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Discussion Starter · #1 ·
Hello Everyone,

I have a Kohler Command CV732-3011 on my Kubota 54" Commercial ZTR that suddenly started burning LOTS of oil. Here are some specifics:

Kohler CV732-3011
Serial Number: 4401404961
410 Running Hours
Engine Oil & Filter Changed 2 - 3 times a season & using SAE 30 as recommended by OEM

In the course of a couple of weeks, the engine went from burning no oil to burning a quart in 2 hours of running time. Engine runs great - no starting, idling, or loss of power issues. It's not leaking oil anywhere and does not smoke (blue, white or black) on start-up or while running. Plugs are not fouling (no soot, tar, evidence of overheating, etc.) and the gap is correct. Engine compression is about 125 pisg on both cylinders (wet method) and does not bleed down after a couple of minutes. Read online that improper float adjustment could be the issue so I rebuilt the carb and set float per OEM recommendations. I don't smell any gas in the oil and the oil is not getting a "burnt" smell or dark color over time. Switched to SAE 40 but haven't seen a difference.

I'm stumped so any recommendations are appreciated. Thanks in advance for your support.

LSUSIEGEL
 

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See if you're getting oil coming out of your breather tube. That will indicate if you're getting crankcase pressure.

Crankcase should have a vacuum @ -4" of H20 minimum. You can't read crank vacuum with a standard vacuum gauge, most read in inches of Hg. You need a water manometer, or a vacuum gauge that reads in H20 (water)

At 410 hours, I'd expect to see -7" of vacuum. A new Command Pro will usually run above -10" crank vacuum.

You read crank vac at either the breather tube, or the dipstick tube.
 

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Discussion Starter · #4 ·
You most likely have a blown head gasket.
Thanks harry16 - with a blown head gasket, would I still have good compression?
See if you're getting oil coming out of your breather tube. That will indicate if you're getting crankcase pressure.

Crankcase should have a vacuum @ -4" of H20 minimum. You can't read crank vacuum with a standard vacuum gauge, most read in inches of Hg. You need a water manometer, or a vacuum gauge that reads in H20 (water)

At 410 hours, I'd expect to see -7" of vacuum. A new Command Pro will usually run above -10" crank vacuum.

You read crank vac at either the breather tube, or the dipstick tube.
 

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Discussion Starter · #5 ·
See if you're getting oil coming out of your breather tube. That will indicate if you're getting crankcase pressure.

Crankcase should have a vacuum @ -4" of H20 minimum. You can't read crank vacuum with a standard vacuum gauge, most read in inches of Hg. You need a water manometer, or a vacuum gauge that reads in H20 (water)

At 410 hours, I'd expect to see -7" of vacuum. A new Command Pro will usually run above -10" crank vacuum.

You read crank vac at either the breather tube, or the dipstick tube.
 

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Discussion Starter · #6 ·
Thanks Bob. What do you mean by oil breather tube? If the vacuum isn’t adequate, what can that indicate? I’ll get the correct vacuum gauge and check at dipstick.
 

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A couple of things can pressurize your crankcase. Blown head gasket, or bad ring is most common. Notice the small cylinder on the top of the left rocker cover in the picture below. There may be one on each side on the CV730 and those are the crank vent filters. They are attached to a tube that comes off the top of the block. That is your crank vent tube and it acts to recirculate crankcase fumes back through the engine as a form of EGR (Exhaust Gas Recirculation) pollution control.



If there is to much pressure in the crankcase, it will carry oil along with the fumes and you'll start to burn oil. If you're burning oil, the plugs will be a dark black. If the plugs aren't black, you're not burning oil you're leaking it.

