Lower unit leak test

[rdenis]

Pulling the lower unit to find my gearcase water source - can I pressure/vac test the unit in a tub of water once I've pulled it? Should it be supported in a full down position or does it matter (presumably not laying on its side)?

 

[Daviet]

Re: Lower unit leak test

Sure, pump it to 10-12# pressure and submerge in water and look for bubbles.

 

[wilde1j]

Re: Lower unit leak test

Drain the gear oil first. You haven't said what motor, but the V4 and V6's should hold some pressure or vacuum for at least 45 minutes.

 

[rdenis]

Re: Lower unit leak test

Whoops its 1979 Johnson 115 V4. Drained it this am only to find beige milkshake - never seen oil emulsify like that - probably some air in there too.

 

[lindy46]

Re: Lower unit leak test

Yup, water getting in somewhere. Make sure the seals/washers are on the drain and vent screws - that's the most common source of water intrusion.

 

[rdenis]

Progress

Progress

Alright after much saga in getting my lower unit off I finally did the pressure tests this am in a big tub. The lower unit holds pressure of 10 PSI for over an hour - dropped to 8 but that is a small leak in my hose connection/Mityvac. Also did the Vac test to 15 inches for an hour and it holds the same.

So it has got to be the top fill hole right (since this is where I connected my pressure tester)? Its the only variable left as far as I can tell, since everything else is sealed and holding.

The one thing I am thinking is the washer - on the top fill screw it is plastic - on my pressure tester I use a rubber O-ring and I had to tighten it with a vice grip to eliminate initial air bubbles. To me this appears to be a problem with the washer mating the surface of the thread housing - seems likely the plastic washer perhaps cannot tighten enough against the surface.

I guess I should run the test again from the bottom fill hole to verify the source is the top fill screw. If it turns out my theory is correct, is there any reason not to use a rubber O-ring instead of the plastic washer?

 

[Daviet]

Re: Lower unit leak test

Some lower units use an o-ring, but the screw has to have a grove in it to seal it properly.
I have never had a problem with the plastic washers not sealing properly. Make sure there is not an old washer still in the housing and the plugs are not damaged.

 

[HighTrim]

Re: Lower unit leak test

The plastic washers are "crush" washers, and can only be used once. They are not expensive, I buy them by the bag.

I always test from the drain hole. After the lu passes the original 10psi test, I bump it up to 16-18 psi. It should hold that.

 

[rdenis]

I found the leak!!!

I found the leak!!!

Okay so I redid the tests from the lower drain hole and once again pressure held and I was like WTF???? Then I decided to turn the drive shaft by hand (in neutral) and thar she BLOWS - burp, bubble, bubble, bubble from somewhere under the water pump housing.

I have a new kit so I am going to instal that now and see if my leak goes away.

Crossing my fingers....

Rich

PS - Thanks for all the helpful suggestions from everyone here!

 

[Daviet]

Re: Lower unit leak test

You have 2 seals, back to back, in the bearing housing under the water pump as well as an o-ring around the bearing housing.

 

[rdenis]

Re: Lower unit leak test

Thanks Daviet - do the back to back seals orient a particular way or is it obvious?

 

[rdenis]

Re: Lower unit leak test

Sorry one other question - is it wise to lube the seals and O-ring lightly with waterproof grease before putting on?

 

[Daviet]

Re: Lower unit leak test

The bottom seal keeps the oil in (spring down) and the top seal keeps the water out (spring up).
I always use lube on the o-rings and seal contact area, some don't.

 

[rdenis]

Re: Lower unit leak test

Thanks!

 

[rdenis]

Re: Lower unit leak test

I am having a b**ch of a time getting the seals out of the upper driveshaft bearing housing - I've tried driving them from the edges with a small screwdriver but no go - I do not want to end up scoring the inside of the housing so I didn't apply too much force. Is there a trick to this (or special tool I need)?

Also the replacement seal I received is all one piece (not sure if the OEM is one or two as the diagram shows two) and would appear I need to remove the bearing in order to install it correctly. Can I drive the bearing out or do I need a really small puller?

 

[Daviet]

Re: Lower unit leak test

If I remember correctly, the seals go in from the top and the bearing from the bottom. I think I used to use a thin punch and come from the bearing side (bottom) and drive the seals out of the top. I don't have access to a manual right now, will try and look it up tomorrow if someone else doesn't chime in with some advice
I don't think I have ever seen anything except 2 single seals put in back to back, but times change and maybe they make them as 1 unit know, although the parts breakdown still shows 2 seals.

 

[rdenis]

Re: Lower unit leak test

Thanks very much for that Daviet - I'll keep working at it. I think you are right in coming from the bearing side and driving it out the top. There seems to be at least two different diagrams of this same engine - one showing two back to back seals and OEM part #321453 and then there is the diagram from glmmarine.com that shows one seal and OEM part #341280.

The part in the seal kit I got is from glmmarine.com and of course one piece, which is what lead to my initial confusion! But I am sure it goes in from the top the more I look at it.

The damn bearing makes it awkard to drive the seal out since you have to come at an angle which makes me nervous about scoring the walls. But I'll just be patient and take my time. (I tried putting a small bearing puller on the bearing but there isn't much to grab and the puller arms kept slipping off - didn't want to further risk damaging the bearing so I gave up on that idea).

 

[rdenis]

Re: Lower unit leak test

Upon further review and confusion of GLM's Johnson catalog, seems there are several errors in their diagrams - the one piece seal apparently is for the 1985 and newer models. The seal kit has numerous seals for different engines of different years and some of the seals have part numbers which match GLM and some don't. In any case I think I have two back to back seals that sould work if I can get the other ones out! What a mess....

 

[rdenis]

Re: Lower unit leak test

Okay I got the seals out. Now to put in the new ones, install the waterpump kit and preesure test.

Thanks Daviet and everyone else - I'll holler if I have any more problems!