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Old 08-03-2009, 09:01 AM
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Question about flushing engine block

I was hoping someone would give me ideas about flushing the coolant from my engine block. This weekend I am replacing all my cooling components (rad, water pump, therm, hoses etc.) and I want to be sure all the old coolant is removed before I refill. Probably a simple task, but its all new to me.

Thanks in advance!
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Old 08-03-2009, 09:17 AM
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Any evidence that the old coolant is rusty?

If you are just replacing the coolant, you can drain the radiator, fill with water, idle to temperature, drain, etc. a few times. That will get most of the old coolant out.

If you want to do something more active, your parts store sells flushing tees that can go into one of your heater lines. Flushing this way won't do a lot unless you take your thermostat out, IMO. With the thermostat out, you can run the engine with your garden hose connected to the tee and flush out whatever is in the cooling system, and loose enough to be flushed.

BTW - I don't trust the plastic flushing tees enough to leave them in the heater hose. If I flushed with a tee, I would replace that hose with a new section of hose. Heater hose is cheap, and ruptured hose is a common cause of breakdowns. Good time to replace all the heater hoses, if you have not yet.

There are many chemical treatments that you can use to remove (supposedly) rust and sediment. Can't vouch for the effectiveness of the modern products - the ancient products used oxalic acid, which really dissolves rust, but is not very environmentally friendly.

I don't think there's much more you can do in your driveway. You can take the radiator to a shop and have it boiled and rodded out, but again that's an ancient technique which isn't widely available today. Today, you'd just replace the radiator.
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Last edited by tgreese : 08-03-2009 at 09:21 AM.
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Old 08-03-2009, 09:17 AM
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There are 1/4" pipe plugs in each side of the block. Take them out. You may have to stick a screwdriver through the crud that has formed over the hole.
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Old 08-03-2009, 09:24 AM
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Quote:
Originally Posted by tgreese
Any evidence that the old coolant is rusty?

If you are just replacing the coolant, you can drain the radiator, fill with water, idle to temperature, drain, etc. a few times. That will get most of the old coolant out.

If you want to do something more active, your parts store sells flushing tees that can go into one of your heater lines. Flushing this way won't do a lot unless you take your thermostat out, IMO. With the thermostat out, you can run the engine with your garden hose connected to the tee and flush out whatever is in the cooling system, and loose enough to be flushed.

BTW - I don't trust the plastic flushing tees enough to leave them in the heater hose. If I flushed with a tee, I would replace that hose with a new section of hose. Heater hose is cheap, and ruptured hose is a common cause of breakdowns. Good time to replace all the heater hoses, if you have not yet.

There are many chemical treatments that you can use to remove (supposedly) rust and sediment. Can't vouch for the effectiveness of the modern products - the ancient products used oxalic acid, which really dissolves rust, but is not very environmentally friendly.

I don't think there's much more you can do in your driveway. You can take the radiator to a shop and have it boiled and rodded out, but again that's an ancient technique which isn't widely available today. Today, you'd just replace the radiator.

Thanks, yeah I'm replacing everything so I just thought I would take the opportunity to clean it all out.
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Old 08-03-2009, 09:25 AM
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Quote:
Originally Posted by Chevelleguy
There are 1/4" pipe plugs in each side of the block. Take them out. You may have to stick a screwdriver through the crud that has formed over the hole.

Thanks! I'll check to see if I can find them and drain the block from there.
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Old 08-03-2009, 10:11 AM
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Quote:
Originally Posted by Chevelleguy
There are 1/4" pipe plugs in each side of the block. Take them out. You may have to stick a screwdriver through the crud that has formed over the hole.

Do you know how many gallons of fluid goes into a complete cooling system for a 360?
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Old 08-03-2009, 11:07 AM
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I don't have a book here at the office, but I think it is around 3.5-4. Get coolant from Walmart and then go over to the food department and get an equal amount of distilled water. It's a lot cheaper than buying pre-mix. Don't use tap water in your new, clean system.
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Old 08-03-2009, 11:09 AM
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Old 08-03-2009, 11:10 AM
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Quote:
Originally Posted by Chevelleguy
I don't have a book here at the office, but I think it is around 3.5-4. Get coolant from Walmart and then go over to the food department and get an equal amount of distilled water. It's a lot cheaper than buying pre-mix. Don't use tap water in your new, clean system.

Will do....thanks for the help!!
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Old 08-03-2009, 03:04 PM
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Prestone makes coolant flushes. But I just use a flushing tee and a garden hose.
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Old 08-03-2009, 04:25 PM
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Quote:
BTW - I don't trust the plastic flushing tees enough to leave them in the heater hose.

And for good reason. I bought my '93 Suburban in '94 and the PO had installed one. I never thought about it or used it. Around '99, my wife was driving down the interstate when the plastic broke dumping all the coolant quickly. She never smelled a thing. Motor overheated rather quickly. I had to replace it with a new one.
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  #12  
Old 08-03-2009, 07:38 PM
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I had to put a new radiator in my Cummins Dodge. After the new radiator, I used one of those radiator flush kits that you add the chemicals, run it up to operating temp for a few minutes and let it cool. Next day I drained the system. A lot of gunk came out with the water. I flushed the radiator for a couple hours before it ran clear.

I'd give that a try...........
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  #13  
Old 08-04-2009, 08:01 AM
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Quote:
Originally Posted by aallison
I had to put a new radiator in my Cummins Dodge. After the new radiator, I used one of those radiator flush kits that you add the chemicals, run it up to operating temp for a few minutes and let it cool. Next day I drained the system. A lot of gunk came out with the water. I flushed the radiator for a couple hours before it ran clear.

I'd give that a try...........

So you installed the new rad first? Then flushed the block using a kit? Or did you flush first then replaced the rad?
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Old 08-04-2009, 08:15 AM
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It is best to flush the motor before putting in a new or fresh clean radiator. If you do it after, junk in the motor and heater core will have a chance to get stuck in the radiator. I have used a bunch of different flush products over the years and the best one is Mr Clean cleaning solution believe it or not. I think the other stuff is a way for Dupont and other manufactures to rape our check book. I typically flush lots of fresh water through the system without the thermostat installed as well. Then run it for a couple days on just water and flush with water once more before putting coolant in. Pulling the lower plugs is also a good idea, as mentioned.
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Old 08-04-2009, 09:51 AM
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Quote:
Originally Posted by fulsizjeep
It is best to flush the motor before putting in a new or fresh clean radiator. If you do it after, junk in the motor and heater core will have a chance to get stuck in the radiator. I have used a bunch of different flush products over the years and the best one is Mr Clean cleaning solution believe it or not. I think the other stuff is a way for Dupont and other manufactures to rape our check book. I typically flush lots of fresh water through the system without the thermostat installed as well. Then run it for a couple days on just water and flush with water once more before putting coolant in. Pulling the lower plugs is also a good idea, as mentioned.

Sounds like a good plan, Thanks!
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Old 08-04-2009, 09:57 AM
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Quote:
Originally Posted by JFlu
So you installed the new rad first? Then flushed the block using a kit? Or did you flush first then replaced the rad?

Best to use the old rad. But mine had split a seam and I had it out before I realized how much gunk had collected in the water passages in the block.

Were I to do it what I would consider the right way, I'd remove the thermostate, toss in the stuff and run it up to operating temp. Once cool, drain everything I could, flush it real good, replace hoses, thermo, etc. Then put the new radiator in it.
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