There is an old 13b I'm looking at buying that has a rusty coloring around the coolant line inlets. (see attached picture) I've only bought one other 13b that had rusty looking crap like this one and I found out later it had a old blown coolant seal. Is coolant rust indicative of a bad seal? It's entirely possible that I am crazy, so I'm not discounting that just yet.

Any thoughts you rotary people?

 

Rust means a poorly maintained cooling system. It does not automatically mean it has a blown seal, but I wouldn't put it past an old engine that it does have failed seals. If you purchase it, use a garden hose and try and blow out all of the rusty water as best as you can in the reverse direction of flow.

Install the engine and run an aluminum safe radiator cleaner through the engine and flush it out. It will not look brand new, but it's the best you're gonna get without a tear down,

 

It's nothing to worry about by itself.

 

half the engine is cast iron, you're bound to have some rust in the cooling system, even if the coolant is clean.

 

Especially if tap water was used during a coolant service to bring the coolant mix to 50/50. I have seen plenty of cast iron blocks free and clear of rust with proper maintenance, but it's rare.

 

never once seen a rotary come apart that didn't have some rust in the coolant passages. some look much better than others though.

 

I work on more than rotaries at the shop. Some engines are better than others, but all rotaries I have seen have some rust to them. I would expect that new housings and a better quality coolant or a different type, such as a long life HOAT coolant would fare better.

 

all the new irons i received had rust in them too, as mazda uses straight water on assembled blocks as a quality control test of them apparently. the rotor housings i didn't run into that issue with, they were machined then boxed and sent off.

 

At the end of the day, minor surface rust is not a big deal. I didn't know that brand new ones would arrive with surface rust. I would have expected them to be treated with cosmoline, similar to brake rotors.

 

newp, maybe not all series of irons are treated the same way but many of the "new" FC parts i received came from an engine that actually had been run before, but showed almost no sign of wear. these parts came from independent shops that deal with factory new parts too.

the examples were series 5 thick cast turbo rear irons, which may perhaps have been an exception in this case so i may in fact be wrong and not all irons go through this process before sold.