Exhaust pipe leak at manifold

[DonaldSmith]

I am moving my situation to a new topic, so as not to get buried in the topic that I highjacked. 

My leak seems to be caused by the pipe not aligned with the manifold.  The loose flange had been distorted by excessive cranking.  But the gasket did not seal, so it leaked, both sides near the overworked bolt.

 

 

The pipe is 2" O.D, and extends several feet under the floor, where it joins with a 1-3/4" pipe which extends to the muffler.  I saw-cut through the smaller pipe near the joint, freeing the larger pipe.

 

 

The pipe reduces to 1-3/4" at the (flange?) (ridge?) (boss?) where it fits into the manifold.  So the original design, with a flat gasket, should work, with a little exhaust sealer for good measure.  I'll keep the pipe in proper position by undoing the support by the muffler and and adjusting the height of the pipes with a scissor jack. 

 

Wish me luck

 

  

[DonaldSmith]

(Where's my Edit button?)  The highjacked thread is "1952 Cranbrook Exhaust Doughnut".  So the earlier Mopars used a flat gasket instead of a doughnut.   I saw a Plymouth parts diagram showing the big flange with the two bolt holes welded to the end of the pipe.  My pipe may have been an aftermarket version.  

[Sniper]

You might be able to find a thicker flange to replace your bent one, but the flange doesn't do the sealing anyway.  The ring around the end of the pipe is what seals to the gasket, so look closely at how that fits up.  Your gasket might be have a center hole that is a little too big leaving barely anything to seal up against that ring. 

[DonaldSmith]

Ring - that's the word I was looking for.  The pipe end is 1-7/8", the ring is 2-7/16", and the gasket hole is 2-1/4".  Not much room for error.   I need a smaller gasket or a lot of (cop-out) exhaust sealer.    

[Plymouthy Adams]

personally I think a new down pipe welded to a bit better flange (thicker) is in order...the sealing surface of the small pipe shoulder/flange as shown is for a donut as further supported by what appears to be a dished flange for the cup of the pipe sealing ring.  Your surface as pointed out by sniper is just to small and with the obvious over tightening has not sealed and has instead bent the ears of the flange...lessening the over all clamping effect.  Further that manifold appears to be weakened by a crack and may well be the next failure item here and you will need to tread with caution for sure.

[DonaldSmith]

For the record, The epoxy blob makes the cast iron look worse than it is.  The casting extends past the bolt, and should be adequate, if I don't crank the bolt to try to align the pipe to the manifold.   It would take some unusual stress to pop off the outer edge of the casting.   Or maybe someone dropped the manifold, once upon a time. 

 

 

I just bought a donut and a conventional gasket, my choice, plus the adaptor to reconnect the other end of the pipe.  (One of those hole-in-the-wall independent parts places that has everything, at a good price, D&D in Troy, Michigan.  The NAPA guy sent me there.  NAPA is usually better than O-Reilly and the lot.)

 

[DonaldSmith]

I fixed the exhaust leak. I went with flat gasket and ample exhaust sealer.  (A second trial donut was the right diameter, but still too thick.) 

 

I cut the pipe from the manifold at its joint with the smaller pipe downstream. That let me remove the pipe to straighten the loose flange and the ridge at the manifold end, and properly align the pipe with the manifold.  I sanded, cleaned wetted down the mating surfaces of the pipe and manifold. per the JB Weld Exhaust Sealer instructions. 

 

I trial-fit the pipe to the manifold, so its other end was at the height it wanted.  I undid the pipe hanger near the muffler, supported the muffler and its the pipe with a scissors jack, and aligned the pipes with a splice fitting, 2" to 1-3/4". 

 

I went with a new flat gasket, the same size as the old one.  I was concerned that the gasket opening was noticeably larger than the 1-3/4" end of the pipe, but realized that the bolts would keep the gasket aligned.  I thoroughly laid down sealer on the pipe ridge and on the top surface of the gasket.  I tightened the bolts, and filled the annular (ring-like) space with more exhaust sealant.  I followed the sealer instructions.  I waited at least a half hour, and ran the engine for more than 10 minutes. 

 

At the coupling, I sanded and wetted down the pipe surfaces.  I laid down a bead of sealant on each pipe, slid the coupling over the pipes, cranked down the nuts, and filled the annular spaces with sealant.  I installed a hanger to support the pipes at their proper height.  Again, wait a half-hour or more, run the engine for 10 minutes or more.  Quiet, except for the muffler's usual burble.