BX2200 Misfire and Dark Coolant

[Kubota77340]

Morning all,

Thanks again to all who helped with my BX2200 electrical issues last month- everything works on my tractor for the first time since I've owned it!

New problem popped up while running it this week. Was mowing with a finish mower (48" Land Pride) and the tractor bogged down and misfired/stuttered. Load seemed to make some difference as the frequency and severity decreased with lower loads, but with virtually no load (mower off, running down the road) it still misfired some. No dark smoke or anything during these events, just a loss of power. I was running with 4WD engaged as the area I was mowing was soft.

After shutting down and cooling off, I noticed the coolant overflow bottle contained dark liquid- popping off the cap and looking it it did not appear to be oily, but rather sooty and I'm suspecting a head gasket issue. A crack would (I think) introduce oil into the coolant that would be obvious, I would think.

My BX has the D905 engine, if that is useful information. Radiator was new (maybe 50 hours) when I bought the tractor. Any advice/thoughts would be helpful.

Thanks!

 

[RCW]

Just for giggles, start it from cold and take radiator cap off. Just an idle and when cold, so nobody gets burned.

If there are bubbles in the top tank of the radiator, it's a decent indication of a head/head gasket is issue.

Not definitive, but a good rule of thumb.

 

[Kubota77340]

Thanks, RCW. Will do that tonight.

 

[85Hokie]

I would do what RCW mentioned ...... I am curious if the engine overheated - and if it will start up normally.

DO you own a infrared thermometer? One of those laser pointed thermometers? Handy things to have - they can tell what is getting hot and what is not.

Let us know what you come up with when you fire it back up

 

[Kubota77340]

I would do what RCW mentioned ...... I am curious if the engine overheated - and if it will start up normally.

DO you own a infrared thermometer? One of those laser pointed thermometers? Handy things to have - they can tell what is getting hot and what is not.

Let us know what you come up with when you fire it back up

Will do. Temperature gauge works and it gave no indication of getting hot. Starts normally most of the time, though yesterday it took an unusually long cranking to get it going. Oil is clean and of correct quantity so I know no substantial amount of oil is getting into the water if there is a crack.

I don't have a thermometer in my troubleshooting kit, that's a good idea and another reason to head to Harbor Freight today!

 

[je1279]

Could be an injector issue as well but that wouldn't explain the dark coolant. When was the last time the coolant was changed?

 

[Kubota77340]

Could be an injector issue as well but that wouldn't explain the dark coolant. When was the last time the coolant was changed?

Changed about 3 years ago when I bought it. Went through the big freeze here in Texas so I'm afraid of a crack, but will do the recommended troubleshooting to see what's up.

 

[Jim L.]

The dark stuff in the coolant overflow tank is a big clue to me. As RCW suggested, it is a quick check to open the radiator cap when cool and then watch for bubbles.

I would be less inclined to cold damage if it had antifreeze. More inclined that at some point in the past it was overheated and now premature failure at the head.

Another thing to do is to drain a slight bit from the oil drain. If you see water then there is another big clue.

 

[Mark_BX25D]

You can get a test kit that will tell you for sure if there is are exhaust gasses in the coolant.

test kit exhaust gas in coolant at DuckDuckGo

DuckDuckGo. Privacy, Simplified.

duckduckgo.com

 

[je1279]

Another option is to use UV dye in the coolant to see if it is mixing with the oil. This is only if head/head gasket failure cannot be determined by other means previously mentioned.

 

[North Idaho Wolfman]

Contaminated fuel / algae, water, or other crud.

 

[lugbolt]

Another option is to use UV dye in the coolant to see if it is mixing with the oil. This is only if head/head gasket failure cannot be determined by other means previously mentioned.

generally speaking on Kubota smaller diesels, coolant won't get into the oil if the head is cracked or the head gasket is leaking. The combustion and compression pressure is much higher than cooling system pressure (500-2500 psi vs 10-15 psi), and we already know from physics that pressure always moves from high to low. SOME automotive stuff, head gaskets and cracked heads will allow pressurized oil to leak from an oil passage to a coolant passage, but that's not common at all with kubota.

