Opinions on this rear iron, please

[j_tso]

Hi, I'm a rebuild virgin.

I'd like to know which rear iron you think is better, I think both are useable.
The engine is an S4 non-turbo. It's going to remain standard, going into my first gen.

First the one that came with my block, it's fine all over, except there's some corrosion on the coolant pipes, but what got me concerned is the amount of wear on the water jacket at the bottom:

I've seen these completely breaking, so I sprung for another used iron.

This one's water jacket looks much better and has much less corrosion on the pipes, however,

There was some surface rust on the shiny parts. Most of it was removed with carb cleaner and a cotton cloth. I used a little steel wool too, but that didn't really help. There's still some speckles visible, but it's smooth as glass to the touch.
Here's before and after:


Another thing on this one, on the exhaust side carbon has crossed over the coolant seal. Seal failure? I haven't posted a pic because there's still much cleaning to do, but there doesn't appear to be any breaks in the metal. So I'm guessing the rubber itself had a small cavity in it.

so which is worse, thin water jacket, or speckles on the sliding surface?

[Ender]

I doubt you'd want to use the rusted iron. Pitting is evil, and since it sounds like it isn't surface rust, it is pitted.

The other one pics would be helpful. If the seal groove and plate surface can be cleaned to where there is no carbon, no pitting, no wearing of the seal retaining edges, and no out of factory spec deformation (check with super thin feeler gauges and a straightedge), then you should be able to reuse it. I think the exhaust side is a common place for coolant seals to give out, and then the hot gases just shred the metal if it's run much at all after a seal goes. I've seen some pretty wicked erosion.

Try rotaryresurrection.com, he has some tech tips with pics related to your questions there.

[j_tso]

Thanks for the response.

The one with the carbon worn through the coolant seal is the same as the one with the chamber rust. So, I'm probably not using that one.

The first pic is the one that's fine except for that one spot on the coolant jacket, how bad does that look? Would a closer pic be more helpful.

[Phoenix7]

post all the pics you can. This is great reference.
I think Rotary Resurection isn't hosting the how-to thread anymore.

[j_tso]

Sure, here are more:

The top one is the water jacket I'm questioning on the non-rusty chamber iron.
The bottom one is from the iron that has the rust, which I've decided not to use.


I know I'll have to do more cleaning, but the walls appear to be intact. The top has the minute "chip", it does get to normal size at the lower end.

It's not as bad as the broken ones on this Mazdatrix page:
http://www.mazdatrix.com/faq/sidehsgs.htm

And if you go to the Rotary Resurrection forum, the rebuild write up is being sold as a set of PDFs on CD for $25.

[Ender]

Hm...

Well, about the thin part of that wall. Good things:
+The height of the wall closest to the seal appears fine.
+I don't see any cracks

Can you tell what kind of event removed a little off the corner? For example: impact, erosion, rust, et cetera. And is it right at the bottom where combustion occurs? I think it's a little iffy, but if it's a somewhat budget rebuild I'd probably use it.

[j_tso]

Yes, it's at the very bottom of the housing.

I think it may have chipped from corrosion, but that's only spot on the whole engine where it's like that. I picked at it some, but not much more than caked up coolant comes off.


And yes, this is a budget rebuild.

[Ender]

As for coolant nipples in the irons, I pulled/cut them out (I think there are three...), tapped a thread, and inserted brass barbed nipples. I've had those damned things break on me and they're a pain to fix while the motor's in the car, so I did it during my build. I would recommend it. I think you'll need a couple 1/4" fittings and a 3/4"? fitting (and taps to match, of course). It's just preventative and not really necessary. You have to be careful tapping the big one, you need to oil it and back it out frequently. That one took me like an hour or so to tap.

[RETed]

I wouldn't hesitate to use either unless you're looking for a long-term motor lasting 200k miles?
Surface rust you can knock down with 1,000grit sandpaper and liberal use of engine oil.
Pitting is minor - you'd get minute blow-by, but like I said, you're not building a long-term engine.
Even the corroded water jacket is normal.
The seal is the primary component that seals off the two sides.
So as long as the "wall" stays intact, it'll support the o-ring no problem.
I'd say that as long as you see some kind of horizontal surface, you're still good - again, I stress that this is not for a long-term engine.


-Ted

[TehMonkay]

The second one looks like the coolant seal blew and they let it sit like that for a while.

[j_tso]

thanks, everybody.

I'm going to use the non-rusty one, if it lasts a few years as a weekend joyride I'll be satisfied.

[TehMonkay]

If it's a weekend joy ride and you take care of it it should run for a while