About to buy, need advice about knocking

[isantop]

So, m about to buy a new 2G GS (guy seems to think it's an RS, but I'm not complaining there). It's in decent shape, needs some paint but tires, brakes, suspension, etc. all seem fine. The one concern I have is there's a loud knock sound coming from the valve cover area. It sounds like rod knock, but here's the thing: it's not constant at all.

It only happens above around 3k RPM and under heavy throttle. Under 50% or less throttle, it sounds great, and its always great under 3k RPM.

My understanding of rod knock, was that it will always be heard. Because of this, I'm reluctant to call it rk definitively.

Any ideas?

 

[turtlebain]

That sounds like some lifter tick.

 

[isantop]

That usually doesn't cause problems, right? Also, any way to make it go away, as it's really loud and a bit obnoxious.

 

[trboeclpse98]

Have you checked the oil level?

 

[isantop]

Yup, it was clean, and maybe only a .25 quart low. Definitely not alarming at all.

 

[lowboost13]

That usually doesn't cause problems, right? Also, any way to make it go away, as it's really loud and a bit obnoxious.

Yes, if it is lifter tick then there is a way to make it go away, you can get 3g lifters. They are fairly cheap around 80-100$ shipped. just have to bleed them and pop them in, but thats only if it is lifter tick.

 

[synthetek]

Yes, if it is lifter tick then there is a way to make it go away, you can get 3g lifters.

Its not a 4g63 its a 420a

 

[LarryJoe]

I didn't think 420a's had a lifter problem.

 

[turtlebain]

You can get lifter tick on any car. But it's just not as common on 420a's. How loud is it, and can you post a video? If it is indeed lifter tick it can probably be solved for very little (refer to 2gnt) and is not harmful, but annoying.

 

[bryanwheat]

I wouldn't jump into it hoping for the best and easiest outcome. 420a's are notorious for spinning bearings due to not having baffles in the oil pans. If you can't afford to buy another engine for it or build one for it than i wouldn't take the chance.

 

[Mischif]

Rod knock can occur intermittently. A FAILING bearing may not always knock but as rpms and load increase the knocking will tend to occur more. Also a FAILING bearing may only knock at certain rpm ranges, for example at 2k until 2.3k and then again at 5k for another 500 rpms. Once the bearing is completely shot is when it will knock regardless. A failing bearing can cause excessive damage if left to run out the rest of its life. From scratches on the cylinder walls, to deep cuts in the bearing journals, as well as out of roundness to the rods.

 

[crazyquik22023]

If it is rod knock you would not hear it from the top end of the motor aka the valve cover as the OP is. You would hear it from the block. The car probably has some kind of lifter issue which is the knocking noise you are hearing.

 

[bryanwheat]

If it is rod knock you would not hear it from the top end of the motor aka the valve cover as the OP is. You would hear it from the block. The car probably has some kind of lifter issue which is the knocking noise you are hearing.

Bottom end noises can conduct into the top of the engine and appear to come from the head. It happens all the time. There is no reason to make assumptions on anything without first hearing the noise from a video. Kind of funny that we have a bunch of guys debating what a noise is without first hearing the noise.

 

[zcox122]

Bottom end noises can conduct into the top of the engine and appear to come from the head. It happens all the time. There is no reason to make assumptions on anything without first hearing the noise from a video. Kind of funny that we have a bunch of guys debating what a noise is without first hearing the noise.

Agreed.

 

[isantop]

Agreed.

I hadn't taken a video. It's definitely pretty loud, though. That said, it's more dependent on the throttle position than the rpm.

EDIT: For better or for worse, it sounds EXACTLY like this guy's problem:

http://www.dsmtuners.com/forums/420a-bolt-tech/342943-98-eclipse-rs-engine-knock-noise-video.html

I'm inclined to think what he has is the same problem, since it's the same engine and all. I'll check a couple of things when I get there though.

Right now, I plan on listening with a screwdriver and pulling the ignition wires one by one to see if it goes away. If it doesn't, it's probably not rod knock, right?

Anything else I should check?

 

[bryanwheat]

I hadn't taken a video. It's definitely pretty loud, though. That said, it's more dependent on the throttle position than the rpm.

EDIT: For better or for worse, it sounds EXACTLY like this guy's problem:

http://www.dsmtuners.com/forums/420a-bolt-tech/342943-98-eclipse-rs-engine-knock-noise-video.html

I'm inclined to think what he has is the same problem, since it's the same engine and all. I'll check a couple of things when I get there though.

Right now, I plan on listening with a screwdriver and pulling the ignition wires one by one to see if it goes away. If it doesn't, it's probably not rod knock, right?

Anything else I should check?

If it sounds like the one in the video than it is a bad rod bearing. Lifters sound nothing like that.

 

[lowboost13]

Its not a 4g63 its a 420a

sorry about that

 

[gotclutch23]

Deff sounds like a rod bearing if you can get the car cheap enough id say go with it and use it as a project. If its alittle expensive just wait and buy something with a 4g63 turbo youll have loads more fun

 

[isantop]

Deff sounds like a rod bearing if you can get the car cheap enough id say go with it and use it as a project. If its alittle expensive just wait and buy something with a 4g63 turbo youll have loads more fun

Given two top-condition cars at the same price (One GS, and one GS-T), I'd actually have the GS. Turbos are great and all, but I prefer the N/T gas mileage, and less need to worry about crankwalk.

