crank seal

[Boyd12]

can sealer cause a crank seal to leak?

 

[etemplet]

Anything you put on a crank seal or any surface needs to be impervious to the environment in which it is installed. For a crankshaft seal it needs to be unaffected by fuel/oil and moderate heat. The wrong product will definitely deteriorate and cause problems. All sealants and products are not created equal. Lots of times we cause our own problems. Good luck

 

[Boyd12]

I noticed that there was a little sealer that had gotten on the crank seal when it was assembled. It doesnt look like much but I didnt know if it could cause the crank seal to leak.

 

[etemplet]

It's something I do which isn't always necessary but I put a thin coating of Ultra Gray RTV on the circumference of the lip seals. Many lip seals are metal with a coating already applied. I just like to make up for imperfections.

 

[Boyd12]

would the excess cause the crank seal to leak?

 

[etemplet]

You're asking of the product/sealant pushing out between the partings would deform the lip seal enough to cause a leak? It is an unnecessary risk that I won't take when assembling critical parts. Will it leak? Probably not.

 

[Boyd12]

the image on the right is the one i am talking about. a little bit of three bond that was on the cases ended up on the seal. the engine has a very SLIGHT leak when doing the leak down test. I didnt know if the sealer on the crankshaft seal shown in the image would be enough to cause a leak.

 

[mikidymac]

That is pretty common and should not cause a leak.

You need to mix up some dish soap and water and spray the entire engine until you find where the air bubbles are coming from to find your leak.

 

[etemplet]

Sometimes you leak test equipment is leaking and not the part you are testing. LOL Check everything. Good Luck !! +1 on the dish soap... you need to find the leak.

 

[Boyd12]

That is pretty common and should not cause a leak.

You need to mix up some dish soap and water and spray the entire engine until you find where the air bubbles are coming from to find your leak.

Sometimes you leak test equipment is leaking and not the part you are testing. LOL Check everything. Good Luck !! +1 on the dish soap... you need to find the leak.

 

[Boyd12]

I have used a LOT of dish soap on this engine! I must say, it is REALLY clean! I put 5 lbs of pressure in it and came back almost an hour later and there was about 1.5 lbs of pressure still in it. the leak appears to be tiny. i have tested and retested the equipment and find no leak. Thanks to both of you for your help!

 

[Sportster-2001-951C-Stock]

Doesn't sound like enough of a leak to worry about, IMO.

 

[etemplet]

Agreed hardly any leak at all. Our mechanical seal test required a drop of less than 3 pounds in 5 minutes but you have to factor in the volume of the container you are testing. Air is very difficult to seal.

 

[mikidymac]

You should be pressure testing at 6-9 psi and it should leak nothing for a minimum of 3 minutes according to Group K. I like to use 10 minutes.

Make sure you are checking the cooling nipples and oil fittings for leaks with your soap too as your air leak could be going into the cooling or oil passages.

 

[Sportster-2001-951C-Stock]

How'd the cooling system leak check go? I'm no fan of base gasket inward water leaks.

 

[Boyd12]

You should be pressure testing at 6-9 psi and it should leak nothing for a minimum of 3 minutes according to Group K. I like to use 10 minutes.

Make sure you are checking the cooling nipples and oil fittings for leaks with your soap too as your air leak could be going into the cooling or oil passages.

The sea doo manual states 5psi for 3 minutes. I would think 6-9 psi is WAY too much. I have the cooling nipples and oil passages with no signs of a leak. A large leak would be a LOT easier to find.

 

[Boyd12]

How'd the cooling system leak check go? I'm no fan of base gasket inward water leaks.

it passed the cooling system check. yay!

 

[Boyd12]

Agreed hardly any leak at all. Our mechanical seal test required a drop of less than 3 pounds in 5 minutes but you have to factor in the volume of the container you are testing. Air is very difficult to seal.

"Our mechanical seal test required a drop of less than 3 pounds in 5 minutes" Is that a SD spec? SD is 5lbs for 3 minutes with no leak. I like your test better!

 

[Sportster-2001-951C-Stock]

I think of it as how much is too much, they're all gonna leak some amount. A gross leak will make a difference where a small leak won't be an issue. That is, as long as the small leak doesn't become a gross leak based on the "where there's smoke there's fire" rule.

