Need Help With '41 Exhaust Leak

[neil morse]

I recently got a new exhaust system from Waldron's and had it installed by a muffler shop.  After a few weeks, it had developed a leak at the expansion joint in the Y-pipe just under the manifolds.  The joint in question is shown in this pic of the pipe before it was installed.

 

 

I could hear the leak, and could feel it by holding my hand above the upper, front side of the expansion joint.  I took the pipe off and found this damage to the "doughnut" gasket at the joint.

 

 

I put the pipe back on with a new set of gaskets, being careful to follow the procedure in the shop manual on the order in which to tighten up each joint.  However, after a single heat cycle, the pipe is leaking in exactly the same spot.  I made sure the bolts are tight, and they are at their maximum.  Those two plates are absolutely clamped together.

 

I called Waldron's, and the guy I spoke with was friendly but couldn't offer any particular help.  He did say that it might help for the straight pipe to extend further into the lower pipe, and said they would fabricate a longer pipe for me if I couldn't otherwise solve the issue.  He also suggested that a product called "exhaust paste" could help.  I searched the internet and found several suppliers.  This is one:

 

https://www.wurthusa.com/Chemical-Product/Miscellaneous/Exhaust-Assembly-Paste-4-94-Fl-Oz-Tube/p/0890100045

 

I'm going to send for another set of gaskets and give it another try.  Has anyone worked with one of these joints?  Any other suggestions or comments?

 

Thanks in advance,

 

Neil

[Bloo]

I have used a lot of Wurth products when working in European car shops, but have never seen that particular exhaust paste and I am not sure what it is or what it is like.

 

If someone said "exhaust paste" to me, the first thing I would think of is Walker Acousti-Seal. It might or not be similar to stove cement. Acousti-Seal is a black tarry substance that you don't want on your hands because it will never come off until it wears off. It cures with heat and becomes fireproof but brittle. It is most useful for slip joints in exhaust, because it seals them, but what is rarely mentioned is that the joint will seal up with less clamping force, and also that it acts as an INSULATOR. This is a big deal because when it is time to take the slip joint apart, it won't be as warped, and the brittle Acousti-Seal will break up and turn to powder when you twist on it. Better yet, if the slip joint still won't come apart, when you put a torch on the outer pipe it will expand a lot and come off, because the Acousti-Seal acts as an insulator. If the joint were instead allowed to rust together, the torch would heat up both the inner and the outer pipes and both would expand and the joint still wouldn't come apart.

 

Acousti-Seal can be good on flat gaskets on exhaust pipes as well when the flatness of the flanges is questionable. It wouldn't have occurred to me to use it on a donut gasket because they are meant to move a little, but I wouldn't be opposed to trying it.

 

Maybe extending the pipe would help. Some flanges like that do have a little more pipe that extends through the donut. The thing that stands out to me is that the plates were clamped together tightly. Normally I don't think that would be true with that type of donut gasket. Maybe the donut is a little too small and the flanges are bottoming too soon?

 

Edited July 28, 2022 by Bloo (see edit history)

[Matt Harwood]

They make exhaust donuts like the one you've got but with a steel core. It's less flexible but the steel core should fit into the upper and lower pipes and hold the donut in place at the joint. That way the gasket material is just sealing the joint while the steel sleeve is handling the structural integrity. Your auto parts store should have a bunch of them--ask if you can go back there and look at them and see which one will fit best. I used them for a while between my cracked exhaust manifolds and the old Y-pipe and they worked pretty well.

 

It should be something like this, although I've seen them where the steel flange sticks up on both sides of the donut to fit into both sides of the joint and reinforce it:

 

[Bloo]

Isn't there a central pipe sticking down the middle of the upper piece, locating the gasket on the flare? It looks like it in the pictures. Wasn't that what the Waldron rep was potentially going to lengthen?

[EmTee]

Yes, it does look like the doughnut fits onto a stub of pipe.

 

 

Seems like that should slip into the lower pipe if it's really a 'slip joint'.  The way it is looks more like the joint where a manifold mates with a headpipe.

[neil morse]

Thank you all for your helpful responses.  I'm sorry for any confusion about the configuration here -- I posted the only photo of the pipe that I have from before it was first installed, and it's a bit unclear.  Yes, Bloo is correct.  The upper pipe reduces in diameter and then extends through the doughnut and down into the lower pipe.  I can post much better photos of the whole thing once I get it apart again.  The "extension" portion is only about an inch or an inch-and-a-half.  Again, sorry to be so vague but I can't measure things until I get the pipe off again.

 

The thing that jumps out at me so far is what Bloo said about the size of the doughnut.  It just doesn't make sense to me that those two plates are in contact.  It seems like the doughnut should be a bit bigger so that it is still under tension forcing the inside diameter to seal against the upper pipe.  But I'm thinking these doughnuts must be standard items?  Matt's post makes me think that maybe I can find a doughnut that's a bit fatter.  The first doughnut (installed by the muffler shop) was provided by Waldron.  The second one (which looked pretty much the same) was one I got from Bob's.  I will look around at some local shops, as suggested by Matt.

 

I will report back after I disassemble it again and can post better pics of the upper pipe.

 

 

[Wayne R]

Neil,  in case this helps---when you rea tach   make sure the  connection is  dead parallel  to each other,.

and when you connect   move the  attachment  plates around  to another position then you  did  at the  first time.

 

Here in my opinion is the best paste on the market---CRC  Maniseal.

[Wayne R]

Sorry   did not realize  its made in Ausy  and NZ---may not be available in  USA---not sure.

