1999 bobcat 763 shooting oil everywhere on back side of motor

[jyoniak]

Hi, I have a 1999 763 with 2050 hours I use at my Landscape Supply yard and recently oil started going everywhere behind the motor. I had a mechanic come out today and he said I had a blown piston. It still runs fine though just smokes real bad since all the oil on the motor. I believe.. Would it still run with a blown piston? Someone please help. He said I needed to spend $5500 for a rebuild. If oil is leaking could it just be a gasket? What is a for sure sign it is a piston causing oil everywhere?

 

[Tazza]

A blown piston i can't see blowing oil everywhere behind the motor.... It's inside the engine so there should be no external leaks. A piston crack or hole burnt into it, would cause excessive blow by and blue exhaust smoke.
Does it run a turbo at all? if an oil line is damaged ot could leak oil out and smoke too.

 

[Fishfiles]

on the back side the motor is a blow-by tube , this tube vents the crankcase to atmosphere ---- if a ring broke , a cylinder wall galled up or a piston got a hole in it you would see blow by pressure with oil mixed in blowing out the tube --------yes it will run with 3 or even 2 good cylinders ------to confirm the problem you should do a compression test of all cylinders , going thru the glow plugs holes is the easiest way

 

[jyoniak]

on the back side the motor is a blow-by tube , this tube vents the crankcase to atmosphere ---- if a ring broke , a cylinder wall galled up or a piston got a hole in it you would see blow by pressure with oil mixed in blowing out the tube --------yes it will run with 3 or even 2 good cylinders ------to confirm the problem you should do a compression test of all cylinders , going thru the glow plugs holes is the easiest way

The mechanic said cylinder 2 has no compression.. The breather tube on top of the heads is where the smoke and oil are shooting out.. Anyway to stop it from shooting everywhere? Any idea how much it is to fix it? Does it need a total rebuild that would cost round $5500?

 

[Miker67]

The mechanic said cylinder 2 has no compression.. The breather tube on top of the heads is where the smoke and oil are shooting out.. Anyway to stop it from shooting everywhere? Any idea how much it is to fix it? Does it need a total rebuild that would cost round $5500?

"Anyway to stop it from shooting everywhere?" Lol, duct tape?!? Seriously, if its coming out the vent tube, you could try capping or clamping it. Try using a mirror while its running to pinpoint the exact leak spot and you will probably be able to tell pretty quick if you can seal it or not.
That being said, lets say that any one of a number of evil scenarios has taken place and that particular cylinder has in fact lost its ability to maintain proper compression, I wouldn't run that machine any more than was necessary to get it onto a trailer, and back off again into a shop. The fact that it will run on only 2 cylinders does not mean it is wise to do so, since the metal fragments that were formerly part of the now non-functioning cylinder are slowly (or worse yet, quickly) making thier way around your engine, galling up everything that is near and dear to your motor.
The good news is that I have yet to spend $5,500 on rebuilding a motor of this size. If you have the mechanical aptitude to pull, teardown, reassemble, and reinstall yourself, you should be able to cut that cost down to half that $5,500 or less, assuming you can save the major components like block, crank, and head. Last motor like this I did was $1200 for parts including new connecting rods and pistons, and my machining bill was less than $500.00. I don't fully remember, but I think it was in the $200 - $300 range.

 

[Miker67]

"Anyway to stop it from shooting everywhere?" Lol, duct tape?!? Seriously, if its coming out the vent tube, you could try capping or clamping it. Try using a mirror while its running to pinpoint the exact leak spot and you will probably be able to tell pretty quick if you can seal it or not.
That being said, lets say that any one of a number of evil scenarios has taken place and that particular cylinder has in fact lost its ability to maintain proper compression, I wouldn't run that machine any more than was necessary to get it onto a trailer, and back off again into a shop. The fact that it will run on only 2 cylinders does not mean it is wise to do so, since the metal fragments that were formerly part of the now non-functioning cylinder are slowly (or worse yet, quickly) making thier way around your engine, galling up everything that is near and dear to your motor.
The good news is that I have yet to spend $5,500 on rebuilding a motor of this size. If you have the mechanical aptitude to pull, teardown, reassemble, and reinstall yourself, you should be able to cut that cost down to half that $5,500 or less, assuming you can save the major components like block, crank, and head. Last motor like this I did was $1200 for parts including new connecting rods and pistons, and my machining bill was less than $500.00. I don't fully remember, but I think it was in the $200 - $300 range.

And I guess to answer your specific question, does it need a full rebuild? Only a teardown will tell that, but whenever I take a motor down far enough to have a piston out so it can be replaced, I just do everything. That way I know that the rest of the components aren't going to fail in another two weeks for the same reason the first one did.
A little extra money now, but if in 6 months another cylinder goes, you would be kicking yourself for not having spent it.