Like the title says, I noticed a little bit of smoke coming from under the hood and checked it immediately when I got home. I noticed the coolant overflow tank was empty which is weird because I fill everything at the beginning of driving season. Whatever, dumb mistake, I fill it up and park the car for 2 weeks. Pull it out of the garage yesterday and its all gone again! No leaks on the ground or anything. The car still runs strong, not like it has any noticeable issues, and it shows a good temperature on the gauge. The thermostat was just replaced over the winter. I have no idea where the coolant is going. Any ideas that anyone can think of? I am by no means a mechanic, so maybe Im overlooking something easy.




Also, I noticed some odd looking “rock like” things in the bottom of the overflow tank. Anyone see these before?

 

When you say tank do you mean the radiator overflow/coolant tank? And you say that you can see no coolant leaking out of the car? Those are some pretty bad symptoms. The coolant has to go somewhere.

Overheating plus coolant consumption usually points to one thing...head gasket. Are you experiencing any misfires?

At least it sounds like you're replacing the motor anyways.

The following paragraph is probably going to be considered blasphemy and may get me flamed off this forum. If you are easily aggravated and/or a mechanical perfectionist please do not read any further. Just close out the thread.

With that said here goes...

If it is your head gasket and you simply don't have the time to do it correctly try a bottle of Blue Devil head gasket repair. I personally was able to get 30,000 miles more out of a Honda Civic using this stuff. And I even know endurance race teams (in Chumpcar and 24 Hours of Lemons) that have saved their race using the stuff. Just keep in mind it's still a ticking time bomb and don't beat on the car.

 

I may have found or answered my own question...and it might sound very stupid or small. Just researching some today, it sounds like it could be as simple as a bad radiator/coolant cap. The very faint smoke could be the coolant escaping through the cap as gas. And thinking now, I did notice what seemed to be 1/2 a gasket on the inside of the cap ripped away...hopefully thats all it is.

 

You aren't going to lose a significant (read: noticeable) amount of coolant in a gaseous form. A drip may burn off a hot surface such as the engine or exhaust but will leave a trail of dried up tears and devastation.

But yes replace the cap.

Could also be intake gaskets or some losses through the cylinder head bolt threads. It is recommended on older engines to remove the head bolts one at a time, clean the threads, and apply sealant the reinstall. Do this with the coolant drained of course. Many of the head bolts holes in the block are open to the coolant jackets.

GD

 

I agree that a bad cap won’t lead to significant mystery coolant loss. But my experience with small block Chevy’s is rather limited so listen to the grizzled vets on this forum.

 

Pull your engine oil dipstick. The coolant might be in the crankcase.

 

Single most common cause of that is the water pump... the weep hole leeeeeks onto the INSIDE of the pulley, it slings everywhere in a fine mist and disappears. Sometimes you see a trace running down the INSIDE surface of the lower rad hose and MAYBE drips once in awhile.

Next most common is intake gaskets.

It is virtually NEVER a head gasket. Put that out of your mind until all else is eliminated.

All 17 bolts in each head go into coolant. All 17.

 

Thanks everyone. Im going to start going trough everything starting at the easiest solutions, working towards the hardest. Haven't been able to start on it yet though.

One big thing I should mention, when there is coolant in the tank and I drive the car, there are a lot of bubbles. It almost seems like its boiling, not that it is, but thats the kind of bubbling that is happening in the tank.

 

Just from researching a bit, the disappearing coolant and bubbles does make it sound like a blown head gasket... is there any way to check that directly? Im slowly building a new engine but it wont be ready for awhile. ResIpsa might have the qucik fix trick I try.

 

You can pressurize the cooling system and see if if it bleeds down, or won't hold pressure at all. That will point you toward a leak.

 

Google "Lisle Combustion Leak Detector." A bit pricy for a one-off test, but not as much as pulling cylinder heads unnecessarily.

 

right. you can get a tester that can test for the presence of exhaust gasses in the coolant mixture. if you find exhaust gasses in the coolant mix, most likely its a leaking head gasket. especially if you are seeing LOTS of bubbles in the coolant as the engine runs. is there a smelly white smoke from the exhaust ?

 

I’ll have to look into the tests before I go ripping anything apart

All the symptoms:
-Little bit of white smoke coming from under the hood
-Coolant quickly disappearing
-Bubbling in the coolant tank

-Car runs strong still
-Dash thermostat reads prefect temperature

 

Pull the spark plugs and look at them. If one or more cylinders are burning coolant, you will see the difference.

 

Most of the parts stores will rent you the kit around here. You just pay for the chems. Much less expensive.

 

I had a similar issue and mine turned out to be a air leak in the system. An air leak will cause bubbling in the coolant tank a cause evaporation. I was about to get the exhaust gas tester when I noticed my carpet being damp on the Passenger side. My heater core had a small pinhole at the very top and would not leak fluid all the time.

 

Also remember that bottle will fill with excess coolant as it expands and then suck it back into the radiator when it cools. If your coolant system is low often times it will completely empty the overflow tank as it cools. Have you verified that you are starting off with a 100% full and bleed coolant system? If you are starting off with a half filled radiator it will bubble in the over flow tank as the coolant expands pushing out the air, and when it cools it will suck all the coolant out of the overflow into the radiator. Otherwise as said check spark plugs for signs of coolant, leak tester, and I'll add you can smoke test the system. Any smoke out of the tail pipe?

 

Loop the heater hoses together, bypassing the heater core. If it stops losing coolant, your heater core is leaking.

 

I’ll repost this just because this seems to be the case on most problems outside of leaking hoses for me. Good luck!

 

Them rock things in the coolant reservoir may be some stop leak crap! Seen it a lot on the n=star Caddys where
folks would dump the stopleak or other voodoo head gasket fix when they got the "pulled headbolt syndrome" in
them motors with no radiator cap.
They pour it in there instead on the bottom rad. hose so it went directly in the motor!
Then it clogs the heater core!

Ask me how I know!

BUT Sofa and some others aRE RIGHT!
A pressure test will tell ya!

I bet either a leaking heater core or the water pump weep/casting hole.