Bobcat 773 Blowing Smoke and Oil

[Andy Martin]

Hi.

I have a Bobcat 773 with Kubota engine and 2500 hrs. A few days ago I noticed the engine gurgling after shutdown and the temperature gauge was slightly above the operating range. Sure enough it was low on antifreeze. I filled the radiator and replaced the air filter (it was embarrassingly dirty). Upon restart it seemed to be fine so I hooked up my brush hog yesterday and drove a 1/4 mile to mow. I was watching the temperature gauge and it was hot but still in the operating range. Then the engine started smoking and smelling and I drove it back to the house. It was really smoking when I got home and temperature was into the hot range but not pegged. When I started it this morning it smoked profusely and was blowing oil.

I'm assuming it can be broken rings but maybe just a blown head gasket. Can the head be pulled without pulling the engine or should I just pull the engine out? Or is there a potentially smaller problem I should look for first?

 

[thepumpguysc]

Remove the rad cap while running.. bubbles mean compression in cooling system..
WHITE SMOKE?? Does it smell sweet like antifreeze..
Could be a head gasket, could be a cracked head..
How about a stuck closed thermostat..

 

[crewchief888]

most of the kubotas ive worked on never bother to blow a head gasket when they get hot...


they go right to cracking the head....



:drinkup

 

[Andy Martin]

OK, thanks, guys. My plan is to pull the head in the tractor as the engine had such good compression I'm expecting the cylinders to look good.

Any comments?

 

[BSM773]

When you get the head off, lay a straight edge on the surface of the head and make sure it is not warped. Mine warped years ago so I took it to a machine shop and resurfaced it, been working fine for prolly 10 years now.

 

[thepumpguysc]

Let us know what you find.. I might be able to put you intouch w/ somebody if you need a head.

 

[Andy Martin]

Got the head off my 773. It is obviously cracked between the injector chamber and the inlet valve in cylinder two and three.

 

[crewchief888]

Got the head off my 773. It is obviously cracked between the injector chamber and the inlet valve in cylinder two and three.

View attachment 159793

thats typically where they crack....

:drinkup

 

[Andy Martin]

I'm also seeing a mark I can't feel in cylinder two. Possibly a broken ring? It would only have had less than an hour if I have a ring broken.

 

[lantraxco]

Just damn.... :Banghead

 

[Andy Martin]

I'm looking for a head

 

[crewchief888]

I'm also seeing a mark I can't feel in cylinder two. Possibly a broken ring? It would only have had less than an hour if I have a ring broken.

View attachment 159794

ive seen them is worse shape that still ran....


:drinkup

 

[Andy Martin]

Thanks for your sage advice! I thought to check #1 and #4 (no head cracks) and found the same scoring. Again I couldn't feel the marks, so it's just going to get a new head.

Thanks again!

 

[Andy Martin]

Any advice on installing the head gasket. I have a service manual but it does not mention coating the gasket with anything. I have the torque, pattern, and repeat after hot.

Thanks, Andy

 

[thepumpguysc]

check your in-box.. good luck

 

[crewchief888]

head gasket goes on dry.

i typically dont re-torque after a heat cycle, just go 5 ft/lb over.

run your torque pattern, wait 5 or 10 minutes, then re-torque,
if any of the bolts take torque, ( the center bolts typically will) repeat the process until you get a consistent "no torque"

:drinkup

 

[Andy Martin]

Thanks CC888!

One more question. Is there any reason to stay with propylene glycol coolant?