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Flushing Engine in Car


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10:38 PM
Jul 11, 2021
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I have made some progress on my project, slowly but surely.

I decided the next item up should be the coolant system. Got the radiator drained of what coolant was left and got the radiator out. After looking at it, I finally figured what was meant by rows and determined mine is a two row. Also looks like the tubes are 9/16”. I have a 440 and have had cooling issues over the times I had driven the car (not in the last 25 years).

It was going to be too costly to put a new core in the existing radiator, so I did some research and ended up purchasing a Champion CC503, 3 row radiator. Supposed to be good up to 700 HP. Also purchased a Stant Superstat thermostat for increased flow and a Flowkooler 1679 water pump. I still need to get a new fan clutch.

So, I have never looked that closely at coolant flow and thought that by taking ou the thermostat and dumping water down through the hole, it would flush things out. Nope, just goes right out through the lower radiator hose. I would like to be able to flush the system out as good as I can before installing the new parts. I know the best way is to get at least some freeze plugs out, but I am not going that far. Just too much work to get them out and new ones in and I am not pulling the engine at this point. Possibly considering pulling the block drain plugs, but hoping there is an easier solution. Once I pull the water pump, are the openings into the block accessible, so that i can fashion a hose to push water through there to flush things out? Also wondering if I could put a small electric pump between the two radiator hoses to run water through the system and probably a filter to catch any debris. Would use some water and vinegar to break up some of the calcification and maybe run some of the CLR radiator flush through it and the flush it a couple of times to get it cleaned out.

Any thoughts, suggestions or ideas would be welcomed. Want to get it as clean as I can without it taking me weeks to get it done.

Thanks in advance!
The best way to flush the cooling system is with chemicals to break down the rust and corrosion. Pretty much need the system to hold the water. If you can put the old radiator back in and get a chemical flush kit. It requires filling the system with water and the chemicals and they need to be able to get into all areas of the cooling system to work. Just running a hose through the system does very little other than the easy ,loose stuff.
I've been using a 1 to 9 ratio of molasses and water to de-rust parts with fantastic results. And now I have a 400 in my 78 dodge magnum that needs flushing. I'm going to experiment flushing it with this mix. The car has been sitting for years and the so called coolant is very rusty. I've also installed a stainless steel screen in the upper radiator hose to catch any big pieces of anything that will plug the small radiator tubes. Plus i have plenty of time to let this mixture do its magic. I'm buying the molasses today...
Biggest issue I have seen with these cars are the bock water jackets are just full of rust. If you do pull the side drain plugs and it is a trickle coming out strongly recommend pulling at leas one freeze pug on each side and flush the crap out of it, only way to get it out since it is so much scale rust in them, just FYI
I was told many years ago by a master mechanic at the Chrysler/Plymouth dealership where my dad worked that because of the high nickel content in these earlier MOPAR blocks, the cooling systems have a tendency to develop rust. Not sure if it's true but I always remembered the coolant in my dad's '67 HEMI GTX being more brown than green.
I've also been told by a respected MOPAR engine builder that inline coolant filters are helpful after the system is thoroughly flushed.

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Interesting idea on the inline coolant filter....but back to your problem. As mentioned above, put the old radiator back in, use a chemical flush, use distilled or deionized water. I like to take out the thermostat and run the water/chemical mix for 2-3 days. Flush with plenty of distilled water....rinse & repeat. Install thermostat and coolant...good to go
What car, engine and what exhaust Manifold or headers do you have? There are some freeze plugs easy to get to. When you see all the junk inside you will be glad you manually cleaned them out. You can’t get this junk out any other way.

Then go get Thermocure by evaporust. It works excellent. For cleaning the system. summit Racing sells it. One 32oz jug does 3 gallons of water. Must flush all antifreeze and have only water in the system.
Forget the home remedies, just buy this product. The most amazing Coolant cleaning job I’ve ever seen.
Thank you for all of the input. It has been a journey so far and hopefully everything will come together.

I probably should preface that the car has not run in 25 years, is not currently running. I am planning to do the best I can and get everything flushed out, new parts added and etc., before firing it up. So, that makes it a bit of a challenge to get things flushed out if it is not running.

