Kucharz:
The name of the coolant that G.M. uses for the engine is called DEX-COOL. It's formulated to protect aluminum engines. DEX-COOL is redish orange in color. hope your car continues to run well. the STS is a beautiful car. Congradulations on a smart choice of car.

 

I've heard some horror stories about cooling problems in caddy's of that vintage. I'd keep on top of it if I were you.

I had a cooling system failure in my car a few months ago and was lucky to get away without any damage.

 

Any of the pre-2003 N*'s can get the curse of the HG. In 100% of the HG failures it is actually caused by head bolt fastener failure. It is more common in 96' to 99' yr model cars. It is caused by bad block casting methods that lead the threads pulling out. After this occurs the threaded bolt bores need to be drilled & tapped out larger and either inserts installed or the best method so far is studs. This can cost $2500 to $6000 to repair. With the value of these mid 90's car's, you really need to have some sort of infatuation going on with the thing. You can find some beautiful cad's with this problem at salvage yards and it seen to be a shame to shoot the horse. Sometimes you have to. Don't be afraid to shoot the horse.

 

some correction is needed here.

the problem goes to ALL ALUMINUM engines, not just nortstars..

one cause is the threads as mentioned above, but an even more common problem is the compromising of head gaskets. although GM will not publish it or acknowledge, this is caused by coolant that has used up its corrosion protection which happens at around 5 years on a new engine and at about 2 years thereafter.

please read our FAQ on the subject as well as the note below.



GM Cadillac Northstar engine features and issues


.

 

Thats a great general knowledge site with great info.

I am talking specifically about the Cadillac Northstar 4.6L engine year model's 1993 to 2002. I am talking about bad casting methods that cause this defect to occur. I am not talking about the cooling system neglect.

 

i'm not familiar with the casting methods you brought up .. can you enlighten me?

what i know is this ..

Exposed Head Bolt Design Leads to Potential Problems...
Most head gasket failures on these engines can be traced either to a cooling system issue or a loss of clamping force.
Clamping force deserves special attention: The engine’s head bolts are exposed to the elements over a significant portion of their length. As the bolts are removed, it is not uncommon for rust, dirt and debris on these exposed areas to damage the block threads. In fact, thread damage is a primary concern on all Northstar engines. In many cases, the threads in the aluminum casting will bond to the fastener due to the countless heating/cooling cycles encountered over several years of use.
As the bolts are removed, some of the threads can literally be pulled from the block along with the fastener.This damage might not be readily visible,so carefully check all threads extending into the cylinder block assembly. Then Heli-Coil all suspect threads to ensure proper clamp loads!

 

The blocks are cast so porous in some cases the leak oil or coolant or both right through the side of the block. When the molds are poured the the hot aluminum is splashed up the sides in the casting and cooling occurs it causes layers & voids. This is a example of the porousity. Blowing air in this head bolt hole comes right through the block in the area circled....... I 'm having difficulty uploading a pic. working on it.

 

This block has threaded inserts intalled This is why the coolant pellets are added on the assembly line.

https://www.cadillacforum.com/forum/...1&d=1268930750

 

This is typical.https://www.cadillacforum.com/forum/...1&d=1268932382 Not seized galled or "bonded" as you say.

 

how do you know if you've blown a head gasket?