Expert: Rob Painter - 11/4/2011

Question
Our 1999 Cadillac Deville (Northstar engine) is loosing water...about a 1/2 gallon a day. We cannot see any obvious reason. It has 103,000 miles. We've owned it six months and it had set up for a year or so. We've been told my a weekend mechanic that it could be a belt, which would be easier to replace than the water pump. The question is, where's the belt, if there is one,and what else could be the problem. Thank you for your time.

Answer
Hello,

It's obvious your mechanic does not understand this engine and if it has gone past the 3/4 mark or over 220 degrees with a 50/50 mix of coolant, this engine has very significant problems.

Since 1982 Cadillac has been using an aluminum engine. This gives you no error for overheating. The engine is literally melting and self destructing!

You may have a bad water pump or a belt slipping as the initial problem, but losing that much water as you call it and no you can't run straight water because you lowered the boiling point to 212 degrees f.
If you are losing that much, you have possibly blown head gasket(s), cracked block. If you look into my archives, you will see many of these problem engines. Actually they are a good engine, just a severe devastating problem when overheated.

Here is another issue-these engines are so notorious for overheating problems and essentially being junk because of this event, you are not going to find a good used engine in a junk yard.
It's been my experience that very good general technicians are not familiar with the aluminum engine and what can happen even trying to repair a problem like yours. They end up fixing the first problem not realizing the collateral damage of blown head gaskets, cracked blocks, holes in pistons, due to overheating issues, they end up living with an engine that just can't be repaired.

I am very concerned that to go through that much anti freeze, that there is catacysmic issues here. I have just dealt with far too many.

Here is what needs to be done if not done already. Pressure test the system with the car on a hoist. Gauge has to stay 15 pounds for 10 minutes. If not holding, you are looking for an external head gasket/intake manifold or block leak. Oil needs to be checked, if milky, head gasket leaking internally, block leaking internally or a piston top has hole.

You need to put tester on cap as well.

Look, I am not trying to be the bearer of bad news, but you simply can not run these engines hot. Also if coolant level is low, there is no circulation and cooling fans will not operate either.

Hopefully, you caught this right before totally destroying this engine, but as I said, the amount of coolant usage in this engine is of grave concern. Quit driving until this problem is repaired if it can be.

Its very common for owners of aluminum engines that have been over heated to contact me when it is too late. These engines also have small cooling jackets and something so minor of accidently leaving a little piece of gasket behind could be fatal to it.

Overheating is the Achilles heel to the aluminum engine. The same holds true for diesels.


Let me know what happens.

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