So, what I decided to do was build some piping out of PVC and I added a threaded fitting on top and one on the bottom, along with a couple of valves (Picture 1). I then connected the radiator hoses to this contraption, pulled the 1/4 horse motor out of my drill press, added a bigger pulley, found a belt and mounted it to a 2 X 12 running across my fenders (Picture 2). After some adjusting, I have that running and if calculations are correct, should be spinning the water pump at about 2400 RPMs. I started off by putting some vinegar and water through it, let it sit for a while and I would run the pump for about 5 minutes. I drained all of that out and then just used straight water. The third picture was the second flush. I have flushed about a half dozen times with just water and am still getting brown out of it. The plan, once I get some other stuff buttoned up, is to run 3 to 4 flushes of the Prestone stuff through there, 3 to 4 flushes of straight water, two flushes of Thermocure and then flush with straight water until it is coming out clear. The way the motor sits, it runs clockwise, so it is spinning the water pump the same direction it normally would. I am thinking I might see about reversing the 2 X 12, so then I would be spinning the pump backwards. Not sure if that will break some stuff loose or not. In the mean time I will be working on the other "Stuff". The interior had some mice in it at one point and there was a bunch of crap in the heater box, so I knew I needed to take that out. I also noticed that my heater valve was leaking, so needed to do something with that. Of course heater hoses and radiator hoses and belts all need replaced. Got the new radiator, thermostat, thermostat housing and new water pump, so lots of goodies to put on. Started looking for the Heater valve (Picture 4 below) and it is the black and red variety. After lots of searching and some help from the guy at Oreilly's, found one at Classic Industries. It says for a 75 to 78 Charger (mine is a 73), but exactly what I needed.....not for $300 though. After spending another large amount of time looking I finally decided to go with the metal one (Picture 5 below). The bolt holes do not match up at all and with my car having AC, the lines are right in the way. So, I am going to reach out to a friend that does welding and see if he can make me a bracket, possibly out of aluminum. Finally decided to tackle removing the heater box. Probably was not as bad as I expected. Took hoses loose, AC connections loose, three nuts off of the blower motor housing, four nuts on firewall side holding heater box in, removed and labeled vacuum lines, took two plastic pieces off above the hump. It dropped off the firewall and after a little finagling I was able to get it out of the car. My car is too close to my wall, so can't get the passenger door all the way open, if I could, would have been much easier. Got the heater box split apart and the heater core out. Didn't look too bad, but found a place that said they would pressure test it and check it out at no charge and straighten the tubes going into it. He called the next day with not good news, heater core was leaking. So, could attempt a repair on it or could put a new core in it for $225. I opted to go pick it up and there was no charge. So, then I started the research for the replacement. Never seems like the numbers in the manual match up, but I was finally able to find the replacement on Summit Racing, so that is ordered and hopefully will ship from the factory early next week. Will have to do so cleaning and painting of a rust inhibitor on the firewall inside the car (Picture 6 below) as the mouse nest was right in that area and they must have been peeing all the time back there and pooping. Will just do a quick clean and vacuum and then paint it. Down the road when I am doing a resto on the car, I will repair and/or replace all the sheet metal that has issues. I also bought radiator hoses (Picture 7 is the one on the car now and Picture 8 is the new one) and at least the upper radiator hose is not a match. I thought I had researched the heck out of it and thought I had the right hose. The upper hose I bought is a Gates 20630. Picture on Amazon looks like that is the right one, but on other sites, that same part number shows what i got and it is too tall and won't go under the AC hose.

So, probably a little frustrated that it takes so much time to do the research and then I get the wrong part. Probably nothing different than what everyone else experiences.

Anyway, that is my update. Sorry for making the email so long, but hoping that if someone else comes along and needs to do the same things, maybe this will help you out a little bit. Or if someone has an easier way to do something, that will help me out.

Thank you!

Wow quite the involved process. Just use the Thermocure and don’t waste any time or money on prestone flush.

if you can figure a way to heat the water that would be most beneficial.
Go to home depot & grab a gallon jug of muriatic acid for etching concrete. Drain your system & add water & a cup or 2 of the acid. It can be nuetralized after a flush & rinse with baking soda mixed in water on the last few flushes. Then proced to flush till clean water is shown then let it sit a day, with the system full of clean water & rinse once more...
CAUTION: dont let any acid near any chrome, and dont let it sit on any aluminum(water neck), it will break the metal down & destroy chrome.