Loud Engine Knock at Cold

**Loser** · 05-01-2010, 08:55 AM

Hi,

I bought my Blk/Blk 2001 Trans AM WS6 new. Now I am up to 150K miles and am starting to have issues. I just found this site and will be searching it shortly. My main issue is that I have a knocking sound coming from the drivers side of my engine. It happens when the motor is cold and goes away mostly after about 15-20 minutes. It is quite loud when the motor is cold though. Since it goes away, I don't think it is a thrown rod, but I'm no mechanic. Anyway, hopefully I can find some pointers here. I love the car and want to fix it and keep driving it.

Tom

**pajeff02** · 05-01-2010, 09:00 AM

Welcome to the site! Sorry to hear about the problem you are having.

**Loser** · 05-01-2010, 09:20 AM

Hi,

I bought my Blk/Blk 2001 Trans AM WS6 new. Now I am up to 150K miles and am starting to have issues. I just found this site and will be searching it shortly. My main issue is that I have a knocking sound coming from the drivers side of my engine. It happens when the motor is cold and goes away mostly after about 15-20 minutes. It is quite loud when the motor is cold though. Since it goes away, I don't think it is a thrown rod, but I'm no mechanic. Anyway, hopefully I can find some pointers here. I love the car and want to fix it and keep driving it.

Tom

**35th-ANV-SS** · 05-01-2010, 09:40 AM

How loud exactly? Can you post a vid? Our engines are notorious for engine ticking at cold start and then going away after it warms up.

You could start by checking to make sure you don't have any bent pushrods. Easy to change and cheap to replace if one is bent. Other than that, the lifters are notorios for being louder, but if it's really loud I wouldn't drive it until you figured out what the problem was.

**Loser** · 05-01-2010, 10:02 AM

I had a 76 pickup once that threw a rod but kept running. It sounds exactly like that when it's cold, but it goes away after a while. It seems to be coming from the second cylinder from the front on the driver's side.

I'm thinking of pulling the cover and looking at the push rods. There is a fuel line that runs across though. I'm not very experienced at working on engines, so it makes me a bit nervous. Anyway, I called around and I can get some stock pushrods for $20 each about 30 minutes from here, so I'm going to see if I can get the cover off now.

**importhater81** · 05-01-2010, 10:04 AM

Sounds like piston slap.

Could be a lifter that bleeds down.If it was lower end,like a rod bearing,it wouldn't go away when warmed up.

**Loser** · 05-01-2010, 11:00 AM

The valve cover is off. I'm not sure what to look for. I see 8 8mm bolts. Are there 8 pushrods per side? Are the push rods the rods above the 8mm bolts? Is there anything special about removing the bolts that I need to watch out for? Do they need to be torqued to a certain level when I put them back on? Do the push rods just pull out?

**Loser** · 05-01-2010, 11:33 AM

Pulled off the first four rockers and checked the push rods by rolling them on a flat surface. They are all straight. The springs and rockers look fine. Is there anything else I can check before I put the valve cover back on?

**KMdef9** · 05-01-2010, 05:29 PM

Originally Posted by Loser

Hi,

I bought my Blk/Blk 2001 Trans AM WS6 new. Now I am up to 150K miles and am starting to have issues. I just found this site and will be searching it shortly. My main issue is that I have a knocking sound coming from the drivers side of my engine. It happens when the motor is cold and goes away mostly after about 15-20 minutes. It is quite loud when the motor is cold though. Since it goes away, I don't think it is a thrown rod, but I'm no mechanic. Anyway, hopefully I can find some pointers here. I love the car and want to fix it and keep driving it.

Tom

Common issue with most. I think most refer to it as piston slap b/c it's a kind of quiet knock and is ignored.

I guess it depends on how loud it is? Did it just get alot louder than normal?

**Cutlass** · 05-01-2010, 06:01 PM

I merged these 2 threads together for you

**tatertot91** · 05-01-2010, 07:20 PM

Sounds like you might have a spun rod bearing
How's your oil pressire?

**planemech2** · 05-01-2010, 07:53 PM

+3 for piston slap. You get used to it.

**Loser** · 05-01-2010, 09:09 PM

Oil pressure is good. The noise is loud. It sounds like a rod banging against the side of the block. Everyone thinks it is a thrown rod until it runs for about 15 minutes. Then it quiets down. After about 30 minutes, it is completely gone until the car cools off again.
I ran the car with the valve cover off, and it sounds like something is banging towards the top of the block in the second cylinder from the from on the driver's side. It is so loud that the neighbors have commented on it.

It still has plenty of power though.

Is piston slap fixable? The dealer told me to scrap the car because it wasn't worth fixing. It would need a new engine.

**DIRTY JERZY** · 05-01-2010, 09:32 PM

scrap the dealer

**tatertot91** · 05-02-2010, 05:34 AM

still sounds like a spun rod bearing, very common to hear the noise you're hearing and then it going away after it heats up. I would open the motor up if your neighbors have commented on it. Sounds too loud for piston slap.

**DaddySS** · 05-02-2010, 06:00 AM

I think there are only a couple possibilities - lifter, or rod, wrist pin, etc. I have seen situations where a belt will make it sound just like a rod so although not likely, pull the belts and check. Second, drop the oil and check for bearing, etc. material in the pan/drain plug/oil.

If you bought the car new it is not likely that you had never had piston slap before and now you have a severe case.

If it is a rod, bearing etc. then a short block or service engine will run you around $3500

**Loser** · 05-02-2010, 08:45 AM

If I do end up needing a new block, then it will be cost plus installation. It was a reach for me to dig into the push rods. I am definitely not prepared to try to replace a block.

**JRENIGAR** · 05-02-2010, 09:10 AM

My car had this problem, turned out to be a cracked flywheel!!!! I mean it sounded just like a knocking engine. Hope this is your problem, and not the rods or bearings...

**tatertot91** · 05-02-2010, 02:32 PM

Originally Posted by Loser

If I do end up needing a new block, then it will be cost plus installation. It was a reach for me to dig into the push rods. I am definitely not prepared to try to replace a block.

Chances are you won't need a new block. Most likely would want to have the crank looked at.
There are possibilities that the noise you are hearing is something else, just a heads up.

**Loser** · 05-02-2010, 03:53 PM

I was running the car with the valve cover off. As I loosened the bolt on the third rocker from the front, the level of banging reduced by about half, but it started making a rattling noise. I tightened it a bit until the rattling stopped, but the banging was still reduced quite a bit.