Good Afternoon, All--
So this is probably a pretty dumb question with an obvious answer, but sometimes in the heat of battle with a car, obvious things can be missed!
For reasons I will not get into here at length, I wanted to check my head gasket by doing the cylinder pressurizing test, looking for bubbles to appear in the radiator fill neck.
The basic procedure -- as I took it -- was to ensure each piston, in turn, was at the top of it's compression stroke with both valves closed. Then, using a compression test hose in place of the spark plug, pressurize each cylinder and watch for bubbles to appear in the radiator fill neck.
My problem is that with high pressure air pumped in (95 psi, the max. on my compressor), the piston is pushed down until the exhaust valve opens, and all the air just escapes thru the exhaust, rather than putting the pressure against the various sealing surfaces in the combustion chamber. It's almost a simulated cylinder firing, with the crank rotation. I even tried putting the car in gear (manual) and setting the parking brake in that hopes that that would hold the crank relatively steady. It does not -- the entire drivetrain spins and the car "squats" as the parking brake attempts to hold the vehicle still.
With too low a volume of air, it just seeps past the rings and wafts out the dipstick tube.
I suspect I'm missing some really easy portion of this test that somehow allows me to pressurize the cylinder without having the car run me over in the process, and it could be as simple as getting a regulator and metering a certain PSI of air during the test.
Any thoughts? If there's a recommended PSI for this test, can someone chime in?
Thanks!
Dave
So this is probably a pretty dumb question with an obvious answer, but sometimes in the heat of battle with a car, obvious things can be missed!
For reasons I will not get into here at length, I wanted to check my head gasket by doing the cylinder pressurizing test, looking for bubbles to appear in the radiator fill neck.
The basic procedure -- as I took it -- was to ensure each piston, in turn, was at the top of it's compression stroke with both valves closed. Then, using a compression test hose in place of the spark plug, pressurize each cylinder and watch for bubbles to appear in the radiator fill neck.
My problem is that with high pressure air pumped in (95 psi, the max. on my compressor), the piston is pushed down until the exhaust valve opens, and all the air just escapes thru the exhaust, rather than putting the pressure against the various sealing surfaces in the combustion chamber. It's almost a simulated cylinder firing, with the crank rotation. I even tried putting the car in gear (manual) and setting the parking brake in that hopes that that would hold the crank relatively steady. It does not -- the entire drivetrain spins and the car "squats" as the parking brake attempts to hold the vehicle still.
With too low a volume of air, it just seeps past the rings and wafts out the dipstick tube.
I suspect I'm missing some really easy portion of this test that somehow allows me to pressurize the cylinder without having the car run me over in the process, and it could be as simple as getting a regulator and metering a certain PSI of air during the test.
Any thoughts? If there's a recommended PSI for this test, can someone chime in?
Thanks!
Dave