Hi All, I just rebuilt my Stihl 024 AV WB with a new Meteor piston. I initially only vacuum tested it (w/o the Stihl adapter), and saw held vacuum for minutes, even with turning the crankshaft. Saw runs well, but wanted to do also a pressure test. So I got the appropriate Stihl adapter and found that as before that the saw holds vacuum but was surprised to find that it does not hold pressure. I checked the seals, they look good. Other areas (backside of cylinder, area between tank and engine block) are a bit more difficult to get to. So before I tear the whole saw apart (again), any suggestions for a newby on where obvious leak areas might be. Is a pressure leak as seriuos as a vacuum leak? Thanks!
Stihl 024 AV holds Vacuum but not Pressure... can't find leak (yet)
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It must hold vacuum and pressure. Check intake boot, pulse hose, anywhere that’s sealed with a gasket or seal. If your going through a saw it’s good practice to replace crank seals even if the originals look good. It’s cheap insurance and will (if they’re installed correctly) eliminate having to tear the saw down a second time.
Yup, just as serious. I’d now plug the oil pump & pressure test it underwater in a bucket. It will be obvious where the bubbles are coming from.
You should be testing at 14” Hg negative & 8 psi positive, what test values are you using?
You should be testing at 14” Hg negative & 8 psi positive, what test values are you using?
Tomos770
ArboristSite Guru
I would say crankseals....
They (the lip) seal in on direction better then in other.....
They (the lip) seal in on direction better then in other.....
Finally had time to track down issue.... Very small hole in the rubber air intake manifold. On vacuum it sealed itself, on pressure it leaked. Replaced it and no issues anymore.
Thanks for feedback.
Stefan
Thanks for feedback.
Stefan
Glad you found your leak. What method did you use ? Soapy spray ?
No, the soapy spray did not work for me.
after I checked the integrity of the impulse line (wich was fine), I basically disassembled the saw again, and replaced the intake boot (I had reused the old one as it had looked good), and retested, no problem with the new boot. Held vacuum and now also pressure for over a minute without any change. Problem solved. My old boot had a very small crack just where it meets the flange on the cylinder.
THe saw now has beautiful idle and response and runs like new with high compression (I refinished cyclinder and put a new piston/rings in it). Happy I spent the time and learned some things, and have again a wonderfully versatile saw.
after I checked the integrity of the impulse line (wich was fine), I basically disassembled the saw again, and replaced the intake boot (I had reused the old one as it had looked good), and retested, no problem with the new boot. Held vacuum and now also pressure for over a minute without any change. Problem solved. My old boot had a very small crack just where it meets the flange on the cylinder.
THe saw now has beautiful idle and response and runs like new with high compression (I refinished cyclinder and put a new piston/rings in it). Happy I spent the time and learned some things, and have again a wonderfully versatile saw.
T1, I always replace seals and carb kits on older saws!
Absolutely. It would be foolish not to. Even if a saw seems to run good I always replace crank seals. Peace of mind alone is worth it.
Tomos770
ArboristSite Guru
Knowhow from our fellow over here...
