another exhaust thread... leaks under power

[rainman19154]

95 Lego.... either 120K or 200K+.... history on the car is vague.

 

 

At idle the leak isn't audible. Rev it up to 2k and it's still not distinct. Power brake (tranny damage, I know) and you can hear it.

Going down the road it's very apparent. Go past a solid wall or a large truck that will reflect sound and it's a strong roar.

 

I think the leak is between the second smaller Cat and the short 12-14" section. Perhaps it is at the back end of that short peice and the longest section, but both of those peices are in generally good shape. The flange on the small Cat feels pretty rotted on the topside where it joins to the short section.

 

Frankly all the joints on the Cats are ugly and rusted, but that last flange seems worst just judging by feel.

 

I was hoping to see some distinct dark soot to mark where the leak is but not the case.

Looking at the condition of the Cat's flanges, I've very leery of taking anything apart. Unless I'm pretty certain it will bolt back up, I'd rather leave it as is.

 

Many posts here suggest going to an independant exhaust shop that will work with me on a small scale, but I've had no luck finding one. I have devoted time and research but so far I'm zero on that issue. (If anyone wants to reccommend a shop in Philly, I'm open to input. It's a big city but I'm not finding anything in the east/northeast sections.)

 

 

At this point, my next move will be to try the 'glob of JB Weld' tactic. And if it works, great! But what are the downsides to that? If it doesn't seal will I be any worse off?

[porcupine73]

Well first you have to figure out where it is leaking. That can be tricky if trying to go by sound while driving. Generally I pull up on four ramps and then with the engine idling I look underneath the vehicle. It's much easier to pinpoint the source of the sound/leak when you can see it and your ears are near it.

 

Then once the source is found the owner can determine the best course of action. Muffler bandage can work on some of the gaskets. Because on rusty soobs, replacing the gasket usually doesn't work because the pipe mating surfaces for the gasket are so rusty the new gasket won't seat right anyway.

 

If it's the donut gasket with the springs right after the rear cat, that is fixable if the flange isn't completely rotted away (it's fixable even if the flange is rotted away if you use a split flange).

[johnceggleston]

i would think that the likelyhood is pretty high that that the leak is at the donut gasket. they are not expensive, but regardless of where the leak is located, you will probably need bolts to put it back together. most of this stuff is available at your local advance auto parts store. i can't find the stuff online at the website but if you deal with a knowledgeable parts person, they probably do have it in stock.

 

spring bolt kits are 8-9$, donut gaskets ~5$, flange mid-pipe gaskets are ~2$.

[Fairtax4me]

Get the car up on stands or ramps start the engine and have a friend cram a rag in the tail pipe while you listen/feel around the pipes for the source of the leak.

 

I thought my car had a leak back when I bought it. I did the rag test and didn't find anything definitive. It still has the same beehive buzz a year later.

[rainman19154]

Well first you have to figure out where it is leaking. That can be tricky if trying to go by sound while driving. Generally I pull up on four ramps and then with the engine idling I look underneath the vehicle. It's much easier to pinpoint the source of the sound/leak when you can see it and your ears are near it.

 

This is what I did today... but it requires a good bit of back pressure before it manifests itself. I really couldn't determine anything.

 

I had a neighbor stand by the car while I did a good shot of power braking. He thought the leak was forward of the front seat- just about where the Cats end.

>> BTW this neighbor turned 90 last month.... I'm not asking him to crawl under my car.<<

 

 

 

If it's the donut gasket with the springs right after the rear cat, that is fixable if the flange isn't completely rotted away (it's fixable even if the flange is rotted away if you use a split flange).

 

The Cat flange feels like it's pretty messed up on the top side of the joint. The worst I can discern is that the belled lip is pretty well gone on about a 1/3 of the circumferance. With a little luck, it can go back together and seal up.

I'm not gonna fight the rusted hardware. I all ready plan to use new spring bolts and nuts, so if the pieces on there give me trouble I'll just cut em off and move on.

 

On another thread, I've seen a two piece item from Napa that should help when dealing with a damaged flange. It's basically two piece hoop and the two bolts join each half of the loop.

Unfortunately, I can't think of where I've seen a NAPA. Pep Boys, Autozone and Advanced are all close but I dunno what they're going to offer.

