Thread: Knock Sensor leaking or Spark Plug

Let me try again. I've replied 3 times already and the computer has gone into some odd loop which meant I've had to turn it off before the message was posted. And it's a pain with only one finger to type!

It cannot leak from the knock sensor. The threaded hole is blind so there is nothing behind there to leak.

Get a piece of plastic tubing. Put one end into an ear and run the other end along the offending area. If there is a leak, you'll hear it.

Could I suggest that the most LIKELY explanation is that you have a blowing exhaust manifold gasket which causes a sharp "chuff" and can even be mistaken for a noisy tappet.

Regards Philip A.

Thanks for the replies, that eliminates the knock sensor, done all the stethoscope thingy and you would swear that No 4+6 plug sound like they are the culprits, put soapsuds around them, nothing.
Have done a complete compression test, all are around the 140-150 except No6 @ 120 No 2+4 @ 130.
What I have failed to mention tho, is I just had it converted to injection LPG, and on investigating the chuffing noise, I removed the rocker cover, discovered the installer never removed the valley cover to drill and tap the new injector holes.
Me thinks, the drill and tapping fillings have gone down and lodged on the intake valve seats on 2-4+6, giving this chuffing noise, if the head gasket has gone between 4+6 why the odd pressure?
John

Phillip regarding the exhaust, I can’t seem to get two bolts out of the heat shield to remove it to check the exhaust manifold, but have hand blocking the exhaust pipe with no difference to the noise, not saying that’s conclusive.
BTW in my last post it should have been drill, tapping filings or debris not fillings.

John

It certainly sounds like a valve problem in 4 and 2 and 6 are marginal. I guess you mean the lower intake manifold when you say the valley cover.

Weird and as you say could be caused by debris. Of course could be sticking/burnt exhaust valves but bit too much of a coincidence.

How slack is that? I hope you can get them to pay for it!
Regards Philip A

It's entirely possible that shavings are present on the valves, But they should blow out with a hard thrashing.
When the injector holes were drilled and tapped the installer should have used a blower (e.g. backwards vacuum cleaner) to pressurise the intake runners and prevent bits dropping in. Ask him to show you how he did this. Otherwise he has a repair job on his hands.