Command Pro engines don't run a pan gasket, they just use a sealer between the aluminum pan and the block. They are notorious for developing oil leaks at right around 400 hours as the pan bolts loosen from the aluminum block/pan expanding and contracting. There is a tube that passes between the pan and the block right behind the oil filter. It is sealed with an o-ring. That tube carries oil from the oil pump to the oil filter base. That o-ring will harden from heat and start to leak, but it's right behind the oil filter housing and most of the time you can't see it. The oil will usually leak down the engine mounting hole onto the top of the drive pulley/clutch. Since they are spinning when the engine is running, it will sling the oil all over the underside of the frame and it's hard to detect just looking down at the top of the engine (unless you notice oil spots on a concrete garage floor when it's parked). Take a peek at the underside of the frame below the engine. If it's wet from oil, there's a good chance that o-ring is leaking.

Another place to look for a hard to find oil leak, is the oil cooler lines as they come off the oil filter housing. Same thing... Cooler lines expand/contract from heat and the hose clamps start to loosen. Leaks on top of the pulley set up and gets slung all over the underside of the frame.

I've had 3 customer Command Pros this Spring doing exactly what I've just described. Customers swore they were burning oil, but they were ALL oil leaks. One of them the local Kohler dealer told the customer his $1,850 CH750 was shot and he needed a new engine which they would kindly install for $600. It was an oil leak at the cooler lines I charged $85 to fix (See "Treating People Right" post in this forum). The other 2 were the O-rings on the oil pump passage tubes.
 

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Discussion Starter · #8 · (Edited)
Thanks Bob - great advice & well written. I’ll check all of these things when the sun goes down & heat index is below 113F! I’ll make water manometer from clear tubing and measure vacuum at the dip stick or breather. I looked earlier this week & didn’t see oil under the engine or around the PTO clutch. My guess for now is a blown head gasket. Thanks again for the detailed response & I’ll let you know what I find.
 

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Discussion Starter · #9 ·
A couple of things can pressurize your crankcase. Blown head gasket, or bad ring is most common. Notice the small cylinder on the top of the left rocker cover in the picture below. There may be one on each side on the CV730 and those are the crank vent filters. They are attached to a tube that comes off the top of the block. That is your crank vent tube and it acts to recirculate crankcase fumes back through the engine as a form of EGR (Exhaust Gas Recirculation) pollution control.



If there is to much pressure in the crankcase, it will carry oil along with the fumes and you'll start to burn oil. If you're burning oil, the plugs will be a dark black. If the plugs aren't black, you're not burning oil you're leaking it.

Command Pro engines don't run a pan gasket, they just use a sealer between the aluminum pan and the block. They are notorious for developing oil leaks at right around 400 hours as the pan bolts loosen from the aluminum block/pan expanding and contracting. There is a tube that passes between the pan and the block right behind the oil filter. It is sealed with an o-ring. That tube carries oil from the oil pump to the oil filter base. That o-ring will harden from heat and start to leak, but it's right behind the oil filter housing and most of the time you can't see it. The oil will usually leak down the engine mounting hole onto the top of the drive pulley/clutch. Since they are spinning when the engine is running, it will sling the oil all over the underside of the frame and it's hard to detect just looking down at the top of the engine (unless you notice oil spots on a concrete garage floor when it's parked). Take a peek at the underside of the frame below the engine. If it's wet from oil, there's a good chance that o-ring is leaking.

Another place to look for a hard to find oil leak, is the oil cooler lines as they come off the oil filter housing. Same thing... Cooler lines expand/contract from heat and the hose clamps start to loosen. Leaks on top of the pulley set up and gets slung all over the underside of the frame.

I've had 3 customer Command Pros this Spring doing exactly what I've just described. Customers swore they were burning oil, but they were ALL oil leaks. One of them the local Kohler dealer told the customer his $1,850 CH750 was shot and he needed a new engine which they would kindly install for $600. It was an oil leak at the cooler lines I charged $85 to fix (See "Treating People Right" post in this forum). The other 2 were the O-rings on the oil pump passage tubes.
 

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Discussion Starter · #10 ·
Bob,

I removed the tube from the breather to the air intake and had pressure coming out of tube. There was also pressure coming out of the hole where the tube connects to the air intake. There is also pressure (not vacuum) coming out of the dipstick hole. I got under the mower and there are no oil leaks from the o-ring behind the oil filter or on the tubing to and from the oil cooler as you discuss above. On my mower, this area is accessible and there are no leaks. I have attached pictures of both plugs. They are pretty new and are now showing some black "crud" on and around the electrode.

