My engine was knocking from the bottom end, and we figured it was the connecting rod big end bearings. There was one pretty worn out, and one was goners. the other two seemed alright. So I changed all four of them anyways. Everything seemed alright putting the rods and the oil pan back together. But, after about a day and a half to two days, the same knocking sound came up again. At idle, it sounds pretty faint or nothing at all. But when I start driving it, the knocking gets alot louder and the engine starts loosing power.

Any idea where I might of got wrong, or what the problem might be? Thanks!

 

You can't just change out the bearings and expect things to be good. the journals and caps are damaged, i.e., grooved, ovaled, scratched. You need to have the crank ground for roundness. And, since you had bad bottom end bearings, you suffered from low oil pressure, did you not? That can damage other engine components. Starve the upper end of oil, damage cylinder walls from lack of oil... Really, probably need to rebuild the entire engine. Certainly are going to need to take the bottom end apart.

 

Actually, you CAN just change out the bearings and expect everything to be good. I did that on my 87 4r 40,000 miles ago.

HOWEVER

You have to change ALL the bearings and make sure that the crank is not too messed up. If the crank is out of round and you change the bearings, you are still screwed. Why did you not change the main bearings and thrust washers also?

 

could it be timing chain slap? just tossing it out there

 

Or wrist pins?

 

How long was it knocking before you decided to change those bearings? Did you lube the bearings with anything when you installed them or did you put them in dry? Did you prime the oil system before actually turning the key to start it up?

 

I think I would want to know how much the crank was out of true. Did you use plasti-gage (SP?) before putting everything back together? I bet your new bearings are shot again because the crank is in need of attention.

Trying for the quick fix does not always result in a true fix...it's just that, a quick fix.

 

How can you change the wrist pins while the crank is still installed in the truck?

If someone was going to go that far and take the water pump/oil pump/crank pulley and transmission + clutch off the truck, they would probably elect to just install a completely new rotating assembly.

 

I don't think he was refering to being able to change the wrist pins while the block is assembled, I think he was refering to them being his source of the knock.

 

not wrist pin, not valve train noise not anything else bu rod bearings. He said the noise went away after he half that job and the noise came back shortly thereafter. I am 100% certain it's the rod bearings again.

Sorry if I am being harsh, but I really don't have much sympathy for people who deal with rod knocks this way and then come back here asking for advise and/or complaining it didn't work.

So here's my advise, tear apart the engine, rebuild it the correct way, take the crank and rods to machine shop to have checked or go get another used motor.

 

Eh, I did the same thing, when I bought my truck it had pretty much gear oil in it so I did not hear the knock but after that first oil change I sure did hear it. I tore the oil pan off and changed the rod bearings, plastiguage showed it at the far end of the specs but still in specs, crank and caps did not look so good but I didnt really care to remove the engine or trans and the knock came back. I bought a long block to put in but wanted to wait for the engine to go before I put it in, I have about 10k on that knock, redline it everytime I go out wheeling and still going strong no louder than before.