2004 Cayenne light knocking

[JFP in PA]

By running either a compression or leak down test on each cylinder.  If you have a cylinder head to water jacket leak, you can also detect it by analysis of the coolant for combustion byproducts.

[lewisweller]

6 hours ago, Supra-p!g said:

 

The Indy also said that I likely was hearing lifter noise when I heard the intermittent thud sound.

 

Head gasket? How can you tell if that is going bad besides water in the oil, or water out the tail pipes? I have none of that, and no smoke ever, but black carbon buildup on exhaust tips. I can see old oil stains (maybe it puddled in that area at some point) in the middle bolt on the side of the right hand bank where I heard the lifter noise.

 

Thanks,

Mike

 

 

 

Hi Mike, my head gasket revealed itself as over heating at idle, it transpired that the gasket being metal was not broken but was leaking from the cylinder 2 or 3 of bank 1, the hot gases at idle entering the cooling system just boiled it up, if you revved the engine or was driving normally it would be able to maintain a normal temperature as the water pump flow is high enough to manage. Another way was sniffing the coolant in expansion tank obviously when cold, it smelt of fuel and that's a dead give away. 

Another noise I had on bank 1 unrelated to lifter or head gasket in fact was the SAI pump check valve from the exhaust is stuck open. This pulses exhaust gases back in the SAI pump and makes a blub blub blub pulsing noise in time with the firing rhythm of the bank 1. This has destroyed the SAI pump and it's full of carbon, I capped off the pipe and cleaned out the SAI pump. Problem solved sort of, in this climate I don't need SAI pump and it only for quicker cat warm up and emissions, so actual performance it has no effect. I just left them plugged in to avoid a check light although I do see a code about SAI pump under limit air flow or something like that sometimes, but never a check light.