No compression on number 5!!!

[URquattroGus]

Sat here waiting for recovery back home.

Crusing at 80 and then heard a light knocking sound.

First time I've used the RAC. He comp tested all 5 pots and found that the one nearest the bulkhead had no compression. All others were 175 PSI.

Oh f*ck! There is a top end rattle. It doesn't sound too loud though.

Fingers crossed it's not too bad.

What can it be, presumably a dropped valve, holed piston?

[A80Avant]

Good luck. Shouldn't be knock. You have knock sensors.

sent with Nokia 6210

[UrS4boy]

Good luck. Shouldn't be knock. You have knock sensors.

I am pretty sure that he meant "banging and crashing", not knock as in pinging/pinking.

[URquattroGus]

Its not a really loud banging or anything as you would expect, more of a ticking sound. Who knows

[Pirvu Eugen]

Maibe is just an bad tappet blocked open....and the sound you hear is just the cylinder wich is not firing...
You should..iff not made yet...remove the cams cover and inspect there...
If you dropped a valve...will not sound like an light knock..i am pretty sure will be loud.
Hope is not too bad...
Goodluck!

[UrS4boy]

Reasons that No.1 and No.5 exhaust valves burn

Unfortunately, it sounds like a valve issue. It is not common for these I-5 20vt's to drop a valve but it has happened. Hope it isn't too bad.

BTW, No. 5 is prone to burning its exhaust valves (along with No. 1) if you run Stage 1+ software (i.e. with a 3 Bar map, around 280 hp) on the stock exhaust manifold. Running an RS2 turbo and injectors with Stage 3 software on a stock EM would almost guarantee to burn the No. 1 and 5 exhaust valves. Just a matter of time.

http://forums.quattroworld.com/s4s6/msgs/196904.phtml

[Rocco]

.the only one time I had not compression then I had communicated 2 cylinders because complete broken. Head

[diesel des]

Or dropped a seat?

[URquattroGus]

I am not running stock em, I have the 034 rs2 style manifold. Anyway, will have to open her up and see what's amiss!

[jsws3]

I am not running stock em, I have the 034 rs2 style manifold. Anyway, will have to open her up and see what's amiss!

I hope it's not to bad after all the time and effort you have put in .

Best of luck .

[prj]

Aww, that sucks.

Keep us in the loop please.

If all others are 175 PSI it is some problem with that given cylinder, as if it was a global problem (fuel supply leaning out and so on) you would have bad compression in at least one more cylinder.
The fact that it let go while cruising also means that most likely there was fairly crude mechanical failure, which has little to do with power.

I guess the truth will be revealed once you take the head off.

[Rocco]

Aww, that sucks.

Keep us in the loop please.

If all others are 175 PSI it is some problem with that given cylinder, as if it was a global problem (fuel supply leaning out and so on) you would have bad compression in at least one more cylinder.
The fact that it let go while cruising also means that most likely there was fairly crude mechanical failure, which has little to do with power.

I guess the truth will be revealed once you take the head off.

yeah, when i had my head problem i had no compression in 2 cylinders "side to side"

i hope you can solve it the cheaper as possible- in my case i just put another used head and problem solved

good luck

[andy10v]

A mate had a similiar problem, 7A cam had snapped for no apparent reason, no compression on one cylinder.

[adam g]

Such a failure at cruise is odd indeed, very doubtful a holed piston - Ive only melted them at WOT.

[AndyP]

The good news is that it still turns over enough to do a compression test, when my exhaust valve snapped it did this, and the engine locked completely

http://www.s2forum.com/forum/showpost.php?p=515665&postcount=236