Author Topic: Exhaust doughnuts blown out after only 1400 miles.  (Read 82 times)

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Offline udidwht

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  • Year: 1994
  • Model: Southwind Storm 28ft
  • Chassis: P30
  • Engine: 454TBI w/4L80E
Exhaust doughnuts blown out after only 1400 miles.
« on: July 16, 2021, 06:16 PM »
I replaced both exhaust doughnuts before my return trip home (HB,Ca. - Renton, Wa.) and the passenger side one started getting noisy again when close to home. Crawled underneath and I'll be damned the doughnut on the passenger side is nearly gone after roughly 1400 miles. Wondering if an flaky EGR can cause this? This RV has 454 with electric driven EGR on the passenger side of the engine below the air cleaner housing. This issue popped up while in southern Ca. and I bought (2) Fel-Pro Duralast doughnuts and replaced both. The passenger side one was completely gone except for the metal ring the gasket is attached to. Roll forward...~1400 miles the same gasket (passenger side)
is again having to be replaced. It still has some gasket material around the metal ring but not much.

One other thing I noticed...prior to removing everything the bolts the hold that the flange up seem to bottom out on the threads before cinching down on the springs. Of the (3) bolts one of the springs could easily be moved up/down and the other springs spun once tightened. I'm thinking the bolts did not tighten enough and air drawn in eroded away at the gasket. The drivers gasket side looks great after the return trip.

Vehicle is in signature.
1994 Fleetwood Southwind Storm 28ft
P30 454 TBI w/4L80E
68,295 miles and counting....(01/07/21)

Offline Oz

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Re: Exhaust doughnuts blown out after only 1400 miles.
« Reply #1 on: July 17, 2021, 12:26 AM »
If you've got super hot exhaust blasting away at those donuts because there's a gap and not properly fitted, yeah, they're not going to last very long.

Offline eXodus

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Re: Exhaust doughnuts blown out after only 1400 miles.
« Reply #2 on: July 17, 2021, 04:24 AM »
yeah lean exhaust would do that. Any codes or bad mpg?

But also loose bolts.

Get Tap and run the holes clean before you replace with new bolts.   The bolts should have flange where they are then sitting at the correct depth.
Those springs shouldn't move.  When I changed mine - they treads where compressed almost all the way.

Offline Eyez Open

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Re: Exhaust doughnuts blown out after only 1400 miles.
« Reply #3 on: July 20, 2021, 12:11 AM »
Well if you have a smog pump engine.... a bad gasket seal issue will be greatly magnified. GM set up the timing so late about 25 % of the combustion process is burned up in the exhaust manifold. After Burners with no bite is very descriptive.