 

You guys sound like there is a good chance it's repairable, so I will give it a try.

Certainly I'll use anti seize on the nuts n bolts. Is there anything to apply to the gaskets between sections or does all that go together dry?

[davebugs]

Try an exhaust shop for that short piece of pipe. I gave up on fixing them years ago.

 

By the time you get 2 bolt kits to try and replace the flange, and the donut gasket. Swear a bunch, end up with than a less than a bullet proof repair. It's easier and more cost effective to have a shop do it.

 

My local shop charges me 40.00 to replace this piece. And as has been pointed out I have them do a lot of these, so you may need to spend a few more bucks.

 

But it's one of those things better to be done by someone with the correct parts, tools, and know how. More efficient and cost effective in my opinion.

[rainman19154]

Yeah, I'm leery of tearing into it, even if I get all the parts... for the reasons you describe.

But I'm having zero luck finding an independant exhaust shop around. Mieneke and Midas are what I'm seeing so far. I guess I could try them but from what everyone else has said, I'm gonna get a sales pitch instead of an affordable repair.

[porcupine73]

On another thread, I've seen a two piece item from Napa that should help when dealing with a damaged flange. It's basically two piece hoop and the two bolts join each half of the loop.

Unfortunately, I can't think of where I've seen a NAPA. Pep Boys, Autozone and Advanced are all close but I dunno what they're going to offer.

 

Yes that is the split flange. NAPA has them, but they didn't have the right size when I went there. Autozone had all the sizes in the exhaust section so I got a couple and used the one with the tightest good fit. I used new genuine springs but rigged up something using 1/4" stainless bolts and fender washers because I needed longer bolts than stock.

 

You only need the split flange if the flange on either the rear cat or the pipe are gone. If both are gone two split flanges might work. I've seen them both ways, sometimes it's just the donut that rusts out and the flanges are in ok shape, or sometimes the flange on the rear cat also basically disappears.

[rainman19154]

Yes that is the split flange. NAPA has them, but they didn't have the right size when I went there. Autozone had all the sizes in the exhaust section so I got a couple and used the one with the tightest good fit. I used new genuine springs but rigged up something using 1/4" stainless bolts and fender washers because I needed longer bolts than stock.

 

You only need the split flange if the flange on either the rear cat or the pipe are gone. If both are gone two split flanges might work. I've seen them both ways, sometimes it's just the donut that rusts out and the flanges are in ok shape, or sometimes the flange on the rear cat also basically disappears.

 

Booyah!! Someone chimes in that has experienced my pain.

 

Yes, I ended up at Autozone too and bought a split flange there. They do have a range of sizes. I selected the 2"-2 1/4" size but I won't know for sure if that is the right one until I get into it. Guess I should go back and give my self more options.

..... Do you remember what size you used?

 

I'm striking out finding the bolt and spring kits.... my split flange comes with bolts, but no springs. I've even thought of going to a dealer for the set.

But you ended up with differant bolts anyway? I'm thinking of putting a second jam nut onto the bolt if I can't find a spring kit.

What about reusing the old spring? Is it salvageable?

[porcupine73]

Hello. Sorry it has taken me so long to get back to you, somehow I missed this thread in my list.

 

Let me see....I think it was a 2-1/4" split flange I ended up using. It gets a little tricky in this area, which is why I bought a couple in different sizes and then picked the tightest one that would fit.

 

Yes I used aftermarket stainless steel bolts from the hardware store, because I needed longer bolts than the stock, because the split flange rests maybe a good inch behind where the original factory flange on the cat sat (which was now gone). So the stock bolts weren't long enough.

 

But then the holes in the split flange didn't quite line up with where they were in the original flange, which is why I went with 1/4" bolts so I would have some wiggle room.

 

You know I think I might have used a larger piece of the split flange on the top, and a smaller piece on the bottom iirc now. It was whatever ended up being the best fit.

 

My split flange didn't grip the pipe like vise grips. It was actually relying on the weld lip where the original flange was on the pipe to keep it from slipping off the exhaust pipe.

[rainman19154]

Hello. Sorry it has taken me so long to get back to you, somehow I missed this thread in my list.

