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Old 09-09-2009, 01:55 PM   post #1 of 12
wh500special
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Default White Smoke from exhaust

I have a Kubota ZD28 with a 28hp 3-cylinder Kubota diesel engine (yes, I realize it isn't a CUT but this problem is related). It has about 2800 hours on it and has been running working flawlessly for this past year that I have owned it.

Occasionally on startup it will blow white smoke for 30 seconds and will then clear up. Sometimes I think I smell antifreeze in the exhaust but I can't be 100% sure. It doesn't seem to use coolant and I have not found any oil in the coolant or coolant in the oilpan. The white smoke mostly seems to be assosciated with shutting the engine down "hot" after working hard versus letting it idle to cool for a few minutes.

The other day while mowing I somehow managed to snag the plastic draincock fitting (mounted in a somewhat vulnerable position on the tractor frame) on a branch and it broke off. The coolant rapidly started to dump but I smelled it pretty quickly and got things shut down before the temp gauge hit the red area. But it got hot fast. I don't think it technically overheated, but it was hot.

A surprisingly meager $6 later to replace the broken fitting, some new coolant, and I was back in business. I started the tractor up and drove it from the spot where it had sat for a few days. It smoked a bit at startup, but nothing that I really thought was out of the ordinary given what happened. I parked it in the shed (only drove it a minute or two to get it back up by the house after the field repair) and it sat for a couple days.

Yesterday I had to mow so I started the tractor and had a pretty bad cloud of white smoke accompany the warmup for perhaps a minute or more. It seemed to stumble a little more at startup than usual, but started easily and quickly. It did completely clear up shortly though and I went ahead and mowed for a couple hours. Everything worked as powerfully and smoothly as always. I let it idle for 5 minutes or so to cool down after using it and noted that for about 30 seconds during the idling it blew some grayish smoke then cleared.

I shut it off, let it cool and later checked all the fluids. Everything was fine. Although the radiator was still pressurized (is this normal even after a complete cooldown). Again, no water in the oil, no oil in the water. So I restarted it and had another white smoke cloud that cleared in about 30 seconds. I shut it down and started to dread what might be the causes.

I did notice while the engine was running after mowing that the coolant recovery bottle was bubbling from air escaping the radiator overflow tube. And the crankcase breather was emitting some smoke too (but it always has since I have owned it). I expect some problems given the hours this thing has on it but it really still runs and mows like a new machine.

I'm looking for suggestions on what to check. I am thinking head gasket. Hoping that it isn't a cracked block or head. Really, it runs great. Just smokes at startup. I *think* I detect a whiff of antifreeze in the smoke but I'm not 100% sure. Perhaps it is extra fuel from a fouled injector?

The headgasket job looks to be pretty simple on this machine due to the position of the engine. But if this sounds like it might just be a characteristic of a 2800 hour engine I hesitate to open anything up. My biggest fear is a puddle of coolant sitting on top of a piston when I try starting it that can hydrolock the motor.

Steve
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Old 09-09-2009, 04:52 PM   post #2 of 12
Kenneth H
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Default Re: White Smoke from exhaust

I don't make my living working on engines, but the only thing that can cause white smoke in a diesel is water. I would suspect a head gasket since you are loosing very little.
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Old 09-09-2009, 06:22 PM   post #3 of 12
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Default Re: White Smoke from exhaust

Steve, smoke color in a diesel usually has different causes than a gas engine. White smoke on a gasser generally = coolant getting into the combustion chamber whereas it is usually a totally different problem in a diesel.

Generally, white smoke in a diesel = unburnt fuel in a cold engine, i.e. incomplete combustion.
Most common causes are:
1) One or more glowplugs aren't working which causes incomplete combustion in a cold engine.
2) You could have one or more injectors that are not atomizing correctly, i.e dribbling excess fuel, also a cause of incomplete combustion.
3) Injector pump is not timed correctly. I wouldn't suspect this unless you've had it off and/or have tried to adjust it.

It could also be as simple as bad/contaminated fuel.

