G35 Exhaust Knock

[MrqzD77]

Hello everyone! My name is Dennis and i am new to the G35 forum. I just got done purchasing a 2005 Infiniti G35 Coupe and honestly its a really clean car. I looked up the Carfax and it came out clean as well. The last owner of the vehicle had the car serviced at the dealer all the time.

Now my question is... On the driver side of the car I noticed that right underneath the car I can hear a knock. It doesn't seem like its coming from the engine. The knock seems to be coming from the cat's. The knock doesn't get louder as I accelerate but it does stay subtle. The last owner told me that he had it checked out with the dealer when it just had 80,000 miles. Now it has 110,000 miles. They told him that he had must of hit one of the cat's while going over a bump or something. I'm a little worried that this might actually be some sort of lifter knock. Any ideas what it could be anyone? Input would be greatly appreciated =)

So again just a recap. If you listen to the car from the engine bay the knock is hardly noticeable but if you listen to it from underneath the vehicle you can hear the knock coming from the exhaust. Its on the driver side of the vehicle next to the wheel well.

[WDRacing]

Probably going to have to put it up on jack stands and have a look underneath. I use ramps myself, just a personal choice there. Chalk the wheels regardless of how you get it up, then start the car, leave it in park/neutral with the parking brake on, slide under the car and see what there is to see. Could be as simple as something rubbing.

Safety Tip, Wear safety glasses and gloves.

Welcome to Nico!

[MrqzD77]

Thank you for your help sir.

I put the car up in jack stands today and took a screwdriver to pinpoint the problem. The knock is strongest when I get to the Driver side catalytic converter.
I tried listening through the oil pan as well but got nothing. So I'm pretty sure that it's my Catalytic converter knocking. I've never heard a catalytic converter knock before is this normal?

[Nicodomeus]

What "sound" is the knock making? Does it sound hollow? Sharp? Dull? Can you hear it IN the pipe at the end of the exhaust? Or does it sound above the pipe underneath?

[WDRacing]

If the inside of the catalytic converter breaks down it can fall apart and cause knocking/rattling noises.

[Nicodomeus]

If the inside of the catalytic converter breaks down it can fall apart and cause knocking/rattling noises.

I am thinking the lesser route and he is missing a hanger lol

[WDRacing]

Could be.

[MrqzD77]

I checked it out again yesterday and you can't hear the knock at the end of the exhaust. The knock sounds dull from my perspective, could be wrong. I decided to use a wrench to put pressure on the cat by using the frame of the car as a support point and as soon as I start putting pressure on the cat the knock gets louder. Someone told me it could be the heat shield? I'll try posting a video today so you can all get a better hear.

[WDRacing]

Well that's a good thing! You know it's not rod knock!

[MrqzD77]

Awesome! Well I got the Cat down, now I just need help with a couple of other things.

I juts finished draining the Transmission fluid and refilling it. It has never had one done so I took it to the dealer for its first time. I have heard that flushing the Transmission can cause problems. My G35 has 110,000 miles. So I decided just to drain and refill for now. Now my question is should I drain and refill the Differential oil as well? Can I do that at home or does it need to be done at a shop?

I also learned that my front struts are going out as well as the compression rod bushings. The dealer wanted to charge me over $2,000.00 to fix these two problems.

Do the struts need to come from the dealer? Or can I buy them somewhere else? My G35 came with the sport tuned suspension so I don't know how it will affect it. Can the job be done by myself or will it have to be done at the shop?

For the compression rod bushings, would it be better to just replace the bushings or replace the entire compression rod? And also could I do this at home or at the shop?

They also told me I needed new belts but I can replace those. As well as new tires and i juts found out the tires for my car are over $300.00 each! Wow....

