Need help with stihl 041 av pressure test problem

[Robert Kugler]

There is a hole in the cap

sorry hedgecutter, I got my mentors mixed up......

 

[Robert Kugler]

Thanks Randy, I will; and thanks again for the help.
Bob

Hi Randy,
I had to cancel my order to the stihl dealer because they wanted to backorder everything.
I found the o tings at Grainger, and they have both viton and buna-n.
I noticed that the viton has a hardness of 75shoreA, while the buna-n has a hardness of 70shoreA. I have no idea what that difference means for relative hardness is; or whether the shore scale is linear (i.e more than a few % difference).
My question is: Will the harder viton o rings be soft enough to conform and seal properly in the frame seat, and also will viton be ok for the o rings on the pump internal shaft?

Thanks,
Bob

 

[hotshot]

Hi Randy,
I had to cancel my order to the stihl dealer because they wanted to backorder everything.
I found the o tings at Grainger, and they have both viton and buna-n.
I noticed that the viton has a hardness of 75shoreA, while the buna-n has a hardness of 70shoreA. I have no idea what that difference means for relative hardness is; or whether the shore scale is linear (i.e more than a few % difference).
My question is: Will the harder viton o rings be soft enough to conform and seal properly in the frame seat, and also will viton be ok for the o rings on the pump internal shaft?

Thanks,
Bob

Yes Sir, that’s all I use in the 041s & they work fine.

 

[Robert Kugler]

Yes Sir, that’s all I use in the 041s & they work fine.

Great!
Thanks Randy.
Bob

 

[Robert Kugler]

Great!
Thanks Randy.
Bob

Hi Randy,
I got the viton o rings for the oil adjuster seal and put them in. They stopped the bubble leak , but the pressure test still fails, although more slowly.
I re bubbled the oil cap, and that is fine also.
The tank side crank seal passed, but the clutch side seal is confusing me.
The crankshaft seal around the oil pump worm-gear driver passes the bubble test, but the two drive pin holes in the worm-gear driver are bubbling.
Does that mean the worm-gear piece is bad, or am I missing something?
#4 in the snapshot below.



Thanks,
Bob

 

[hotshot]

Good job on the o-ring fixes.

Sounds like the inner worm gear seal has hardened up & is leaking, that’s part 9643 003 1160.

Don’t think those pin drive holes go all the way through, but I’ll pull out a worm gear & look at it.

When I pressure test those, I use a 5/8” copper tubing stub with a sliced notch cut out in one end, then I can see the tiny seal to bubble test it. Hold the copper stub on with the clutch, or just use the locking nut if an early 041 series.



Edit: Both of those drive pin holes are blind, so no leaks are possible there.

 

[Robert Kugler]

Good job on the o-ring fixes.

Sounds like the inner worm gear seal has hardened up & is leaking, that’s part 9643 003 1160.

Don’t think those pin drive holes go all the way through, but I’ll pull out a worm gear & look at it.

When I pressure test those, I use a 5/8” copper tubing stub with a sliced notch cut out in one end, then I can see the tiny seal to bubble test it. Hold the copper stub on with the clutch, or just use the locking nut if an early 041 series.

View attachment 843106

Edit: Both of those drive pin holes are blind, so no leaks are possible there.

Hi Randy,
Not sure I understand. I have the clutch off, and I am looking at the worm gear around the eng of the crankshaft. I think I know the seal you are talking about (is it #15 in the snapshot I posted?). Is that seal on the inside of the worm gear? If so, can I just pull the worm gear out if I back out the oil pump?
Are your tools for checking the seal with the clutch in place?
Sorry for my inexperience.
Bob

 

[hotshot]

Hi Randy,
Not sure I understand. I have the clutch off, and I am looking at the worm gear around the eng of the crankshaft. I think I know the seal you are talking about (is it #15 in the snapshot I posted?). Is that seal on the inside of the worm gear? If so, can I just pull the worm gear out if I back out the oil pump?
Are your tools for checking the seal with the clutch in place?
Sorry for my inexperience.
Bob

Yes, IPL item #15, the tiny crank seal inside the worm gear.

