HamadUP

Hi guys,
I left my '71 C3 big block in storage for 10+ years, it was working fine when I parked it. now when I decided to get it out and "refresh" it, I was surprised that it was puking coolant out of the expansion tank when it gets to normal temp, to make a long story short here is a list of things that I have done so far :

- checked all hoses/pipes .. all good and looks new (I ALWAYS use 50/50 antifreeze, NEVER used straight water)
- replaced cyl. head gaskets with new fel-pro ones.
- replaced water pump.
- replaced thermostat.
- replaced radiator cap.
- took off and cleaned the expansion tank.
- flushed/cleaned all the coolant passages in the block/heads and also cleaned the radiator (aluminum dewitt)

And after all that, I was shocked when I see that it still puking water out (I used straight water for now just to check if I have any leak, plan to drain it out and put antifreeze if all goes well).

Did I miss anything? .. I care to hear your opinions.

HeadsU.P.

I don't know why, but people are so quick to fill a radiator and slap the Rad Cap on as soon as possible. Now they can't see what's going on with the coolant level and they can't see if air pockets are still trying to escape.

Any time the coolant system has been worked on, put the front end up on ramps. Fill the Rad but leave the level at least 3" below the top.
And leave the Rad Cap off ! Let it idle. Let it warm up. Let all the bubbles work themselves to the highest point. Let it run to the optimal temp.
Then and only then should you even think about putting the cap back on. Let the air out. Burp it. Top it off. Then cap it.

C6-CYa

^
Except we don't have a radiator cap on the radiator?

In this Texas heat (103), mine overflows from the expansion tank every time I park it. It doesn't overheat driving it though. Normal?

HamadUP

I did my best to make sure that it "burbed" out all the air, I was using this thing that I got from amazon :


I triple checked that I have no leaks. Anyways, I'll go to sleep now and will try again tomorrow afternoon. I really want to get back to drive that thing as I did 25 years ago, at that time it was my only car and drove it daily, I think I made 10k miles in the first year I got it!

MelWff

Have you pressure tested the radiator cap?
Is it a 15lb cap?
When cold are you filling the expansion tank 1/2 way?
What temperature does the gauge show?

Mr D.

You never mention what your coolant temp is other than normal when this happens. Losing coolant through the overflow hose at normal temp degrees just doesn't happen. Water boiling point is 212F, at 15 psi (radiator cap) that boiling point is increased to 249.8F. A 50/50 mix of water and antifreeze will add 11F buffer to those number so in reality the car pukes out the overflow when the water temp is 260F or higher. A defective/worn radiator cap will cause this, but you already changed that.

Your cooling system is building up excessive pressure, a cooling system exhaust gas test would be next on your list.

blue427

It may be that you're filling your expansion tank to much,if I fill my tank up 1/2 way it spits out,so I only fill it 1/4 full than it doesn't spit at all. My bb runs 180 degrees,when really hot out at a traffic light it'll go to 190. Might be worth a try.

calwldlife

let it puke.
keep eye on temp
should find its level
worry when temp rises or keeps puking

HamadUP

Thanks guys for all the tips, I learned a lot from you guys all the past years and I'm still learning. I'll try again tonight and will let you know, hopefully things will be good.

Jebbysan

As stated....filling it up too high will cause that issue, it is as described, an "expansion tank".....but first thing to do is put a coolant pressure tester on the system and rule that out 100%.
What lb. cap did you install?

Jebby

Boswell

I went through a similar situation many years ago. Coolant puking out overflow tank after reaching operating temperature. I used a coolant combustion leak detector. Also known as a "radiator sniffer". Test came back positive, so pulled heads hoping it was a gasket failure. Found hairline in the combustion chamber of the head. The exhaust gases being pushed through the crack were pressurizing my coolant system. The sniffers can be found just about anywhere from parts stores, Amazon, and harbor freight. The cheap ones work just fine.

Prysmian46

I agree, sounds like over pressurization coming from combustion gases. The system is probably seeing pressures of 20 psi or more. Extremely hard on coolant system components. By the way, I use an 11 pound cap instead of the 15 pound. My 82 CE runs at 180 to 190 with a 180 high flow therm when the outside temp is 90 to 95 degrees. So i see no reason to use a 15 pound cap in a 40 year old engine. But that is just me, a retired mechanical engineer.