coolant drain from engine block

[Rocko973]

Just curious: The procedure for "Draining and Filling Cooling System" per the service manual on my 2003 Silverado says to only "open the radiator drain cock" in order to drain the coolant. Yet in a separate section, it mentions that you can drain the coolant from the engine block from the two drain plugs underneath the block, one on each side. I am wondering why they do NOT say to also drain the engine block in their procedure for "Draining and Filling Cooling System"? Do you all also drain engine block when you do your coolant replacement? Or do you not bother and only do the radiator drain? Wouldn't you think it would be better to drain both?

 

Thanks!

[Wires]

Those engines are designed to hold coolant in the block in case there is a catastrophic leak in the coolant system. They probably don't recommend it since you can get air pockets in the block (unless you apply a vacuum to the system to pull out the air).

 

When I did mine, I drained the rad, topped it with new coolant, and then I popped out the thermostat, and popped off the top rad hose (return to the rad). Then had my wife crank the engine over while I held the hose in a bucket. You need to pull the thermostat, or you won't get any fluid unless the engine is hot.

 

Had her crank (I think she started it?), until the coolant looked new. Sort of the same deal when flushing brake lines.

[bossier62guy]

Just curious: The procedure for "Draining and Filling Cooling System" per the service manual on my 2003 Silverado says to only "open the radiator drain cock" in order to drain the coolant. Yet in a separate section, it mentions that you can drain the coolant from the engine block from the two drain plugs underneath the block, one on each side. I am wondering why they do NOT say to also drain the engine block in their procedure for "Draining and Filling Cooling System"? Do you all also drain engine block when you do your coolant replacement? Or do you not bother and only do the radiator drain? Wouldn't you think it would be better to drain both?

 

Thanks!

On my previous vehicle I did indeed pull the engine block drains to get as much old coolant out as possible. When I did the 02 I looked at the situation and blew it off. If it were easier I would have done it.

[Rocko973]

On my previous vehicle I did indeed pull the engine block drains to get as much old coolant out as possible. When I did the 02 I looked at the situation and blew it off. If it were easier I would have done it.

Thank you! Yes, those engine block plugs don't look that easy to get to, so I probably won't do it either. I'll just try to change out the coolant more frequently.

 

And thanks to "Wires" as well for your reponse. Your method sounds good, but I don't think I will go that far. I will just follow the procedure in the service manual and drain only the radiator... but more frequently now.

 

Thanks!

[txab]

I'd pull the lower hose, if you don't have a rad. petcock. I would re-fill with fresh clean water and run it until the thermostat opens, then drain again. Or as suggested pull the thermostat so water will circulate immediately. Drain and re-fill with fresh dexcool.

[Rocko973]

I'd pull the lower hose, if you don't have a rad. petcock. I would re-fill with fresh clean water and run it until the thermostat opens, then drain again. Or as suggested pull the thermostat so water will circulate immediately. Drain and re-fill with fresh dexcool.

I am pretty sure mine has a drain cock, and I believe that "refilling the radiator with clean water and running it until the thermostat opens" is the procedure for "flushing" the coolant per the factory service manual, right? Also, when you say to pull the thermostat, as described by Wires, are you reconnecting the hose back onto the water pump somehow? Thanks for your input...

[Rocko973]

<p>So why did GM put those drain plugs underneath the engine block in the first place?  I am pretty sure I don't have those on my Corvette, also by GM, nor on any of my other non-GM cars. Under what conditions would you drain the block other than if you were re-building the engine, if they don't recommend draining it during a regular coolant replacement job?  Or is that it?</p>

[txab]

I am pretty sure mine has a drain cock, and I believe that "refilling the radiator with clean water and running it until the thermostat opens" is the procedure for "flushing" the coolant per the factory service manual, right? Also, when you say to pull the thermostat, as described by Wires, are you reconnecting the hose back onto the water pump somehow? Thanks for your input...

On mine I can remove the thermostat and put the thermo housing back on the pump, hook everything back up and run it

[Rocko973]

On mine I can remove the thermostat and put the thermo housing back on the pump, hook everything back up and run it

Oh! I see...now.

 

Thanks!

[DaveH71]

<p>So why did GM put those drain plugs underneath the engine block in the first place?  I am pretty sure I don't have those on my Corvette, also by GM, nor on any of my other non-GM cars. Under what conditions would you drain the block other than if you were re-building the engine, if they don't recommend draining it during a regular coolant replacement job?  Or is that it?</p>

 

The holes are there from the sand casting process, its allows the coolant jackets to be cast as hollow. A common misconception is that they are there for if the coolant freezes, they will pop out, hence the name freeze plugs. Draining the block can be done whenever you want to replace the entire coolant capacity, or when its contaminated, or when you rebuild, etc. It's not that GM doesn't recommend draining the block, it's just that it isn't always needed. Most people are content with just replacing the majority in the coolant system other then the block, and in most cases that is plenty.

[Wolfmanjohn]

Rocko, your Corvette does have those drain plugs "for your convenience". If it's a C5, you'll be able to see them, but because of the wide crossmember under the motor, that's about all you'll be able to do, 'cause there ain't no way you're gonna be able to get to them, regardless of the number or configurations of universals you use. Might as well just give them a C5 wave and move on.

[Rocko973]

Rocko, your Corvette does have those drain plugs "for your convenience". If it's a C5, you'll be able to see them, but because of the wide crossmember under the motor, that's about all you'll be able to do, 'cause there ain't no way you're gonna be able to get to them, regardless of the number or configurations of universals you use. Might as well just give them a C5 wave and move on.

You are so right! After reading your post I went out to the garage to look for them again, and boy are you right about not being able to get to them without having to remove stuff. One is right above the oil filter, and the other one above the what I think is the starter motor, both in very tight spots, i can barely get a peek at them. Well now that I know what they are really there for, thanks to you kind folks on this forum, I am surmising that all engines (at least GM engine blocks) have them. Thanks for educating me...

[GuyGene]

What about using the Prestone back flush drain kit? I've used those two times, and it seemed to work great. You do have to cut a heater hose (forgot which one), but the little plug supplied with the kit works great, and then you have a kind of permanent back flush attachment. Maybe the newer trucks systems don't need to be back flushed. I'm a believer in keeping clean fluids though!