That worm gear will always be pushed out of the case from air pressure during the test, if you don’t hold it in with that copper stub. No need to pull the oil pump out to remove the gear.

If you have bubbles there, replace the seal.

Do you need a pic of the stub installed on a saw during test?, with the clutch carrier installed to hold it in? I could pull an 041 saw apart & take one tomorrow.

 

[Robert Kugler]

Yes, IPL item #15, the tiny crank seal inside the worm gear.

That worm gear will always be pushed out of the case from air pressure during the test, if you don’t hold it in with that copper stub. No need to pull the oil pump out to remove the gear.

If you have bubbles there, replace the seal.

Do you need a pic of the stub installed on a saw during test?, with the clutch carrier installed to hold it in? I could pull an 041 saw apart & take one tomorrow.

Thanks Randy. I think I understand now. I put that stub around the shaft and put the clutch nut on. This will hold both the stub and the worm gear in place while I do the pressure test.
Is that it?
Maybe the test was failing because the pressure was pushing out the seal(?)

Bob

 

[Robert Kugler]

hi Randy,
You were right......I cut a piece of clear plastic tubing, gooped up the worm gear and seal with soapy water, then put the clutch nut on with the tubing to hold the seal down, and the bubble test passed. I had to use thick soapy water so it would not dry while I put on the clutch nut.
The bubble test passed....Thank You!
This leaves me with the same problem though. There must be a leak somewhere else.
The background of this is:
I am using a "cobbled up" blood pressure tester to do the pressure test. Instead of an arm cuff, I used vacuum fittings to adapt the cuff hose to a piece of impulse line which is connected to the crankcase impulse fitting. This setup holds pressure because when I pinch this impulse line with a pair of needle nose, the gauge stays at 300mm(hg), so the tester is working.
300 mm is only 5.8 psi, but the crankcase wont even hold that.
As you instructed me before; I repaired the oil adjust shaft O ring, and that passes the bubble test (al least at 5.8 psi). The bubble test passes on the oil cap vent (the cap is tight), and I also tested the cavity at the end of the oil pump. That passed.
the crank seals on both sides passed, but I had to retain the worm gear as you said.
There is a rubber plug in the top of the crankcase next to the impulse line fitting, but I bubble tested that also and it passed.
The spark plug is tightly seated in the cylinder, and both the intake and exhaust ports are blocked with 1/8 inch plumbing rubber placed under the intake and muffler fittings. These parts have the rubber pinched tightly.
I am at a loss. Can you think of anything else that can be leaking? I really don't want to pull off the cylinder or split the case unless there is no other way.....
Thanks,
Bob

 

[Bob Hedgecutter]

So- after a long extended period of elimination and testing of each and every orifice on the exterior of the saw- we are about a full circle back to the gasket that seals the two crankcase halves- leaking crankcase gasses into the oil tank?

 

[hotshot]

hi Randy,
You were right......I cut a piece of clear plastic tubing, gooped up the worm gear and seal with soapy water, then put the clutch nut on with the tubing to hold the seal down, and the bubble test passed. I had to use thick soapy water so it would not dry while I put on the clutch nut.
The bubble test passed....Thank You!
This leaves me with the same problem though. There must be a leak somewhere else.
The background of this is:
I am using a "cobbled up" blood pressure tester to do the pressure test. Instead of an arm cuff, I used vacuum fittings to adapt the cuff hose to a piece of impulse line which is connected to the crankcase impulse fitting. This setup holds pressure because when I pinch this impulse line with a pair of needle nose, the gauge stays at 300mm(hg), so the tester is working.
300 mm is only 5.8 psi, but the crankcase wont even hold that.
As you instructed me before; I repaired the oil adjust shaft O ring, and that passes the bubble test (al least at 5.8 psi). The bubble test passes on the oil cap vent (the cap is tight), and I also tested the cavity at the end of the oil pump. That passed.
the crank seals on both sides passed, but I had to retain the worm gear as you said.
There is a rubber plug in the top of the crankcase next to the impulse line fitting, but I bubble tested that also and it passed.
The spark plug is tightly seated in the cylinder, and both the intake and exhaust ports are blocked with 1/8 inch plumbing rubber placed under the intake and muffler fittings. These parts have the rubber pinched tightly.
I am at a loss. Can you think of anything else that can be leaking? I really don't want to pull off the cylinder or split the case unless there is no other way.....
Thanks,
Bob