Once the engine warms up to it's normal operating temperature it'll burn the excess fuel more completely so thats why you may not notice it once it's warmed up. Course seeing black smoke on a warmed up diesel can have the same cause as the cold engine w/white smoke.

Check your glowplugs and make sure they are all working.
Since you are now noticing the engine performance suffering some, you may want to pull the injectors and have them bench tested, that may bne a good winter time project
Let us know
Dave
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Old 09-09-2009, 09:43 PM   post #4 of 12
rscurtis
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Default Re: White Smoke from exhaust

The bubbles in the overflow bottle are the telltale sign of a combustion leak into the cooling system. Hopefully it's just a gasket, not a cracked head.
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Old 09-10-2009, 01:11 AM   post #5 of 12
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Default Re: White Smoke from exhaust

Here are some other things for you differential diagnosis...
When Engine Emits Blue or White Smoke
1.Cranking speed to low
2.Injection pump timing incorrect
3.Injection pump automatic advance is faulty or not operating
4.Injection nozzles faulty or sticking
5.Excessive wear in liners and/or stuck piston
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Old 09-10-2009, 03:57 AM   post #6 of 12
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Default Re: White Smoke from exhaust

One other thought is the glow plugs might not working as intended Volfant stated and the bubbling in the over flow might be just the fact that you had some trapped air in the engine when the drain **** was broke off and the air escaped into the overflow tank.

What I would do is mow one more time and keep a eye on the overflow and if it did it again then I would start to think it is the head gasket.
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Old 09-10-2009, 03:59 AM   post #7 of 12
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Default Re: White Smoke from exhaust

you might not see coolant in the oil but you will see oil in the coolant; check the radiator and see (I havent a clue about this machine tho if it even has a radiator lol) if theres oil floating along the top...
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Old 09-10-2009, 09:35 AM   post #8 of 12
wh500special
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Default Re: White Smoke from exhaust

Holy smokes guys, THANKS for the info.

I did some additional poking around on the net and it sounds like Kubota's engines will run virtually forever but leaking head gaskets seem to be somewhat common. Thankfully, a relatively minor problem.

I wanted to arm myself with a little more info - which you guys gave me - before talking to my Kubota dealer. I called today and he said that the gasket is the most likely cause, but it - of course - could be anything. He's checking on parts availability in their warehouse now.

His first question was if I'd used ether to start it (never have). Apparently that can wreck the engine and cause similar symptoms.

I wondered if I could possibly have a dribbling fuel injector too. Would that problem manifest itself in any way other than a little smoke? This thing runs VERY smoothly and has incredible power to run the 72" deck thru moderate grass at full speed (8mph). It starts easy but does/did make some gray/black smoke at startup - especially if I short cycle or skip the glowplugs. I have started it to move it down to about 25 degrees F, so the plugs seem to work OK.

I am still banking on the head gasket and praying that that's the extent of things.

The tractor has been sitting for a few days and I went out to look things over this morning and get serial numbers for ordering parts. I noticed a little seepage at the junction between the block and head. Just a little smudge of stuff that collected dirt and grass last time I mowed (I clean it pretty regularly looking for leaks). It seems to be mostly between cylinders, but overlaps the rearmost one a bit. I suspect when I open it up I will find coolant in that hole.

I am not seeing any oil floating in the radiator but it could be there. The bubbling in the overflow tank hade me think it could be the head gasket too.

Once I find out the parts costs I will get them ordered. He said he might have them in stock. It looks like all I am going to need is a valve cover gasket and a head gasket. I'll replace the T-stat too and asked if it needs new head studs and will do those as well if needed. Hopefully it pops off easily since I recall doing a Farmall H one time that had the head virtually bonded to the block (took a lot of cussing, prying, and wedges to get it off).

Thankfully my little problem happened now instead of after harvest begins because that makes the dealerships a madhouse.

