Disappearing coolant: C-2

[Mark F.]

For the first time this summer, I drove my '65 300hp Powerglide to a local eatery. It's always run warm, but this time it was running at 210 degrees on a 85 degree evening. When the car cooled down, I checked the coolant level and found it about 3 quarts low.

This car sits in a VERY clean garage (because it's my wife's garage, and she permits me to park the car in it) and I've not noticed any leaks (we have cats, the the coolant is dangerous for them).

I checked for leaks (hoses, water pump, heater core and connections, and evidence of internal engine leaks) but have found nothing. I checked the temp gauge against an I/R gauge today and found the gauge to be accurate.

Any ideas where my coolant is going?

Mark

[Joe L.]

Re: Disappearing coolant: C-2

Mark-----

In a pre-1973 Corvette, there are only 3 things that account for coolant loss. First, of course, is a leak of some kind. Apparently, you've ruled that out. Second, is overflow from the radiator or supply tank. Since pre-1973 Corvettes have no coolant recovery system, whenever the radiator cap pressure-relieves, some coolant will be lost out of the overflow. This is quite normal and is the primary reason that coolant has to be topped off with regularity in a pre-1973 Corvette. While you might not see any coolant on the floor in the garage, that does not mean that this is not occuring at other times on the road. Usually, you won't see this kind of overflow in the garage.

The third possibility is the more onerous. That involves internal leakage in the engine due to a defective head gasket, cracked block/heads, or otherwise. Such a condition can result in coolant leakage to the oil system (less likely) or coolant leakage into the cylinders (more likely). In the latter case, the coolant leakage into the cylinders is "processed" with the fuel/air charge and discharged through the exhaust.

[Duke W.]

Re: Disappearing coolant: C-2

Did you do a coolant change recently? Upon refilling there is always some air in the system, which will self purge, but you need to check the coolant level after each cycle and fill as necessary (expansion tank half full when cold) until the level stabilizes.

Duke

[Donald M.]

Re: Disappearing coolant: C-2

Mark, to check for head gasket or internal cylinder leakage, first run car without the rad. cap and let it warm up (top rad hose hot) and look inside the surge tank, if you see air bubbles,you likely have a head gasket leak. Next, rev the engine manually and check for large amounts of white smoke exhaust, this means you are burning the coolant with the fuel/air charge as mentioned earlier. However, it's my best guess that your coolant is being lost thru the overflow hose while driving, especially when your engine is runnng 210 deg. My'67 327/300 never runs hotter that 180-190 even in 95+ temps here in FL.Check for wetness under the overflow hose outlet area.
Don

[Wayne K.]

One more possibility...

would be a slow leak around a bolt that enters the cooling system. It leaks slowly when the system is under pressure but goes unnoticed because engine heat burns it off before it leaves a trail.

[terry leeker]

Re: One more possibility...

An internal leak you can have that won't show as foam in the radiator expansion tank is a leak into one of the intake manifold runners from the adjacent jacket water passage. They tend to leak when the engine is cold. Start the engine after it has sat overnight and smell the exhaust within a minute or two of starting (please use moderation - 10 or 15 min. is tooooooo long). You will get the normal amount of condensation but if the coolant has or is leaking in to the cylinders, the exhaust gases will have that sweet ethanol glycol smell.

[Jeff S.]

Re: Disappearing coolant: C-2

You could use one of the oil sampling labs to quickly establish if you have antifreeze contamination of crankcase contents. I use Blackstone (~$20) once/year when I change oil; they do fast work & will work with you on any special items of concern. Link follows: http://www.blackstone-labs.com/gas_engines.html