After having my oil pan replaced, my 97 SC2 ''s exhaust has a louder different note to it which seems to be coming from forward of the driver's seat/firewall.

Under the vehicle inspection resulted in no holes located in downpipe, flexpipe, or exhaust manifold itself, unless it is right above the flange that connects to the downpipe on the side closest to the engine where I can't seem to get a good look.

There is no hissing so I am ruling out a cracked manifold. I can hear a bit of a tapping sound, but I am not sure how loud that is relative to normal operation because I never paid attention to it before.

There is also now a gurgling sound that seems to be coming from the upper portion of the exhaust manifold. Yet to determine if it is near where the runners meet the engine or if it is lower on the manifold or if it is just generally coming from that area. I have read that the gurgling sound will appear when people increase their exhaust piping diameter because the velocity of the exhaust gases is reduced relative to the manufacturers piping diameter which has been sized so that the gurgling doesn't take place. Mine is unmodified. Something related to reduced back pressure which is no longer High Enough to push the gases along fast enough.

The car seems to have more pick up going up hills then it has in years.

I only hear the gurgling sound clearly when I take my foot off the gas from accelerating while working the throttle from under the hood.. I can only really hear it under the hood. It is mixed in with the general noise so I cannot discern it while sitting in the driver's seat.

Does this sound like an exhaust manifold leak issue? The exhaust manifold was disconnected from the engine and the entire exhaust lowered out of the way to put in the new oil pan. It was done by the same clueless dude who messed up my valve cover gasket. It is the original exhaust manifold gasket that has about 70,000 miles on the rebuilt engine. I'm thinking it got wrecked or shifted during the process of exhaust manifold removal and reinstallation.

Can these be reused? I was not charged for a new one. Is it best practice to replace these in such a case?

Trying not to jump to conclusions but it fits in perfectly with the lack of attention to detail demonstrated by this so-called mechanic. I did not say anything about it when I picked up the car because I figured the rest of the exhaust system was old enough that if a hole formed when they were handling it I would not hold them responsible since it needed to be replaced anyway. I had not popped the hood at the time. But it seems to be getting louder and I have inspection in November so I decided to investigate yesterday for the first time.

I do have a back pressure tester but I have no idea what the spec is for a dohc s car.

Time for the soap and water test? Any other confirming diagnostic tests?

Thanks.

 

Okay got up off my **** and did an internet search. Seems like a back pressure of 1.25 to 1.5 PSI at idle and a back pressure of 3 PSI at 2000 RPM are acceptable limits. The articles are all focused on excessive back pressure but the lower limit should be a good place for me to start. I'm not sure how much of a drop a leaky exhaust manifold gasket would cause so I don't know if I would be able to see it by measuring at the front O2 sensor. Only one way to find out. Of course this test will not confirm it is the exhaust manifold gasket but it would seem to limit it to everything in front of the cat.

 

 

Not sure what you mean by fabricated tube style. From the 100% coverage of rust I'm thinking cast iron but not sure.
There is no exhaust mani heat shield on the DOHC S cars. He definitely removed the manifold as the nuts and studs are all cleaned up and you can see the threads.

No rumbling or backfiring when I take foot off gas. Just an overall louder sound from under the hood and the gurgling I described, which really sounds loudest at the height of the pipes coming off of each cylinder, but not necessarily louder right up at the block where the mani meets up.

The head pipe is only a few inches below the level of the rest of the manifold, so there could indeed be a leak there. I'll look at the bolts, though if they were PB Blastered they probably have rusted over by now.

I even left the guy an exhaust flange gasket and a pack of exhaust studs and nuts on the front seat in case he had difficulty getting them off or one snapped or needed to be cut and drilled.

The package was unopened.
I'll check

Thanks

------------
This keeps popping into my head when I think of the mechanic:

" What we've got here is failure to communicate.
Some men you just can't reach.
So you get what we had here last week,
which is the way he wants it. . .
well, he gets it.
I don't like it any more than you men."

Cool Hand Luke 1967

(used in GnR's "Civil War")

 

Is that a flat gasket or doughnut style gasket, derf? I had a similar problem with a Ford Ranger I owned years ago. Bought it brand new and within 5,000 miles, I had an exhaust leak. Took it back, they replaced a gasket. Couple of weeks later, that one popped. After the third trip to the dealer, I said the hell with it and fixed it myself. They kept replacing the old flat gasket with another flat gasket, My fix was a doughnut style gasket that fit inside the hole and torqued down to Charlie specs. It never leaked again. And I went back to the dealership and told my salesman he owed me $2 plus tax for the part. My labor was free. And Glenn was a good guy and paid me.

 

ItsI a flat gasket. $2. More expensive to ship from Rock Auto than to buy by itself.

I checked the bolts at the manifold flange to header pipe connection. Mega rusty w no sign of penetrating oil or Blaster having been sprayed. I can see the over spray at each stud and bolt that holds the manifold to the head. And it is definitely a cast piece of iron.

I need to get a piece of heater hose and isolate the location. Will try soapy water first.

 

 

What's a tapling? I said there wasn't really any tapping.

Maybe the extra umph is in my head.

I actually thought there was a hole in the header pipe before the flex pipe section and that it was relieving a small amount of backpressure, letting the engine breath a bit easier./
Turns out that I actually pulled that out of what apparently was a dream, cause there is no hole where it should be.

Since the guy doesn't seem to respect a torque wrench, I'll check the torque on the manifold bolts tomorrow, then soapy water.
Should the manifold fasteners have loctite (the temporary kind?) Seems like all the heat cycling and vibration might loosen them up.......

 

 

If locktite was used, I sure hope it's the blue and not red. Blue is medium strength, red is for a tight bond.