I have a 1995 Chevy Blazer 4WD with 4.3 L vin W engine.

Its exhaust is really loud and I can see all kinds of places where there are leaks but would like to attack the worst first.

I will describe my observations from rear to front.

1. Tailpipe is gone and there is a hole in rear of muffler. Despite this fact, most noise seems to be coming from the front of the car.

2. Pipe from muffler to catalytic converter seems solid.

3. Pipe & Crossover pipe from catalytic converter to manifolds as well as O2 sensor seems solid.

4. Gaskets between pipes and manifolds may be gone as it seems the noise is coming from this area.

5. There are small cracks in both exhaust manifolds but I don't know how much noise these are contributing.

When hood is open noise seems to be underneath. When under car, noise seems to be up front someplace.

I suspect that #4 is where I need to focus my money but any insights into how to accomplish job #4 or the importance of #5 are greatly appreciated.

Thank-you!

 

Sounds like #4 would be a good start by changing the donut gaskets. If the manifolds are cracked it is very possible that they are leaking too. Most of the time the manifolds crack do to excessive heat i.e, plugged cat or muffler.

 

Do you have any advice for getting the nuts off these studs without breakage? Mine are so rusty, they don't even look like nuts & studs. Thanks!

Chevy dealer wants $5 each for the studs and $7 each for the springs. So that's 72 bucks if I have to cut!

I don't think there are any obstructions or excessive heat. It's driving and running fine. I am the original owner. There are 210,000 miles on this thing so maybe just cracked from age?

 

Spray them with PB Blaster and let them soak. You probably won't be able to get them out without using a impact gun if they are as bad as you say they are. I would check your local parts store and see if they can get the studs and nuts. not sure about the springs mine doesn't have springs i don't think. Or i don't remember it having any when i had it apart.

The manifolds could crack over time i guess but i've personally never seen it happen.


Hope this helps.

 

Napa has studs, springs & nuts for about six bucks... so down to $36 for the whole set at least. I have some PB Blaster and an impact gun... I also have those hardened spiral nut removers from Craftsman.

Hmmm... I would know if I had an exhaust obstruction or overheating at some point, right? That would cause other issues or symptoms?

Yes, very much! Thanks.

 

Well on my 02 sonoma the exhaust manifold was cracked when i bought it. It sounded like the manifold gasket was leaking it wasn't real loud either, just loud enough to be noticable. I took the heat sheild off and it was cracked all the way back to the head. Felt a little sluggish i thought when i bought it but its a 2.2L so its not very powerful to begin with, so i didn't think much of it at first. Come to find out the cat was clogged.

Since it had to be replaced anyway we "modified" it if you get the point. LOL. and it actually ran a little cooler, gas mileage went up and got some power back. It ran fine down the highway and everything, i drove it home 165 miles and couldn't even tell the cat was clogged. i figured it was pokey b/c its a 4 banger automatic.LOL

Might even check Autozone for your bolts and nuts and springs, they might have them in the help section.

 

Last time it was running sluggish we thought maybe the catalytic converter was clogged. So I drilled a small hole underneath to prove/disprove this theory. The small hole did not increase the noise or improve performance but based on physical observations, mine seems quite empty.

Anyway... turns out my problem was a bad fuel pump and now I have a small hole to patch in the cat.

I'm hoping my cracked manifold is not serious and will focus my efforts on the donut gaskets as they really seem like 75% of the noise.

Thanks for your help.

 

No prob. I would def do the donuts first, you dont want to mess with the manifolds if you don't have to.


If the cat is really clogged up you will def be able to tell something is wrong. I just took care of mine since i was messin around under there,
Lol. The warmer the engine gets the less power you will have when it gets really bad. When they went out on my friends car with 100,000 miles it ran fine cold then when it warmed up it would only go about 40mph. It doesn't sound like thats a problem for you though. if you feel ballsy (not sure if your state does vehicle inspection or not), you could clean the cat out and when you have it apart weld 2 o2 sensor bungs together and weld them ontop of the one that is already there and put the o2 sensor back in after you get it done and that will keep the check engine light from coming on because it takes it out lf the exhaust stream a little bit so it won't read as much pollution. I am not suggesting you do this because its illegal but you can do with it what you want.....

 

The only time the light came on was when my EGR clogged and stuck open.

I'm in IL but in a zip code exempt from the annual inspections.

But despite that, my plan is as follows and still open to more opinions and suggestions...

1. Change donuts and replace studs/springs as needed.
2. Patch small hole in Cat.
3. Replace muffler/tail section from flange behind Cat.

 

You should not have any cracks in your manifolds. There are bunch of Blazers in junkyards right now so they shouldn't be too bad if you have to replace them. To find out exactly where your leaks are get about 4 ft of old garden hose (I like the 1/2" variety) and then you can start the truck and put one end up to your ear and probe around with the other. Call it a poor man's stethescope. You can pinpoint where you exhaust is leaking within that 1/2". As far as the studs/nuts/springs go Dorman has a kit with all the items in it. I think it's about $6 or $7 but you get it all. When you pull one of the stude you are not supposed to reuse it. You can also try to put some hydrogen peroxide on the rusty nuts. It works pretty good too. I personally like the Amsoil penetrant but it's just personal preference. I just replaced my whole exhaust system on my 94. Didn'y start that way. Just wanted a Cat-back. Then the converter was bad (emissions test) and adter that the crossover (Y) pipe was toast and leaking so.... Good luck. Just have patience. If you have even a propane torch (like a Bernz-O-Matic) you can get up enough heat to heat the manifold stud area and they'll come out easier