The case of the missing anti-freeze

[Dave Rifkin]

Okay guys I have a situation that has puzzled my mechanic for the past few weeks so I am reaching out to the experts for suggestions.
I have my '69 Corvette at a local shop for some work and they called me with a concern about the anti-freeze level in the car.
Apparently they started the car up and noticed a puff of smoke coming from the left tail pipe. The mechanic thought he could smell anti-freeze so he checked the radiator and noticed that it was half empty.
He pulled the plugs thinking that he'd find one, or more, with a "steam cleaned" apperance if there was a coolant leak but, no luck.
Today he called me to say that he pressurized the system for about 30-40 minutes and the car only lost maybe 2 lbs over that period of time.
I had them change the oil and no mention was made of coolant in the oil.
The car starts up fine and runs great but, there is this puzzling issue of the missing coolant.

Do you guys have any ideas as to what could be the problem? At this point the mechanic is leaning towards a problem with the heads (porous head or a cracked head)

Thanks,

Dave

[Mr. Chevy]

Dave, if the head has a porous area and if the leak is not that bad you could try the GM stop leak tabs that the dealerships sell. They are little tablets of organic matter that help seal cooling systems and they work fantastic. Gm came out with them for the porous aluminum heads on the newer cars that would leak slightly due to casting abnormalities. They help clot the system and really do work. They will not hurt the cooling system and you can put several tablets in at a time.. Just go to a Chevy/GM dealership and ask for the cooling system stop leak tablets and they should have them in stock.

If your problem is more severe I would pull the heads and check them out more carefully and do a proper repair... The problem is most probably in your heads I would guess. I am no "expert" though........

Hope this was of some help.....

Rich

[njsteve]

A small head gasket leak/cracked head will not show up on a radiator pressure check. Radiator pressure tests only go to about 15 psi during the check. A tiny defect in a head gasket may experience 160 psi from the piston's compression, forcing the burnt gases into the coolant.

Since the 15 psi radiator check doesn't go anywhere near the compression psi range, it will show up as a false negative on the test.

http://www.blockchek.com/index.htm

You can buy the kit at your local Napa store.

This is the thing to use to check to see if you have a head gasket, crack etc. Neat stuff. It is basically a test tube with a one-way check valve at the bottom. You hold it in the radiator opening and fill the tube to the indicated level with this blue fluid. You then apply suction via the squeeze bulb which draws the vapors up through the one-way check valve from the radiator and up through the column of blue liquid. Any hydrocarbons existing in those vapors will turn the blue liquid to yellow indicating that there are combustion gasses in the cooling system. If it stays blue, that means no leaks.

I borrowed this same contraption from my mechanic buddy a few weeks ago when I thought my Charger was running hot and I saw air bubbles in the coolant. It reassured me that there was no problem.

Just for kicks, when the fluid wouldn't change color from the blue, I checked it by holding a capful near the running exhaust pipe and it immediately turned bright yellow.

[mockingbird812]

Good stuff Mac!!

[njsteve]

By the way, the car has to be running during the test.

Oh, and the fluid will go bad and turn yellow after a few years sitting on your shelf, or if you leave it open near a running engine. That was the "fee" my buddy charged me for letting me use it - I bought him a new bottle of the blue testing fuid for $7 at the local Napa store.