Rod knock symptoms

[matt98eclipse]

Hey guys i just bought a 98 gst for my wife. I towed the gst home cause it was really far drive from my house. Well got home and took it for a spin around the block and and noticed a slight knocking or tapping sound around 3k or higher. The higher rpms i go the faster the knocking or tapping sounds comes.

At idle the motor sounds great idles perfect. I do remember hearing the belts or a belt squeeling when i first start it up.


I need your guys help to pinpoint were this noise is coming from??

 

[nightgamer]

video?

 

[live4my4g63]

spun bearings man check your dip stick and if the oil has any metal shavings that make the oil look like glitter then a bearing is bad for sure

 

[ziggo0]

stick rod knock into youtube and you'll hear it.

 

[white92talontsi]

could be lifters. could be a bad harmonic balancer. Usually a rod knock will be the loudest when there is no load on the engine. If you quickly goose the throttle you will hear the knock whenever the rpm reaches its peak right before it falls off. It can be bad enough to knock all the time.
If you want to know for sure if its a bad rod bearing without dropping the pan you can do this.

Pull all the spark plugs.
Starting with cylinder number 1, rotate the engine to Top dead center on cyl number 1. Then rotate the crank enough for the piston to start the down stroke and stop. Using a long screwdriver push down firmly on the piston. If the bearing on the cylinder has play then the piston will drop down a little.
Do this for the other 3 cylinders.

 

[matt98eclipse]

Hey guys i appreciate the help. I was told i could also remove 1 spark plug wire at a time then start it and if the knock goes away on 1 of the cylinders then thats the cylinder with a bad rod bearing. Well i did this and knocking sounds the same no matter what spark plug wire is off.

The knocking sound is coming from around the timing side. Also i looked at the oil on the dipstick and it does look a little glittery.

I took a video earlier heres the link guys.

YouTube - knock.3GP

 

[cabbageman97]

WOW that does not sound so good what so ever. Sounds like a main bearing honestly. And check the crankpulley for your belt squeeling, or could be the bearing starting to go on your alternator.

 

[2gGSX]

100% rod knock, sorry dude.

 

[97Bstd420]

that sucks. You didn't check the car before you bought it?

 

[95talongirl]

Yeah, sure sounds like a lower end knock. I has hoping to hear ticking to say it was just lifters!

 

[BogusSVO]

if the knock did not go away when you pulled the spark plug.. I would say look at your balance shafts... not good either way

 

[matt98eclipse]

if the knock did not go away when you pulled the spark plug.. I would say look at your balance shafts... not good either way

This is what i was leading to also. If i just remove my balance shaft would i be ok or no??

 

[ziggo0]

You should remove both.

 

[jbl_5star]

huh, i have something close to that.. everyone tells me its just chatter from lifters, but i dont think so because it sounds like a diesel engine??

 

[matt98eclipse]

If it is just a balance shaft bearing couldn't i just delete the balance shafts and be ok?

 

[white92talontsi]

This is what I have come to call a "No Load Rod Knock"

Basically the rod will knock the worse when there is no load on the engine. In your video when you rev the engine up and hold it at a steady RPM there is pretty much no load on the engine.

Picture this. Number 1 cylinder is on the compression stroke. The plug fires pushing the piston down, The rod bearing is forced down onto the crank shaft. The piston travels down and makes it upward stroke, The rod bearing is still being pressed down onto the crankshaft because now we are making an upwards stroke.

It is very hard to explain but when there is pretty much no load on the motor then the rod will knock the most.

To test this theory start the engine and let it warm for a minute, Quickly and sharply goose the throttle and watch the RPM gauge. When the RPM reaches its peak RPM right before it falls off then this is when there is the least load on the bearing and you should hear the knock then at its loudest point.

The next step for your problem is when you start to hear the bearings squeak. When you hear the bearing start to squeak this is when you have actually "spun" the bearing. When you take the motor apart you will see that usually 1 half of the bearing will actually "spin" around and end up on top of the other half of the bearing.

 

[matt98eclipse]

This is what I have come to call a "No Load Rod Knock"

Basically the rod will knock the worse when there is no load on the engine. In your video when you rev the engine up and hold it at a steady RPM there is pretty much no load on the engine.

Picture this. Number 1 cylinder is on the compression stroke. The plug fires pushing the piston down, The rod bearing is forced down onto the crank shaft. The piston travels down and makes it upward stroke, The rod bearing is still being pressed down onto the crankshaft because now we are making an upwards stroke.

It is very hard to explain but when there is pretty much no load on the motor then the rod will knock the most.

To test this theory start the engine and let it warm for a minute, Quickly and sharply goose the throttle and watch the RPM gauge. When the RPM reaches its peak RPM right before it falls off then this is when there is the least load on the bearing and you should hear the knock then at its loudest point.

The next step for your problem is when you start to hear the bearings squeak. When you hear the bearing start to squeak this is when you have actually "spun" the bearing. When you take the motor apart you will see that usually 1 half of the bearing will actually "spin" around and end up on top of the other half of the bearing.

Thanks man. Do you know what probly caused this to happen?? Is it possible if the crank isnt to bad that i could just buy a new set of standard size bearings and throw them in and it be fine or no??

 

[white92talontsi]

This normally happens due to a lack of lubrication and over revving. It is possible to repair it as long as it has not been run in this condition for too long. You really wont know until you get it torn apart and see the condition of the crank journal. I have repaired quite a few like this but the problem was caught early in the "knock" stage.

Make sure when you start removing rod caps that you keep them in order, and make sure when you take the bearings out that you make sure the rod is also perfectly clean when you put new bearings on it.

Its really hard to tell you what to do without seeing the damage, Its possible that the rod bolts stretched also. If it was over-revved then the bolts probably stretched.

 

[matt98eclipse]

Awesome man ill be takin it apart tomorrow and ill keep you updated with pics on what i find! I hope i can just throw a new set of bearings in and be good. Also i really dont think it was due to overrevving cause the cars a auto.

 

[matt98eclipse]

UPDATE: Well guys it was in fact rod knock. Cylinder 1 rod bearings were gone. I also found 1 balance shaft bearing laying in the oil pan and started looking around in the bottem end and noticed another balance shaft bearing was completely out of its spot. So that one was almost ready to go to!! So ill be lookin for another short block.

Heres some pics

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[JusMX141]

Hope you didn't pay too much for the car.

 

[matt98eclipse]

Naw justin i got the car really cheap. So i guess i cant be to pissed about it. I already got another 7 bolt bottem end im gonna be pretty much swapping all the parts over too. Oh hey bud what the hell type of socket do i use to remove the stock 7 bolt head studs.

 

[white92talontsi]

Is that water in the oil I am seeing? Sure looks like it. Lack of lubrication killed it!

Someone correct me if I am wrong since it's been awhile since i pulled one of these heads apart but i remember it being either a 12mm 12 point or a 14mm 12 point socket.

 

[BlackMount]

12mm 12 point sounds bout right

usually what I do at the junkyard when I'm pullin a 4g63 head is, i take a deep socket, and a hammer (12mm) and pound it on then brake it loose.

 

[95blackGsTurbo]

I know of a local running 7-bolt longblock if you are interested PM me Matt. Head comes off with a 12mm 12 point socket. Sounds like a pretty shady seller.
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BlackMount, Not around here. Whole DSM's are stripped in a day here.