The cylinder was tested, made a mistake and finally found TDC. After that, no intake leak. I think you missed that post.
I eventually went on to skip the leakdown test since the harbor freight leakdown tester had mixed reviews and was pretty inconsistent as well. The harbor freight tool is regulated to put out only 15 psi no matter what you put in.
What I did in the end was just feed each cylinder compressed air at TDC. I fed each cylinder 100 psi since my compressor can't deliver much more.
The engine was cold when the tests were performed.
To get to the spark plugs on this vehicle, the hood, wiper cowl, wipers, and intake plenum need to be taken off just to reach the plugs.
Everything that I have read when googling around shows that a leakdown test when cold is fine and 100 psi fed to each cylinder is fine. I do understand what you mean about the compression ratios and the equivalent in PSI when running (not sure of the CR but can tell you that the front cylinders were about 165 with the engine cold and not even pressing the gas so you have a point).
Not arguing with you all...trying to learn. When I get the intake manifold on and the myriad of harnesses and vacuum lines, I am going to start the engine again and verify bubbling. After that I am going to pull the serpentine belt off of the water pump and run it for a few minutes to see if that is causing the bubbling.
If that doesn't work...well as before it is junk time real soon...but would be happy to try the head gasket test if the pump idea doesn't work.
Originally Posted By: yonyon
No, the leakdown test as performaed isn't conclusive if only for the reason that one cylinder wasn't tested at all. That cylinder is the one that had an open intake valve and allowed air to blow out through the in door.
Now, how about the pressures involved? Are they appropriate? I don't know offhand the compression ratio of your engine, but I think gasoline engines tend to use compression ratios in the neighborhood of 8.0:1 to 11:1. That means that cylinder pressure during cranking can be as high as 11 bar which is roughly 160 psi. If 160 psi is possible before the engine even starts, then once it fires up and has combustion going on the pressures could be just a tit-bit higher. How much air pressure did you feed in during your leakdown test? Did you perform the test with the engine at full operating temperature?
I eventually went on to skip the leakdown test since the harbor freight leakdown tester had mixed reviews and was pretty inconsistent as well. The harbor freight tool is regulated to put out only 15 psi no matter what you put in.
What I did in the end was just feed each cylinder compressed air at TDC. I fed each cylinder 100 psi since my compressor can't deliver much more.
The engine was cold when the tests were performed.
To get to the spark plugs on this vehicle, the hood, wiper cowl, wipers, and intake plenum need to be taken off just to reach the plugs.
Everything that I have read when googling around shows that a leakdown test when cold is fine and 100 psi fed to each cylinder is fine. I do understand what you mean about the compression ratios and the equivalent in PSI when running (not sure of the CR but can tell you that the front cylinders were about 165 with the engine cold and not even pressing the gas so you have a point).
Not arguing with you all...trying to learn. When I get the intake manifold on and the myriad of harnesses and vacuum lines, I am going to start the engine again and verify bubbling. After that I am going to pull the serpentine belt off of the water pump and run it for a few minutes to see if that is causing the bubbling.
If that doesn't work...well as before it is junk time real soon...but would be happy to try the head gasket test if the pump idea doesn't work.
Originally Posted By: yonyon
No, the leakdown test as performaed isn't conclusive if only for the reason that one cylinder wasn't tested at all. That cylinder is the one that had an open intake valve and allowed air to blow out through the in door.
Now, how about the pressures involved? Are they appropriate? I don't know offhand the compression ratio of your engine, but I think gasoline engines tend to use compression ratios in the neighborhood of 8.0:1 to 11:1. That means that cylinder pressure during cranking can be as high as 11 bar which is roughly 160 psi. If 160 psi is possible before the engine even starts, then once it fires up and has combustion going on the pressures could be just a tit-bit higher. How much air pressure did you feed in during your leakdown test? Did you perform the test with the engine at full operating temperature?
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