Expert: Rob Painter - 5/7/2010

Question
how do you tell if you cracked the block or just blew a head gasket if there is white smoke coming from tail pipe?

Answer
Hello,

There in no guaranteed diagnoses without tearing the engine down. The heads have to come off for a first step. The heads may require machining and being checked for cracks at a machine shop.
As for a head gasket, the damage from being blown, is obvious. If you eliminate these items as being the problem, the cylinder walls will need to be checked for a cracked water jacket.

The problem is that you do not know what you have without a visual examination after tear down and after the machine shop knows the condition of the heads.

More importantly, is once you determine the problem, you need to figure out why it over heated in the first place to cause this event. You don't want to change a headgasket, mill the heads, have them checked for cracks and find that the engine still overheats and you do damage again.

These Cadillac aluminum engines can never be subjected to over heating or they end up like yours.

This has been a know problem with their engines since 1982 forward. The 4.1, 4.5, 4.9 and northstar had these issues. In fact, many came new with a factory knock from poor fitting wristpins for the pistons. You would think for the money they got for these cars new, that they would have come with a decent engine.

I have owned 25 Cadillacs from new to used and I love them, but some owners get offended when I call them money pits, as you are about to find out. In the event you have a cracked block, you cannot just go to a local junkyard and get a used engine because chances are the used engine you buy is no better than what you have.

The last time I priced a new GM long block for one of these was $3,800 not counting labor, fluids and accessories. You could be looking at $5,000 installed.


I am not trying to be the bearer of bad news, but I am all too familiar with Cadillac overheating problems. Worse yet, there is no one thing that can cause this event. Bad water pump, plugged radiator/cooling system, radiator cap, dysfunctional electric fans can cause over heating.

Recently someone wrote me about over heating. I suggested possibly the water pump. The pump was changed which had a broken impeller. At the same time, chunks of rust fell out of the engine. Now that engine was fixed but highlights the problem.

At any rate, this is not going to be a cheap repair for you.

I have been real lucky. Personally, I was very careful about overheating. The Allante I just traded off with 62K original started running warm last summer above 80 degrees. I never let the gauge even go to 3/4 or I would shut it down. Good thing it was a convertible because I had to use the heat and defroster to get the gauge to the 1/2 way point.

I am too old to work on cats anymore. I now drive a Chevy Suburban with a gas guzzler 454, but it has a cast iron engine and those you could run hot without doing damage.

Good luck to you and tell me what you find.

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