Well, luck hasn't exactly been my friend lately. Seems the '84 I purchased a few months ago has developed a knock. Either that, and it was there the whole time and the sound from the (nearly) open headers masked it until I could get a proper exhaust on.

I isolated it to the #4 cylinder, but haven't done any research beyond that (valve cover/oil pan removal). Just a sound scoping. Can't really tell if it's from the top or bottom. Just that it's the #4 cylinder.

I don't think it has anything to do with the upper valve train. The knock is a knock. Not a click, tap, or the like usually associated with the valve train. Sounds more like someone hitting two wooden dowels together (the hollow thunk). It's not very loud (yet), but definitely noticeable.

So, I'm thinking it may be a rod bearing. At this point, I'm thinking (and hoping) the damage may be minimal due to how quiet the sound is. Also, the engine compression is great, and the valve train is whisper quiet, so for the most part, everything else is in good shape.

Can I just drop the oil pan and replace the rod bearings? Obviously checking the crank for damage and looking for what may have caused it in the first place.

((Or, other ideas on what the sound may be or how to diagnose what it is?))

 

Took the valve cover off when I got home. It looked brand new underneath! No deposits, no buildup, nothing. Everything was exceptionally clean aside from a layer of fresh clean oil. Very evident this engine's been taken care of.

Here's a sound clip. Anyone able to diagnose the noise?

YouTube - MOV032.MOD

 

Sounds like a rod knock. Not hard to repair, you do need to jack the engine up to drop the pan, and the ones I have done I had to jack up the transmission as well, but some people have gotten away without that. Don't run it too much until you fix it, or it'll get a lot worse. Also, take it apart before you get parts, it may have undersized bearings in it already.
As a side thought, I have had a C4 transmission with a bad torque converter make a similar sound, but it was more in the upper rpms.

 

Sounds like a rod knock. Not hard to repair, you do need to jack the engine up to drop the pan, and the ones I have done I had to jack up the transmission as well, but some people have gotten away without that. Don't run it too much until you fix it, or it'll get a lot worse. Also, take it apart before you get parts, it may have undersized bearings in it already.
As a side thought, I have had a C4 transmission with a bad torque converter make a similar sound, but it was more in the upper rpms.

 

AB--

It is really difficult to say just by listening to the video. But, if it is a rod knock, I replaced both mains and rods in my first engine in one day. It may be different on a Bronco, I don't know. If it were me I would want to know what caused it; and if the case could also have affected the mains. The main concern when 'rolling them in' is to not allow oil to get on the back of the bearing or mounting surface. I found brake cleaner in a squirt can to help clean surfaces with any oil on them, or even suspect of not being perfectly clean. It cleans and dries quickly.

The bearing you take out will be stamped how much the crank/rods were turned, and that will tell you which ones to replace them with. Clevite 77's are good, and a lot of supply houses have them.

If it were me I would remove the oil filter and cut it open to see if anything is in the oil ... metal bits, shavings, sand from an ex. girlfriend. Hell hath no fury like a little sand in the oil!

Also: I'm assuming that is not a recently rebuilt engine? Because if it is, the knock could be a set of **** poor new timing gears. I ran into the same problem with a new set on a new engine. Oh, and just because it looks nice under the v.cover, does not indicate condition of engine. It could of had a head job recently.

I hope you don't have ARP rod bolts, because if you do, it is APIA to remove the caps!!

If you want me to look for a cheap set of r.rockers at the coming swap meet, let me know.

 

Auto or manual trans? Could be a loose flywheel or torque convertor bolt/nut.

Manual fuel pumps have also been known to cause a knocking noise.

 

Thanks for all the info everyone.
This has been a really frustrating situation, since my '81 is still down for the count (waiting on money to repair the valve train), and now the '84 decides to develop an engine knock.
I can't afford to fix either, and I can't stop driving the '84 because then I'm out of a vehicle. ((They need a smiley for pulling your hair out.))


Okay, venting aside.

Glad to hear that a rod bearing isn't difficult to repair. Is that the same case if it's a main bearing? I would think the crank would need to be removed if it was, which would require the timing cover removed, timing gear pulled, etc.

I tried listening to the fuel pump, but the sound is coming more from the rear of the engine, around the 4 / 5 cylinder.

It's also a manual transmission.

I agree that I'd definitely like to know why the bearing failed. Last thing I want is it happening again. I don't know much about the history of the engine other than it was well taken care of, so I'm curious why this would have happened. I don't know if its ever been rebuilt.
I also didn't think to keep the old oil filter to look through... Wish I had.


Alright...so jack up the engine, drop the oil pan, remove it, feel for loose bearing caps, see what caused the problem, check for crank damage (and hope), replace bearings. Put back together.

I'll be sure to keep the surfaces nice and dry until they're installed. Other tricks while installing? Is there something to keep them from turning?

 

Keep from spinning: You'll notice when you remove one bearing, there will be a little 'tang' on one side, which looks like someone bent the edge with a 1/4" wide pair of pliers. Note where the tang locks into the rod cap. That is what keeps them from spinning ... that and a good supply of oil between crank and bearing!

Mains: You can carefully 'roll' them out, and roll the new in, one at a time, retorquing each as you go. Be sure to lube each. I did both mains/rods in a few hours. With the pan and all, it's a full day project. I did not replace the rear main because I didn't know if it would disturb the main seal. The crank stays in the block. You'll have to rotate crank quite a few times. Do them in order so you don't loose track ... like I did.

Remove breaker bar from v.dampener bolt BEFORE starting engine.

 

Ahh, that makes sense. And makes sense why it's called "rolling" them in. Okay, that does sound a lot easier. Of course, again, hoping that there's no damage to the crank.

 

When rolling out the old bearing and rolling in the new one, use a small cotter pin in the oil hole to catch the bearing. Find one with a small enough head to just fit into the oil hole, and bend the legs out 90 degrees from each other about 1/2" down from the head, then cut them at 1/2" to wind up with a T 1" across and 1/2" tall. You may have to bend it at an angle to match the oil hole as well, you want both legs to sit flat on the journal surface.
Once you make the pin, just unbolt the main cap, find the oil hole, instert the pin and hold it in place until it contacts the bearing, and then keep rolling it around until the bearing is out. The new one rolls in the opposite way. The thrust bearing is a major pain, the last one I did I had to assist it most of the way with a flat bladed screwdriver.
For the rods, you should get some thin 3/8" tubing to put over the studs while the cap is off so you don't nick the journal with them. No rolling needed, but pulling the spark plugs is a good idea. Just unbolt the cap, install stud protectors, push the rod up until you can fish the bearing out, install the new ones and put it back together.
Use assembly lube on the bearing faces, but make sure the bearing back and bore in the rod or block is clean and dry. This is hard to do on the upper side of the mains, but a shot of carb cleaner and then letting it dry or blowing it out with clean air usually does the trick.

Usually a loose flywheel will rattle and also it'll scrape the block plate making a whole bunch of noise.

 

Don't overlook the oil pump,I would replace it with a good Melling and clean the pick up real good.Check the pan for rust,if in doubt,replace it.They are known for rusting out.You don't want to have to pull it again down the road,for a pump or pan leaking.You may even find evidence in the pick up,or the pump may even be at fault.It's just good insurance.Clean and check that crank real good,you don't want to waste the whole job.

 

What weight oil are you running? Has it been changed recently?

 

X2. Good advise. Melling. You might want to do the EFI pan conversion while there: Grinding off the raised tabs on the pan so you can use the one piece efi years pan gasket. Yours may be different, but with mine I had to drop the pan, then reach in and undo the o.pump before removing the pan. Oh, and make REAL sure the engine is raised and SECURE before reaching in. I know you have two arms, but it's best not to loose one.

 

Yeah, this is definitely a situation that calls for a new oil pump. I have no ideas as to why the bearing failed, so I don't want to chance it happening again.

Currently, I have 10w-30 in there and it was changed a week ago. The thing is, I don't really remember it knocking until after the oil change. Then again, I had only done an exhaust on it a few days prior and before that, I couldn't hear ANYTHING (open headers). So I may have just overlooked the sound.
It was the first oil change I had done on the vehicle since I bought it, since I didn't drive it until recently. IF (if) it started right after it's first oil change, could that point to anything?


When I did the cam on my '81, I was able to take the oil pan off without removing the pump. But, that may have been due to the fact that the engine slipped off the jack and moved backwards a good 3 - 4 inches ((What a pain to get it back forward!!)
And don't worry, I always put wooden blocks between the motor mounts and the chassis. Last thing I want is an engine falling on me! Of course, my father-in-law's missing his arm, so my wife has experience in that area and I shouldn't be too bad off if that happened.



One other question: Is there anything I can do to slow damage from driving it? Thick lucas oil, etc.? I have no choice but to drive it since it's my only mode of transportation to and from work at the moment.

 

The sound is coming more from the rear of the engine. Is it possible it could be a flywheel bolt on a manual trans?