Need help with stihl 041 av pressure test problem

[Robert Kugler]

Wow. Outstanding thread on the subtle (and not so subtle) aspects of pressure testing and troubleshooting an 041 oil pump! Great stuff, guys..., especially the encouragement factor.

My only comment would be that I hope the saw was pressurized prior to (and while) being submerged to eliminate the possibility of water migration into the case. Even though the main leak would currently appear to be via the oil system and would not likely provide a very convenient path to the crankcase, that doesn't necessarily mean the oil seals couldn't still allow water into the bearings/case (or pass a vacuum test) even though they've passed a couple of bubble pressure tests so far. That may change once any larger leak sources have been fixed. And once the saw seems to have passed all the air leak tests using pressure, vacuum testing is a must to ensure the absolute integrity of all components subject to air leaks, especially the oil seals.

Good luck with it!

Thanks Pogo.
I pressurized it immediately after putting it in the bucket.
When I took it out, i removed the spark plug and poured 1/2 container of fuel mix oil and turned the crank. After a couple of turns, it belched oil all over the bench
Bob

Tom and Randy, thanks very much rot yhe help
Bob

 

[Robert Kugler]

Get the old o-ring off the control shaft and put it back together Bob. The missing piece may have fallen down that threaded area. Not ideal, but unless you split the cases you won’t find it.

OK!!....Forward--> !
Thanks Tom
Bob

 

[Robert Kugler]

Get the old o-ring off the control shaft and put it back together Bob. The missing piece may have fallen down that threaded area. Not ideal, but unless you split the cases you won’t find it.

Tom / Randy,
This is now a background project due to my problems with the O ring.
I now know that I never really had the O ring installed correctly on the oil control shaft. That had been my problem all along. It worked too easily.
no matter what I do, the O ring rides up the shaft when I try to put the shaft down.
I have tried poking the O ring down with a pick, a small screwdriver, and a piece of tubing around the shaft to keep it from riding up when the shaft goes down.
I have also tried pulling a cable tie around the O ring and compressing it while I screw down the shaft.
I have tried these things with both Buna N and Viton. Nothing worked.
Do you know of any tricks to get the O ring and shaft down into the cavity?
Thanks,
Bob

 

[PogoInTheWoods]

Do you know of any tricks to get the O ring and shaft down into the cavity?

My guess is you are using an incorrect 'O' ring. It should fit very snug in the groove and barely seem to protrude above the surrounding shaft. A correct one will not ride out of the groove and up the shaft upon installation.

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[PogoInTheWoods]

And in the interest of furthering the vac/pressure testing, and in lieu of the 'O' ring problem, simply block the oil control shaft cavity with something and proceed. Plumber's putty, bubble gum..., any number of choices to temporarily seal the shaft cavity to continue the testing process for other potential leaks. With any luck, everything else will be tight and your only remaining issue is the adjuster shaft 'O' ring. And while you're at it, do a vacuum test to determine the integrity of your crank seals. You'll have that much more out of the way and be that much closer to having a running saw.

 

[Robert Kugler]

My guess is you are using an incorrect 'O' ring. It should fit very snug in the groove and barely seem to protrude above the surrounding shaft. A correct one will not ride out of the groove and up the shaft upon installation.

View attachment 848603

View attachment 848605​

I just ordered the original Stihl part 9646 945 0490
hopefully that will fit correctly
Bob

 

[Robert Kugler]

Well, I finally figured this out. I learned a ton of stuff about this saw!
The oil adjuster O Ring would not fit snugly in the groove because the old O ring had shriveled up and stuck to the groove. The old pieces stuck in the groove were enough to make the new ring not fit. I fixed that and changed the O Rings in the oil pump. After that, I changed the seal around the worm gear drive. Doing that, I was able to (almost) pressurize the saw. The pressure was good enough to pop out the oil pump (because I had not put in the C Clip.
The pressure now bleeds down in 2 - 3 seconds, so I am going to replace the shaft seal on the flywheel side, and also the seal in the worm gear drive.
I have both of these seals. but I am not sure how to replace the shaft seal in the worm gear drive. It looks as if the steel washer is pressed in to hold the seal in place. Does anyone know how to get that washer out so I can change the rubber seal? I don't want to destroy it by doing the wrong thing.
Number 16 is the washer I want to remove, so that I can change the seal (#15)

Thanks for any help,
Bob
PS: The Viton O Rings fit great, and I used those.

