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Hi guys! Yesterday I noticed that the bottom radiator hose was not tight and it was leaking coolant. I went Autozone and picked up a concentrated Peak coolant/antifreeze (green) and poured about 2/3 gallon of it and 1/3 distilled water. I ran the engine with the radiator open and I notice that the coolant is red!

At that point I was like f-it I'm going to flush it... So I went back to AutoZone (using a different car) to grab another gallon of coolant, catch bucket, waited for the car to cool down then started flushing... Took off the bottom hose from the radiator to drain the orangeish coolant, took off the top radiator hose so I can flush whatever is going in the engine with a garden hose. After that, I used the hose to clean the radiator. I ran the hose until clear water came out of the hose and radiator.

After that, I reconnected everything, filled it with a gallon of concentrated coolant and gallon of distilled water. Drove around for 20 mins, then waited for the radiator to cool down. So after all that... I checked the radiator fluid and its still kinda red...

Soooooo... did I miss anything??? I don't think I have a reservoir... Also as I'm typing this I remember that I have AC, but the coolant doesn't circulate there, does it?

Sorry, this is the first time I'm doing it! Thanks! Hope I didn't ruin my baby :(

It's a 69 coupe with a 302 engine if that's helpful.
 

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Does it have a automatic transmission?
Do the transmission cooler lines connect to the radiator?
If the answer to both is yes, the trans cooler inside the radiator is busted. The transmission fluid and coolant are mixing and your transmission will have to be flushed out too.
 

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Sounds like you still had red coolant or a lot of rust in the block, heater core and hoses. Takes a while to get it all out. Try to open the block drain plugs at the bottom, take out the thermostat to allow the coolant to circulate from the block out the top hose (disconnected from radiator) and let it pour into your catch pan from the top until it's onky clear water that you're putting in at the radiator cap. Once you believe you have nothing but clear water everywhere, drain it all completely, fill the entire system with white distilled vinegar and close the system then run it until operating temperature. Let that sit overnight and flush everything out ( I recommend a panty hose filter before the radiator... you won't believe all the crap that will come out) until you have nothing but clear water again. Drain and flush that as many times as necessary, cleaning out your filter, and fill the entire system with 60% coolant and 40% distilled water.
 

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You missed the heater core.
You will never, and don't really need to, get all of the rust sediment and staining that discolors the coolant out of the radiator, block, heads, heater and hoses short of dissembling and treating them.
Yes, you can run water through it until it comes out as clear as a mountain stream. Well drop a rock into that mountain stream and watch it get cloudy until the sediment settles again.

GM was smart to make DexCool orange so it will always look normal to Chevy owners with an iron block.:eek:
 

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Oil or transmission fluid in the coolant will turn it milky. If your coolant has a red tinge it's rust still coming from the cast iron. Did you flush with citric acid?
 

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Discussion Starter #7
Does it have a automatic transmission?
Do the transmission cooler lines connect to the radiator?
If the answer to both is yes, the trans cooler inside the radiator is busted. The transmission fluid and coolant are mixing and your transmission will have to be flushed out too.
Yes, its automatic... I'll have to trace all the lines this weekend.
 

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Discussion Starter #10
Sounds like you still had red coolant or a lot of rust in the block, heater core and hoses. Takes a while to get it all out. Try to open the block drain plugs at the bottom, take out the thermostat to allow the coolant to circulate from the block out the top hose (disconnected from radiator) and let it pour into your catch pan from the top until it's onky clear water that you're putting in at the radiator cap. Once you believe you have nothing but clear water everywhere, drain it all completely, fill the entire system with white distilled vinegar and close the system then run it until operating temperature. Let that sit overnight and flush everything out ( I recommend a panty hose filter before the radiator... you won't believe all the crap that will come out) until you have nothing but clear water again. Drain and flush that as many times as necessary, cleaning out your filter, and fill the entire system with 60% coolant and 40% distilled water.
Wait pure distilled vinegar and not dilute it? Like 2 gal worth???

Also pantyhose filter on both top and bottom hose?

Might have to try this one. It's good its kinda rainy here so I don't drive her a lot.
 

