Adding coolant to a radiator??
Thread Starter
Racer
Joined: Aug 2011
Posts: 455
Likes: 7
From: Lewes Delaware
Adding coolant to a radiator??
I just removed the stock radiator from my '72 and had it repaired (small hole soldered). Got it all painted up and ready for the re-install. My assumption is after everything is hooked back up, just add antifreze until full. Then do you run the engine with the cap off and keep adding fluid until she's topped off? Is there any issues with air pockets and how do you deal with them? Any tips or tricks much appreciated.
Instructor
Joined: Jul 2008
Posts: 105
Likes: 1
From: germantown tn
OK i have a overflow take , does not fill at radiator , first time i did it filled tank up which i thought was enough started and turned on heat , it started to overheat and the level in the tank never dropped, next time i did it i filled through the radiator hose from the thermostat and through the tank to the level on tank, after starting and driving around block i had to add maybe 12 ounces to top , so my trick (maybe if you have the tank to fill to) is add from the hose
Thread Starter
Racer
Joined: Aug 2011
Posts: 455
Likes: 7
From: Lewes Delaware
I don't have an over flow tank, just the radiator. I'll try the tip of filling through the top hose. I'll be using 100% Prestone mixed to 50/50 with distilled water.
Instructor
Joined: Jul 2008
Posts: 105
Likes: 1
From: germantown tn
probably the same deal and will work better , no way really to know how much to add because there is some left in there , if you loosen the clamp on the radiator you can just turn hose up and it is a nice funnel
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
If you have no overflow tank, then you must leave air space at the tope of the radiator for fluid expansion as it heats. And, yes, you can leave the cap off and run it until the thermostat opens and circulation exhausts any trapped air. Just add distilled water to top off the coolant; it won't change the mix ratio that much.
Put the cap on before you shut off the engine. When you shut the engine down, you can get additional 'latent heating' which could cause the water to boil, since it isn't pressurized.
Put the cap on before you shut off the engine. When you shut the engine down, you can get additional 'latent heating' which could cause the water to boil, since it isn't pressurized.
Safety Car
Joined: Sep 2007
Posts: 4,458
Likes: 331
From: Indy Indiana
you're making it too complicated... fill it to the top, at least within 2 inches, let the pressure cap do its job. if it is too full it will spit fluid until the level is correct. check it again after a trip and after it cools down, top it off again if need be. same is true even if you have a side tank.
Drifting
Joined: Apr 2006
Posts: 1,911
Likes: 2
From: gold coast queensland
Make sure you have a 1/8 hole drilled in the flat section of your thermostat. This will allow the air to escape through the closed thermostat and out of your radiator on initial fill up. If your using premix 50/50 then fill your coolant mixture to the top of the radiator neck. Wait a while( say 2 minutes) as that 1/8 hole is pretty small and needs a little time to allow the air/coolant to escape meaning the coolant level will settle and most likely drop a tad. Wait and fill as many times as it needs until it no longer drops. Put your cap on and go cruising. Because you have no expansion tank it may burp the excess out once your engine is at operating temp but check it after cool down and see its level 
Last edited by gingerbreadman1977; Oct 6, 2011 at 05:50 AM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Team Owner
Joined: Jun 2000
Posts: 38,923
Likes: 1,482
From: Southbound
Cruise-In II Veteran
Check the owner's manual. There is usually a blurb about topping up the radiator.
If it's aluminum radiator, it has no cap and is filled through the surge tank.
If it's a copper/brass radiator, it has a cap and is filled through the cap to within one inch of the bottom of the neck.
If it's aluminum radiator, it has no cap and is filled through the surge tank.
If it's a copper/brass radiator, it has a cap and is filled through the cap to within one inch of the bottom of the neck.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Correct. For non-tank applications, there is usually an embossed mark on the side tank for where to [cold] fill the radiator. It's not complicated, joewill; take off cap, fill to line, start car and let run till warmed up and air is expelled, refill to mark on radiator, reinstall cap and drive away. One could also fill to the top of the tank, put on cap and drive away. Most would just belch out the excess once it warmed up; a few would overheat due to an air pocket that didn't get cleared.
Lots of choices. Let's see what the OP decides is best for him/her.
