I recently had another thread going about my little "plenum project." To sum it up, I replaced the plenum plate, PCV, timing set, water pump and thoroughly cleaned everything along the way. Put it all back together, seafoamed it, replaced fluids cranked her up and she runs better than before, however....

Now I have a low end knock that I didn't notice having before. I remember there always (since I have owned it) being a random 'ticky' type knock in the area where the motor and trans meet, generally. I never really pinpointed it because as I said it was a random thing.

The knock I hear now is louder and a little deeper. I originally suspected a rod bearing because that's what it sounds like. After cold starting this morning, there was no knock until I revved to ~1800-2000 rpm. Let off the gas, knock seems to go away. I crawled under the truck and don't really hear anything alarming at idle. If it was in fact a rod bearing, wouldn't it potentially make more noise after a cold start and even possibly get quieter after it warms up? At the least it would always be there, correct?

Maybe things aren't as bad as I was assuming.

I've read about checking torque converter bolts as loose bolts make a similar noise. What is the process in getting to those bolts? Didn't really find anything in the FSM, it only references removing the trans to check the torque conv.

 

You have to remove the starter so you can get the inspection plate off.

 

My brother in law has an old Bronco with the 351 Windsor, can't remember what year, it needs new rod and main bearings. On his it'll be fine till it reaches normal operating temperature then it will loose oil pressure and knock like crazy, the knock turns into a bit of a growl when he turns it off.

 

Rod knock will get louder as the engine warms up. When cold, the oil is thicker, and pressure is higher. As it warms, apparent pressure will drop off some as the oil thins.

Your best bet would be to put a mechanical oil pressure gauge on it. See what pressure does over time/temp. If you start getting really low pressure as the engine warms up, chances are good you have a bearing problem. If you catch it soon enough, you can replace bearings and oil pump, and be golden. If you wait to long, it gets more expensive..... wait long enough, and you may toss a rod.... then it's new motor time.

 

If your gonna be under the truck, drop the pan and make sure its clean as well as the oil pump pickup screen. I followed your other thread,and yes you were careful. But alot of the sludge and gunk had to go somewhere. I made this mistake on my very first plenum job,and it cost me dearly. Since then,and several plenum jobs later, I always drop the pan.

 

I just crawled under it with a stethoscope and had my wife gently rev the engine to the pojnt where it would make the noise. I hear normal "movement" in the oil pan area but if I put the scope right on the face of the inspection plate (or plate that is on the front of the bellhousing) I can hear it the loudest. It's kinda hard to track though, but definitely more noticeable around the flywheel area.

My oil pressure stays above 40, between ~40-55 or so...that's by the gauge in the dash (not mechanical). Should I always expect to see the pressure lower if a rod bearing is bad? Mine seems to run a bit on the high side if anything.

I failed to mention earlier that the trans was rebuilt before I bought it and the TC was replaced with a remanufactured unit. I have receipts from a trans shop that did the work...not that it has a bearing on anything.

When I get re-motivated to tear back into it, I'll pull the inspection plate off and hopefully find what's causing it. Still gonna drop the pan and check oil pump screen, etc. while I'm at it.

 

When I first bought my 2000 it had a noise, but was more of a ticking, but would come and go like you describe. The crank sensor failed, I replaced it and to my surprise the noise also stopped.

 

In order to get the inspection cover off, you have to remove everything you would have to remove to drop the pan in any event. All that will be left is the pan bolts...... ain't gonna get any easier.

 

I hear ya. So it's just the two tranny braces, starter, insp plate and then the pan will come off?

 

Yep..