In my experience with 2-strokes, leaks around crank seals create an unsteady idle where it's difficult to dial in a consistent idle mixture. Too rich one moment and too lean the next.

 

[mikidymac]

A fresh engine will hold 8psi indefinitely.
Any leak on a fresh engine is an issue. Your engine shouldn’t have any leaks. They all won’t leak and shouldn’t leak anything. And every engine should be tested, new or old. I have found them on fresh engines even when everything was done correctly.

8 psi for a minimum of 10 minutes is standard, been using that for 25 years.

Here you go from the man himself.....,
http://www.groupk.com/tec-airleak.htm

 

[Sportster-2001-951C-Stock]

A fresh engine will hold 8psi indefinitely.

"The perfect engine will lose no pressure for about 3 minutes. "

Some people will spin the crank to several positions while performing the test.

I argue against conditions for a motocross engine are more extreme than a PWC engine unless there's data to back this up, rate of fuel consumption creates heat that destroys oil film and internal components, not transitional horsepower peak lasting a few seconds. Yes, peak HP/cc might be twice but I bet average BTU's consumed/cc is considerably more in the case of a PWC:

"The realities of air leaks If you were to pressure test every personal watercraft engine at your local lake on a Sunday afternoon, you would find about 40% of them to have minor air leaks. Another ten percent will have major air leaks. Despite these potentially fatal leaks, most of these "leakers" will run for some time before they destroy a piston. These same air leaks that would be almost instantly fatal to a motocross engine, are easily tolerated by a watercraft engine...why? The answers are related to H.P. per cc and engine loads. "

"In fact it's very common for air leaking engines to start and idle very nicely. "

This isn't true in my experience, every leaky crank seal I've found was causing terrible idle mixture control. Rotax engines, like many 2-strokes, are known for their propensity to run away instead of idle if an appreciable air leak is present. This is a strong argument for the practice of starting the Rotax briefly, out of the water on the trailer.

Or you could save a bunch of time by using one of these:
https://www.leyboldproducts.com/media/pdf/90/c7/87/Fundamentals_of_Leak_Detection_EN.pdf

 

[Boyd12]

A fresh engine will hold 8psi indefinitely.
Any leak on a fresh engine is an issue. Your engine shouldn’t have any leaks. They all won’t leak and shouldn’t leak anything. And every engine should be tested, new or old. I have found them on fresh engines even when everything was done correctly.

8 psi for a minimum of 10 minutes is standard, been using that for 25 years.

Here you go from the man himself.....,
http://www.groupk.com/tec-airleak.htm

"The perfect engine will lose no pressure for about 3 minutes. "

Some people will spin the crank to several positions while performing the test.

I argue against conditions for a motocross engine are more extreme than a PWC engine unless there's data to back this up, rate of fuel consumption creates heat that destroys oil film and internal components, not transitional horsepower peak lasting a few seconds. Yes, peak HP/cc might be twice but I bet average BTU's consumed/cc is considerably more in the case of a PWC:

"The realities of air leaks If you were to pressure test every personal watercraft engine at your local lake on a Sunday afternoon, you would find about 40% of them to have minor air leaks. Another ten percent will have major air leaks. Despite these potentially fatal leaks, most of these "leakers" will run for some time before they destroy a piston. These same air leaks that would be almost instantly fatal to a motocross engine, are easily tolerated by a watercraft engine...why? The answers are related to H.P. per cc and engine loads. "

"In fact it's very common for air leaking engines to start and idle very nicely. "

This isn't true in my experience, every leaky crank seal I've found was causing terrible idle mixture control. Rotax engines, like many 2-strokes, are known for their propensity to run away instead of idle if an appreciable air leak is present. This is a strong argument for the practice of starting the Rotax briefly, out of the water on the trailer.

Or you could save a bunch of time by using one of these:
https://www.leyboldproducts.com/media/pdf/90/c7/87/Fundamentals_of_Leak_Detection_EN.pdf

today it was 2lbs in 2 minutes which is way too much. i have checked this from top to bottom and cannot find the leak. I read the Group K article and is states using WD40 causes the leak to be audibly more apparent. I tried it. I didnt hear a difference.