Bubbles In My......Radiator

[CatGuy]

I may not be able to pursue this much since winter is closing in and my unheated, uninsulated garage will soon be in the 30's, but I thought I might ask. The other day I checked the strength of the coolant in my '26 Roadster (with water pump) and the level was low enough that I had to start the car to get the level up enough to get a, hopefully, accurate reading. As soon as I started it the tester pulled up foam. A little bit later I was able to get actual coolant. I'm thinking of eventually (when it warms in the spring or we buy a heated shop) doing a 'Leak Down Test' on it to see if it's got a blown head gasket......or.....worse. I never see any smoke of any color out of the exhaust. Is it always possible that the water pump which leaks is drawing air into the system? I did do a compression test on it in the spring. It showed..... 'Dry: 35 40 40 40' 'Wet: 45 40 45 45'

[Jerry VanOoteghem]

You could run the engine for a few minutes, then check your oil to see if it looks milky. If so, there's coolant in it.

It's also entirely possible that your pump is sucking in air, as you suspected. Add coolant until the level comes about even with the Ford logo on the front of the radiator. That's where they seem to like to "settle in". Then check it often for a level drop and or leakage on the floor or in the oil.

If you're not going to do much with the car until Spring, then drain the radiator, since you are suspect of a possible head gasket leak.

[jab35]

I'd change the oil too. And squirt some new engine oil on top of each piston jb

[Luke]

Scott,

Pressurising each cylinder à la the leakdown test and looking for bubbles in the radiator is a good way of determining if you have cracks or head gasket issues, a simple compression test is unlikely to assist a great deal in diagnosing that.

Of more concern though is your garage temperature issue. I'm reminded that here 'down under' when I was a working as young motor-body builder we used to heat up our dollies with the gas torch when the temps got below 0C, but otherwise shrugged off the ambient temp and just hit things a little harder/quicker until we worked up a head of steam ourselves. Hard to do perhaps when all you're involved with is a pressure test, but perhaps a few pushups beforehand might do the job?

Luke.

[CatGuy]

How much pressure should I use? I assume not much and using too much would be bad? Don't laugh.....I actually thought of getting a fitting and using a bicycle tire pump.

[TXGOAT2]

You're not likley to use too much pressure. Combustion pressure in Model T engine can reach well over 300 PSI. It would be best to use around 125 PSI and apply air continuously. The cylinder which you are testing must be at TDC on the compression stroke, so that both valves will be closed. Compressed air will cause the engine to turn, so you will need to have the car in high gear and you will need to securely block at least 2 of the wheels so that the car cannot move forward or backward if the engine turns due to the air pressure. A device can be assembled from a pipe bushing and an air hose adapter and chuck to allow connecting compressed air to the engine cylinder via the spark plug hole.

[Scott_Conger]

Waterpumps need grease

Grease mixes with hot water and coats as much surface as you will provide grease for, and provides a nice scum that clings to various nooks and crannies.

starting a water-pump equipped car and immediately pulling up foam is not likely a head gasket leak

starting your car and eventually seeing discrete bubbles IS likely a head gasket leak

keeping coolant so low in the system that a sampler cannot reach it is running the coolant too low

[Norman Kling]

I agree with the above about possible compression or combustion leaking into the cooling system, however, if you find that when parked for a few weeks at a time, and the coolant level doesn't drop, you probably do not have a leak.
Here is a personal experience which happened to me about 55 years ago. I had a Model A and decided the cooling system needed to be cleaned out, so I put some washing detergent in it and ran it for a while then drained. I ran the water hose in it for several times and drained. Later filled up and drove around. It was like Lawrence Welk's bubble machine! It took a few weeks to get it back to normal. So depending on what you have used to clean the cooling system and what kind of bubbles you have?
Norm

[CatGuy]

Waterpumps need grease

Grease mixes with hot water and coats as much surface as you will provide grease for, and provides a nice scum that clings to various nooks and crannies.

starting a water-pump equipped car and immediately pulling up foam is not likely a head gasket leak

starting your car and eventually seeing discrete bubbles IS likely a head gasket leak

keeping coolant so low in the system that a sampler cannot reach it is running the coolant too low

I had forgotten about the grease in the water pump. Last year year I ran some cleaner through my 'A' for that same reason, but it never dawned on me I should for the 'T', too.