Radiator & Engine Flush

[Patrick67BJ8]

I went to drain a little bit of radiator fluid to reseat my petcock valve and rusty fluid came out.

It’s been about 40 years or so since I last did a radiator flush and I’d like input on how to do it including chemicals, etc. I recall having to take the thermostat out?

Car ran hot when idling for about 5 minutes or so while adjusting my newly installed “fast idle solenoid” for my AC, yes, it’s still hot in Texas.

I overrode the engine electric fan and noticed a lot of air from the fan not going through the fan but directed to the area around the fan. Kinda like a waste of misdirected air. Anyone else have this problem to? I could see the need for a flat cover for between the radiator and the front of the shroud and maybe one below the radiator too.

 

[Bob_Spidell]

I ran some Prestone flush--there's two strengths, don't recall which one I used--in my '65 Mustang the other day to try to get some crud out of the radiator. It didn't do squat. Since it's been 40 years, here's what I'd do:

1) Run a flush per the instructions.
2) Drain and pull the radiator. Have it rodded or at least cleaned by a shop if there's any evidence at all of any crud--rust or crystallized antifreeze--in the core (there probably will be).
3) Remove the thermostat and backflush the block with copious quantities of water from a hose. Even after the 'flush,' backflushing the radiator in the Mustang pushed a lot of rust flakes and crystallized AF out of the block.
4) Put it back together. Replace hoses if they're not pristine, and check the belt while you're at it. Refill with fresh AF and distilled or deionized water (your preference).

I think the flushes might do OK on scale buildup, but since I've used distilled water with AF exclusively for many years I never have any.

 

[Patrick67BJ8]

I ran some Prestone flush--there's two strengths, don't recall which one I used--in my '65 Mustang the other day to try to get some crud out of the radiator. It didn't do squat. Since it's been 40 years, here's what I'd do:

1) Run a flush per the instructions.
2) Drain and pull the radiator. Have it rodded or at least cleaned by a shop if there's any evidence at all of any crud--rust or crystallized antifreeze--in the core (there probably will be).
3) Remove the thermostat and backflush the block with copious quantities of water from a hose. Even after the 'flush,' backflushing the radiator in the Mustang pushed a lot of rust flakes and crystallized AF out of the block.
4) Put it back together. Replace hoses if they're not pristine, and check the belt while you're at it.

I forgot to mention that I had a larger core put in the radiator in 2007 and while doing a frameup restoration, which was finished in 2013 I had the radiator cleaned out by a radiator shop. I seem to recall that there was a cleaning solution and then a neutralizing solution several years ago?
I have all new hoses, thermostat, etc.
thanks

 

[Bob_Spidell]

How rusty was your coolant? I never see anything but a wisp of rusty coolant when I drain; if that's all you have one of the milder flushes should work. I haven't seen the flush/neutralizer on the shelves in a while (but I haven't been looking either). If I used anything stronger I'd really backflush--that seems to have the most effect. The flushes won't dissolve rust flakes.

Check the top of your rad, where the tubes are, if that's clean a mild flush/backflush should be plenty. The Mustang had green, crystallized crud which I suspect was solidified AF; the flush didn't do a thing on it.

 

[Keoke]

;

It’s been about 40 years or so since I last did a radiator flush ---WOT!

Send radiator out to good shop and have it recored with serpentine larger core , then after reinstallation have block pressure back flushed, & refill with protective coolant.​

 

[John Turney]

While I had my radiator out for my AC install this last winter, I soaked the interior with white vinegar (a gallon is only a couple of bucks). I then backflushed the radiator with air to agitate. That seemed to clean out what crud I could see on the top of the core. Then rinse and neutralize with baking soda and flush again. While I had the radiator out, I could get to the block petcock under the exhaust manifold (headers on mine). That took a little bit of poking to get it to flow clearly.

 

[John Turney]

I overrode the engine electric fan and noticed a lot of air from the fan not going through the fan but directed to the area around the fan. Kinda like a waste of misdirected air. Anyone else have this problem to? I could see the need for a flat cover for between the radiator and the front of the shroud and maybe one below the radiator too.

Is your electric fan right up against the condenser or in front of the cross-braces? I put mine in front of the cross-braces and made a duct from the fan to the condenser to direct the air into the condenser.

 

[Patrick67BJ8]

Is your electric fan right up against the condenser or in front of the cross-braces? I put mine in front of the cross-braces and made a duct from the fan to the condenser to direct the air into the condenser.

I have a little space between the fan and the condenser. No brace. I have a Jule Frame and it doesn’t need it.

 

[Deleted member 21878]

i just did a flush on mine. my radiator was good but i was not sure i got all the crud out of my engine when i put it together. i used the prestone one because it is supposed to desolve the rust... which is what i worried might still be in the engine.

first thing is how to get rid of the old coolant? lots of places to recycle oil but not many to recycle coolant. i ended up taking it in town to a toilet and flushing it since that water is all treated.

i wanted to work this fluid thru the system for a few days. instead of dumping in and using the engine, i decided to pump it thru. i removed the thermostat. then put the cover back on. nect i connected the top hose where it would go on the radiator to a pvc pipe. then clamped another hose on the top of the radiator. connected both thru pvc fittings to garden hoses. put one garden hose in the bucket and then put a sump pump in the same bucket and attached the other hose. allowed me to recirculate the fluids thru. the hose i had come back in to the bucket i ran thru a funnel with a screen on it to catch any crud. also set the sump pump up on a block of wood to keep it off the bottom of the bucket.
then when i was done i connected the top garden hose to the spigot and ran the bottom hose out in the yard. turned the water on and let it run for a while to flush out any left over cleaner. you have to be careful how much water you let run in the radiator. it can not take full house pressure.

after you flush a while, then open up the drain tap on the radiator and drain it. when i went to fill it back up, i filled the engine first thru the thermostat housing until it was up to the thermostat. then the rest of the way thru the radiator. also drilled a hole in the thermostat cap to let air thru and checked it in a pan of hot water to be sure it was opening properly.

yup all the work and got hardly any crud out of it. so i guess i did it for piece of mind.

and if you do it this way, put a valve on the return hose. even if you shut off the pump, it will still drain from the engine and run all over the floor once the bucket is full. i would come out a couple of times a day and run it for 15 minutes. did that for 3 days.

 

[steveg]

Drone Dog wrote: "...you have to be careful how much water you let run in the radiator. it can not take full house pressure."

Good point. My radiator guy said to be careful of the heater core. That can be the weak point. Might be a good idea to jump the heater hoses for the backflush.

I did mine with this simple setup using a stocking for a filter:

Results - rust flakes and WaterWetter muck:

After that, for a while I ran the Tefba cooling system filer (from eBay). Removed it later when it was done trapping the few bits left after the backflush.

 

[Legal Bill]

I forgot to mention that I had a larger core put in the radiator in 2007 and while doing a frameup restoration, which was finished in 2013 I had the radiator cleaned out by a radiator shop. I seem to recall that there was a cleaning solution and then a neutralizing solution several years ago?
I have all new hoses, thermostat, etc.
thanks

This update is pretty important. So you are not fighting 40 years of crud, you are just trying to get up to date from the last time you personally performed a flush. I would just drain the old stuff, fill with water and use a mild commercial flush agent and drain it again. Maybe do a fresh water flush after that and then fill with 50/50 mix.