[Nicodomeus]

Struts you can get wherever you please as long as they fit. Does not have to be Nissan. I am fairly sure KYB makes them FOR Nissan anyways.
Here is some info for those Bushings and struts and such my friend

post6551224.html?hilit=g35%20compressio ... s#p6551224
post6026657.html?hilit=g35%20compressio ... s#p6026657

here is a youtube of a howto for the replacements of the bushings
https://www.youtube.com/watch?v=Unc0S9kRieM

and "sport tuned" really is just the TYPE of parts used, not necessarily a "tuned" car.

Did you ever figure out the knock?

[WDRacing]

I'd change the trans fluid every 30k. Do the diff at the same time. The diff can be done at home.

There's a filter inside the sump of the trans. That dude needs to be changed out as well. This gets overlooked a lot. Just changing the fluid isn't enough, although it helps. If the filter is clogged the pressure inside the valve body won't be correct, shifts will suffer etc. There's also a bunch of old fluid inside the torque converter that doesn't come out when you drain the pan. At best, you changed out half of the fluid.

I just did my BMW yesterday. After I changed the filter and refilled the sump, I drove and repeated the drain and fill procedure 2 more times. This gets most of the old fluid out. The other method involves disconnecting the return line after you've swapped the filter and refilled the sump. Once disconnected you start the car and put it in drive, the old fluid inside the torque converter will travel through the system like normal and come out the return line on the way back to the sump. You simply keep filling the sump until the fluid that comes out of the return is fresh. The BMW doesn't have a servicing port or a dipstick under the hood. So I don't use that method.

The shocks and suspension system components can all be purchased from aftermarket vendors. I don't see why you couldn't do most of the work yourself, but I'm assuming you're a competent mechanic.

Here's a vid of the compression bushings being changed out.

[youtube]http://www.youtube.com/watch?v=Unc0S9kRieM[/youtube]

[MrqzD77]

Well everyone its been a couple of weeks the car is running fine at least from what I can tell!

The Good News
1.I changed the differential oil.
2.Drained and refilled the transmission fluid twice but I think its going to need one more.
3.I changed out the spark plugs as well and now the car is doing better on gas.
4.The catalytic converter is damaged from the inside but due to my budget has not been repaired.
5.I got two brand new tires in the front since the old ones were close to worn out completely and unsafe to drive on.
I did all the work myself by the way! Except replacing the tires haha

Now the bad
1. Antifreeze is a pretty dark color so Im going to have to flush it out soon!
2. Front struts are almost out but due to my budget will not be replaced any time soon.
3. There is a pinging noise coming from the back of the engine.
4. Looks like the transmission mounts might be due for a change or the cars transmission is going out.

Here is a video of the engine bay.
https://www.youtube.com/watch?v=swpXoIt ... e=youtu.be

[nissangirl74]

Dark antifreeze (almost always) indicates a blown head gasket which could explain the pinging you are hearing from the back of the motor. The darkness is oil.
You're going to have to replace those struts or you're gonna keep eating up front tires.
Transmission mounts at 110K is not unreasonable. I'd try that first before pricing transmissions.

Good luck!!

[WDRacing]

I recommend doing a static compression test on the motor. A compression test is a very good reference point for engine wear. Bad compression numbers are very telling.

[MrqzD77]

Well everyone checked out the coolant once again and I can say false alarm! The way the reservoir is pointed makes it look like the coolant is dark. Im actually going to flush it anyways in a couple of days because the last owner of the vehicle did not bother doing it!

[MrqzD77]

If anyone would like to know. Just an update on my G35 since my last post.

The oil change has been done.
Transmission filter and gasket replaced with drain and refill included.

I did however run into a problem with the car battery but got it solved.

Did run into code P1065 which is ECM/PCM back up malfunction. Had it checked out at the dealer and the codes were erased for now. Hopefully they do not come back up.

Catalytic converter has not been changed due to a low budget and bills have been overwhelming. Transmission mount needs to be replaced as well and the struts are still waiting to be replaced.

Sway bar bushings also replaced.

Car is running great! Hopefully it doesn't cause me anymore trouble, would love to keep it forever! =D

[WDRacing]

Glad she's running well!