Cadillac Owners Forum banner

1 - 12 of 12 Posts

·
Registered
1987 Fleetwood Brougham
Joined
·
239 Posts
Discussion Starter #1
Alright, so the Brougham didn't fare to well on eBay, so I'll be hanging onto it for a while. Recently, the exhaust stink has gotten worse from the car, and now it's not really pleasant to drive. The smell is definitely pre-cat converter, since it smells just like my Camaro does, so I guess I'm going to have to do a few gaskets. So far, I can see there's two manifold gaskets, obviously, and a gasket where the y-pipe meets the little butterfly thing for the warmup mechanism (whatever it's called). Are there gaskets that I'll have to replace for the smog pump or are they welded to the manifolds? I'm pretty much just trying to size up how big of a job I'm jumping into if I want to replace gaskets.

Also, are some gaskets more prone to fail than others on the 307? Maybe I should try the manifold gaskets first? I can hear the engine doing a little exhaust leak tapping near my feet somewhere, so it's definitely driverside.
 

·
Registered
Joined
·
57 Posts
My car had a leak at the Y pipe. it wasnt because of the gasket though, The thing rusted through. Lol, thats what I get for buying a car quite literally on the east coast. The exaust on the 307 is fairly simple. if your going to be replacing all the gaskets and finding leaks, it might be smart (and educational) to just drop the exaust and have a close up look. that shoudlt be TOO hard, with the exception of finding and freeing rusty bolts. Good luck either way though
 

·
Registered
Joined
·
201 Posts
Frankie.......
I have a leak as well that Im trying to find. A mechanic friend told me it was because somone had put exhaust manifold gaskets in when the had the heads off. He and others say that they shouldnt be installed (which sounds strange to me). He said the head and manifold should be cleaned and put together metal to metal.

Later
 

·
Registered
1987 Fleetwood Brougham
Joined
·
239 Posts
Discussion Starter #5
Metal to metal from manifold to head? Sounds like it's going to leak all over. You know, with the quality of manufacturing in the late 80's, I'm sure that metal on the manifold is perfectly matched to the metal on the heads. I bet they weren't even made at the same factory! Even if they were, after 20 years, they ain't gonna be no more.

I'm getting a good glugging now from the driver's side. I think it's the same as ever, but since I have 4 brand new tires on the thing all the road noise is gone and I can really hear it. It's probably at the y-pipe junction, so I'm just gonna stick it up stands this weekend and crawl under there while it's running. A sniff test on a carbureted vehicle running 87 octane is normally a pretty good indicator of leak location. Plus, that V8 has a decent stroke, so the noise at idle should give it away.

The rusted bolts will hopefully come out after a soak in PB Blast. That stuff is magic in a can for $2.50 at the parts store. I have impact tools too, so at long as the head is still on the bolt, it's coming out. I just hope I don't snap any off in the heads.

Putting the exhaust back on should help my gas mileage too, right? Last time I checked, before new tires and an alignment, I was getting 13mpg. I'd love to have the original 17mpg back :D
 

·
Registered
1987 Fleetwood Brougham
Joined
·
239 Posts
Discussion Starter #6
Alright, so I redid the entire exhaust from the cat converter forward on the car, and it smells SOOOOOOOOOOO much better now. For those of you who haven't done it, I'll lay it out nice for you.

First, you've got the exhaust manifolds. They take a simple metal crush gasket, but the auto parts store will stock two. Get the smaller of the two. Also, GM decided to put some metal locking tabs about the bolts that fasten the manifolds to the heads. I assume they're there to keep you from servicing your own vehicle. Do whatever you can to get them off; you won't be putting them back on. My manifolds are now in place, sans locking tabs, with green locktite on the threads, and stainless lockwashers. They shouldn't roll themselves out.

Second, you have the heat riser flapper deal. This connects with a simple metal crush gasket as well. They had it at the local parts store.

Third, you have the pipe that joins the two manifolds together. To my surprise, there are actually no gaskets in place here. Apparently GM thought a metal-to-metal tapered seal would hold up. Me, I'm not so optimistic, so they were reconnected using 700 degree copper silicone gasket maker. It seems to seal them up nice.