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Wait pure distilled vinegar and not dilute it? Like 2 gal worth???

Also pantyhose filter on both top and bottom hose?

Might have to try this one. It's good its kinda rainy here so I don't drive her a lot.
You can try vinegar (acetic acid). The acid level is relatively low so it's not as aggressive as a purpose-made citric acid flush (like the Mercedes-Benz product). Flush is done without a thermostat in the system. You can add a panty hose to the upper hose at the thermostat housing if you'd like.
 

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Yeah I like nature's fixes for things haha. Distilled vinegar is cheap and effective, easily obtained, and not so harmful if you spill it compared to some comercially-available things. Fill the whole system with that, get it hot once, let it sit overnight and STAND BACK FOLKS! BE AMAZED! when you drain it. I do this every couple of years and my water pumps and radiators live longer for it. All that stuff floating around in there is abrasive to radiators, water pump bearings and seals, thermostats, heater cores, even hoses. You can even let rusty parts soak in vinegar to remove it, use vinegar to get rid of mold and stains and bad odors. Clean your laundry iron, oven racks, and washing machine tub with it...Some people like the apple variety and even take some internally. It's dirt cheap...
 

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Discussion Starter #14
Thanks. Finally back at it! Drained the radiator once again from the drain plug to get this crap out! I'm just happy it didn't come out milky!
738698


After draining I took off the hose that's connected to the thermostat housing and saw this...

738699


Guess I need a new housing... It just sucks because it's hard to get to the other screw because the AC pulley and compressor is in the way...

738700


I'm going to see if my buddy has a short wrench so I can get the second bolt out...

After I replace the housing I'll try the vinegar trick and refill it!
 

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Thanks. Finally back at it! Drained the radiator once again from the drain plug to get this crap out! I'm just happy it didn't come out milky!
After draining I took off the hose that's connected to the thermostat housing and saw this...

Guess I need a new housing... It just sucks because it's hard to get to the other screw because the AC pulley and compressor is in the way...

I'm going to see if my buddy has a short wrench so I can get the second bolt out...

After I replace the housing I'll try the vinegar trick and refill it!
I resort to breaking out my swivel sockets and a 6" extension....
 

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I have always used washing soda for such flushes, easy on the WP bearing. 2 cups of washing soda 50 mile drive and then Completely flush heater core, block (remove block plug (s) & radiator.
you must run a filter in the top radiator hose before you drive and check it for debis a couple of times as you drive because it will get clogged, chunks of crud.
Once flushed to your liking, refill system with distilled water and coolant. I also use a zinc anode at that cap but you could use a block plug zinc anode as well. Same principal as on a boat, zinc being the lest of the metals in your cooling system, any electrolysis will attack it first.
For cars not driven often a battery switch will help with this a reduce electrical system connector oxidation.

I have used vingear soak to remove rust from parts.

good luck which ever way you go.
 

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Follow all advice above..

The pan on the left was the initial system drain, nice..

Bucket to the right was a reverse flush of the heater core.....not nice

(core subsequently replaced)


Sent from my SM-G950F using Tapatalk
 

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Discussion Starter #19
Is it bad if I leave the distilled vinegar in there for 2 days?

So I drain the vinegar, fill the radiator with water and put a filter on the top hose, run it/drive a few miles, then drain/clean filter and repeat until filter is clean?
 

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Is it bad if I leave the distilled vinegar in there for 2 days?

So I drain the vinegar, fill the radiator with water and put a filter on the top hose, run it/drive a few miles, then drain/clean filter and repeat until filter is clean?
It won't hurt to leave it in a couple days. It's just separating the electrochemical bond between differing metals and lime, calcium, etc and accumulated rust (iron oxide). Keep refilling and draining (garden hose tap is fine) with the thermostat out until it's all clear, cleaning your filter in between, and making sure you flush the heater core and hoses, too. Drain ALL that water and refill with 50/50 coolant mix, or I prefer 60% pure coolant and 40% store-bought distilled water (trapped clean rain water works in areas where there is no acid rain). Don't forget a good Robertshaw or other high-quality thermostat in 180 or 195 degree range, and one with a tiny gas relief hole on the body is a good idea.
 
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