: 95 STS corrosion



soccer_caddy
01-23-04, 02:17 PM
Hi everyone,
I haven't seen anything posted about corrosion so I wanted to throw this out there and see if anyone has any input. I have a '95 STS with 125k on it. I bought it 5 years ago with 60k and have maintained it very well ever since.

At 97k the mechanic found pin holes in the coolant pipes which were a result of corrosion. He filled with rust inhibitor and re-ran the pressure test. All was good. Last summer the water pump went out (120k) and it had some corrosion in it. My mechanic thinks I should dump the car but I love it and it runs great. Am I running the risk of the engine going? I have read that the Northstar motor can be very expensive to replace. Thanks.

Patrick

DaveSmed
01-23-04, 05:57 PM
I bet the coolant changes were neglected. The coolant doesn't turn rusty like it would do in an iron block, so it is often overlooked.

BeelzeBob
01-24-04, 12:27 AM
Hi everyone,
I haven't seen anything posted about corrosion so I wanted to throw this out there and see if anyone has any input. I have a '95 STS with 125k on it. I bought it 5 years ago with 60k and have maintained it very well ever since.

At 97k the mechanic found pin holes in the coolant pipes which were a result of corrosion. He filled with rust inhibitor and re-ran the pressure test. All was good. Last summer the water pump went out (120k) and it had some corrosion in it. My mechanic thinks I should dump the car but I love it and it runs great. Am I running the risk of the engine going? I have read that the Northstar motor can be very expensive to replace. Thanks.

Patrick
The 93/94/95 Northstar engines were factory filled with the conventional, green silicated coolant which needed to be drained and replaced every 2-3 years/24-32K miles, whichever came first. If it was truely "well maintained" it would have had the cooling system drained and refilled with fresh coolant 4 to 5 times by now. The coolant maintenance intervals are spelled out in the service manual and the owners manual clearly.

The corrosion inhibitors in the coolant (the silicates) deplete fairly rapidly in aluminum engines so the coolant must be replaced to replenish the corrosion inhibitors. I do not know of any satisfactory silicated corrosion inhibitor "additives" that will protect the engine so whatever was added was not the recommended service or maintenance procedure. The coolant MUST be replaced. Period. As stated above, the coolant may look fine (the aluminum corrosion characteristics do not "color" the coolant like rust from an iron engine) and the coolant may check fine for concentration (the ethylene-glycol is still fine...the corrosion inhibitors are what are depleted) but it still needs to be replaced every 24-32K or 2-3 years.

The water pump at 120K doesn't sound abnormal. At 120K it didn't owe you a dime. Was the coolant pipe corroded from the inside out or the outside in...??? Big difference. The real concern for extended operation with depleted coolant is the failure of the head gaskets. The steel core of the gaskets can start to corrode from the water jackets outward causing the gasket to fail when it reaches the combustion chamber seal. It literally rots out from the inside out due to the corrosion caused by the depleted coolant.

Personally, I wouldn't worry. Change the coolant several times to get it refreshed and on a regular maintenance schedule. Just drain and refill...don't so any invasive flushing, chemical cleaning or anything. Just drain and refull with fresh 50/50 green coolant/distilled water. When the sytem is drained, disconnect one of the radiator hoses and pop in 6 of the GM coolant supplement pellets or two tubes of the BarsLeaks "golden seal" powder. This sealant was installed at the factory in the engine and needs to be replenished just like the corrosion inhibitors in the coolant. Drive it and enjoy it. The head gaskets can be replaced without any problem if they do eventually fail and hopefully if you get it on fresh coolant and maintain it thusly in the future it will hold off any future damage.

You should find a mechanic that is familiar with aluminum engines/Northstars/Cadillacs for the future so the maintenance will be correct. Get the service manuals for the car so that you can have the correct info. If you do have to have the head gaskets replaced, make positively sure that the mechanic knows Northstar engines, has the service manuals and follows the correct repair procedures. That is why they have a reputation as being hard to repair....the "mechanics" do not take the time to get the manuals and follow the correct procedures .... then they blame their problems on the engine.

carnerd
01-24-04, 12:33 AM
wow I guess you really know what your talking about! clap clap clap :jawdrop: