Can a radiator be too full?

[RECHRGD]

The last couple of weeks I've been driving the car in some of the hottest weather we've had since I changed out the heads and cam.  The car seems to run a little warmer since the swap, but nothing out of the ordinary.  Anyway, after driving in traffic for awhile last week, the engine got up to around 210/215 degrees.  When I parked it about a pint of coolant burped out via the overflow tube on the overflow tank.  Before running the car a few days later I topped off the radiator and drove it with no issues.  Saturday was the hottest day of the year and I was out in it.  After driving several miles through town and then on the open road for a bit, I parked the car at FastbackJon's Charger meet.  I later noticed that it had burped out about the same amount of coolant again.  But when I had parked it the temp gauge read about normal, 190 degrees or so and the engine did not seem too hot.  On the way back through town, I stopped to do some shopping (engine was about 215 degrees) and when I came out of the store there was another pint or so deposited under the car.  I then drove another several miles to my car storage area and the temp stayed pretty much the same even after losing probably over a quart of coolant.  When I shut the car off, no more coolant came out.  I've always kept the radiator as full as possible and this is the first time I've had this issue.  So should I just leave it a quart or so low or is there another issue going on.  Come to think of it, the cap has been on there several years.  Think it might be going bad?  Thanks, Bob

[TylerCharger69]

Well...the radiator itself should be full....sometimes you may have to jack up the front of the car as to remove all of the air bubbles.  As far as the overflow....it should NOT be full....there is a cold level and a hot level.   It's purpose is to take in expelled coolant and also return coolant.  The location of the overflow has bearing on the situation too.  You don't want it mounted too high  or too low from the top of the radiator itself.

[hemi68charger]

Factory service manual states not to fill any closer than an 1.5 inches from the neck. Every car I've ever owned seems to find equilibrium in coolant. Some spit nothing up, some spit up some until that balance is met... If she's cooling fine and you know your thermostat is opening properly, I wouldn't fret. Down here in Texas, I'm running distilled water only with the product called "Water Wetter"....... Water Wetter has lubrication characteristics for your water pump seals, which you need..........................................

[RECHRGD]

Thanks for the replies guys.   I think I'll just leave it as is and keep an eye on it.  Bob

[lisiecki1]

as your coolant heats up there's going to be expansion and your overflow tank will fill to the hot level marked on the bottle, as the radiator cools the radiator will suck approx. the amount of hot fill to cold fill back into the radiator as expansion turns into vacuum during cooling.  If you have the radiator completely full and the overflow completely full there will be some leakage until the coolant reaches it's normlized level as stated in a previous post.

[Charger-Bodie]

Factory radiators have a plate inside....That is the full mark.

[hemigeno]

Factory service manual states not to fill any closer than an 1.5 inches from the neck.

If you're not running a sealed system with a pressurized/sealed overflow tank, this is the way to go - unless you like wasting antifreeze.  The stock setup with the rubber overflow tube will just burp out any "excess" coolant, as determined by how hot your car happens to get and what it's starting fill point was.  If you have an overflow tank system that isn't sealed up very well, it works nicely to catch the excess coolant but I wouldn't expect it to draw that coolant back in when the radiator cools down.

The exception might be if the coolant has been drained down for any reason, as an overfill to the radiator neck will allow any air bubbles in the coolant system to be collected in the top of the tank without running the coolant level down.  Not a big deal really, since most of us are usually Nervous Nellie types when checking fluid levels after a draindown (at least I am).

[Just 6T9 CHGR]

Well...the radiator itself should be full....sometimes you may have to jack up the front of the car as to remove all of the air bubbles.  As far as the overflow....it should NOT be full....there is a cold level and a hot level.   It's purpose is to take in expelled coolant and also return coolant.  The location of the overflow has bearing on the situation too.  You don't want it mounted too high  or too low from the top of the radiator itself.

No overflow bottles on a 2nd gen....just puke to the ground....EPA nightmare

I always keep mine 1" below the neck to allow for expansion

[68X426]

hemi68charger: curious about Water Wetter. How is it any different for lubrication than an antifreeeze with additives for the pump seals? How long have you used it?

[maxwellwedge]

It's sounds like the typical, good old fashioned Mopar puke till I'm happy with the level cooling system. We've lost more cats this way 

[375instroke]

Overfilled radiators have a way of finding their proper fill level by themselves.