New Knock

[turbojimmy]

So I had to pick up the Ty from the shop tonight. Had to get it inspected. Didn't want to pass, they finally got it through. Done with the Ty...not good for my sanity....it's for sale....but I digress.

So the guy that helped me get all my cars home pulls up in the GN (I drove the Ty home). It was knocking hard at idle when he pulled up. WTF? This is definitely a new behavior - like today new. I know knocks are impossible to diagnose over the net, but here goes.

Sounds like it's coming from the front. It's deep - not a light metallic sound like a rocker tap. I *think* (but it may be my imagination) that I can feel it if I put my hand on the IC. If I give it some throttle it smooths out - goes away. At low RPMs and idle it's very obvious.

Any ideas? I put a new cam and timing chain in a few months ago. That job included a new water pump. I'm hoping the new water pump might be bad.

TIA,
Jim

 

[FJM568]

Only one thing to do to check it...Pull the pan and start with #5 and #6 rod bearing and work your way forward...Sounds to me like it would be a rod knock...revving it loads the rod a little different than at idle and changes the sound...It WILL get worse...Don't run it anymore until you check it out...

Reason I suggested start at the back was that the back two rods are the last to get oiled, so if any garbage to plug up the system, most of the time, it's the back that goes bad first...You could just try to wiggle each rod and check for excessive play on all of them before you start...One wiggles too much, you've found it...

Good luck...

 

[turbojimmy]

Thanks for the info. I just had the pan out a couple of weeks ago, too. Grrrr.

So, say wiggling the rods don't make any difference. When I pull the caps, what am I looking for? I know scoring would be bad, but what are other signs?

Thanks,
Jim

 

[FJM568]

The bearing shell half should fit snug in the cap and in the rod...If it's hammered, it'll most likely just fall right out...Also, you will see a wear pattern in the bearing, or flaking, or maybe some other type of discoloration...It will be obvious...

 

[turbojimmy]

Would a rod knock go away when it's cold? I started it up this morning to see if I could get a better idea where the noise was coming from. There's no noise today.

I didn't wait for the car to warm up. I assume the noise would've returned.

Thanks for the replies,
Jim

 

[FJM568]

If it's cold enough and the oil is thick enough, yes, it could hide the noise until the oil warms up(the thicker oil is taking up the increased clearance)...

When I bought my 85, somebody had done that...spun a rod bearing, chewed up the crank, replaced the rod bearing, put heavy weight oil in it, and sold it...When I changed the oil, within the first 50 miles after, rod knock

 

[turbojimmy]

Yeah, it's crazy cold for April. Was snowing earlier. I have synthetic in it, though, I didn't think it got thick.

I'm going to drop the pan anyway, better safe than sorry. Better catch it now than before I take out the crank and/or the block.

Thanks,
Jim

 

[Iceman]

Before you pull the pan.Check your balancer bolt.It may be lose!

 

[turbojimmy]

Originally posted by Iceman
Before you pull the pan.Check your balancer bolt.It may be lose!

I just got done checking it. It's not loose - I was hoping for an easy answer.

I listened to it with a stethescope earlier today. Everything sounds good (valve covers, alternator, water pump, etc.). When I get to the timing chain cover - as close to the crank as possible, I can hear it. I'm afraid it might be rod bearings....

Thanks for the replies,
Jim