The Stovebolt Site Forums The Shop Area Engine Shop coolant system pressure test

Weather has finally turned good - time to get back to work, but I still think I have a leak from the coolant system into the engine oil. The head has been checked OK. I thought that I would do a pressure test on the radiator / coolant system. Borrowed the test tool from autozone, but none of the adaptors would fit the neck of my 46 radiator. My only other thought is to adapt a fitting to go into the water temp sensor hole, along with an additional bit of jerry rigging. Does anyone have a better idea?

Use a rubber expansion-type freeze plug that will fit the radiator neck hole below the overflow tube, and center-drill the bolt to accept a short length of rubber tubing and a Schrader valve from an old inner tube or a tubeless tire valve. Then use a bicycle pump to put a little pressure on the system- - - -maybe 3 or 4 PSI. DO NOT use an air chuck- - - -you'll blow out the radiator core or the heater.
Jerry

Thanks Jerry - interesting. I will have to see what I can find in the next few days.
Bob

Presumably, the pressure limitation is based on the design of the original copper radiator, right? I am temporarily using an aluminum after market radiator that came with cap rated at about 14 psi. This should allow a pressure around 5 to 10 psi, right? Still trying to figure out the pressure gauge that I can attach to the line for the duration of testingthat wont leak air and be sensitive to low pressures.
Bob

The pressure limit also refers to optional heater. Perhaps even to seals in the water pump? Maybe others will say "do not " worry. I worry about anything outside of specs.

A 140 degree thermostat was standard - it was fully open at 170 degrees (alcohol coolant).
The highest temperature optional thermostat was 156 degree - it was fully open at 194 degrees (permanent anti-freeze).

Most likely a 0 pressure radiator cap?

http://chevy.oldcarmanualproject.com/chevyresto/4684.htm

If you just want to test the engine, get a couple of long flexible radiator hoses and take the radiator out of the equation by joining the two hoses with a piece of exhaust tubing with a brass inner tube valve stem soldered into it. Then, assuming the heater core isn't in the mix, go ahead and crank the pressure up. I've tested a race engine block and heads for cracks and seep leaks by plumbing a garden hose up that way and using city water main pressure. I found a tiny sand hole halfway down a cylinder. I installed a sleeve in that hole and saved a lot of expensive machine work.
Jerry

Thanks all for the support. Maybe the following will help someone else. I was able to cobble together a decent test system. I found an expandable plug at Ace for the top opening of the radiator. I found a bourdon tube dial type tire pressure gauge at Ace that read clearly in the range of 0 to 10 (and beyond) AND would allow me to unscrew the external piece that fit on to the tire Schrader valve. A few brass bits adapted it to a 1/4" barbed nipple. Amazon had a Schrader valve that terminated in a threaded fitting. I did have to turn down the tip of the valve slightly to get my air chuck onto it - my compressor does adjust to very low pressure, no damage to any cores. Some fuel line allowed me to couple this into the radiator overflow port. The results were good.

Bob

Did you find the source of the coolant leak? I was suggesting putting the expansion plug into the radiator neck below the overflow tube and adapting the air to the center bolt that expands the plug, but your way seems to have worked also.
Jerry

Apparently, I have no engine leak - pressure remained steady and the radiator water level remained constant. I have a couple of others theories on how the water might have gotten in the engine, but I wont mention them here - I really don't want someone replying "that was stupid, how could you let that happen". So I can move forward again.
Bob

He who claims that he has never done anything stupid is very likely a liar. A lying stupid liar.
We are a very fair and understanding crowd on this site without exception. No one has ever ridden another about doing something stupid...
Well, no more than 2-3 times a week anyway.
It seems that folks are easier on those who come clean about their mistakes. Commiseration is what it is known as.