 

Let me see....I think it was a 2-1/4" split flange I ended up using. It gets a little tricky in this area, which is why I bought a couple in different sizes and then picked the tightest one that would fit.

 

Yes I used aftermarket stainless steel bolts from the hardware store, because I needed longer bolts than the stock, because the split flange rests maybe a good inch behind where the original factory flange on the cat sat (which was now gone). So the stock bolts weren't long enough.

 

But then the holes in the split flange didn't quite line up with where they were in the original flange, which is why I went with 1/4" bolts so I would have some wiggle room.

 

You know I think I might have used a larger piece of the split flange on the top, and a smaller piece on the bottom iirc now. It was whatever ended up being the best fit.

 

My split flange didn't grip the pipe like vise grips. It was actually relying on the weld lip where the original flange was on the pipe to keep it from slipping off the exhaust pipe.

 

Your remark about it catching on the weld- that is pretty much how I pictured it going. Hopefully there is enough of the flanged end for the split flange to catch on. I will keep in mind the option of using two sizes as a pair. It's more likely to be irregular and "whatever it takes" will have to be the philosophy for tackling it. I WILL pickup some 1/4" stainless bolts.

Did you double nut to lock it, or did u use a jam nut?

[porcupine73]

I double nutted it to lock it. Probably didn't have to use stainless but I wanted to stand a chance of taking it apart in teh future if needed. But those kind of bolts are so cheap you could just use a bolt cutter and replace them instead of buying stainless if desired. The 1/4" stainess at first I was worried about the strength of them, they seemed kind of small compared to the stock bolts. But they have held up ok so far.

 

You should have at least the weld lip from the original flange to catch on. That doesn't really rust away. Unless the pipe itself starts rusting through but that is not as common.

[95Leg]

I just finished fixing what sounds like the same problem on my 95 Legacy last night. On mine, the flange right behind the cat had rusted away, so there were just 2 bolts hanging on by the other pipe, which was still in good condition.

 

The hardest part for me was cutting away the old bolts, that process took a couple of hours trying different tools (If they are original, don't even bother getting out the wrenches). That alone was enough of a pain that I think it would have been worth it to pay some money for someone else to do this job! If it was up on a lift, I think it would have been much easier, but just having it jacked up, there isn't a whole lot of room to work with. If you have a 3" cutting wheel of some kind, that would probably be best. Otherwise, a dremel with large cutting disks will do ok. I ended up cutting away the springs first, which then gave me a good shot at the bolts. Eye protection, gloves, and long sleeve shirt are a good idea, since sparks will be flying. If anyone has better ideas, please use those, since this process seemed to take forever. I originally got out my bolt-cutters, but again, there is not enough room under the car to use those when you just have it jacked up. I tried a hacksaw blade and sawsall, but those didn't work well either with the cramped conditions. Save the bolts so that you can compare the length when you tighten up the new bolts.

 

Once you get those off, the next problem is finding the right parts. I went to my local Advanced Auto Parts.

 

They had 2 kinds of split-flanges. One I think was made by Walker, and involves 2 pieces which bolt together, and then it has 2 additional holes for the spring bolts, I think it was 19.99. It looks like the better solution, but there is not enough room behind the Cat heat shield to use it. I bought it, and then realized that I was going to have to do some major cutting to the heat shield in order to use it, so I decided against it. Instead, they also have a type which is just 2 half-circles, and it only has 2 holes, so you slide the 2 spring-bolts into the holes, and that is what keeps the 2 half-circles together to form a full ring around the pipe. It ends up being much skinnier than the other kind. I think it was 13.99. Mine used the 2" type. You might want to take a tape measurer with you, and make sure the circles line up to give an inside diameter of 2". The sizes aren't marked on the boxes, so even though I asked for 2", I receive 2.5" instead, and had to make another trip back to exchange.

 

The bottom of my cat heat shield seemed to extend out further than the top. When you install the split-flange, install it so that the bottom half is going to sit closer to the pipe end and not require as much room. Even oriented that way, I had to take my dremel tool and cut off a strip about a 1/2" off the bottom of the heat shield. The guy at the parts store said he used to work at a muffler shop and they had to cut into the heat sheilds at times.

