GX390 Oil seal failures

[caveman]

Hello all, new to the group. I have an issue Im trying to work out on my GX390. I just recently started failing output shaft seals. I believe this was caused by a cooling issue (mouse next in cooling fins) but has been resolved. The last seal I installed I started the engine and measured the output shaft temp just near the oil seal. The temp climbed to 193F before the seal started leaking. The shaft has no nicks or damage, I lube seals when I install and they are installed flush with the housing per service manual. Any thoughts would be great as Im tired of laying out on the cold ground looking at a leaking seal Thanks Bob

 

[Denny]

Is there a groove in the crankshaft where the seal rides? If so get a Speedy Sleeve and seal from NAPA. Is there any play in the crankshaft? Up and down or side to side? Might have a worn crank or bearings. An autopsy might be needed.

 

[karl]

That or there is too much crankcase pressure and the freshly installed seal is the path of least resistance.

Once thought a snow blower had a bad seal, turned out the breather tube got pinched behind the airbox.

 

[madprofessor]

turned out the breather tube got pinched behind the airbox.

It's a fact that oil leaks freely from really bad gasketing (or seals), but you need to know if that's the case when it's parked and cold or when it's running. Are you certain there was no leak before it reached 193-degrees F.?

too much crankcase pressure and the freshly installed seal is the path of least resistance.

I can huff and puff enough to bypass any seal with a pumped-up-enough crankcase. It needs to be running with positive internal pressure to leak if it only does so when you're not watching it. I'm certainly OCD about stuff, but eliminating variables like that is what it would take to satisfy me if I were looking for a cause of a leak.
I've seen incredible damage done to bearings and seals from grossly over-tightened chains and belts. Where does that apply to your setup?

 

[caveman]

Hello all, new to the group. I have an issue Im trying to work out on my GX390. I just recently started failing output shaft seals. I believe this was caused by a cooling issue (mouse next in cooling fins) but has been resolved. The last seal I installed I started the engine and measured the output shaft temp just near the oil seal. The temp climbed to 193F before the seal started leaking. The shaft has no nicks or damage, I lube seals when I install and they are installed flush with the housing per service manual. Any thoughts would be great as Im tired of laying out on the cold ground looking at a leaking seal Thanks Bob

Ok I don’t think it’s temp. I just installed another seal an within minutes before it heated up was leaking. There appears to be negative pressure in the crankcase. I grease the shaft and seal to avoid damaging. I’m installing seal flush with the case. There is no up- down shaft movement. No nicks in the shaft. Running 5w30 oil. The leak is through the shaft to seal …not the outer seal to case. Any thoughts would be appreciated

 

[karl]

Are you installing # 91201-Z1C-003 , dimensioned 35mm X 52mm X 8mm?

Also I gots to ask , how did you conclude that there is negative pressure in the crankcase ?

I mean there is not much to this, its not the right seal, or something else is wrong.

 

[Master Hack]

Are you buying quality seals? There are plenty chinese junk seals out there. They may work well on Yak grease, but not so much on hot motor oil.

 

[karl]

Are you buying quality seals? There are plenty chinese junk seals out there. They may work well on Yak grease, but not so much on hot motor oil.

Genuine honda # 91201-Z1C-003's are the way to go. I use knockoff china parts sometimes, but accept they may not work right or last. You
get what you pay for.

 

[caveman]

Are you installing # 91201-Z1C-003 , dimensioned 35mm X 52mm X 8mm?

Also I gots to ask , how did you conclude that there is negative pressure in the crankcase ?

I mean there is not much to this, its not the right seal, or something else is wrong.

Not OEM. But that’s the seal p/n and dimensions
To determine the pressures I used pressure/vacuum gauge…kinda messy with oil coming off the splasher

 

[madprofessor]

Can you put a micrometer on the shaft and check for diameter variance all the way around where the seal rides on it? I'd say use a runout gauge and just watch the needle move as the shaft spins, but then you'd be checking variance outside of where the shaft/seal contact is made.
EDIT: The negative pressure, that should be negligible thanks to the breather.................Where does the breather come from on a Honda GX390? I'm thinking of the folks who mistakenly use the breather tube on Predators to run a pulse fuel pump, or that tap the valve cover for it but tap on the wrong side of the flapper valve in the cover. Just musing here, can't think clearly right now.

 

[Master Hack]

It might be tough to get a mic on the shaft at the seal contact area, without disassembly but its a good idea. If your shaft is worn, there are seals made for undersized shafts. ( no doctor visit needed). Not necessarily here but they are available.

Double-lip oil seal for worn shafts

Double-lip oil seal for use on worn or grooved shafts or increased runout.

ahpseals.com

 

[caveman]

Can you put a micrometer on the shaft and check for diameter variance all the way around where the seal rides on it? I'd say use a runout gauge and just watch the needle move as the shaft spins, but then you'd be checking variance outside of where the shaft/seal contact is made.
EDIT: The negative pressure, that should be negligible thanks to the breather.................Where does the breather come from on a Honda GX390? I'm thinking of the folks who mistakenly use the breather tube on Predators to run a pulse fuel pump, or that tap the valve cover for it but tap on the wrong side of the flapper valve in the cover. Just musing here, can't think clearly right now.

I took the pressure reading at the oil fill- dipstick location…very messy. Last night I installed another seal…this time with RTV on the outer seal that mates with the block. Have ran for 35 minutes with no leaks? I hope that 1mm film of RTV has been the issue. I’ve used RTV on all the seals that leaked. Strange

 

[Denny]

You might want to switch to a 10w30 also. 5w may be too thin of an oil. Especially on a worn engine.

 

[Master Hack]

You might want to switch to a 10w30 also. 5w may be too thin of an oil. Especially on a worn engine.

We have yet to establish exactly how much wear is on this. Sounds like it might be substantial tho. My 390 is perfectly oil tight.

 

[karl]

I hate to say it, but i think hes just damaging the seals on install. Ive never seen the crank wearing down where the the oil seal contacts without thousands of hours of runtime, that should be way beyond the lifespan of the engine.