AQ131A Heat Exchanger Pipe Seals

[djhinca]

The boat is a 1986 Bayliner Capri, with AQ131A/275. I recently noticed that the copper pipe between the heat exchanger and the exhaust manifold has developed an intermittent leak, right at the heat exchanger coupling (see photo). Imagine,, after only 31 years of use!... During the first 15 minutes or so, it deposits about 1/2 gallon of raw water in the bilge. After that, it eventually reduces to a very slow drip. I assume that the rubber seal in the coupling slowly swells during operation, eventually stemming the initial leak. Nonetheless, the boat (and its owner..) are getting up in years, so I know that nuisance leak will eventually get worse. I've ordered new seals (VP part# 418412) and will add replacing them during this year's winterization. My question relates to installing those seals. I've read in numerous posts some negative comments regarding these heat exhanger "push-in" pipe connections and I guess it's fair to say that they wouldn't win "best seal of the year award" any time soon. So, would it be prudent to treat the pipe end, the fitting and rubber seal with permatex (or equivalent) gasket sealant during the install? I'd appreciate some advice on this point.

 

[dennis461]

The fitting in your picture requires an o-ring.
The copper must be clean, the o-ring lubricated and inserted correctly.
It must go nearly straight in.
And fully in.
Then it will not leak unless the plastic is cracked.

The other end gets the rubber washer which fits onto the pipe flange.
You also do not need a gasket or caulk at that end...
Unless you have rust on the exhaust manifold.
For mine is made a gasket, use the rubber also.

Now on my boat, my leaks could not be fixed until I bent the copper tube to line up exactly at each end.
If the copper pipe is slightly bent, then it is hard to get good alignment and seal at manifold. the o-ring is more forgiving..

 

[djhinca]

Thanks for the advice - sounds like you've had your share of hassles with this repair. I've checked the VP schematics for this assembly and for the entire AQ131 series A-D, they show a rubber seal # 418412 on the heat exchanger end. Based upon your info though, I'll anticipate that it may require an O-ring instead. If you have a VP part # or some size info on what O-ring you actually used, I'd greatly appreciate having it.

 

[dennis461]

Two different seal part numbers in this link.
I keep a couple of spare o-rings, 22mm I.D. 27m O.D.
If memory serves me, this size worked for me.
However, i had a problem with the HX inlet once and that also takes an o-ring.

Today's leak was the thru-hull for shift cable :-(

http://www.volvopentastore.com/Cool...on_id.868249709--store_id.366--view_id.782375

 

[jerryjerry05]

These aren't O-rings. The seal that goes in there is a grooved seal that fits over the flange end of the copper pipe.
​​It just pushes in and seals itself.
​I've found a tiny bit of lube helps.
Just make sure the plastic fitting is smooth and clean.
​ANY rough parts?? replace.

 

[PiratePast40]

In a perfect world, there should be no other sealant needed. On the AQ130s that I've worked on, the copper pipes have been a bit off and didn't always seal correctly. For the ones that didn't seal, it took a tremendous amount of time to get them bent back into position correctly so they were both square and seated all the way. I wasn't always successful and have used red permatex as a sealant after the pipe and square cut o-rings are seated. It takes a bit of finesse to get it in the correct area and clean it up so it doesn't look like a hack job. I let it cure before firing it back up to check for leaks.

If you're planning on replacing all the seals, be extra careful during the disassembly. That is when the copper lines are most likely to get bent and out of alignment.

 

[djhinca]

Thanks to all for some savvy advice. I think I'll try packing the existing connection with red permatex first and resort to a complete seal replacement this Fall if the leak persists...

 

[dennis461]

Thanks to all for some savvy advice. I think I'll try packing the existing connection with red permatex first and resort to a complete seal replacement this Fall if the leak persists...

Good luck with permatex, it did not work on my boat. :-(
And for clarity here, I am talking a AQ131, not A130.
The tube from HX outlet to exhaust manifold uses two DIFFERENT 'rubber's. One is an o-ring, as the forward end of the copper tube doe not have a flange.
The aft end takes the grooved rubber part.

Here is a picture of a tube which matches the one on my AQ131C
http://www.ebay.ca/itm/Volvo-Penta-...ash=item3ac859030e:g:oUEAAOSwMmBVsDxD&vxp=mtr