[Den41Buick]

I don't know if this will help you but I had the same issue. My solution was to reuse the old doughnut. 

[neil morse]

1 hour ago, Den41Buick said:

I don't know if this will help you but I had the same issue. My solution was to reuse the old doughnut. 

Please tell me more.  Was the old doughnut "fatter?"  That seems to be the problem I'm having.  I haven't had time to do anything about this since I posted a few days ago, but I'm going to start next week searching locally to see what I can find.  From what Matt Harwood said earlier, it looks like all 2" doughnuts are not the same.  If I could find a fatter doughnut, I think the problem would be solved.

[Den41Buick]

From what I can remember I installed the new doughnut and the leak continued. I swapped it out for the doughnut that was already there which was different in shape. I cannot recall if it was fatter or not.  With two 41's it sometimes gets blurred. I have replaced the y pipe in both of them. 

Good luck Neil.

[neil morse]

I have gotten a new doughnut that's a bit thicker and I'm ready to give it another try.  The Walker Acousti-Seal recommended by @Bloo sounds like a good idea, but it seems to be unobtanium.  I haven't spent a whole lot of time searching the Internet, but everywhere I have found it so far it is "out of stock" or "unavailable."  Any other ideas on where to get the Walker's or for an alternative product that would work?  As always, thanks in advance for your help.

[Bloo]

That is odd. I know of no other product like it. There could be others, but I have not seen any. Someone told me it is like "stove cement" as used on wood stoves and flues(?). That is completely unverified. I just looked around and you are right, everyone is out. I did see that Autozone was willing to "ship to home", estimated delivery Aug. 5 (to central WA) so they must have a little left in a warehouse somewhere. Now that you bring it up, I think the last time I tried to buy some I couldn't get it on the shelf locally and had to go to Amazon or something (they are out of stock too right now).

[neil morse]

2 hours ago, Bloo said:

I did see that Autozone was willing to "ship to home", estimated delivery Aug. 5 (to central WA) so they must have a little left in a warehouse somewhere.

Thanks, Bloo!  I missed that in my search.  I just ordered it.

[Lawrence Helfand]

I had sealing issues as well and tried a few seals the best being from looking through the box at my local O Riley's. Still had leakage from both pipes and ended up using a muffler paste to seal every crevice. As its water based you can gob it on  and clean up with a sponge to keep it neat. Its my nose rather then my ears that tell me I have a problem as engine fumes easily enter the cabin even on the fairly well sealed Buick firewall. 

[neil morse]

Update

 

I took the pipe apart again and found the problem.  First, here's what the upper pipe looks like where it reduces in size from 2.25" to 2" and fits into the doughnut.

 

 

The problem is that the OD of the pipe that fits into the doughnut is too small.  The ID of the doughnut is 2.049".  The OD of the pipe (which is slightly out-of-round) varies from 1.965" to 1.984".  There is just too big a gap for the doughnut to ever seal, even when completely compressed.  This little video shows how loose the fit is.

 

 

If I were more experienced, I would have noticed this right away.  I talked to John, the owner of Waldron's, this morning about the problem.  He's going to make me a new upper pipe, and said he thought he could have it done and shipped out by Thursday.  In the meantime, I have gotten some of the sealant that Bloo recommended, and I will use that as well.  So I'm hopeful the problem will be solved.  I will keep you posted.

[EmTee]

I'm glad to hear that you found the problem and Waldron's is standing behind their product.  In the meantime I was going to suggest using a pipe expander to improve the fit.

 

https://www.harborfreight.com/large-exhaust-pipe-expander-57184.html

 

[neil morse]

3 hours ago, EmTee said:

I'm glad to hear that you found the problem and Waldron's is standing behind their product.  In the meantime I was going to suggest using a pipe expander to improve the fit.

That's a great idea, and if Waldron weren't going to send me another pipe, that's exactly what I would do.  John at Waldron's told me that sometimes the tool they use to shrink the pipe down from 2.25" to 2.00" goes overboard and they end up with a pipe (like mine) that's too small.  He said they can then remedy the problem by expanding the pipe back to the correct dimension.  I don't know why they didn't catch the problem with my pipe (and I didn't ask), but it sounds like a QC problem.  In any event, I'm happy that John is willing to make it right.

[Larry Schramm]

John at Waldron's is a good guy.

[neil morse]

13 minutes ago, Larry Schramm said:

John at Waldron's is a good guy.

Yes, for sure.

[neil morse]

Update

 

I'm happy to report that I got the new pipe from John at Waldron's and the new gaskets that he supplied as well.  What a difference!  The OD of the new pipe was 2.009.  And most curiously, the doughnut gasket he supplied had an ID of 2.006.  So a very snug fit indeed.  I guess all 2" doughnut gaskets are not created equal, but that's quite a jump from the 2.049" doughnut that I got from Bob's Automobilia.

 

Here's a shot of the pipe with the doughnut -- quite a difference from the earlier combination.

 

 

I had ordered the Walker sealant recommended by @Bloo, which AutoZone said they had in stock.  Turns out what I got was a "replacement" for the part number for the Walker sealant, something made by Yale Automotive.  

 

 

So I put it all back together today, using a coating of the "Muffler Cement" on the pipe where it fit into the doughnut.  So far, so good.  I can't hear any exhaust leak, but I'm quick to admit that I had trouble hearing the leaks in the first place.  Both Don and Konrad heard them immediately, but I'm just not experienced enough to know what to listen for.  But I can't feel any leaks this time.  And the past leaks were very evident.  In any event, I can't imagine a tighter fit on the doughnut, so I'm hoping this chapter is done!