On top of that, I'm a bit of a traditionalist in that I think the mark of a great sports car is handling and feedback, rather than speed. As such, I'm not concerned about how fast I go, but more how much fun I have when I do it (and even my RS that I have now delivers quite well there. I just want a sunroof, and power doors, and ...)

That said, an excellent condition 99 GSX came up for $2350. It was gone before I could get a reply, but damn, I'd jump right on that!

EDIT: I should clarify that I don't have a problem with turbo cars, they just aren't for me.

 

[trboeclpse98]

The sound on that video is definitely rod knock. Turbo cars are not necessarily gas guslers, I have a 98 GST with a big turbo tuned with DSMlink and I get about 26mpg combined street/ highway driving, it all depends on how you drive the car.

 

[turtlebain]

The sound on that video is definitely rod knock. Turbo cars are not necessarily gas guslers, I have a 98 GST with a big turbo tuned with DSMlink and I get about 26mpg combined street/ highway driving, it all depends on how you drive the car.

It's not even his video.

OP, you said the sound was apparent in the upper RPMs which is why lifter tick was even suggested in the first place. In the video, the sound is made at idle. How do you know the sound in the video is even rod knock? Cameras frequently pick up audio in funny ways. By OP's vague discription it isn't obviously rod knock. More info needed here.

As far as the n/t vs. turbo discussion.. You can't be serious..

 

[trboeclpse98]

It's not even his video.

OP, you said the sound was apparent in the upper RPMs which is why lifter tick was even suggested in the first place. In the video, the sound is made at idle. How do you know the sound in the video is even rod knock? Cameras frequently pick up audio in funny ways. By OP's vague discription it isn't obviously rod knock. More info needed here.

As far as the n/t vs. turbo discussion.. You can't be serious..

I know it's not his video, he mentioned that his car was making the same knocking noise as the one in the video.
I spun a rod bearing on my car a long time ago and it would only make the same knocking noise when I would let off the throttle and the RPM's were dropping but after driving around for a week like that it became obvious that it was rod knock.

The only way to really tell is for him to post a video.

 

[jayson427]

when i had lifter tick on my car i couldnt hear it when inside the car and it was reved up. if you say its really loud i kind of lean more towards something else besides bad lifters. the guy could of put new oil in the motor so i wouldnt judge on clean oil, he might even know its messed up and is just playing dumb. like stated above rod knock can be intermittent in "some" cases so i would be cautious unless you enjoy engine building

 

[isantop]

Supposing it is Rod Knock:

It probably isn't bad yet, right? If it is bad bearings, then this early on, would I be able to get by without needing a reground crank and new rods, or are those standard for this type of replacement. I have no problem doing rod bearings. I don't want to have to do the entire bottom end.



For a better description:

• At idle, the car is quiet and sounds great.
• If you give it a little gas (RPM at 2000) it's quiet and sounds great
• With a little more gas (RPM at 4000) you can hear it while you apply the throttle, but once you let off, it will go away immediately.
• While driving around, I barely noticed it. Usually, it sounded fine. If I got on it a bit, with heavier on the throttle and higher in the power band, then it sounded like a really aggressive exhaust (almost like a diesel). I actually asked him if it was a leaky exhaust manifold while we were driving. I didn't realize it was a knocking/ticking noise until after I opened the hood.

I'm going to go look at it again today. I'll try to find out exactly where the sound is coming from. I'll take a video too.

 

[bryanwheat]

Supposing it is Rod Knock:

It probably isn't bad yet, right? If it is bad bearings, then this early on, would I be able to get by without needing a reground crank and new rods, or are those standard for this type of replacement. I have no problem doing rod bearings. I don't want to have to do the entire bottom end.



For a better description:

• At idle, the car is quiet and sounds great.
• If you give it a little gas (RPM at 2000) it's quiet and sounds great
• With a little more gas (RPM at 4000) you can hear it while you apply the throttle, but once you let off, it will go away immediately.
• While driving around, I barely noticed it. Usually, it sounded fine. If I got on it a bit, with heavier on the throttle and higher in the power band, then it sounded like a really aggressive exhaust (almost like a diesel). I actually asked him if it was a leaky exhaust manifold while we were driving. I didn't realize it was a knocking/ticking noise until after I opened the hood.

I'm going to go look at it again today. I'll try to find out exactly where the sound is coming from. I'll take a video too.

This question is 100 percent impossible to answer. It could need the crank turned and rod rebuilt, it might not. Chances are that it will need machine work. Another thing to factor in is that there will be metal particles in the engine. IF there is a bearing failure the whole engine needs to come apart and be cleaned. I would assume the absolute worse when buying a car like this. Going into something like this being optimistic will end up costing you a lot more money and down time than what it's worth. What are they asking for this car anyway?