Today's Mystery coolant problem

[Vette66AirCoupe]

RE: '66 Big Block, with A/C.
On the way home from a show on Sunday my nose was suddenly assaulted by the dreaded heavy smell of anti-freeze, and I do mean suddenly! Of course this had to happen on top of the Delaware Memorial Bridge! I thought for sure I had a major leak so I drifted down to the toll booth watching the temperature gauge like a hawk as well as the windshield for some tell tale steam. Nothing. I decided to press on and made it several miles to home without overheating, smelling anti-freeze all the way. When I got home there were droplets of anti-freeze on the engine and the underside of the hood but no dripping or hissing. I let it sit and came back a half hour later. No drips. Took the cap off and the anti-freeze level was about 3 inches from the top. Today I got my hands on a pressure tester and pumped the system up. I heard hissing at the top hose connection to the radiator. I tightened the clamp and the hissing stopped. So far so good. I added some water, maybe a half pint or so, to get the level up to about 2 inches from the neck which is where it always had seemed to be in the past. Now here is where my concern comes in. The pressure tester indictates a slow but steady drop in pressure from the 15lb index mark I pumped it up to with the engine off. So I started the engine to see if I would gain pressure quickly with it running. I let it run till warm and witnessed a slight gain in pressure but nothing radical, just a slow gain that you would expect with the warming of the engine. The pressure rose to about 22 lbs. at which time I shut the engine down. It had reached normal operating temperature. It sat for 5 minutes while I stuck my head everywhere but up the sidepipes listening and looking. Nothing. No foam on the dipstick either. Where in the hell is the pressure I'm puming into the system leaking out? It's really two different issues. #1 is where did the coolant come from under the hood? I'm hoping that was just the result of the loose clamp. #2 is where is the pressure going? If I see no external leaks, don't have sudden pressure gain in the cooling system when it's running and have no apparent evidence of anti-freeze in the oil can I rule out a head gasket problem? Oh, and the cap tested at 15 lbs and held like a rock so I'm sure the tester itself is not leaking. Anybody have any ideas? :confused

 

[magicv8]

If you have a heater, put paper under it to see if it gets wet.

 

[IH2LOSE]

Tunr on the defroster and see if it turns up on your winsheild. Mat have a leaking heater core,Or a bad tester.

 

[JL66REDCPE]

Perhaps you could make up some soapy water and a small brush like you would use to test for a gas leak on a barbecue. Pump up the system with the pressure tester maybe to 17-18 lbs. At each Connection/possible culprit brush on some of the soapy water and see if there are any bubbles which would indicate a leak. Some but not all of the connections/possible culprits would be; the water pump shaft, the area around the thermostat, both ends of the heater hoses and radiator hoses, and if I remember correctly there is a hot water shutoff valve on a/c cars. Also check to see if a prior owner put a ball valve in the system to stop heater area water flow for the summer months. Check every possible suspect. The suggestions from magic and larry were excellent. Also get under the car and look at the air vent in the water pump. You can see if any coolant has been leaking there. If so the water pump may be going bad.

 

[wallyknoch]

Not exactly within the scope of this thread, but sort of related to overheating and a long way from home. As long as you have water or coolant merely twist the radiator cap loose back to the first notch. This will take the pressure off the cooling system that forces the coolant out. This worked for me on a couple of occasions. Once in 1964 for 1200 miles from New Orleans to Dearborn in the 62 Vette with two blown head gaskets, and the other time with a bad water pump on my 57 Bird half way back from San Jose to Dearborn in 1970. I didn`t nurse either of them, 70+ MPH all the way with zero overheat problems. I just monitered the coolant at every gas stop. Once back here I up graded the Vette to a 1964 30-30 cam and scraped the 097, and also dumped the 62`s FI heads for the better 1964`s FI heads. The Bird, I just changed the pump.