Pressure test of RV shaft and crank seals

[AKnarrowback]

Hi guys.

I'm finally getting around to figuring out why my 97 GTX launches oil out of the mag cylinder plug hole after it sits for a week. I can burn the oil off and it runs perfect, park it and a week later the mag side is oil soaked again...

The brass fittings in the rv cover aren't showing any signs of leaking. I pulled the cover off, sprayed any oil residue off everything and set the cover back in place with clean paper towel over the rotary valve. No oil dripping at all.

The rv shaft seal on the valve side shows no sign of leaking.

I put 5 psi in the rv/crank shaft chamber and have these numbers, at 10 minutes it was down to 4.3psi, at 20 4.1ish, at 30 4.0, at 40 minutes it was at 3.8ish. I did drain the oil out before the test.

The shop manual calls for 5 psi on the test, but the rest of the procedure is for a motor sealed up for an overall test not isolated to the shaft area alone. So, based on the wider range of experience out there than I have here does this loss of pressure sound like a crank seal could be failing? Or is there an acceptable, pressure over time, loss with a seal that is still considered "good".

 

[AKnarrowback]

I just tried pulling vacuum on each of the fittings. Using the mightyvac I put around 28in on the fittings, the side giving me the problem (mag) let a little oil through, the pto side fitting didn't let oil through.

I pressurized the oil tank to a couple psi and am going to let things set overnight, check for any fresh oil at the fittings in the morning.

 

[etemplet]

Put a Valve on the Oil line feeding the Rotary valve chamber and be done with it. BUT when you figure out what the problem is let us know. LOL I'm interested in your process.

 

[etemplet]

I understand pressurizing the oil tank but if you disconnect the line you can put more pressure on the system. Lip seals can easily take 20psi. I know they can take a lot more but 20 or lower would be more than enough I suspect. I wouldn't do that with the rest of the engine but that chamber.... yes indeed. A few ounces is all it takes to lock up the engine.

 

[mikidymac]

When you pressure test a new engine you should do 8psi for a minimum of 10 minutes. It shouldn't leak at all. With your pressure dropping at just 5 psi you have a bad seal. If oil isn't leaking into the rotary cover from the rotary shaft seal then your only culprit is the inner crank seal.

 

[AKnarrowback]

Dang.......

You were supposed to say "no problem, it'll fix itself"!

Time to save the pennies, get the tools warmed up........... (I'm just gonna run it until then).

Thanks.

 

[mikidymac]

A lot of people solve this issue by putting a ball valve on the oil feed line from the tank then put your lanyard on it when you are done so you always remember to turn it on. Some do this for years before actually fixing the problem.

 

[AKnarrowback]

I have a source that can get me BRP crank, with no shipping (yes!), for 350. So I'm going that route as soon as my "super incredible deals" sell on ebay.

In thinking about it though I always wondered, if you found the proper grease, if packing that chamber full and capping the lines would solve the problem. Not the best solution but having to replace the whole crank for a five dollar seal is the one design flaw I have never liked in Rotax RV motors.

I remember one member saying he has done this on his 787 and it is still going.

 

[etemplet]

You would do better just to put the valve on there. Even if you forget and leave it closed it will likely maintain an oil level for a period of time. If your engine isn't locking up on cranking after about 2 weeks... you really don't have much of a leak. It only takes a couple of ounces in the case to cause an issue.

 

[mikidymac]

Grease would not be a good idea. The rear rotary shaft bearing is shielded to the cavity side so you can't get grease into it plus it would not lubricate the brass gear correctly. Just a bad idea.

 

[AKnarrowback]

This sort of describes my thinking. Something that will loosen up when the engine gets warm but won't leak out when cold.

 

[AKnarrowback]

A guy can wish...... but a new crank looks like the only answer.

 

[AKnarrowback]

That's my gas tank.

That's the oil tank.

Well what's that IV bag by the exhaust???

That's my bacon grease injection resevoir.....

 

[mikidymac]

Mmmmmmmm Bacon! Better than a converted diesel that smells like french fries.

 

[GGuillot]

Once you get it apart and go to put it back together, just put sealant, whatever you use on the case halves, in the grooves of the inner crank seals to stop it from leaking.

 

[etemplet]

Mmmmmmm french fries.

 

[etemplet]

Transmission sealer. You said you wanted to "hope" that stuff might do the trick.

 

[AKnarrowback]

It says it lubricates the water pump, that's made of metal, the crank is made of metal so it must lubricate it as well????......

 

[etemplet]

I the ladies at the Auto Parts store talking about "Blue (something)" Said it was $50 per quart I think but it works great. I guess the rednecks around her don't change parts on the dump trucks. LOL

 

[DanSquires]

I have a source that can get me BRP crank, with no shipping (yes!), for 350. So I'm going that route as soon as my "super incredible deals" sell on ebay.

In thinking about it though I always wondered, if you found the proper grease, if packing that chamber full and capping the lines would solve the problem. Not the best solution but having to replace the whole crank for a five dollar seal is the one design flaw I have never liked in Rotax RV motors.

I remember one member saying he has done this on his 787 and it is still going.

Might have heard that from me.. I'm not running one but have a buddy that has for several years. Works for him, so, who am I to argue.

 

[etemplet]

The issue with grease is that it is basically wax with oil mixed in. When the oil goes away all you have is wax. Then it will all begin to heat up. How about a thicker gear oil in there rather than the thin stuff we mix with fuel?? You got me thinking now. You could run a 75w-90 Synthetic that you could suck out and replace at some point (I like clean oil) . There is also 140w but perhaps the 75W-90 might do the trick. Get the good slippery stuff and try it !!!

This has potential.

 

[AKnarrowback]

Just like you described.

And I still don't know why some of my pictures are loading sideways...

It's really thick oil, like pudding. Write ups on it say it is useful in situations where a seal with some wear is leaking. I used the mighty vac on the carb side to draw a vac and a funnel on the other line. A good amount of injection oil came our before the new oil did. Many questions still but I'll give it a shot. If the machine can sit for a week and not smoke like St Helens when I start it then I'll cross my fingers and see how durable things are. If I get a sign there is still a leak then the new crank is getting ordered. I'll take one for the team on this experiment.

 

[mikidymac]

Once you get it apart and go to put it back together, just put sealant, whatever you use on the case halves, in the grooves of the inner crank seals to stop it from leaking.

I hope that was a joke.
Filling a seal with sealant will not stop it from leaking, it will still leak right past the seal lip and the crank.

 

[mikidymac]

Instead of guessing at what might work, either replace the crank or just put a valve on the oil feed line. Either will get you going.

Although the smoke cloud from leaking seals has to help with the Alaska mosquitos.

 

[etemplet]

I retired from CHEVRON.... I can't read what type it is but it looks like Ethelyne Propylene (EP2) Is that grease??? I wouldn't do that but I want to try the 75W 90 on my cousins ski It will protect the gears better than the other oil. May lose a horsepower or 2. LOL