 

[PogoInTheWoods]

Glad to hear there's new progress.

I believe removing the worm gear and driving out the seal and ring together from the back (inside/out) would be the safest method for reusing the ring. Prying from the top (front?) may have unexpected results.

 

[Robert Kugler]

Glad to hear there's new progress.

I believe removing the worm gear and driving out the seal and ring together from the back (inside/out) would be the safest method for reusing the ring. Prying from the top (front?) may have unexpected results.

So do I use a punch and small hammer through the hole in the gear and tap out the washer?
Thanks,
Bob

 

[PogoInTheWoods]

That would be my approach vs. prying from the top with a hooked tool. Getting under (behind?) the seal obviously gives a bit of cushion to the force being applied to the ring. On the other hand, there's probably a conventional all-in-one replacement option for the seal that includes the O.D. ring if going that route becomes necessary. Googling '12x16x3 oil seal' turns up several possibilities without having to dig too far. I've not researched it, but it seems like it would be a better and more convenient option anyway. Perhaps @hotshot has some insight on the subject.

 

[Robert Kugler]

That would be my approach vs. prying from the top with a hooked tool. Getting under (behind?) the seal obviously gives a bit of cushion to the force being applied to the ring. On the other hand, there's probably a conventional all-in-one replacement option for the seal that includes the O.D. ring if going that route becomes necessary. Googling '12x16x3 oil seal' turns up several possibilities without having to dig too far. I've not researched it, but it seems like it would be a better and more convenient option anyway. Perhaps @hotshot has some insight on the subject.

Thanks Poge, I will try that.
Bob

 

[Patrick1903]

Reviving this thread - it looks like Bob hasn't been on the site in 1.5 years. Just wanted to see if any resolution was found. I may be looking at some leaking o-rings in my 041 oiler.

 

[PogoInTheWoods]

I'm still watching the thread if I can be of any assistance beyond what's already been discussed.

 

[Patrick1903]

I'm still watching the thread if I can be of any assistance beyond what's already been discussed.

Thanks. I’m still trying to figure out what I’ve got going on. I have another thread about my 041 rebuild (top end) and now at the point where I’m looking at other issues. Suspecting oil in crankcase and way over oiling to the bar and chain. I posted pics of the bar in the other thread if you care to see that. I’m starting by replacing the pump o ring and rubber ring (at opening to oiler). So I’ll see what things look like after that. Thanks!

 

[PogoInTheWoods]

As possible points of interest relative to the entire content of this thread, I'll give it a bump just for the hell of it, and because I have two 041s on the bench right now and one is as bad as it gets when it comes to chasing all 12 of Randy's possible leak locations. LOL And because it's also one of the more thorough threads on the subject anywhere.

My additional $.02 with two points that weren't actually brought up previously;

If the oil fill cap pressure test fails, there will also probably be obvious bubbles in the oil tank (if it still has enough oil and isn't already leaking around the case gasket). This renders the cap bubble test unnecessary if done prior to draining the tank, though the cap would still fail accordingly.

Additionally, if a pressure test fails miserably but the saw will still pull a vacuum and hold it, (which is rarely possible under normal circumstances), the crank and worm seals are probably just fine while oil is being drawn into the crankcase via bad 'O' rings in the likely spots. This temporarily seals any vacuum leakage that would otherwise occur under a crankcase pressure test.

I just realized the latter last evening after a bit of head scratching and more than a few WTFs? Same principle as smearing grease around a seal that passes pressure (no bubbles) but otherwise fails vacuum, but in reverse. Just wish I would have figured it out before pulling the clutch, flywheel and ignition to test the crank seals!
They could still leak after the other(s) are tightened up, but continuous pumping on the MityVac to around 5psi seems to indicate they're ok.

Anyway, for a 'no stone unturned 041 leak test methodology seminar', this is certainly the right place. LOL