The Stovebolt Site Forums The Shop Area Engine Shop Radiator Overflow...

Hi all, I just got my 46 3/4 ton pickup home yesterday and found that the radiator overflowed about 1/2 pint of fluid. My question is, when adding an overflow can to my radiator, should it have one or two hose fittings on the top? I see the original ones on the old Chevy parts sites have two hose fittings. How does the cooling radiator suck back the lost fluid after it cools down? Or should I go with a can with one hose fitting? My truck has a 216 w/ a four speed and I use it as a driver (2-3 times a week)

it'd be much easier to just not overfill the rad - the level should be a couple inches down to allow for expansion when the water heats up - filling it to the top is a common mistake, and why it pushed that small amount out, let it show you the proper level

Bill

Thanks Bill, I will try that today...

Overflow bottles are always a good idea as they increase utilization of your rad.

Any I've seen with 2 hose fittings have one as the hose to/from the rad, and the other as an overflow in case the bottle gets full so it can puke on the ground. If you look inside these bottles one goes right to the bottom, and one would be near the top. The one at the bottom of the can is where the fluid goes in, and when the fluid cools off, since the cooling system is a sealed system, it produces vacuum and sucks cooling back into the rad until either the bottle is empty or the rad is full.

The hose at the top of the tank is for overflow in case it's needed. If you have a can with only one hose fitting it needs to overflow through the cap or fill area of the can (whatever you're using).

Since you use it as a frequent driver I would definitely recommend that you use an overflow bottle. Having the rad full at all times (not just when it gets warm) will help with cooling. I hope this helps.

I would like to see some pictures of how others mounted an overflow tank. I myself do not run one. Like mentioned above, I have the coolent a few inches down and have not had any issues. Of course, a HOT day here is 68 degrees!

AND if you do add an overflow tank, you need to use a different cap for a reason I forgot? Be careful about the pressure rating. 4lbs? I can't remember.

DMGfifty,

What brand/style of overflow tank will you be using? The original accessory radiator expansion/overflow tank/condenser mounts differently from modern-style tanks.

The original-style over-flow tank (radiator overflow condenser) had to be used with a no-pressure radiator cap. If this is the style tank that you have, and you do not have installation instructions, instructions are on-line.

I will offer a different conclusion regarding the added cooling benefit from an overflow tank (and, I could be wrong). The amount of full-temperature fluid in your radiator (when running and when being cooled by the fan/etc) would be exactly the same with and without an overflow tank. Once the engine warmed up, and if you cooling system has no leaks, and the cooling system works as it should, at operating temperature the coolant would fill the radiator to the same extent (at the same pressure) with/without an overflow catcher/condenser/over-low/expansion tank. Maybe someone could explain why there would be a cooling benefit, (one way or the other)?

Thanks to all...I tried what Bill said above, and left the radiator seek it's own level and it seems to run fine (No more leaks) (I need to put a temporary "Temp" gauge inside my cab to check the real temp, but it seems to run just fine (Todays here in Florida is 77, but the forecast for FL is in the mid 80's this weekend) so I let you all know how it works... and again thanks for all your inputs…John

PS…I have an overflow can on the way “Just in Case”…

...for one thing it is a "recovery" tank. I've been in situations where the engine ran hot and "pushed" the coolant over into the puke jug. As the engine cooled it sucked it back in.....and I saved $16 for a gal. of coolant.

Around here the "hot rod" folks use the simple chrome "bottle" to simply catch the overflow so it doesn't get all over the bottom, or top, of their engine compartment...but the little "bottle" will only hold that top couple inches that Bill mentioned anyway so why fill it up if you know its coming back out. (Might need a higher pressure cap?) I don't run one on my 37 and it IS known to heat up especially when in a parade. The puke jug doesn't help there..only when it cools and "recovers" what would otherwise be lost.

The added cooling capacity is on crossflow radiators. You gain the use of the top row or 2. With a down flow radiator a recovery tank is still a good idea. You can still leave the level in the radiatordown an inch or 2.

Tim,
I have not given it that much thought. Interesting topic..

Here is my set-up which I like because I never get any coolant in the driveway or on the truck. Original type set-up with a no-pressure cap. I also use a 160 degree thermostat which helped a lot in the summer verses the 180 that was in it.
http://www.flickr.com/photos/advance-design_parts_co/8129179135/in/set-72157631867396207

Even with an overflow tank your pressure of your cap shouldn't change. As was mentioned it's so that the coolant that overflows can be sucked back in. The reason you fill the rad right up and use an overflow tank is so that you're utilizing the entire rad the entire time the engine is running, which helps with cooling, believe it or not.