What did I do? Oil tank "popped"

[treeroot]

I have a stihl MS 391. I think its 3 years old.

I have had many issues with this saw including the chain not getting enough oil. I have learned to regularly clean the bar channel, clean the chain cover, clean the area where the oil comes out. This has helped a lot. I use a air compressor and blow out all these areas about every 2 gas tanks.

Recently the saw has been leaking oil when sitting. I did some reading I figured the hole where the oil comes out to the bar is probably clogged. So I followed a video which used a air compressor to blow this hole out.

I was cleaning the saw out tonight, and although it hasn't been leaking oil latley I figured I'd blow this hole out as preventative maintence.

Anyways, I put the air compress nozzle on the hole and gave it a bit of air and about 3 seconds later all of a sudden a fairly loud "POP" and oil shot everywhere.

I think my mistake was leaving the oil fill cap on the saw when doing this.

I can't figure out what popped... I wiped the saw down, opened and closed the fill cap and sat it on the floor. A bit of oil leaked out, but I'm not sure if its residual oil from the blow out or I popped something apart.

I don't have bar oil to fill it up (ran out today) so I'm crossing my fingers the pop was the oil fill cap. I can't recall if the cap popped off or not because I panicked and tightened it when the pop happened.



Any idea if I did some damage that I need to fix? If so, what is most likely wrong with the saw?


The other saw I've owned have had a rubber line under the oil tank which carries oil to the bar. I figured that's what popped off, but I can't find the line on this saw.. It should be right under the handle/oil tank if its like the other saws I've owned, but I can't find it.

 

[Justin Taylor]

First your saw should have a adjustable oiler, you can turn a screw to the max so you get more oil on your bar. The thing that probably poped is under the clutch we’re the Oiler is there is lines going to the tank. Ask if you have any more questions

 

[Justin Taylor]

And you shouldn’t have to keep using an air Compressor to the tank

 

[Mad Professor]

The oil pump has an inlet hose that goes to the tank and an outlet connector/elbow. You probably blew one of those off with the air.

To access the oil pump you need to remove the clutch.

Post chainsaw questions in the chainsaw forum. The guys there will help you out.

 

[treeroot]

Took it all apart.. oil line isn't leaking.

The oil case popped apart. I have no idea how this happened with about 40psi of air. You'd think the air will blow out the oiler holes.

Maybe the case was already splitting???

Either way... It's not fully split.. when I squeeze the halves together i can see movement and where they are splitting..

I'm wondering if I can clean it up really well and expoxy them together?

I read its quite a job to change the oil tank as its part of the main chasis. I don't mind the work, but if expoxy will fix it then I'd like to try that first.


I did fill the saw with oil and started it.. It's spraying out from under the muffler where the split is

 

[Mad Professor]

Took it all apart.. oil line isn't leaking.

The oil case popped apart. I have no idea how this happened with about 40psi of air. You'd think the air will blow out the oiler holes.

Maybe the case was already splitting???

Either way... It's not fully split.. when I squeeze the halves together i can see movement and where they are splitting..

I'm wondering if I can clean it up really well and expoxy them together?

I read its quite a job to change the oil tank as its part of the main chasis. I don't mind the work, but if expoxy will fix it then I'd like to try that first.


I did fill the saw with oil and started it.. It's spraying out from under the muffler where the split is

Bummer. That housing is part of crankcase too, crack there will cause a vacuum leak.

Lots of work but I'd be looking for a dead donor saw to swap your parts onto.

Post your problem in the Chainsaw Forum here. Someone might have suggestions. I've not done much work on those "clamshell" type saws.

One more thought, and less work. Find a straight gassed saw and put your piston and cylinder on it. LOTS less work..

@pioneerguy600 can you move this to chainsaw forum?

 

[Justin Taylor]

Took it all apart.. oil line isn't leaking.

The oil case popped apart. I have no idea how this happened with about 40psi of air. You'd think the air will blow out the oiler holes.

Maybe the case was already splitting???

Either way... It's not fully split.. when I squeeze the halves together i can see movement and where they are splitting..

I'm wondering if I can clean it up really well and expoxy them together?

I read its quite a job to change the oil tank as its part of the main chasis. I don't mind the work, but if expoxy will fix it then I'd like to try that first.


I did fill the saw with oil and started it.. It's spraying out from under the muffler where the split is

I have a extra crankcase for that saw if you need it

 

[treeroot]

What would you ant for the crankcase?

 

[treeroot]

Bummer. That housing is part of crankcase too, crack there will cause a vacuum leak.

Lots of work but I'd be looking for a dead donor saw to swap your parts onto.

Post your problem in the Chainsaw Forum here. Someone might have suggestions. I've not done much work on those "clamshell" type saws.

One more thought, and less work. Find a straight gassed saw and put your piston and cylinder on it. LOTS less work..

@pioneerguy600 can you move this to chainsaw forum?

Thanks!

Where would the vacum be? in the oil case?

Any thoughts to epoxying it?

 

[Justin Taylor]

What would you ant for the crankcase?

Pm sent

 

[lone wolf]

I have a stihl MS 391. I think its 3 years old.

I have had many issues with this saw including the chain not getting enough oil. I have learned to regularly clean the bar channel, clean the chain cover, clean the area where the oil comes out. This has helped a lot. I use a air compressor and blow out all these areas about every 2 gas tanks.

Recently the saw has been leaking oil when sitting. I did some reading I figured the hole where the oil comes out to the bar is probably clogged. So I followed a video which used a air compressor to blow this hole out.

I was cleaning the saw out tonight, and although it hasn't been leaking oil latley I figured I'd blow this hole out as preventative maintence.

Anyways, I put the air compress nozzle on the hole and gave it a bit of air and about 3 seconds later all of a sudden a fairly loud "POP" and oil shot everywhere.

I think my mistake was leaving the oil fill cap on the saw when doing this.

I can't figure out what popped... I wiped the saw down, opened and closed the fill cap and sat it on the floor. A bit of oil leaked out, but I'm not sure if its residual oil from the blow out or I popped something apart.

I don't have bar oil to fill it up (ran out today) so I'm crossing my fingers the pop was the oil fill cap. I can't recall if the cap popped off or not because I panicked and tightened it when the pop happened.



Any idea if I did some damage that I need to fix? If so, what is most likely wrong with the saw?


The other saw I've owned have had a rubber line under the oil tank which carries oil to the bar. I figured that's what popped off, but I can't find the line on this saw.. It should be right under the handle/oil tank if its like the other saws I've owned, but I can't find it.

Thats why I dont put any faith in YouTube repair videos! Yes you should have left the cap off!

 

[treeroot]

Thats why I dont put any faith in YouTube repair videos! Yes you should have left the cap off!

I get your point... But in the long run I'm well ahead by repairing things myself despite this disaster.

 

[lone wolf]

I get your point... But in the long run I'm well ahead by repairing things myself despite this disaster.

Get a shop repair manual and IPL AKA illustrated parts list on here from the beg for manuals thread for your specific model.

 

[Mad Professor]

Thanks!

Where would the vacum be? in the oil case?

Any thoughts to epoxying it?

The crankcase around crankshaft must be sealed to allow the fuel mix to pump from intake to combustion chamber, it makes a pressure and vacuum inside housing. Mix goes from intake to crank housing, then is forced through transfer ports to combustion chamber.

While this area is under vacuum it also supplies vacuum to the impulse line to the carburator, which pumps the fuel.