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Buick with rusty cooling system


I have a 98 Buick Lesabre V6 and I noticed that the temp gauge never goes above about 150F so I decided to replace the thermostat. When I went to drain the radiator I found that the coolant was very rusty orange color, in fact the radiator cap was caked with rust and I could not see any liquid in the radiator.

Two questions, how did the rust occur and what can I flush the cooling system with. Years ago I seem remember using a mix of baking powder or baking soda and water. Is either of these good? I am very surprised at the rust. A couple of years ago I had a new intake plenum replaced when a leak occurred. The system was filled with antifreeze so I would not expect rust.

Thanks for any advice.


What is the mileage on your Buick? How often has the cooling sytem been flushed before? Did you buy the car new?

If the car does not overheat, you simply need a flush. For environmental reasons I no longer do this myself. A good shop will flush out the old coolant and install new. Since it is organge in color, that was likley the color of the original fluid. I would avoid DEX-Cool, the GM stuff and go to a good universal coolant such as Prestone.

Make sure it is a 50/50 mixture for maximum protection. If you do it yourself, don’t use baking soda; you can put any one of those cleaning solutions in, just avoid very strong solutions, since you system is not clogged up.

This board recommends doing this every 40,000 miles, regardless of what your owner’s manual says.

The car has ~ 120000 miles. I have the car since near new, only 8000 miles when purchased. I never flushed the system but did have the plenum changed and therefor the system drained 2-3 years ago. As I said there is caked sediment or rust on the radiator cap and visible in the filler neck.

Thanks again


It may not be rust but Dex Cool that has sludged. I would try a flush whit whatever flush component and process is recommended then switching to a universal coolant, such as peak global.

I use this product to remove rust from cooling systems.

After the vehicle is driven for the required amount of time, I then attach my coolant flush machine to the vehicle and run clean water thru the cooling system until the black colored coolant is removed. I then add a 50/50 mix of water and antifreeze to the flush machine and run this thru the cooling system until the pure water is removed.


I don’t know what possessed you to put Baking powder/soda in your cooling system, but I bet you didn’t do your car any favors.

If you are lucky, you might only need to flush the cooling system.
I HIGHLY recommend that you pay someone to do the work for you this time.

At worst, you’ve probably damaged parts of the cooling system, from the heater core, to the radiator, to the cylinder heads, the water pump, and possibly the engine block.


I did NOT put baking powder in the cooling system, I just enquired about it. I have since flushed the system with an over the counter radiator flush product and got a good deal of sediment out. It was a tedious task because I made several fresh water flushes and recovered all the water for proper disposal.


Kudos for collecting the drained fluids for proper disposal.

Antifreeze is poisonous. Keep it away from animals. Be sure to keep it in sealed containers that cannot be opened by a curious animal.