Cylinder base & case gaskets are about all that are left.

Did you bubble leak test the spark plug, intake & exhaust block offs just to be sure? I’m assuming you’re testing through the impulse hose.

That air has to be escaping somewhere. As a last ditch effort, you can put it underwater in a bucket...

From the old thread I referenced:
“There are literally a dozen places for those old 041s to have air leaks, and 8-10# air pressure testing with a bottle of kids soap bubbles or Windex will show them all, as you covered three of them!

1) PTO or Right Side Crank Seal
2) Oiler Worm Gear to shaft Seal -OR- Bar oiler gear cover seal
3) Starter/Magneto or Left Side Crank seal
4) Cylinder Jug Base to Crankcase (CC) & the Studs x4
5) Crankcase, Case halves Punch Pins (x2), & the CC Side Halves Case Gasket

Also "bubble check" the oil filler hole (Double checks the internal crankcase gasket integrity when the oil tank is a common casting). Pressure test only.

6) Impulse Line Elbow Fitting at CC & the Impulse Hose
7) #1 Lower Intake Cylinder/Shield Gasket
8) #2 Lower Intake Shield/Manifold Gasket
9) #1 Upper Intake Manifold Block Gasket
10) Bar Oiler Rate Adjuster Screw O-Ring (at rear)
11) Bar Oiler Drive Gear Front Grommet
12) Bar Oiler gear shaft brass plug (back of case)”

 

[Robert Kugler]

Cylinder base & case gaskets are about all that are left.

Did you bubble leak test the spark plug, intake & exhaust block offs just to be sure? I’m assuming you’re testing through the impulse hose.

That air has to be escaping somewhere. As a last ditch effort, you can put it underwater in a bucket...

From the old thread I referenced:
“There are literally a dozen places for those old 041s to have air leaks, and 8-10# air pressure testing with a bottle of kids soap bubbles or Windex will show them all, as you covered three of them!

1) PTO or Right Side Crank Seal
2) Oiler Worm Gear to shaft Seal -OR- Bar oiler gear cover seal
3) Starter/Magneto or Left Side Crank seal
4) Cylinder Jug Base to Crankcase (CC) & the Studs x4
5) Crankcase, Case halves Punch Pins (x2), & the CC Side Halves Case Gasket

Also "bubble check" the oil filler hole (Double checks the internal crankcase gasket integrity when the oil tank is a common casting). Pressure test only.

6) Impulse Line Elbow Fitting at CC & the Impulse Hose
7) #1 Lower Intake Cylinder/Shield Gasket
8) #2 Lower Intake Shield/Manifold Gasket
9) #1 Upper Intake Manifold Block Gasket
10) Bar Oiler Rate Adjuster Screw O-Ring (at rear)
11) Bar Oiler Drive Gear Front Grommet
12) Bar Oiler gear shaft brass plug (back of case)”

Thanks Randy,
I will recheck the block offs and then put it in a bucket of water.
Thanks,
Bob
I will also check the spark plug

 

[Vintage Engine Repairs]

If it’s the same setup as the oil pump in the 076 - don’t forget the o-ring that is inside of the oil pump. It sits on the actuating rod. It holds pressure In the crank case from the atmospheric pressure in the oil passage / tank. If it leaks you’ll have air escaping in and out of the oil galley (out to the bar hole) and the oil tank.

Put a few drops of bar oil down into the oil passage (where the bar rests against) and add pressure to the saw, if it bubbles out, that’s your issue. Blocking the oil tank breather may be required. On the 076 it’s a one way valve in the tank so not necessary, but your saw may be bidirectional so block it If in doubt.

For the 076 It’s a 7x1.5, but confirmation for your saw will be required.

 

[Robert Kugler]

Thanks Randy,
I will recheck the block offs and then put it in a bucket of water.
Thanks,
Bob
I will also check the spark plug

Hi Randy,
I put the crankcase in a bucket of water and found 2 leaks.
one was the oil adjusting shaft that I replaced the O ring on; and the other was the worm gear.
I found that the o ring was riding up the adjuster shaft when I would insert it. The first time I replaced it, I packed the shaft cavity with silicone grease over the top of the inserted shaft to protect it.
When the bubble test passed on this the first time, I think the grease was holding the pressure. On subsequent pressure tests, i think the grease was pushed out, but I thought the o ring was fixed. That was my first problem.
When I saw the worm gear leaking, I tightened the clutch nut down to hold the gear more firmly. This worked for one test, but the seal started leaking again after that.
I tried finding the seal online, but was not able to find it in stock anywhere.
If I order the worm gear, do you think it would come with the seal installed? I see they are separate part numbers on the IPL.
Do you know where I can order the seal?
Thanks,
Bob

 

[Robert Kugler]

If it’s the same setup as the oil pump in the 076 - don’t forget the o-ring that is inside of the oil pump. It sits on the actuating rod. It holds pressure In the crank case from the atmospheric pressure in the oil passage / tank. If it leaks you’ll have air escaping in and out of the oil galley (out to the bar hole) and the oil tank.

Put a few drops of bar oil down into the oil passage (where the bar rests against) and add pressure to the saw, if it bubbles out, that’s your issue. Blocking the oil tank breather may be required. On the 076 it’s a one way valve in the tank so not necessary, but your saw may be bidirectional so block it If in doubt.

For the 076 It’s a 7x1.5, but confirmation for your saw will be required.

View attachment 843379

Hi Tom,
I will replace that O ring, but at the moment I have two other fast leaks (see my reply to Randy).
I got 3 bags of o rings, one type for the pump shaft, and two types for the oil adjuster assembly.

Thanks,
Bob

 

[Vintage Engine Repairs]

Hi Bob,

You’ll be very hard pushed to find Stihl parts online, but a stihl shop will be able to order it in. It should only take finger pressure just to keep that oiler in place. The aim isn’t to apply pressure to make it conform, simply to hold it from popping out.

The oil adjustment shaft o-ring must be the correct size as specified in the manual. If it is, then the grease is creating excessive pressure and pushing it off its recess.

O-rings are surprising little things, they require very minimal pressure between themselves and the mating surface to effectively hold pressure or vacuum, therefore it’s possible you over estimated the required size.

Well done for finding the leaks, it’s a fairly simple fix from here. I’d personally replace all 3 crank seals as a precautionary measure just like one does with the small end bearings, circlips, case / cylinder gaskets etc. You’re in there and it’s very little cost and time.

If you google “bearing supplier” followed by your town / area, pop in with your old crank seals and the saw they fit on, they’ll measure it and sell you new ones. Either that or the specs will be in the IPL.

Either way they’ll only be a few dollars each. Stihl on the other hand will charge 20. Your choice depending on availability. Bearing suppliers seem to offer the whole arrangement - o-rings, bearings and seals.

Warm regards, Tom

 

[hotshot]

That seal #9643 003 1160, is a common metric 12x16x3mm, but may still be available at Stihl. It needs to have a steel OD, and not rubber...as the aftermarket seals will vary in construction.

There’s one on ebay but it looks like he has “950” instead of”003” for the middle number.

The IPL states that a new worm gear #1110 640 7100 comes with a new seal installed, but you can verify when you contact Stihl.

