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George H.
George H., ASE Certified Technician
Category: Buick
Satisfied Customers: 18766
Experience:  ASE Master 15+years
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1993 Buick LeSabre Custom: the thermostat and water pump..l..flush

Resolved Question:

I am finishing up changing the thermostat and water pump on my 1993 Buick LeSabre Custom 3.8 l. I need to quickly flush out the system tomorrow. I plan on using plain water and it will only be above freezing for a few hours during the day.
I can easily flush out the radiator which is currently empty, but I was thinking it might speed up the whole process and lesson the risk of freezing up the engine if I simply leave out the thermostat, fill up the radiator with water, close up the system and run the car for a minute or so-parked. With the thermostat out I wouldn't need to heat up the car to circulate water throughout the system. With the engine running maybe I could open the radiator petcock and slowly add clean water to the radiator opening (cap off) until it runs fairly clearly out of the drain.
Would this unorthodox procedure cause problems? I am trying to get the system flushed out as soon as possible while avoiding the heat up and extended cool down period (several times) that might be a serious issue since I don't have long to work on the car each day and the night time temperatures in my area are in the teens. (I have no place to park the car indoors.)
Naturally, I would then have to install the thermostat, drain water from the radiator, and add 1 & 5/8 gallons of antifreeze to get the mixture up to the proper level.
Submitted: 5 years ago.
Category: Buick
Expert:  George H. replied 5 years ago.

Hello I will help you with your question,


When I get the leaking intake gaskets that fill the cooling system with oil I flush them with Tide by running it with the stat out then removing the upper hose from the radiator and running a garden hose in the radiator while watching it come out the upper hose. Balance the flow so you keep the engine full while the engine is running. Run it til clean.


Block the upper fitting on the radiator where yu disconnected the r hose.


It will take many hours for the system to freeze so you have plenty of time to get it flushed and refilled with antifreeze.


Use the system volume and fill half with straight antifreeze and top off with plain water. Run the engine to mix and you will have the correct concentration


Let me know how I can help you


Thank you



Customer: replied 5 years ago.
Sounds good... Let me see if I am clear on the proceedure: 1.) With the thermostat absent, button up the entire system except for romoving the "radiator end" of the upper cooling system hose and the radiator cap. 2.) Add enough clean water to the radiator to fill it along with some laundry detergent*. 3.) Start the car and let it idle. 4.) Imediately begin adding a continuous stream of clean water in to the radiator (cap) opening to match the outflow of "dirty" water from upper radiator hose continuing until the water comes out clean.

Does that sound right?

Specifically how would you suggest I block the upper opening of the radiator while the hose is disconnected?

*How much laundry detergent?
Expert:  George H. replied 5 years ago.

If you have oil in the system use a cup of Tide detergent before you remove the upper hose and run the engine for 20 minutes with the cap off before you remove the upper hose (careful it will be hot!)


Remove the upper hose and block the fitting on the radiator where you removed the hose.


Run a garden hose at slow flow into the radiator neck and keep just a little flow out of the open end of the upper hose as you run the engine.


Use an old hose to block the upper radiator fitting, there is no pressure you just want to keep the water in the radiator.


Run until the water flows clear.



This procedure is for an oily system, is that your problem?



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