I notice, as I can hear it pretty loudly, bubbles in the overflow tank after I shut down hot. Lasts for up to a couple minutes, really fast at first then slowing down. Very noticable as its loud. Is this normal?

no its not

So what does this mean then?

Assuming you didn't just change coolant it could be:

Defective pressure relief valve in radiator cap (check this first, replace cap).
Bad cylinder head gasket
Possible crack in the block.


Do you see any oil in your coolant? I think they have a test strip kit that will detect the presence of oil in coolant (strip changes color).

Might just be an intake or exhaust air leak letting air into the coolant. Does your car produce white smoke with a sickly sweet smell?

Have you had any other recent cooling problems?

Might be worth doing a compression and leak down tests to your motor, pin point the problematic cylinder.

With motor cool, remove the radiator cap.
Start the car and let it come up to temp.
Be sure the coolant is circulating.
Look for bubbles.
If no bubbles you may be ok.(just trapped air?)

Mike - please elaborate, what vintage car? factory over flow? added catch can? added functional coolant recovery?

Prior to overflow/coolant recovery systems it was necessary not to over fill the radiator or when you shut off the engine the fluid would heat soak (not moving any longer), expand, creat more pressure and spit up a little green stuff. The key is leave about 2" at the top of the core when you fill it. Just adding a catch can doesn't do anything but reduce a little toxic waste polution, which is a good thing... It's still going to puke if the core is over filled.

If this is an actual recover system then what happens is you fill the rad core and purge any air from the system, fill the recover can to the cold minimum level and when the fluid temps rise it purges to the can and as it cools it gets sucked back into the radiator. Factory systems work well aftermarket add on kits work but have to be installed correctly including using the right rad cap.

Last you are not describing opening the rad cap and seeing air bubbles in the radiator are you? That would be the sign of a problem.

Ok thanks for the replies....heres some more background.

The car sat for about 6 years, then I fixed everything that needed attention, started it up and drove it for about 8 months. I then had leave it again for about 6 months. Went I next went out to it, almost all the coolant was gone. There was only a little left in the radiator. I have no idea where it went as there were no obvious leaks or puddles. Family member said they never saw anything either. I think I saw a slow leak from the bottom rad hose(looks like a dried up trail of fluid from the rusted screw ring fastener thing). Oil seemed low as well, but again, couldn't find a leak.

There didn't appear to be oil in the coolant or vise versa....so I don't know what happened to my fluids. No white smoke either.

So I topped my coolant off with PLAIN WATER(filled rad then filled overflow tank), just so I could drive it for a bit. I'm going to flush my coolant and refill with proper mixture shortly....I just wanted to make sure the tranny and rear end was good as I had some problems with them before I let her sit for the 6 months.

Someone had said I might have a blown headgasket as my system pressurizes pretty quick, but not super quick. We did a test for compression gases in coolant and that came back negative. So still unsure of a head gasket leak. I did a compression test when bringing her back to life after the 6 years, and compression looked really good. Haven't done it after the 6 month sit tho, but I assume it should still be good.

So I'm hoping since my coolant is mainly water, maybe the heat soak just caused the coolant to boil early?

If I do have a head gasket leak, or cracked block.....would that make bubbles AFTER the engine is off? I would think it would only make bubbles when it's running.

Again thanks for the help....I promise to never let a car sit for so long again!

It's a 1990 IROC 305 5sp

Where did everyone go? Is there a simple answer I'm missing?? I'm still relatively new to engine troubleshooting.

Thanks

Same questions over... Are you describing opening the radiator cap and seeing bubbles? Or is the overflow spewing into the recovery tank?

I can't see any way bubbling in the overflow/recovery tank is a sign of any major issue. Bubbles in the radiator is a sign of problems...

If your just spewing into the overflow try replacing the radiator cap...

Bubbling after the car is shut off is almost certainly a bad radiator cap. As the coolant heat ups after shut down (heat soak) it is starting to boil because the cap can't hold the pressure up above the boiling point, and this pushes the water out into the overflow tank. Since the cap doesn't hold pressure it also probably doesn't allow the system to draw a vacuum as it cools and draw the water back into the radiator, so the coolant overflow fills up, and the next time you drive it and it cools down it just pushes the water out of the tank the next time it heats up.

You should see a puddle though under the car near the overflow tank though.