You could also put a “wanted” ad in the parts section here, or you can send a PM to @jockeydeuce, as he has some obsoleted Stihl parts.

 

[Robert Kugler]

Hi Bob,

You’ll be very hard pushed to find Stihl parts online, but a stihl shop will be able to order it in. It should only take finger pressure just to keep that oiler in place. The aim isn’t to apply pressure to make it conform, simply to hold it from popping out.

The oil adjustment shaft o-ring must be the correct size as specified in the manual. If it is, then the grease is creating excessive pressure and pushing it off its recess.

O-rings are surprising little things, they require very minimal pressure between themselves and the mating surface to effectively hold pressure or vacuum, therefore it’s possible you over estimated the required size.

Well done for finding the leaks, it’s a fairly simple fix from here. I’d personally replace all 3 crank seals as a precautionary measure just like one does with the small end bearings, circlips, case / cylinder gaskets etc. You’re in there and it’s very little cost and time.

If you google “bearing supplier” followed by your town / area, pop in with your old crank seals and the saw they fit on, they’ll measure it and sell you new ones. Either that or the specs will be in the IPL.

Either way they’ll only be a few dollars each. Stihl on the other hand will charge 20. Your choice depending on availability. Bearing suppliers seem to offer the whole arrangement - o-rings, bearings and seals.

Warm regards, Tom

Thanks very much Tom, I will call that stihl dealer that I was speaking with before; and try to order the worm gear.
I gather that I should just put the o ring on without grease than. Guess I went too far in trying to lube the o ring.
I have 3 bags of o rings that are the size specified in the IPL, so they should be correct. I have seals for both sides of the crank, so I can change them.
I am not sure I want to tackle the bearings yet, but I have had this saw apart and together so many times that I can do it in my sleep. I can open it again if I gave to. I am assuming that if a bearing goes bad it will be noisy(?).
On the worm gear seal: while I am waiting for the "back-ordered" gear and seal; I was thinking of trying to fix the old one.
I have a service chemical called "rubber renew" that I used to resurface rubber drive wheels in old tape recorders. That may fix the seal for a few months. (any thoughts?).
I will also have to get an IR temperature gauge so I can heat the case, if I do have to change the bearings.
Thanks for the help.
warm regards,
Bob

 

[Vintage Engine Repairs]

Thanks very much Tom, I will call that stihl dealer that I was speaking with before; and try to order the worm gear.
I gather that I should just put the o ring on without grease than. Guess I went too far in trying to lube the o ring.
I have 3 bags of o rings that are the size specified in the IPL, so they should be correct. I have seals for both sides of the crank, so I can change them.
I am not sure I want to tackle the bearings yet, but I have had this saw apart and together so many times that I can do it in my sleep. I can open it again if I gave to. I am assuming that if a bearing goes bad it will be noisy(?).
On the worm gear seal: while I am waiting for the "back-ordered" gear and seal; I was thinking of trying to fix the old one.
I have a service chemical called "rubber renew" that I used to resurface rubber drive wheels in old tape recorders. That may fix the seal for a few months. (any thoughts?).
I will also have to get an IR temperature gauge so I can heat the case, if I do have to change the bearings.
Thanks for the help.
warm regards,
Bob

Hi Bob,

Excellent, going with stihl for parts is often the best way forward, though if they are NLA, alternatives from reputable sources can be a good substitute.

It’s good practise to change bearings if you have side loaded them when pressing the crank out, but if you haven’t pressed the crank, they look in good condition, have no play and no abnormal sound then and aren’t rusty, it shouldn’t be an issue.

Note that bearings in their pockets under pressure can sound and feel better than they do when popped out.

I’d personally wait and not try and save an old seal, I understand the impatience side of things as I have been working on an 07 chainsaw for months waiting for parts, but it’s much better to leave the saw apart and get it done properly, than hope a bandaid fix will hold. Maybe start a second project, or clean the rest of the saw parts while you wait, rebuild the carb If necessary etc

Hope this helps