Thread Starter
Racer
Joined: Aug 2011
Posts: 455
Likes: 7
From: Lewes Delaware
I am a follower of the "keep it simple" and "path of least resistance" school of thought. I'll fill the radiator to the correct level, run the car with the heater on, and wait till the fluid starts to circulate. Hopefully I'll not run into the air pocket problem. I had that issue with my Dodge Ram.
Drifting
Joined: Apr 2006
Posts: 1,911
Likes: 2
From: gold coast queensland
a few are saying fill it up and drive off but most would know if you just fill up the radiator to the top and drive away you are in for a nasty shock 5 minutes down the road when the thermostat opens up and your temp gauge pegs out due to only half the coolant thats required being in there actually being there . Its imperative that you either have the 1/8 hole drilled or you warm it up and top it off.
Last edited by gingerbreadman1977; Oct 7, 2011 at 12:40 AM.
Pro
Joined: May 2011
Posts: 581
Likes: 5
From: BC
Cooling systems can airlock and waiting for the thermostat to open isn't always the best way to do it. Because the sensing portion of the stat is not immersed in the coolant it will not open as designed and the engine can get hot enough to boil before it opens. With the rad cap off you stand a good chance of a geyser hitting you in the face when that happens. Plus it's time consuming.
By far the easiest and fastest way is to crack open a heater hose connection, preferrably at it's highest point. If it's not practical to loosen it at the water valve or core, loosen the top heater hose at the intake manifold end. You don't even have to remove it. Fill the rad and just wiggle the hose a bit to the side. You will hear the air hissing out. When you see antifreeze dribbling the block is full. Once the block is full there is no chance of airlock. Tighten the clamp and continue filling.
Tried and tested method. Been in the trade for almost 40 years and this method has served me well.
Steve g
By far the easiest and fastest way is to crack open a heater hose connection, preferrably at it's highest point. If it's not practical to loosen it at the water valve or core, loosen the top heater hose at the intake manifold end. You don't even have to remove it. Fill the rad and just wiggle the hose a bit to the side. You will hear the air hissing out. When you see antifreeze dribbling the block is full. Once the block is full there is no chance of airlock. Tighten the clamp and continue filling.
Tried and tested method. Been in the trade for almost 40 years and this method has served me well.
Steve g
Thread Starter
Racer
Joined: Aug 2011
Posts: 455
Likes: 7
From: Lewes Delaware
Cooling systems can airlock and waiting for the thermostat to open isn't always the best way to do it. Because the sensing portion of the stat is not immersed in the coolant it will not open as designed and the engine can get hot enough to boil before it opens. With the rad cap off you stand a good chance of a geyser hitting you in the face when that happens. Plus it's time consuming.
By far the easiest and fastest way is to crack open a heater hose connection, preferrably at it's highest point. If it's not practical to loosen it at the water valve or core, loosen the top heater hose at the intake manifold end. You don't even have to remove it. Fill the rad and just wiggle the hose a bit to the side. You will hear the air hissing out. When you see antifreeze dribbling the block is full. Once the block is full there is no chance of airlock. Tighten the clamp and continue filling.
Tried and tested method. Been in the trade for almost 40 years and this method has served me well.
Steve g
By far the easiest and fastest way is to crack open a heater hose connection, preferrably at it's highest point. If it's not practical to loosen it at the water valve or core, loosen the top heater hose at the intake manifold end. You don't even have to remove it. Fill the rad and just wiggle the hose a bit to the side. You will hear the air hissing out. When you see antifreeze dribbling the block is full. Once the block is full there is no chance of airlock. Tighten the clamp and continue filling.
Tried and tested method. Been in the trade for almost 40 years and this method has served me well.
Steve g
Is this done with the car running or off?
Thread Starter
Racer
Joined: Aug 2011
Posts: 455
Likes: 7
From: Lewes Delaware
Well after fighting with (and winning) the installation of the shroud, radiator, and water pump...I added coolant to the radiator with the heater hose disconnected from the intake. I didn't get any coolant running out of the intake connection but I could clearly see coolant at the opening. Started it up with the heater on and let it run for maybe 10-15 min. I could see the coolant circulating and I did have to add a bit more coolant. By the time I got done it was dark so the test drive will have to wait til tomorrow.