 

[Kubota77340]

Evening all,

Ran the cap-off test as suggested. Immediately started getting bubbles which very quickly became foam. As the foam broke down after shutdown, it was obviously exhaust soot that was the black particulate. Evidently I have a head or head gasket problem. Hard to invest what Kubota is asking for a new head if that's the problem. Any advice for next steps?

 

[Mark_BX25D]

I don't know of any way to tell if it's the head or the head gasket without pulling the head.

I don't know about your particular tractor, but generally, pulling a head really isn't a hard job for anybody who is handy with tools. A lot of the cost the dealer will quote is in the labor. A reman head is about a grand, it seems. That's just a quick search. A gasket kit will run you about another C note.

All that to say, it's not good news, but it's probably not time to scrap the tractor.

BUT STOP DRIVING IT!

If you get coolant into the oil, you will trash the bearings very quickly.

 

[Kubota77340]

Thanks, it's definitely parked. The trouble for me at the moment is time to mess with it. Probably will be sitting for a month or so. I'm thinking I should drain the coolant in the meantime?

 

[Mark_BX25D]

Thanks, it's definitely parked. The trouble for me at the moment is time to mess with it.

Yeah, that's a common ailment!

I'm thinking I should drain the coolant in the meantime?

Probably not a bad idea to drain it and flush it clean. That has to be done eventually anyway, and it might not be a great thing to keep those exhaust gasses in the coolant. Best case, they are harmless. Worst case, they are harmful. Which way do you want to bet?

 

[swpflipper]

If you're going to drain it and wait a bit to tear into it. You may want to take coolant and oil samples in to be analyzed and confirm the diagnosis. Then you know what your looking for.

 

[Kubota77340]

Morning all, thought I'd resurrect this zombie thread now that I've had a chance to get into the engine.

First, there was no water in the crankcase. Oil is still cleanish and of the right quantity.

Popping the valve cover, there was a waxy buildup on the top of the cover- maybe from condensed water?

After draining the coolant, I can say there was at least some glycol in the solution- it smelled strongly of anti-freeze, even though it was discolored with exhaust soot. I'm hoping this means the big Texas freeze was not the cause of the issue I'm seeing. 100% of the coolant was discolored with exhaust soot- no oily sheen on top of the drained coolant or anything, so I am convinced it is a head issue somewhere. I pulled the intake and found rust, which I suppose could have been caused by condensation while sitting, or by a coolant leak. Pulling the water temperature probe resulted in less than a cup of coolant coming out so I don't think the head was completely full of coolant, which is no surprise since it was making bubbles in the cooling system the last time I popped the radiator cap off.

Pulling the head, I could find no obviously cracks. The rear cylinder looked perfect, still had cross-hatch from honing on the cylinder walls. The front two weren't as good but still no major issues. The center piston has a rough spot that looks like maybe a corrosion spot, or possibly a burn spot from a plugged injector?

I could find no flaws in the head gasket that indicated a leak between cylinder and crankcase or cylinder and cooling system.

The head has no obvious cracks that I've been able to find even with intense lighting. The valve train was in good shape, though the center rocker arms detectable clearance between the valve stems and rocker arms whereas the front and rear did not.

Everything rotates very smoothly when turned over by hand, so I don't think there's a bottom end issue. At this point the only thing I can think is a cylinder head crack that I haven't been able to identify yet, so the next logical question is whether I find a vendor that can find the cracks, or get a new head and put it back together and see if it runs? And with the rough spot in the center piston, do I need to get into the bottom end and replace that, and if so, it looks like a complete overhaul?

-Kubota77340

 

[GeoHorn]

Deleted

 

[85Hokie]

This article might be good to do at home for head/block crack inspection

https://grassrootsmotorsports.com/articles/testing-cracks-home-diy-dye-penetrants/