So, is your diagnosis a head gasket leak? By looking at the plugs, maybe both head gaskets are leaking? While I'm changing the head gaskets, is there anything else you recommend I check/change while I'm in there? I was planning to change the intake manifold gaskets and the exhaust manifold/muffler gaskets as I will have to break those connections loose anyway. Unfortunately, I may have to pull the engine to get the heads off because of the configuration of the engine on the mower.

Thanks for your help Bob.

Mike
 

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That engine is a bum design that utilizes steel sleeves to align the oil galleries from the head to the block. The small seals on those galleries fail and allows compression into the crankcase. The other all too common issue is piston failure from a broken ring.

My suggestion is to simply replace the engine with an equivalent Honda, and never have another issue. I have never had one of these Kohler engines last over 100 hours without a major failure. Chinese product.
 

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Yep... You're burning oil from the look of the plugs. CV732 runs valve guide seals on the intake valves (2503214S), might as well change the valve guide seals while you have the heads off. Wouldn't hurt to lap the valves either. You don't need a valve spring compressor if you got a stout set of thumbs, but it makes it easier when you go to reset the collets.

If you have a set of telescoping bore gauges and a vernier caliper, you could check the bore dimensions while the head was off to see how close you are to needing a set of rings. 400 hours isn't much, but I just had to rebuild a FH691V Kawasaki because the rings were shot from the customer not changing the air filter from the day he bought it....
 

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That engine is a bum design that utilizes steel sleeves to align the oil galleries from the head to the block. The small seals on those galleries fail and allows compression into the crankcase. The other all too common issue is piston failure from a broken ring.

My suggestion is to simply replace the engine with an equivalent Honda, and never have another issue. I have never had one of these Kohler engines last over 100 hours without a major failure. Chinese product.
Beg to differ.... The entire line of Kohler engines are built in Hattiesburg, MS. I just went on a tour of their 400,000 sq ft plant last October and there weren't any Chinese any where in sight;).

BTW... I've never seen a Kohler Command Pro with "seals" on the block/head locating pins. What's the Kohler part# on those seals??

Is the Honda a better engine? Yep... Supposedly so, but it's also double the price as are any of their parts. I've got commercial customers that mow 50 lawns per week and have 2,000+ hours on their Kohlers with nothing but routine services.

Help me understand.... If Honda builds such a superior performing engine, why is it not even an engine option on a $12,000+ Ferris, SCAG, or Exmark commercial machine? You can get a Kawasaki, but nothing with a red blower shroud.
 

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Discussion Starter · #14 ·
Thanks for all the advice Bob Driver,

I had 2 blown head gaskets. The heads and pistons had a good bit of carbon buildup but the cylinder bores looked good. Cleaned everything up, lapped the valves, changed intake valve seals, rebuilt carb while I had it off, and changed breather gasket (the one between the cylinders). Also changed the gasket behind the oil filter and cooler lines & flushed out the cooler with mild solvent.

This Kohler is on a Kubota ZTR and the engine is turned "sideways". Nothing is easy to get to. The muffler is really in the way and has to come off to get to everything (governor, etc.). The muffler and governor were a SOB and fought me to the end! Twisted off one muffler stud getting it off, but thankfully it was sticking out enough that I could get a pipe wrench on it and it came out with some heat. This was a big job for me, but I enjoyed it except for the muffler and governor problems. The 113F heat index we are having was tough, but I got through it.

I cranked it after all the work and it appears to be running fine - no leaks and sounds good. Still needs a little adjustment on the governor but I'll do that next. Hopefully these issues are behind me and we won't have any more problems.

Thanks again for your excellent advice. The commentary from others about their brand preferences really aren't of any help and aren't appreciated. This forum is for those asking for help, not opinions on brand preference.

Thanks again Bob.
 
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