Two cylinders not firing after washing engine compartment

sproggy

sproggy

Joined
Nov 26, 2013
Messages
703
Location
MA
NOt sure why dipping your exhaust in water would be so harmful (unless salt water). The outside certainly gets wet every time it rains and if the pipe is submerged with engine running I assume not much water is making it too far up against the pressure of the exiting exhaust. Of course, turning the car off and the water running in to the muffler and headers? I'm sure plenty of condensation hangs out in there in colder months and any water would quickly be burned off....no?
 
Dizzy

Dizzy

Joined
Feb 5, 2018
Messages
2,436
Location
Santa Fe, New Mexico
All steel has internal stresses, tension.

Uneven temperature will accentuate particular tensions within. The weld that was pulling hard on my header while it was evenly heated, these tensile forces will be even greater is the weld is cold, and the hot metal above it will have to yield on a micro scale. It is a loading/unloading internally.

Castings are heated and cooled slowly and evenly so they don't crack, as castings have incredible compressive strength, but significantly less strength in tension, so we find a bunch of cracked manifolds over time. The welds on header collectors are where trouble begins as the weld puddle kinda ruined the best DOM tube that it was constructed from because it cooled quickly and it imparts structural variation on existing internal stresses, also, welding is much like a microcasting. Uneven heating (beyond a point) means uneven tensile stress, resulting in fatigue. Drive for a while on a cold day, shut the engine off, and you can actually hear the exhaust as it cools because it does it unevenly and rapidly.
 

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