Slight , single " Knock".....not bad, but need opinions!

[roperteacher]

I am not real worried about this deal, but thought I would run it by you guys! I just noticed not to long ago that when my truck is stone cold and then the first 20 miles or so thereafter I can sometimes hear a SINGLE " Knock" ONLY when at idle. It sounds like the old diesels with glow plugs, when the glow plugs would go off just before you started it. The best way to describe it is if someone took a very small hammer and tapped a block of wood they were holding in their hands. I have done lots of research on here regarding Injector knock, and it sure doesn't seem to fit the sympotms others are describing. It doesn't do it when the engine is really warm, or it is NOT what I would consider loud, like others have reported. It only does it at idle so whatever RPM that would be. It pulls great, getting great mileage... increasing each tank, etc. Plenty of power. Purrs like a kitten... . It almost sounds like something is cycling??? From what others have described on here, doesn't seem like an injector. Any ideas? Thanks!

 

[Forrest Nearing]

grid heater...

 

[CAgnoli]

Yup, it's the grid heater, cycles on and off until the ECM doesn't think it's needed any more.



If the ambient temperature is below 60 degrees, that is a faily common noise. On hot 85-90 degree days the grid heater doesn't even cycle.

 

[roperteacher]

Thanks so much guys!! I never thought about that! Here's why... I live in southern Calif... our days have been in the 110's... and only in low 70's night. I'm up with the folks in Paso Robles... Highs in 90's but lows in the mid 40's. When I start er up in the morning lately , overhead has been reading 51-52' outside... so there ya go! Thanks!