The difference between flushing & back-flushing rad

[Coelacanth]

Can anyone tell me the functional difference between flushing a cooling system and back-flushing it, and briefly explain the procedure?

I would assume flushing is pouring water into the rad while running the car until hot, while back-flushing is attaching a garden hose to a flush 'T' installed in one of the heater hoses and flushing it out that way.

My rad is installed, I just have to connect the tranny cooler lines and I'll be ready to flush the cooling system, and want to be sure to do the best job removing all the old coolant & crap. Thanks!

 

[87geeinn]

That's pretty much the gist of it. Backflushing is basically flushing/cleaning the entire cooling system circuit, to include all block/intake passages, lines, and the heater core. You can go ahead and backflush the system without the trans cooler lines attached. They run through a separate line in the side of the radiator. If I were putting in a new radiator, I would have backflushed the system before installing the new radiator. That way you're not getting any junk in your new rad.

 

[John Larkin]

The engine pulls coolant from the lower radiator hose and discharges coolant through the upper radiator hose. You can connect the lower hose, aim the upper hose onto the ground, put a garden hose in the radiator inlet and turn it on. Then run the car. No old coolant will go into your radiator this way. When you are done, remove the lower hose and let everything drain. There will be a little tap water left in your block but nothing major. You can blow the heater core out with an air hose to empty it.

 

[Coelacanth]

Can't I back-flush without the rad hoses connected? And I think I read you can remove some bolts on either side

The engine pulls coolant from the lower radiator hose and discharges coolant through the upper radiator hose. You can connect the lower hose, aim the upper hose onto the ground, put a garden hose in the radiator inlet and turn it on. Then run the car. No old coolant will go into your radiator this way. When you are done, remove the lower hose and let everything drain. There will be a little tap water left in your block but nothing major. You can blow the heater core out with an air hose to empty it.

Great tip, that's what I'll be doing tonight...thanks for the procedure! I finally got the tranny cooler lines bent, extension lines cut/bent/flared and everything reconnected to the F-body rad's tranny cooler fittings last night...turned out great. Tonight I'll give it a thorough flush.

 

[Team Canada]

This may sound obvious, but just make sure you run it long enough to get some heat in the engine or the thermostat won't open to allow the coolant out the top..
I started as a tech at GM when these cars came out new, and we used to sell a flush additive that was great. Im not sure if it is available in the US or not. As the years pass, like all models, they stopped being brought to the dealer for service, but the ones that did, even with higher miles, never had bad build up. Probably because it was before dex cool....

 

[Coelacanth]

This may sound obvious, but just make sure you run it long enough to get some heat in the engine or the thermostat won't open to allow the coolant out the top..
I started as a tech at GM when these cars came out new, and we used to sell a flush additive that was great. Im not sure if it is available in the US or not. As the years pass, like all models, they stopped being brought to the dealer for service, but the ones that did, even with higher miles, never had bad build up. Probably because it was before dex cool....

I'm actually glad you brought up Dex-Cool. Everywhere I've read that the stuff is the worst coolant you can put in your car...class action lawsuits against GM...causes brown film or sludge...I don't dare put that stuff in my vintage cars, but my 2008 Pontiac Torrent has it. Before it does any damage, what can I replace it with?

 

[Team Canada]

You can replace it with any coolant of your choice basically, as long as you have performed a thorough flush out of the dex cool. We just use GM coolant. Be sure to clean the reservoir tank as well, this is often overlooked during driveway flushes and will contaminate the new coolant almost immediately. Scrub the inside of the tank and underside of cap. It does go brown in some cases, but really caused a lot of head gasket failure. If you live in a really warm climate, consider changing your hoses as well.

 

[Team Canada]

That's pretty much the gist of it. Backflushing is basically flushing/cleaning the entire cooling system circuit, to include all block/intake passages, lines, and the heater core. You can go ahead and backflush the system without the trans cooler lines attached. They run through a separate line in the side of the radiator. If I were putting in a new radiator, I would have backflushed the system before installing the new radiator. That way you're not getting any junk in your new rad.

I would recommend hooking up the trans lines first though, unless you dont plan to start the car during the flush , which would not achieve much, and you will have to move the car anyways to clean the transmission fluid off the driveway if they are left unhooked..

 

[Nick Micale]

Good question about "flushing and back flushing", and both are fine.

