The Stovebolt Site Forums The Shop Area Engine Shop Radiator keeps puking

The radiator overflow tube pukes coolant when the engine warms up. I have a rebuilt 235 c.i. with a new water pump and a new radiator but after about 4-5 minutes of running the coolant starts coming out of the overflow tube. I have removed the thermostat thinking that may have contributed to the problem. Any ideas?

Are you overfilling the radiator? These radiators are designed to only be filled (when cold) to just above the tubes, about 1" to 1 1/2" below the bottom of the neck. I think there may even be a fill line on the radiator.

Frist thing to do is put the thermastat back in. Drill a 1/16 hole in the flange of the thermastat and this will allow the air to get past the thermastat. The STAT will help to regulate the flow of your cooling system.

When you fill the Radiator. When do you stop filling? Where is the coolant level when you stop filling it?

Next when you run/ drive your truck what temp is the gauge reading?

Are you using straight water or a mix of water and antifreeze?

I fill the radiator up to where the coolant is at the bottom of the fill tube, I can't see the the tubes within the radiator a 1953 GMC. I tried the 1/16th hole in the flange of the thermostat and when the engine warms up it explodes out of the overflow tube so that's why I removed it. I don't have the gauge hooked up, I'll do that this weekend. I'm running a 50/50 mix of coolant and water.

Buck,
you got air in there somewhere friend. This works sometimes. Jack up the front of the truck some to get the front of the engine a little higher. Take off the top radiator hose and housing, take out the therm. Fill the head with a 50/50 mixture, then put in your 165 degree therm with the hole. Reattach your therem housing and hose to the radiator. Add a little more 50/50 and start up. Let truck down. Let it go thru a few heat and cool cycles over a period of a few days and check the coolant level. It will settle down. Oh yea put on a puke can. Sometimes it takes a little while to calm down and get all the air out.

It,s possible you have a head gasket leaking.
Being the engine was recently built you might
torque the head bolts.

Well, I don't mean to challenge the other guys, but if you are filling to the bottom of the fill neck, you are overfilling. Does it stop puking out after a little bit? If so, leave it at that level and you should be fine.

I aggree that it sounds like the radiator is getting overfilled. The level should be about 1 inche below the bottom of the filler neck.

This allows for the normal expansion for these radiators - the overflow bottle came later and called for totally filled radiators.

I'm drilling my 'stats to 3/16" . I thinks 1/16" may be a little small to move much air. Hell most of my cooling systems got critters far bigger than a sixteenth inch. First one would trap the air in the head.

I would agree that you are overfilling the radiator too. The colant should only go to the top of the fins within the radiator. That is about (guessing) 2" below the filler neck.

It is no wonder your truck is puking. The thermastat is opening up and then the water pump is pumping the hot coolant into the radiator and it has nowhere to go but out the overflow tube.

As for the hole in the stat 1/16 1/8 3/16. Anything is better then nothing.

i had the same problem in "truck vomits"

Change the radiator cap! Every pound of pressure raises the boiling point 3 degrees. Put a 180-degree thermostat and a puke can on it, and forget about a few dribbles!
Jerry

Can you do a cylinder leakage test or cooling system pressure test.
do the cooling system pressure test with the plugs out so you can hear the gurgling hiss on the cylinder that has the head-gasket leak or crack in the head,,,,,,
go with the 180 stat and 50/50 mix like Hotrod Lincoln mentioned .
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If you do not have a head leak or crack, remove the radiator and have it cleaned

I had a problem with my firebird puking. I finally figured out that my fan wasn't pulling enough air through the radiator. same type thing happened to my dad's truck. he pulled the stat. still puked. everybody tried to tell him that he needed a new radiator. i found out that his fan clutch died. no more puke. may not be the case here. those systems should work well as designed. i don't believe it should need a drilled out stat. verify that you have proper air flow through the radiator before you start banging and drilling everything. just a different idea. hope you get it figured out.

The drilled out stat is necessary because the originals were, the replacements aren't. It lets a little water flow in the head to keep it from getting air locked.