aerocorey

'86 Pickup, 22R, knocks briefly during startup and under load and deceleration. I just replaced the head gasket and timing set. It sounds like an exhaust leak to me, so I replaced the manifold. It still does it. It's definately coming from under the hood, but I'm reluctant to say it's a rod knocking. I ran the truck with each plug wire disconnected one at a time...can't isolate any one cylinder making the noise. I still haven't ruled out exhaust 100% because the new stud kit I ordered isn't in yet. I can't get any decent torque on the rear top nut until I replace that stud. If that doesn't do the trick I'm going to try heavier synthetic oil. Any common Yota tricks I'm overlooking? Thanks.

1styota4X4

yea rod knock...Just messising with you. Are you sure is a motor knock? most exhaust leaks do not sound like that. Do you have a mechanics scope or a long screwdriver so you can try and isolate the noise?

aerocorey

I'm not sure it's anything, just sure that it sounds like crap when it does it. It's hard to isolate because it only does it for a second sitting in the driveway with the hood up. On the road going up and down hills I can get it to do it for a few seconds. The fact that is does it while decelerating is what initially got me started thinking it was exhaust.

1styota4X4

it could be a main bearing knock if its doing it on decelerating...but you stated its doing it on both. My motor had a tick for 2k miles and it only did it evey now and again. But i could isolate it to the #2 cyl with the wire off.

grant526

Did you do the head gasket because it was blown? Did you have mixed fluids?

I just replaced then head gasket, timing chain, timing chain guides and tensioner on my buddy's truck because he had a blown head gasket. The coolant and oil were mixed in the crank case. Oops. Now that it's back together, it has a knock, very similar to yours. I'm afraid we are going to end up pulling the engine and rebuilding the bottom end. The tech at the dealer said that it is rod knock from something not getting properly lubed while the fluids were mixed. He probably drove it 60+ miles before he figured out what the problem was.
So if I pull each plug wire, one at a time, I can possibly identify which piston has the issue? Assuming it's a connecting rod bearing?

aerocorey

Yeah, fluids were mixed. I finally figured out it was pinging. Doesn't sound anything like pinging to me, certainly nothing like when my AMC 360 was pinging, but that's what it was. I unplugged the vacuum advance and it went away. I'll get some better gas at the next fillup and give it the Seafoam treatment.

grant526

So your saying the engine is pinging, like premature detonation?
Sounds like you might be off by one tooth on the distributor gear where it mates with the Cam drive gear? Is your timing set correctly? Where do you have it? I believe I set my buddies to 12*

That's an interesting point about the vacuum advance. I'll have to try that. I didn't even think about that possiblity.

Thanks for the insight!!