This tractor has been an excellent mower. I bought it after my old Toro zero turn crapped out one too many times. We planned on only being in this house one more mowing season and all I was looking for was something faster than my CUT/6' deck to make mowing faster and easier (once you 've mowed with a zero turn, going back to a tractor seems like a punishment). This was for sale at a local JD/Kubota dealership after having been traded on a new one. It was priced at "market value" during the summer but when I bought it in the winter with 8" of snow piled on it I gave about 50% of that.

With the high hours I anticipated some minor problems and was prepared to spend a few bucks to keep it going. If it had needed no work I probably could have eBayed it and pocketed about $2k in profit. I had to rebuild the mower gearbox and now the head gasket, but my plan was to resell this thing when we moved at either a modest loss or at breakeven. My issue is more time-related than anything else since I work long and wierd hours.

It is in phenomenal shape with hardly a scratch or dent to be found. It was VERY well taken care of and it is much better condition than you'd suspect for such high hours. In it's history the transmission has been maintained well, the rear axles were upgraded to the new design, and it always was kept inside. I will hate to see it go when I move. It's a very, very nice machine - as are all Kubotas.

Hopefully I can have my parts before the weekend and can get this torn down and buttoned up promptly. I'll update as it goes.

THANKS again for the guideance, suggestions, and advice!

Steve
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Old 09-11-2009, 10:14 AM   post #9 of 12
T126
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Default Re: White Smoke from exhaust

Water is getting into the combustion chamber from one of the sources available ....head gasket blown allowing water to seep into the combustion chamber...not likely or you'd be seeing white smoke all the time.....
cracked cylinder head or cracked engine block...again not likely or it'd be smoking all the time....so that leaves me to guess that it is coming from the fuel source....may be water in the tank....may be condensing in the fuel filter. If you live in a very humid climate and depending on where and how you store the tractor water may be condensing in the fuel filter itself...hey I have seen this on my olf Ford 3000.....we sometimes use it for 20 mins and park it and may not use it for 2 or 3 months...it stays outside under an open shed so it will happen....
A lot of things can cause this problem but this is what I suggest to look for right now.... GOOD LUCK!!!! T
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Old 10-05-2009, 05:37 PM   post #10 of 12
wh500special
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Default Re: White Smoke from exhaust

Again, thanks guys for all the suggestions.

Removed the head - actually, time was at a premium and I had a real mechanic do it - and found that the gasket was indeed blown BUT the head is also cracked.

Bummer.

A new, bare head is a minimum of $800. Up to $1200 depending on the serial number break (I didn't have it readily available when calling for pricing).

Double bummer.

So, it's gonna cost me a LOT more to get this sucker back to A1 shape than I'd hoped. Don't have the budget for this right now, so I am going to button things back up and work on it over the winter when I have more time to do the labor myself. I hate to put money into something with so many hours, but the engine is spotless inside - as is the rest of the tractor - and looks new so it should probably be saved.

Just thought I'd file an update...

Steve
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Old 10-06-2009, 01:10 AM   post #11 of 12
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Default Re: White Smoke from exhaust

Quote:
Originally Posted by wh500special View Post
Again, thanks guys for all the suggestions.

Removed the head - actually, time was at a premium and I had a real mechanic do it - and found that the gasket was indeed blown BUT the head is also cracked.

Bummer.

A new, bare head is a minimum of $800. Up to $1200 depending on the serial number break (I didn't have it readily available when calling for pricing).

Double bummer.

So, it's gonna cost me a LOT more to get this sucker back to A1 shape than I'd hoped. Don't have the budget for this right now, so I am going to button things back up and work on it over the winter when I have more time to do the labor myself. I hate to put money into something with so many hours, but the engine is spotless inside - as is the rest of the tractor - and looks new so it should probably be saved.

Just thought I'd file an update...

Steve
Not to get your hopes up...but, depending on the crack..it might be salvageable...
http://weldingweb.com/showthread.php?p=323347
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Old 10-06-2009, 08:10 AM   post #12 of 12
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Default Re: White Smoke from exhaust

Hate to hear it wh500special. Paul's suggestion could be doable.
Thanks for the update.
Good luck
Dave
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