Radiator flush 2001

I’m pretty new to working on cars. I read my 2001 Sonoma takes 12 quarts of coolant. I’m flushing the radiator and I can see there’s much less than that draining. Maybe a gallon and a half tops came out and about the same went in when I went to flush it.

Where is the rest of the fluid? I’m assuming some of the 12 quarts goes into the reservoir, but where is the rest at?

Probably mostly in the engine block. There may a separate drain for that. Sometimes they are hard to see, such as under a manifold.

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Are they two separate systems or are they directly connected?

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I’m wondering if it’s like the transmission cooling system where the fluids don’t mix yet both pass through the radiator.

Same thing.

Do I need to drain the fluid from the second drain? Will the Royal Blue flush be in my engine if I add it to the radiator?

Yes it will travel through the entire cooling system as you drive don’t forget to turn the heater on so the coolant will go through the heater core also.

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There’s no mention of a second drain in any videos I saw. I replaced the radiator with a ACDelco a year ago. Could it have different coolant capacities?

Engine block drain plug.


thank you.

Just an FYI… that drain Tester showed… I’ve seem machine shops with tools and torches not be able to get those out with the block on the bench. You getting it out IN this 19 year old car is 99.9% impossible.

And I’ve mostly seen them come out with no problem.


Is it not necessary to do? I’ve seen multiple videos on youtube with people flushing their systems with chemicals and not one used the engine drain plug. I would think that not draining it would result in a lot of the chemical flush being left in the engine as well as excess water.

I get around all that trouble by using a coolant flush machine.

Call around to some shops.

You’d be surprised how little they charge for this service.



According to the factory manual, if only draining the radiator, up to 40% of the coolant will remain in the system. The heater system may hold some coolant too. Capacity of the 4.3 with auto trans. is about 13.8 qts. Below is a rudimentary depiction of the block drain plugs on each side.

So you got to get them from the wheel wells?

You get them from under the vehicle. BTW, after you use this flushing chemical, please report back in a couple of months when all your hoses have sprung leaks and your water pump starts leaking.

Are those large holes for spark plugs?

You mean the large round things in the side of the block? Those are the “freeze” plugs.

I just read that I should not drain the two plugs from block. I’m pretty confused. Should I drain them or not?