Prizm exhaust note randomly increased dramatically...what could be going on?

Hey guys,

When I was driving my Geo Prizm earlier this afternoon it lurched forward for a split second and then began to emit a significantly louder exhaust note. Beyond that though, the car still drives fine. I looked at the muffler and everything appears to be okay. Two odd things: (1) when the car is in neutral and I rev it, it still sounds like it normally should and (2) when I parked and was shifting from Drive to Park it sounded like something was rattling (I was able to replicate this sound by shifting again but it wasn't nearly as loud).

Anyone know what might be going on? Besides the loud exhaust note, the car still drives fine. Going to take it to a mechanic tomorrow but was wondering if anyone could help me pinpoint the problem so I'm not blind sided when I go to see him.

Thanks.

Put it on drive, hold the brake down hard and give it some throttle. I suspect your flex pipe is cracked and seperates when engine torque stretches the flex section. If this turns out to be the issue, I'd also look for worn/torn engine mounts.

Few things:

1) What should I look for when I hold down the brake and give it some throttle?

2) If my flex pipe is cracked and my engine mounts are worn/torn out, how much should I expect to pay to get these things fixed?

Thanks.

Engine mounts on that car can be a major PITA. 3 are easy, relatively, but the back one is on the cross member and getting to the thing can be bad. You might have to drop the cross member.

I repair motor mounts with castable urethane. Like $25 @mcmaster.com will do 4 of them. If you're paying someone else to do it, they are not going this route, and mounts alone will probably cost a bill, at least. Price them at rock auto or wherever.

Yeaj, that sounds like flex pipe to me. Every ae101 car on the planet does this. Every. Single. One. Most of the 103s do too, and the ae92s. Toyota likes to break flex pipes.

Camry's too. Last Camry flex pipe cost me a bill, installed at the muffler shop.

A little old lady from my church had this exact same problem with her Corolla. Worn motor mounts led to excessive bending in the flex pipe, and it cracked. I replaced the motor mounts, dropping the subframe was not hard, and put a tack weld on the cracked section of flex pipe (thankfully it was cracked at a spot I could hit without taking things apart). That worked well for about a year , then a muffler repaired it properly when it gave up completely. I think she said they charged $100.

Alright. Thanks guys, really appreciate the input. Going to my local mechanic tomorrow but if he wants too much I'll check out the local muffler shop.

Took it to a local shop today. There was indeed a crack in the flex pipe, they recommended that I go to a muffler shop for that.

They also noticed that there was a crack in the exhaust manifold. They quoted me at $389 to fix it for the whole kit. Reasonable price? Is this something that I should get fixed right away? I've heard that cracked exhaust manifolds can lead to damaged exhaust valves.

I can't imagine how a cracked exhaust manifold could damage an exhaust valve. $389 is definitely way more than you need to spend - it could be the retail price of a new exhaust manifold, but you can just have the crack (in the manifold) welded up at the muffler shop. A new flex pipe should be pretty cheap.

Depends on the crack. A cracked exhaust led to this on one vacation trip:

but it was cracked pretty good. Like hole through it and shattered cracked. And the valve was fine. The valve guide, not so much.

If the crack isn't blowing out exhaust gas, I wouldn't worry too much about it. And you could shop for a used one at the wreckers. Not sure if the cat is in that manifold or not, but I think not on that vintage.

$389 for the flex pipe and the exhaust manifold with labor doesn't really sound out of line. How are the motor mounts?

In reply to Dr. Hess:

Motor mounts are good. Going to pick the car up later today so I'll ask them how bad the crack is. If it's not that bad, I'll see if the muffler shop can weld it up.

If the exhaust manifold is cast iron, it can technically be welded, but "there's issues." If it is the tubular steel one, then I suppose you could get it MIG'ed up. I am pretty sure those came with the tubular one. 4AFE, right? Doesn't hurt to try.

Dr. Hess wrote: If the exhaust manifold is cast iron, it can technically be welded, but "there's issues." If it is the tubular steel one, then I suppose you could get it MIG'ed up. I am pretty sure those came with the tubular one. 4AFE, right? Doesn't hurt to try.

5a. I seem to remember mine being tube, so theres that.