Fourth is the actual connection to the rest of the exhaust. It uses a 3 bolt/spring combo flange and a strange, tapered fiber gasket. You'll have to pull the old gasket out with pliers. The new gasket just pops into the manifold and then you bolt the pipe up via the flange. It'll find it's way on top of the gasket properly and the bolts actually ride on the springs.

I didn't do anything where the pipe mounted to the cat converter, but it appears to be a standard pipe into pipe with a clamp. It seemed pretty sealed up, so I left it alone. Next I have to remove my cat to muffler pipe since it has a couple of small rust holes, and the car should be absolutely silent again.

Oh, and since your bolts will undoubtedly be as rusty as mine, do yourself a favor and buy a can of, "PB Blaster," at the parts store. Soak the bolts down with it, I mean soak, and let it sit for a few minutes. You'll still need and impact wrench or breaker bar to get most of them off.
 

·
Registered
Joined
·
201 Posts
Frankie
How long did it take? Those manifold bolts look really hard to get to. I have to do the same job. You used metal crush gaskets on the manifold, did the fix the noise?

Later
 

·
Registered
1987 Fleetwood Brougham
Joined
·
239 Posts
Discussion Starter #8
johndfw said:
Frankie
How long did it take? Those manifold bolts look really hard to get to. I have to do the same job. You used metal crush gaskets on the manifold, did the fix the noise?

Later
It took me all day Saturday, from about 11am until 8pm. Most of the time was spent trying to get those clips off of the bolts and on multiple trips to the parts store for gaskets, returns, tools, etc... I think I ended up using a 14mm deep socket, a 14mm normal socket, 9/16" deep and normal sockets, 9/16" box end wrench, and I think a 1/2" and 3/8" socket for various small stuff like the heat riser on the driver side.

I just used standard Felpro metal gaskets. It quieted up the front of the car and definitely removed the stink, but I still get a little noise from my rotten extension pipe between the cat and the muffler. I might order one later this week, since they're $15-$20, and clamp it in.

It's not hard to get to the driver side manifold at all once you pull out the air cleaner, heat riser tube, and air snorkle. Just pop the plug wires and it's pretty simple to get a wrench in there. The passenger side is a little more difficult, and it was actually easier to remove some of the bolts from underneath the car. There's just too much A/C stuff in the way from the top. The connecting pipe and flange to the cat are simple to pop off. Just make sure you wear some glasses as a lot of rust'll fall in your eyes :D
 

·
Registered
Joined
·
201 Posts
Thanks Frankie

Thats about what I thought it would take. I didnt feel like doing that last weekend. Maybe next weekend.

Later
 

·
Registered
1991 Cadillac Brougham D'Elegance 5.7 Litre, 1994 DeVille
Joined
·
6,796 Posts
Having no gaskets between the exhaust manifolds and the heads sort of sounds strange but it works. I never had a problem with that before even after putting them from one engine onto another one. Maybe the way theyre bolted on makes them stay flat. Then again I did that on a Chrysler and not on a GM.
 

·
Registered
1987 Fleetwood Brougham
Joined
·
239 Posts
Discussion Starter #11
brougham said:
Having no gaskets between the exhaust manifolds and the heads sort of sounds strange but it works. I never had a problem with that before even after putting them from one engine onto another one. Maybe the way theyre bolted on makes them stay flat. Then again I did that on a Chrysler and not on a GM.
I heard somebody else say that too, actually, but I wasn't going to try it. It had gaskets from the factory, it's gonna have gaskets when I put it back on.
 

·
Registered
1991 Cadillac Brougham D'Elegance 5.7 Litre, 1994 DeVille
Joined
·
6,796 Posts
FrankieSixxxgun said:
I heard somebody else say that too, actually, but I wasn't going to try it. It had gaskets from the factory, it's gonna have gaskets when I put it back on.
Yeah if it had gaskets from the factory I'd put them back on too. Maybe they did something different with them and started having leak problems.
 
1 - 12 of 12 Posts
Top