Coolant level question

[wpavlis]

First off, thanks to everyone who has answered my many questions in the past. I fired up the new 350 that i just installed in my 68 c10 today. During break in as the motor came up to temp the radiator puked a bunch of water. Temperature was fine bit i checked and from what i could tell everything was fine. Finished the break in and temp held rather steady the whole time. When it cooled down i checked the coolant in the radiator and it was an inch or two low. I filled it back up and took a quick test drive around the block and it puked some more coolant again.

Now to my question. Is this normal on an open system? I have never owned a vehicle without a coolant bottle. I am guessing this is just the system equalizing and if i had a coolant catch bottle it would get sucked back in as the radiator cooled back down. Does that sound correct? Thanks again for all the help and advice.

[truckster]

In an open system there's usually about an inch between the top of the radiator and the coolant level. There has to be room for expansion.

[wpavlis]

That is what i figured. Thanks for confirming!

[Wrenchbender Ret]

You probably had an air pocket that cleared out.

[wpavlis]

I have a quick follow up story. When this happened i was using straight distilled water. I did this just in case i had some kind of leak during the break in period. I figured that if i did have a leak it would be less mess if i was only using water. The plan was to drain some water out and replace it with coolant. What i didn't think about was the fact that the coolant raises the boiling point significantly. After draining out the water and refilling with coolant to get a proper mix, the level has stayed much closer to what i would expect. It also seemed to puke less coolant when fully warmed up. I think the combination of only using water and not ever having owned a car with an open system caused me to get overly worried.

[toolboxchev]

You could have the wrong radiator cap on there. If it is a closed system the cap needs to be for that system.

A open system cap of course would allow coolant to escape out!

[wpavlis]

I believe all radiator caps will allow coolant to escape when the system reaches the rated pressure correct? The difference is that the cap for a closed system allows coolant to be pulled back in from the overflow bottle. Without an overflow bottle it just lets air in rather than maintaining a vacuum. That is how i understand it anyway. Please correct me if i am wrong.

[wpavlis]

Also, to be clear my radiator only vents coolant once. If i fill it all the way to the top it will let a little coolant out when it heats up (i assume due to expansion) . Then it will not do it the next time. I think i just got overexcited it being the first time i ever swapped a motor.

[mattfranklin]

On my break in, it seemed to cool fine when the RPMs were up. When I slowed to idle it started puking. I was running without a fan at that time. I was wondering at that time if I'd overfilled it. I was even thinking about installing a puke can.

When I installed the fan it cooled quite a bit better at idle.

When I also installed a fan shroud it cooled perfectly.

Now it's about an inch or two from the top and no more puking.

I might not need a puke can after all.