Hey guys I have a compression test question. I was compression testing my friends Odyssey van V6. One side is great, the other one is not. last cylinder shows 0 psi middle 120 psi and front is 124 psi. I am sure it is a head gasket or something, but I have never seen 0 psi before. I have seen 20psi and 40 psi but never 0. Do you think it is something worse than a head gasket being 0 psi?

 

Assuming that the compression tester is still working correctly, then there is definitely a problem in that cylinder. What happened to the car to make you think that it was the headgasket to begin with?

I would perform a cylinder leakdown test next, that will tell you what is causing the lack of compression. It's possible the headgasket is blown or the rings are completely shot, a valve is bent or valve lash is extremely tight.