VZ Alloytec - No compresson in Cylinder 2

[maxd344]

Hey Everyone,

I'm fairly noob to Alloytec's (Mainly work on Barras)

I'm looking at my Dads VZ Sv6 with a LY7 Alloytec. It idles rough and misfires. OBD reader showed Clinder 2 misfire but that's it. Replaced plugs and coils which didn't make a difference. Done a compresson test and found Cylinder 2 has basically no comoresson to it (like 2 psi). I've taken the rocker cover off and it doesn't look too poorly treated and can't see any issue with the cylinder cam things.

I'm after your guys input to what it could be? The timing chain feels tight.

Guessing the motor is economically fubar

 

[lmoengnr]

Got access to a borescope? Stick it in #2 plug hole and see if the piston is still in one piece...

 

[Pollushon]

Maybe take it somewhere for a second opinion, it'll take a shop two ticks to confirm. If she's got no comp on a cylinder then yeah, she's a throwaway, assuming it isn't a break in the head gasket. That's not such a bad job but you'd expect some water and oil in places they don't belong

 

[losh1971]

I had no comp and it was a broken valve spring. It's relatively common on the V8. I don't know if V6s have been known to break a spring but it does make a cylinder have 0 comp.

 

[Pollushon]

A way to tell ring from valve or gasket is to put 15ml of oil in the cylinder before the compression test. Turn it for a few strokes. Ring issues will build up a little pressure over a few strokes, valve and gasket won't

 

[losh1971]

Probably time to do a leak down test .

 

[Skylarking]

You can pick up a borescope that connects to your phone for < $10 on eBay…

With a borescope you’d get a good look inside the cylinder and be able to see if the piston was holed or the valve bent. You can even get a very close look at the top of the engine and check the valve springs and see if a spring is broken near the top or bottom coils (but still partly working)…