Quote:
Originally Posted by MountainBrew
Your insight is very much appreciated. I'll see if I can pull the check valve from my compression tester and rig the shop air into it. I install draft beer systems so I have tubing and hose clamps galore.
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Given your background, I hope you made a portable " air " supply that attaches to a CO2 tank. I have one when I need to fill many tires / run an impact in a remote location. I even use it with a stapler for house trim / paneling rather than drag out a compressor. One note, since CO2 is a smaller molecule than nitrogen, if you have a leaky tire it will leak faster. ( Nitrogen is a large molecule and makes up about 75% of air. )
I also use CO2 on a MIG welder when welding oh too rusty 1/8" + thick metal. CO2 is a reactive gas and gives the arc lots of dig. The down side it is a slower weld process and makes lots of spatter.
Quote:
Originally Posted by MountainBrew
In theory (my theory doesn't amount to much), wouldn't running the engine produce the same symptoms? It seems to me combustion gasses would leak into the coolant the same way the shop air would in the procedure you described above. Should I expect to see bubbles or coolant rising by simply running the motor with the expansion tank cap removed?
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Sort of. Using shop air is a simpler method to find a leak. The problems with a running engine are:
Water expands when heated so you won't know if the rising level is due to expansion or a combustion leak.
The thermostat will cycle compounding the expansion issue.
Many times air hides in a cooling system so, is the air making it's way to the rad cap for purge or a combustion leak?
On some systems have coolant flow near the rad cap, this swirling makes it difficult to tell if the water is slightly rising.
When you use compressed air as a test finding absolute TDC can be difficult especially with a worn motor that has low piston ring tension ( RE Cylinder friction ) . Turn the engine to TDC both valves closed then give it a quick puff of air. Watch the engine pulley and if it turns, rotate the engine the other way a bit farther from your starting point and try again.
Be sure to stay clear of rotating engine parts, 100 PSI is pretty powerful when applied to an engine.
Note, some here will make a big fuss that turning an engine backward will throw the timing chain. Any engine that throws a timing chain on reverse rotation is already worn out and is going to throw a timing chain shortly. Gasoline engines sometimes violently " Diesel " on a hot shut down and can run backwards with great force for 5 or so seconds. This shock load is far worse than a manual reverse rotation.
A gas or diesel engine can spring back slightly when turned off as engines tend to stop when a cylinder is on the compression stroke. The effects of stopping on compression can be evidenced by looking at starter ring gear wear patterns. A 4 cyl will have 2 badly worn places 180* out , a 6 cyl 120* and a 8 cyl 90*.
As you are doing the coolant leak you will get leaks from other places: ( In order of worsening engine condition )
Oil cap / crankcase: Piston ring wear. Some leakage here is normal and gets worse as the engine wears.
Exhaust : Exhaust valve and seat face leakage ( Not valve stem / valve stem seal oil leakage leakage ) This gets worse as the engine wears, some leakage is normal on an older engine and does not affect operation much. Valve clearance less than 0 can cause leakage.
Intake / Air filter: Intake valve. As with the exhaust same causes except the motor is really worn out at this point and power will be decreased.