My car has a knocking sound in the engine. You can start to hear it at about 1800 rpms and it gets quite loud, loud enough to where I might be uncomfortable to drive it. The car isn't currently on the road and it hasn't been in a couple of years. To my knowledge the knock is a rod bearing. I currently don't have a car but I have the opportunity to drive a jeep cherokee all winter if I need to. Now my question is, should I keep the car the way it is and drive it until the engine breaks or should I rebuild the motor or buy a new one. I think I would be able to pull the engine myself but I don't like the idea of rebuilding it alone, mostly because I'm 17 and have never done something like that before but I think I could do it. Now what would be the most cost efficient solution to this problem? BTW its a TPI 350 with a 700r4. Thanks

 

Best bet is to find a used low mileage 350 and swap everything over to that motor. Otherwise depending on how many miles are on your 350 you could buy a crank kit and just replace that. The repair manuals tell how to go about it.

 

Why do you think it's a rod bearing?

What's the oil pressure? What was it before the knock started?

 

It's a deeper noise, its sounds somewhat like throwing a rock down a driveway only louder, not pingy. The oil pressure is between 15-20 at idle and will get to around 30 when I rev it a little. I don't know what it was before it started knocking, it was like that when I got it.

 

Doesn't sound like a knocking rod. The description sounds more like a cracked flex plate.

 

Well a few other people have told me it was a rod so idk. May I ask what the oil pressure has to do with anything? And also how does a flexplate make a knocking sound?

 

A rod knocks because it has clearance between it and the crank. When that happens, it is essentially a MASSIVE internal oil leak, bleeding pressure off the pressurized system. A bad rod bearing almost always results in ZERO oil pressure at idle when hot.

Therefore, normal oil pressure at hot idle = probably no bad rod bearing.By being cracked around the crank bolt holes.

 

Okay well is there any way I can be sure that the flexplate is the problem without bringing down the tranny?

 

Yes.

Change the flex plate out.

You do that like this: unbolt the torque converter from the flex plate; remove the crossmember, and support the trans with a floor jack and a suitable length piece of 2x4 or something under the pan; unbolt the torque arm from it; remove all the bell housing bolts, and put 1 in each side that's about 6" long; and slide the trans back as far as it will go. That'll give you enough room to get a box-end wrench up in there.

You can also remove the inspection cover from the BH, and jack the car up or put it on ramps, get up under it while it's running, and see if the noise is coming from in there.

 

I've had a bad flex plate in another car and it wasn't constant. Sometimes it would make the noise, sometimes it wouldn't. A rod knock I've been told generally makes a pattern and sounds more like a purrrr,or ding ding ding im having a lot of trouble figuring out the word I'm looking for lol. The flexplate broke right at mounting screws

 

I still think its the rod bearing. I've been reading about flexplates using search and it doesn't seem like thats what's wrong. The noise is always there above 1800 rmps and gets louder and more frequent with rmps. Right when I turn the engine on it makes the noise for about 1/2 a second. If I hold the motor at about 3 grand with my head under the hood, its quite loud. I've driven the car up and down my driveway and I don't hear any weird noises coming from the tranny area, the engine just makes this knock noise. I can take a sound clip of it with my phone if that would help.

 

If it's a rod bearing, pulling the plug wire on that cylinder should make it go away, or at least change. Try pulling them one at a time.

 

If it makes the noise while starting and immediately after, i mean, you know what the starter ring gear is attached to right? With decent oil pressure it just doesnt seem likely to be a bearing.

 

Alright thanks for all the input, I'll take a look at the flexplate tomorrow and see what I can find.

 

I got under the car and checked the flexplate and from what I could see there wasn't any cracks. There wasn't a cover over it either, is that bad? And the odd thing that I did notice on the flexplate was a piece of metal that was on it. Here's a pic of it. Is this causing the problem or is it stock?

 

You won't be able to see the cracks, if there are any; they'll be at the center, where it bolts to the crank.

You have NO IDEA how many cars have been sold DIRT CHEEP for this problem. Especially "fleet" vehicles at their supposed "end of life". And MOST especially, Chrysler K cars and minivans. Guess how I know that.... as a buyer.

When you listened to it with a piece of rubber hose stuck in your ear from underneath, where did you find the noise to be coming from? was it coming from inside the BH space, or not?

That's a balance weight. Yes it's stock.