Thumpy

Hi guys,

I have a 1989 x-cab pickup with V6 and auto trans. Dad bought it new and pretty much babied it. I doubt it was ever off-road. I have had it for four years and it has 154k miles on it. The head gaskets were replaced years ago under the campaign, but I don't think they had failed. Anyway, the engine has a slight tapping (not really much of a knock) at about 1000-1200 rpm and when under a load. It does not tap when the engine is cold, but it always does it if the engine is warm. If I pull the plug wire from the number 1 cylinder, the sound goes away, leading me to believe it is a reciprocating part in #1. The engine is quiet at idle (warm, cold, load, or not). Would this be a failing rod bearing? I've never had a rod bearing fail, so I am unfamiliar with the sound. I didn't find the exact symptoms when searching this forum.

The engine uses no oil and will return 23 mpg if I keep it under 65 mph - despite the automatic and 31 inch tires.

Thanks for your input!
Dave

kyle_22r

i've had an exhaust leak do that on one of my 4 bangers. couldn't figure it out for the life of me, i thought it was a top end knock.

however, the 3.0 has been known for chewing up rod bearings, has the noise gotten progressively worse?

94x4

Have you yet been able to tell if the "knock" is coming from the top or the bottom of the engine?

Thumpy

No, I have not. I swapped plugs to see if the noise followed the plug. It didn't. The noise hasn't worsened in the last thousand miles. It is nearly inaudible from inside the cab, but easy to hear when outside.