Possible popped freeze plug?
 

(1988 s4 T2)
I have a huge water leak without even turning the vehicle on it pretty much dumps as fast as I can fill it, and its pouring out of the little peekaboo spot on the tranny, I'm asuuming a freeze plug since we hit like 17 degrees last night and had no antifreeze in it. My question is is there a plug on the back plate somewhere around the flywheel or what? I can see the two on top of the housings they are fine.

yes, there are freeze plugs on the rear iron

http://www.reganrotaryracing.com/reariron.jpg

Are you talking about on the passenger side of the car? Check the rear nipple on the iron, I doubt that your lim o-rings would of failed. I mean it COULD have, but not likely. Can you take a picture of around the area where it is leaking from?

I hope you didn't just have water in there. That engine will be corroded really bad if you did and a popped freeze plug would be my last concern.

i've been hearing this a bit lately and it's pure bullshit. i've been running my S5 for 3 years with straight water as it had a failed coolant seal and i've been limping it until i get a chance to rebuild it. i just flush the water out periodically and it is never really that dirty. the only time that water is really that corrosive is when you have air mixed in the system with the water.

so lets stop the urban legend that water is so horrible in the cooling system without antifreeze.

i drive it daily still by the way.

Still, it popped a freeze plug. If any isolated pockets get lodged when they freeze it could break things. DO NOT RUN 100% WATER if it gets near freezing temperatures.

Please take pictures when you take the engine apart to prove it. Just because the engine is still running does not mean it isn't corroding inside. You sound smart enough that I assume you would use distilled water, if your running tap, I would hate to look at your engine.

Again, just because the water comes out clean does not mean corrosion is not building up. Please enlighten me how you get rid of the oxygen in water, which is composed of 2 hydrogen molecules and 1 oxygen molecule.

Urban legend? Have you ever seen a engine that has been constantly tested for long periods of time on a engine dynamometer that is cooled only by water? By the time the testing is completed, the engine block is pretty much ruined as the water jackets are heavily corroded. We call it the sacrificial engine.

And i believe you. I will say this, for anyone running straight water, add an additive to inhibit corrosion buildup and lubricate the water pump.

Some brain food:

http://en.wikipedia.org/wiki/Antifreeze

Most automotive engines are "water-cooled" to remove waste heat, although the "water" is actually antifreeze and not plain water. The term engine coolant is widely used in the automotive industry, which covers its primary function of convective heat transfer for internal combustion engines. When used in an automotive context, corrosion inhibitors are also added to help protect vehicles' cooling systems, which often contain a range of electrochemically incompatible metals (aluminum, cast iron, copper, solder, et cetera).

Antifreeze was developed to overcome the shortcomings of water as a heat transfer fluid. In most engines, freeze plugs are placed in the engine block which could protect the engine if no antifreeze was present, or if the ambient temperature dropped below the freezing point of the antifreeze. If the engine coolant gets too hot, it might boil while inside the engine, causing voids (pockets of steam), leading to localized hot spots and the catastrophic failure of the engine. If plain water is used to cool an engine, it would promote galvanic corrosion.

I have a friend who insists on running straight water because it "cools better". Last year his engine froze and cracked the center iron, so we pulled it apart. Inside it was very, very rusty. Oddly, he had also gone through several water pumps...

Wouldnt distilled water help with the corrosion?

Maybe, as far as I know it mostly just helps prevent mineral deposits (which may look like corrosion).

i admit it's not ideal but it's not nearly as bad as some people make it sound unless you leave it in there for extended periods of time.

tell ya what, i'm going to be tearing it apart in a few weeks so i'll post my findings then good or bad.

from experience though, usually the rust will stay localized unless actual air pockets get into the system, not your oxygen in water description. at which point it then starts to shed and continue to shed rust into the system peeling off layer after layer. even though the internal surfaces may be rusty there isn't an ounce of rust being shed into the cooling system noted by the flushes i have been doing.

light layers of internal surface rust aren't a huge deal.

Distilled water would be worse than tap water. Distilled water will try very hard to replenish it's mineral content and adjust it's PH...and it will do so by corroding metals.

Do you not like your engine or something?

Wouldn't be just as easy to say, iron, water and heat= rust. Have you ever heard of any car manual that say's just add water? Additives like ethanol glycol protect the cooling system from freezing and corrosion.
What does extended periods of time mean. Pure water is rust within a month. I don't know about everybody else but I flush my engine every 24.

"Freeze plug" is a misnomer. They are actually core plugs that fill casting holes, and they are not intended to pop out at a given temperature or pressure.

It does in fact cool better, as he eventually found out, lol.

Purified water is better for the cooling system. In its normal lightly-acidic state it will not absorb a significant amount of aluminum or iron, and when mixed with coolant it will lose its acidity and not absorb any minerals.

Straight tap water isn't so great because the minerals in the water could cause corrosion in the engine cooling system, although the extent depends on the properties of the water in the local area. When mixed with coolant, tap water is OK to use, although I still prefer purified water.