Leak dump elbow / Y-pipe junction

[JEC]

5.7 L Alpha One Gen 2:

Put in new exhaust shutters (the upgraded version, Mercruiser OEM parts) and on in water test now have small leak where dump elbows meet Y-pipe, starboard greater than port side. With engine at idle, can see water leaking from under the rubber coupler at one point where rubber coupler meets and covers the Y-pipe. Tightened the hose clamps and tried relocating them to various points around the circumference of the coupler. Was able to get the port side to almost stop but still have small leak on the starboard side.
I put the couplers back in the same configuration they were in before the shutter replacement.

It occurred to me that the lip on the new upgraded shutters might be sitting somewhat proud of the outer circumference of the Y-pipe and preventing adequate tightening of the
hose clamps. I think I'll take apart the starboard side and look at this and if the shutter outer circumference is proud of the Y-pipe outer circumference I might sand it down
some and see if that helps. I did get the hose clamps really tight with a nut driver. Didn't want to put a ratchet on it to get it tighter.

Anyone else run into this kind of thing? Suggestions for fixing problem?

Keep tightening hose clamps a little at a time? Reorient coupler? New hose clamps? Sealant? Other?

Would appreciate any ideas?

Thanks,

JEC

 

[cr2k]

Re: Leak dump elbow / Y-pipe junction

What you said is what you need to do. Other then making sure they aren't rusted thru.

 

[JEC]

Re: Leak dump elbow / Y-pipe junction

cr2k,

Thanks for your note. The dump elbows looked solid, no internal rust to speak of so I'm pretty confident I can rule out a "rust through"
problem. I also had a pretty good look at the lower rubber couplings when I cleaned them up prior to reinstalling them and they also looked
solid.

Those newer version exhaust shutters do have a lip that sits on top of the Y-pipe as opposed to the older original equipment shutters which
were recessed somewhat below the top of the Y-pipe. It's only leaking between the top area of the Y-pipe and the lower part of the lower
coupling and then leak flows down side of the Y-pipe. It's leaking where the geometry of the components changed due to installation of the
newer shutters so I'll explore that area as stated earlier. I might also try to lower the lower coupling about a 1/4 inch down the Y-pipe and
see if this doesn't give me some more purchase on the Y-pipe for the clamps to act on.

Any other ideas are appreciated. Anyone experience this with an exhaust shutter change?

Thanks,

JEC

 

[cr2k]

Re: Leak dump elbow / Y-pipe junction

Some Pipes and Couplers have a lug cast into them. If you slide the hose over this you will have problems sealing. The lug is a stop for the hose.

Could the water be coming thru the pin holes for the old style flappers?

 

[JEC]

Re: Leak dump elbow / Y-pipe junction

Thanks cr2k,

The lower part of the dump elbow has an external lug as you mentioned that acts as a stop for the lower rubber coupler when it's pulled up from the Y-pipe onto the dump elbow during the reinstall
process. There is a slight dimple on the upper portion of the lower rubber coupler where a prior
installer pulled it up tight against the stop on the dump elbow (didn't leak before) and I used this indentation as a maker for the circumferential
orientation of the lower coupler relative to the Y-pipe to keep the oval "set" in the coupler matched to the oval shape of the Y-pipe. Coupler was never slid over these lugs, just up snug against them, and no prior leaks.

I also wondered if the leak might be coming through the pin holes in the Y-pipe for the old style flappers
but if there was a leak from this area it would also affect the old installation as the pin for the old
flappers just sat loose in there. The new flappers have a round stub that sits in these holes but there is no protrusion of these to the outside of the Y-pipe.

I'll look at the outside rims of the lip on the new flappers this morning and sand them down if they are proud of the outer circumference of the Y-pipe as we discussed. Will also lower the lower
coupling down 1/8 to 1/4 inch away from the stop lugs on the dump elbow and hopefully this will
take care of this. Doubt lower coupler is damaged but will inspect as well when I get it off again.

Thanks for help, will let you know how this worked out when it's fixed.

JEC

 

[JEC]

Re: Leak dump elbow / Y-pipe junction

Got it fixed

Sanded the new exhaust shutters where the circumference of the lip was proud of the circumference of the Y-pipe. Moved the lower rubber coupler down about 1/8 inch from the stop lugs on the dump elbow. Sanded the outer circumference of the top of the y-pipe. Y-pipe there has a little dimple, the way it was cast. There was still a very very slight trickle leak at the starboard side. Tightened the clamps a little at a time until I got the leak stopped. Did not have to "overtighten" the clamps. Didn't want to risk breaking a clamp. Bottom line: I think this was related the proud outer edge of the new shutters: Imperfect plastic going into imperfect cast iron y-pipe.

Thanks cr2k for your suggestions.

JEC

So there are