Curious question about rust

[baller760]

You know how our cars tend to aquire rust on the frame and such? Well, what about the block itself? What if there was some rust on the front of the block or on a rod or something? Would there be a problem as long as it was lubricated with oil? Or would some metal flake off eventually and cause the car to throw a rod? Just a curious question I had when I was talking to my friend about rust the other day.

 

[Ormand]

The outside of the block can rust, without hurting anything, and it does, where the paint gets chipped off. Cast iron is kind of self limiting, it forms a tight rust that doesn't fall off, then it stops. The parts inside of the engine won't rust unless you let it sit for a long time- the oil protects it.

 

[baller760]

Hmm...Interesting. I figured the outside of the block didn't really matter, just the internals. So what would happen if the block sat a long time and moisture got on the crank and rods creating some rust? What would happen to the internals?

 

[CTX-SLPR]

Hmm...Interesting. I figured the outside of the block didn't really matter, just the internals. So what would happen if the block sat a long time and moisture got on the crank and rods creating some rust? What would happen to the internals?

they would grind themselves into junk since you no longer have a flat surface for the bearings to creat an oil film on. Rust on the sides of a rod might seperate and cause oil contamination problems, but if it rusted in the journals you'd probably spin the bearing due to the crank grabbing it or the rod not holding it in place. It take either an open engine in the yard or a gasket failure to put coolant into the oil to rust most engine internals. Cast iron forms a stable oxide layer unless you really try to make it rust when it can exibit exfoliation cracking mostly do to water being forced into the grain structure and busting it open.