Since it is a little too hot here to be working outside at 110 in the garage and 118 outside, I will give some comments and advise about engine cooling since we are very concerned about how and what to do for all our vehicles.

Most all chemical cleaners are acidic or caustic which will almost always remain at least as a trace?

For over 20 years the use of RMI-25 has proved to be the most effective and least expensive way to clean and protect any cooling system.

As far as a GN, the heater core and engine block collect the most crud on the system. Flushing and back flushing both of these is very productive in helping engine cooling.

Remove both hoses to the heater core and run your garden hose through it, and alternate to each outlet and see how much junk will flow out.

Using the heater hose connection to the intake is a good way to flush the block with the garden hose as well.

The use of RMI-25 year-around, with or without antifreeze, will clean the system and keep it that way. Since RMI will keep the crud in suspension, it must be periodically replenished.

 

[Coelacanth]

Unfortunately, RMI-25 isn't easily available here in Canada...and when you do find it, it's way overpriced compared to what you pay in USA. Thanks for the tip on flushing the heater core, I'll do that first.

 

[Nick Micale]

Unfortunately, RMI-25 isn't easily available here in Canada...and when you do find it, it's way overpriced compared to what you pay in USA........

I have a special going on now for RMI of 2-8 oz. bottles for $20 and free shipping in the US, so the additional charge to get it to Canada should be reasonable?

 

[Coelacanth]

I have a special going on now for RMI of 2-8 oz. bottles for $20 and free shipping in the US, so the additional charge to get it to Canada should be reasonable?

Let me know what the shipping costs...recently, any kind of aerosol paint or chemical product costs a good deal more to ship than in the past. When I wanted a few cans of PlastiDip, as it was hard to find locally--and places that had it, were selling it at nearly 3 times the price it sells for in USA, due to the shipping cost increase--I had a forum friend (an RC car forum) from USA ship me 4 cans of the stuff. It arrived without issue.

 

[Heskahoka]

That is actually a pretty darn good deal for RMI.

 

[Coelacanth]

That is actually a pretty darn good deal for RMI.

Not if shipping costs over $30 because it's considered a hazardous material...

 

[626gn]

RMI-25 is non-toxic and biodegradable.

 

[trixdout]

RMI is perfect for any cast iron block. Probably the best coolant additive on the market. It for sure does the work. I never took pictures when I first put it in, but works as advertised...... funny how that it. See if you can make friends with someone who crosses the border frequently. That way you can order the parts and they can carry it across for you.

 

[whitehot1]

What is your zip code in Canada?

Or if you prefer not to give that info out on the web, do a search on ebay for RMI-25. The seller on ebay is zoomt2 and when you do the search for RMI-25 his should be the first ad you see at the top of the list.

I just saw a real good deal on there with free shipping and they do ship to Canada and other countries as well.

 

[Coelacanth]

What is your zip code in Canada?

Or if you prefer not to give that info out on the web, do a search on ebay for RMI-25. The seller on ebay is zoomt2 and when you do the search for RMI-25 his should be the first ad you see at the top of the list.

I just saw a real good deal on there with free shipping and they do ship to Canada and other countries as well.

Not for free. Go on eBay from a Canadian eBay ID and see what the cheapest price, shipped, for an 8 oz. can is. Close to $30 and up. Check it out, I did weeks ago and again just now. Check out some Canadian retailers who sell RMI-25 and see what THEY charge for it. Heck, just try to find someone in Canada that sells the stuff online and see how far you get. It's the same for a good number of aerosols and other such items that are everywhere in USA but hard-as-hell to find in Canada...and when you find them, they're 2 to 3 times the price you guys pay in USA. I'm not making this up, I research stuff for hours before I buy.

Btw, zoomt2 is indeed the cheapest option for RMI-25...at the great low price of over $28 shipped to Canada (8 oz. bottle).

 

[Coelacanth]

RMI-25 is non-toxic and biodegradable.

That's not the point, that's not how Canada Customs views the product. The cost of shipping is what kills it.

 

[whitehot1]

Well all i know is that i can get a 32 oz bottle of RMI-25 for $27.00 shipped from zoomt2. I have never used it before but thought i would give it a try to flush out the cooling system since i've only heard good things about it.

Too bad you can't get a good deal for the RMI-25 shipped to Canada. But if you need it you have to pay the price they set unfortunately.