Whats going on everyone. Well a couple wks ago I bought an engine for my 95 4.9 deville. The engine supposedly has 100k miles on it so I figured it was a deal at only $385. Well anyway, yesterday I finally had the time to finish up everything and make sure I was ready for the road. To make a long story short I bought a brand new thermostat and before I put it in I poured a gallon of Antifreeze in the thermostat housing. Thats when I noticed that at the back of the block I have a terrible coolant leak. Its literally pouring onto the pavement with the engine not running at all. The leak looks to be right underneath the exhaust manifold, but its such a tight space I can't tell exactly where it is. What could this be?

Is it missing a freeze plug? That's the only thing I can think of down there besides and external headgasket leak (which would never pour all over the ground)

Could be a freeze plug, not to scare you but I have seen some blocks corrode in that area too.

Could be a freeze plug, not to scare you but I have seen some blocks corrode in that area too.

An aluminum block corroding through??? :hmm:

Yeah, not sure if it was a casting defect or really poor maintenance but it ate a hole right through the front.
The more we messed with it the bigger it got... it was paper thin.

Okay today I poured water in the thermostat housing again and reached underneath the exhaust manifold. I could feel the water comin right into my hand and It feels like the headgasket has extended beyond the actual head. Thats not a good sign is it :-(

You need to get under the car and look at it.
Headgaskets usually do stick out just a tad past the surfaces.
Feeling around and guessing isn't going to do anything.
Get under there and take a look.

Took a look from underneath and it is indeed the headgasket. Kinda hard to believe that this engine has 100k miles like the junkyard says it has. I've owned 4 4.9 cadillacs and haven't ever seen a headgasket problem.

Now you know why you got such a "deal" on it.

good luck with the refund/replacement

An aluminum block corroding through??? :hmm:

Ever seen aluminum wheels after a few winters of salt? The same thing can happen to the engie

Ever seen aluminum wheels after a few winters of salt? The same thing can happen to the engie

Lets just ignore the basics (thickness of an engine block and the fact that even an iron block will never rust through in hundreds of years...) In fact, I've pulled 50 year old beer cans out of a river that was drained for dam repair. While most of the paint was gone, the aluminum was still perfectly fine.



While aluminum does corrode, it is not the same as iron. aluminum corrodes in a manner unlike anything else. It "coats" itself as it corrodes. The aluminum oxide created is one of the hardest substances on earth next to diamond, and is therefore commonly used in industrial environments as an abrasive. ONce the exposed aluminum is coated with it's oxide, the oxide acts as a protective coating, keeping the underlying aluminum fresh and protected. Therefore, in no way could an engine block or a rim corrode through. If you could keep a rim from ever getting washed (like most engine blocks), you'd find that after a few winters the whole rim would be coated with nice bright white aluminum oxide. If you could wash it off then, the aluminum would be like brand new underneath. However, the constant washing of the rim is what causes other imperfections like pitting, where the aluminum can re-corrode when the oxide is washed away.


Just a little chemistry lesson for you ;)

Interesting, maybe I should get my wheels re-done. I guess I just noticed the 'flaking' on my wheels and assumed the same thing could occur on the engine.

Guess I was halucinating on the one I saw.
Not surprising I guess, I am getting pretty old.
It corroded from the inside out if that makes it any more believeable.

Interesting, maybe I should get my wheels re-done. I guess I just noticed the 'flaking' on my wheels and assumed the same thing could occur on the engine.

That's the little protective coating that they use to shield the wheels. It flakes off, but is impossible to get put back on. My wheels have it too (all of them) but hopefully the chrome wheels I plan on getting won't have that problem.

I knew that, I was hoping they could get it ALL off and then polish the wheels off or something. Guess not?

I'm not positive, I've never seen it done. But I believe when you get wheels refinished they just chuck them up in a lathe, take a couple thousands off the face and re-clearcoat them. Good as new.

Thats what I thought too