Pistons and bores looked good except for carbon build-up as expected. Seemed to be all set, until I got the deck back on and mowed. After about 5-10 minutes, started smoking again, plugs fouled and then heaps of smoke, as bad or worse than before. Went through lots of oil in a few minutes.

Did a leak-down test, which I should have done up front. It passed with 11% leakage on one cylinder and 13% on the other. Hardly any audible hiss anywhere. I am perplexed. No smoke coming out of breather tube, and zero oil. Changed the oil and filter just as a "why not" move, and smoking actually got worse.

Thinking right now must be oil wiper ring. Any thoughts? Given probable cost to do new rings on a 25 year old engine with probably 1600 hours or so on it, may be looking at a re-power situation. If so, can't say I didn't get my money's worth from the old engine.

 

[Steve G]

Also, any ideas on what the source of the oil might be? I thought about the fuel pump (mechanical), as a membrane separates the fuel from oil in the valve cover. All I can think of. Fuel flow is fine however.

If I have to re-power, wanted to ask has anyone here repowered a cub cadet 2185 / CH18S? If so what engine did you use and how did it go?

I see a "plug and play" 25HP command replacement for the CH18S out there. I don't need more power, and it runs around $3,500. Wondering if a CH640 could work, and if so what spec I would need. Same service manual for both CH18 and CH640 , so seems, to one with limited knowledge on the subject anyway, that would be an option. PTO shaft larger though, near as I can tell.

 

[tomplum]

I'm assuming that your oil shows no signs of fuel as the level is ticking down? Oil checked with the cap resting on top, but not screwed on the tube? Yes, fuel can transfer from the pump and also a carb issue such as float valve or the accelerator pump if equipped. The latter you will have a much more pronounced rich condition, black smoke etc.

You didn't mention what you found when you had pulled the heads off? How'd things look and you assembled according to the sheet?

It may be tough to see the smoke from the breather, so temporarily vent it outside. A strange thing that I've had happen on horizontal twins that had breathers that did blow oil mist were exasperated by another external leak, the dipstick seal.

It could be good to know if you are pressurizing the crankcase or not. I don't suppose that you have a manometer laying around? I wonder if you could do the glove test on this?

 

[Steve G]

Appreciate the input.

Faint smell of gas in oil. No indications of rich mix or unburned gas. No black smoke at all. Have had carb float issue you mentioned in the past. Not that. Agree there must be elevated crankcase pressure to have oil being pushed into the combustion chamber. Haven't done balloon but pretty sure what result would be. The question for me at this stage is the route, not so much the cause.

I didn't do the head gaskets, but the guy that did has done it many times for many years. No reason to suspect an ongoing issue there. He also replaced breather reed and gasket. Also, I tried diverting the end of the breather tube outside the air-filter housing away from the carb. as you suggested. Had no effect. Plus no oil even on the end of the tube. Breather system looks solid.

Fuel pump strikes me as one remaining possibility, but again, having no fuel-flow issues. Other than the fuel pump, that leaves the rings near as I can tell. Leak-test good, but maybe the oil-wiper ring is letting oil through. New gaskets, seals and lapped valves make combustion chamber tighter than before and maybe that's why it's gotten worse (more stress on rings, more differential pressure along sides of piston).

Bottom line is if oil is getting past the pistons and rings, regardless of the root cause, I need to re-power it. Time needed and cost of having rings done on a machine with that many hours not worth it relative to cost of a new engine, especially as it's early in grass-mowing season and here I sit with several acres.

Got my money's worth and more from the engine. Have seen CH18S's for around $1,400, supposedly in stock. May be my best option.

Thanks again.