 

Do not buy the Walker donut gasket that Advanced Auto has! They sold me Walker part #31358. It will fit the pipe, but it is not long enough across the pipe, so when I went to tighten everything up, it was not going to seat well, unless I was willing to tighten the bolts up a huge amount. I drove it to the dealership with that gasket in there, and sounded like I was driving a dirt bike. Instead, I bought the gasket from the dealer (part number 44011AC000 for my 95 Leg Sedan) for 11.33. If you put both gaskets on a table, you'll see that the dealer part is much taller than the walker part. The walker website shows to use part #31357, but that is not taller, just a slightly larger inside diameter--so just avoid walker for this project. I don't know if NAPA or someone else sells a better donut, but the dealership is a sure thing if you have one near you. If you go with a different donut, try to compare with whatever amount of the old gasket is left, and see if it is about the same length. The Walker part was enough of difference to see against the small piece of donut that I had left....I originally saw that but thought maybe the old one had been compressed somehow after many years of use.

 

I used the bolts that came with the split-flange. I picked up 2 boxes of exhaust spring assortments from Advanced Auto for around $5 each. It had 2 springs in each box, and I used the smaller springs. I bought these before going to the dealership, so if you are at the dealership, you might just want to get the springs from them, although I don't know if they sell them separate or not.

 

I also used some large washers that I had sitting around. The holes in the flange that is still on the pipe are rather large, so I needed some washers there before the nut.

 

When I tightened it up, I tried to compare to the length of the bolts that I cut off, and I ended up tightening it so that the nut was about the same length across the bolt. I might have gone a little further to make sure the gasket seated well, but it was nice to know that I had tightened them up to about the same length as the ones I took off.

 

The donut gasket was put in dry---no kind of sealant/spray/gel used, and it sounds great today.

 

Good luck....I'm just glad that I can drive around in "stealth" mode again with a much quieter exhaust system.

Edited September 15, 2010 by 95Leg
addition

[porcupine73]

Good write up. Yes a cutoff tool is the easiest way to get the old bolts out of there. I tried bolt cutters but it's tough to get the jaws open far enough even with the vehicle lifted, and those bolts are actually pretty dang strong.

 

Yes I use the genuine Subaru donuts, they're only like $7 anyway so it's not breaking the bank. The spring kit and bolts could probably be aftermarket.

 

If the original flanges are still intact, I try to coat them with rust converter to try to preserve them so it doesn't fail again in the future from the flanges rotting.

[rainman19154]

That write up is a MONSTER! Thanks for all that detail. I appreciate it. I have not tackled this yet, being leary of rust damage and not being able to get it back together in at least as good a state as it currently is. I have gathered some parts... including a gasket from Advanced I'm not sure is right.

 

It's offered as the donut gasket at the back end of the Cat but while it has thickness overall, it's conical (flat on one side, tapered to fit a flange) on the other side. I was expecting a donut with substance on both sides.

 

I anticipate a struggle with the existing hardware. I have a sawzall and bolt cutters, besides a good collection of vise grips and 6 point sockets. Having read your gathered remarks, I may opt for a cheap angle grinder from Harbor Freight... that's a tool that's worth having long term anyway. This could be a good excuse to grab one.

 

I appreciate the response here... it's certainly worth waiting for. I'll post followups as this saga proceeds.

[porcupine73]

I found the air cutoff tool is the easiest to get the old bolts off. I tried a sawzall but it's hard to work it underneath there, even a short blade is too long and the foot of the sawzall is hard to find a spot for it to rest. Else the swazall wants to move while the blad stands still. Also the sawzall has a tendancy to spin the bolts instead of cutting them. The cutoff tool is what I will use again this time (doing this job on my '94 this weekend). The bolt cutters will work if you have a big pair of bolt cutters and have the vehile up in the air high enough to get the jaws open.

[rainman19154]

Yeah I use a sawzall at work. I know they have their difficulties n quirks.

 

I was thinking about clamping the bolt with a pair of vise grips... take some of the wiggle and vibration out that can stymie a good cut. I hadn't thought of the bolt actually spinning but I can picture it. Vise grips could fix that issue, too.

 

Actually I do have a large set of bolt cutters but I know clearance can be a problem underneath the rig.