: LT1 Exhaust Leaks?



N0DIH
02-23-06, 04:57 PM
My LT1 seems to have picked up a couple leaks in the pass side pipe. It sounds like there is one at the manifold to pipe coupling and then farther down there is one on cold days you can see after the cat converter.

It is sounding a little louder and now performance is noticeably down a little at cruise, but WOT seems ok.

Are these common places for leaks?

FASSTWOOD
02-23-06, 09:51 PM
Nodih, I hate to tell you this but i think its one of your exhaust manifold bolts. The right rear is always the one to break. just check your manifold bolts make sure all the heads are there...

ocjmakaveli
02-23-06, 10:58 PM
Have you gotten your broken bolts fixed nodih?

BCs71
02-24-06, 12:30 PM
Broeken bolts or any exhaust leak upstream of the o2 sensors results in false readings of actual exhaust output being picked up by the o2 sensors, meaning that the PCM is getting the false data and compensating incorrectly for data it is being fed.
Therefore, performance can be down along with gas mileage.

There is a gasket between the manifold and cat connection. Hopefully that is the only issue you have. Feel along the bottom of the exhaust manifold and see if the heads for all bolts are there. The manifolds also have a tendency to crack themselves believe it or not, which is hard to detect since there are metal heat shields wrapped over them.

Any leaks after the cats (o2 sensors) will not affect the vehicle's condition or performance, just will be annoying.

Good luck!

caddycruiser
02-24-06, 12:49 PM
This is one thing I still haven't had a chance to look for on my '95, but is really worrying me.

ESPECIALLY after my father mentioned the other day "You know, besides when I test drove it, it really doesn't seem all that much faster than the other two cars ['92 Roadmaster & '93 Fleetwood], but I could be wrong."

I mentioned the bolts to him and after not believing me that this actually happens, he reminded me that there's generally a rattle kind of sound with a leak, and we never noticed anything.

Just need to get in there and finally take a look...:cool:

N0DIH
02-24-06, 01:50 PM
The "new" leak is on the pass side. All bolts accounted for, I guess that doesn't mean they are still attached, I guess they could be rusted to the manifold too.

Yeah, this spring Opti/WP/Timing set install will get longer, gonna pull the manifolds to fix this too.

There is a leak just down around the pass side converter somewhere, can't get under it just yet to look specifically where.

I don't have a garage or driveway, so I have to wait for good and warm weather...

I get noise now on both sides of the engine. This sucks. A Cadillac that sounds like a small block chevy....

Actually the odd thing, mileage is up since the leak started! Not much, but 18 mpg (1 tank though, but it happened recently) compared to 16.5-17.0 in this cold and wind.

Part throttle response is down, even off the line. But WOT seems ok. It is annoying to have to get on the gas as much as I am right now. All of a sudden, so if something broke or rusted through, it just happened this week.

N0DIH
02-27-06, 01:25 PM
I think it might be the EGR tube, are they problems? I just cant see it, but it is in the right place.

BCs71
02-28-06, 12:26 PM
I think it might be the EGR tube, are they problems? I just cant see it, but it is in the right place.

There is a gasket where the tube connects at the back of the intake manifold.

At the pass. exhaust manifold, there is no gasket. The tube has a flared end and the block with only one bolt is around the end of the flare. The block mounts onto the manifold via the bolt, which squeezs the flared end up tight against the manifold.

I guess it's possible the bolt came loose or something....
Boy, it is a real PITA to get at the bolt. Good luck! :alchi:

I've heard of the gasket at the cat converter flange where it meets the exhaust manifold getting bad and leaking. That is very close to the EGR tube mount, so be sure it isn't the leak to feel!

Katshot
02-28-06, 03:03 PM
Can't say I ever had any issues other than the broken bolts and cracked manifolds. You should be able to verify whether the leak is at the engine or not fairly easily when it's cold.

caddycruiser
02-28-06, 03:08 PM
Can't say I ever had any issues other than the broken bolts and cracked manifolds. You should be able to verify whether the leak is at the engine or not fairly easily when it's cold.

What, again, was the cause of the breaking off bolts anyway? Over-torqued or just the wrong grade? I can't remember...:cookoo:

Well that, or why it apparently happens to so many of these cars...

Katshot
02-28-06, 03:58 PM
We were told by Cadillac Engineering that the problem(s) were:
1. Bolts too long for hole.
2. Over torque.

We had far more left-side bolts break, and far more rear cylinders than front. My thoughts on that were always that the heat was greatest on those cylinders so they had the greatest degree of thermal-cycling.

caddycruiser
02-28-06, 04:51 PM
We were told by Cadillac Engineering that the problem(s) were:
1. Bolts too long for hole.
2. Over torque.

We had far more left-side bolts break, and far more rear cylinders than front. My thoughts on that were always that the heat was greatest on those cylinders so they had the greatest degree of thermal-cycling.

Oh, okay, that makes sense now.

N0DIH
02-28-06, 06:54 PM
Yes, that makes most sense of any.

Well, the results of the leaks were the after the cat coupling rusted through and wouldn't hold. The noise was reflecting off something underneath making it sound like the manifold. I did some water in a vacuum line and it steamed only from the leaks in the pipe, the rear driver's side manifold (next to last bolt broken, can't fix just yet), and the back of each muffler.

So seems some exhaust work is in order.

Will the Impala SS aftermarket exhausts fix with some extensions? I want to put in an Dr. Gas crossover. Or am I better off making my own system from prebent pipe and have a shop flare it for me and me install it?