Exhaust question - donut gasket replacement

[vasy]

I plan to remove the 2 bolts (each with a spring around them) to separate the rear cat and the rear exhaust pipe. I'd like to clean out the surface rust on the flanges and put some rust converter on the flanges so they'll last longer. Both flanges are still solid with only surface rust. I cleaned out as much rust as I can without removing the bolts. But would like to do more de-rusting by removing the bolts before putting on the rust converter. Question is: do I need a special tool to compress these 2 springs when I reinstall these 2 bolts? It seems that, without compressing the springs, the bolts might not be long enough to reach the nuts. Also, anyone knows what material is this donut gasket made of? I'll be using a new one. 96 Outback.

Edited April 28, 2013 by vasy

[CNY_Dave]

I've found on similar setups you can get the nut started w/o having to sqeeze the springs.

[vasy]

I've found on similar setups you can get the nut started w/o having to sqeeze the springs.

Thanks for the quick reply. Do you mean on another model year Subaru?

[mikaleda]

I've never had a problem, no special tools neccisary I don't remember having to compress the springs at all.

[mikaleda]

Thanks for the quick reply. Do you mean on another model year Subaru?

They are all the same really it's just a donut gasket, that's the reason for the springs so you don't over tourqe the gasket and break it, wich would be very easy to do with just a nut bolt setup.

[987687]

Part of the idea behind a doughnut gasket is it allows a certain amount of flex, which wouldn't work without springs. I've found it depends what gasket and/or spring bolt kit I use. The generic stuff I get from napa always has bolts that are too short so I end up using vicegrips to compress the springs to get the nut started. After that, zip it together with the impact and it's fine.

[idosubaru]

that nut/bolt is way overtigthened, they aren't normally that compressed.

nice job posting a pic, that's always helpful and would have never been able to cover that with just words.

 

that nut and bolt looks decent, not too rusty.  hose it down really good with penetrant (liquick wrench, PB Blaster, Yield, Kroil) 2 or 3 times the week prior to getting into it and you'll be able to reuse those bolts/springs.  the stock stuff doesn't need anything - just bolt it up and you're golden.

if you get new stuff, mail me those old springs/nuts - they're all rusted away and never reusable around here!

 

sometimes gotta wrestle the exhaust in place, fighting the rubber hangers, etc, but no big deal or special tools.

 

if yo'ure not using stock OEM Subaru then it just depends what you're using if it's long enough or not.  the auto parts stores won't sell anything that's a direct fit/replacement, you'll have to get some standard ones off the shelf...and then they won't be metric and some of them the spring is too small and fits in the hole of the exhaust or they're too big and cover the lip of the flange..etc....i'd keep the ones on there or maybe buy new ones from Subaru if they're not too in$ane.

 

have a wire brush attachment on a drill to get off all the rust first before treating it. it'll clean up quickly with that.

 

I'm not sure if it matters and I'm not sure why, though i've wondered, but some rust treatments have temperature limits.  like the rust converter/primer stuffs.  i also don't know how hot that part of the exhaust gets but someone with a temp gun could find out.  i'd do it with mine but i'll never remember. LOL

Edited April 29, 2013 by grossgary

[Fairtax4me]

That exhaust system looks so nice! Wish mine was that clean. You shouldn't need to compress the springs to get it back together, but you should get the gasket and bolt kit from Subaru, some of the aftermarket parts have fitment issues and can cause leaks.

[vasy]

that nut/bolt is way overtigthened, they aren't normally that compressed.

 

Good observation. I had a rattling noise coming from the exhaust a couple of years ago. I thought it was coming from the loose flange because I can duplicate that noise by hitting the pipe near the rear cat with my hand. So I tightened that flange to compress the springs more. I tightened it as much as I could with an extension pipe on a ratchet. Way too much (torque spec is only 13 ft.lb). I'll use a torque wrench this time. Later found out that the hanger bracket shown in the lower diagram was broken in half (I think only cars with AT has that bracket). Noise gone after putting on a new bracket. I'll reuse the bolts and springs. No reason not to. I also thought about the temp limit on the rust coverter/reformer thing but this is the only type of product I know of that could help extend the life of the flange on the cat. In my case, that flange is still in good solid shape. No penetrating rust after nearly 17 years. It's worth a try in my opinion. I ordered this Rust-Oleum 7830730 8-Ounce Rust Reformer from  Amazon.com yesterday for $9.1 together with some other stuff to get free shipping. Thanks to all for your info. I now know the springs won't give me problem during reinstallation.

[unibrook]

2001 Forester 120k miles.  Both of my flanges on original exhaust had rusted thru.  My FixIt garage guy just cut off the flanges and welded in a piece of pipe....charges $75 per flange repair, near Boston.  Passes inspection just fine 2 yrs later.  He said it won't last forever, but should hold for a couple of years.  He is right so far.

Edited April 29, 2013 by unibrook

[CNY_Dave]

I thought the whole point of having the shoulder bolt was that the shoulder was supposed to bottom... or aren't those shoulder bolts?

 

My front flange completely disintegrated, not even enough for a split flange to grab, so on kine I just have strings going forwards from the rear flange bolts to the body.

[vasy]

I thought the whole point of having the shoulder bolt was that the shoulder was supposed to bottom... or aren't those shoulder bolts?

Everything shown in the pic I posted is stock. The bolts are shoulder bolts.

[MilesFox]

I wouldn't sweat the rust. you would have to be driving around in winter with road salts and not washing the car for 5-10 years before that would rust out.

 

Try to find longer spring bolts. I experiened the same ordeal with napa spring bolts. try the bosal catalog at the parts counter.

 

The donut is somewhat of a steel mesh/graphite/soft metal compacted wad in a donut shape.

 

The spring bolts are designed to allow flex and keep torque. If you just use regualr bolts and nuts, they will come loose from vibration.

 

Ideally you want to keep this junction intact for sake of service, if you ever had to remove the motor or trans. When these fail, people will weld it up, and then you have to remove the whole length of exhaust to perform routine service.

 

When i installed mine, i tightened up the first bolt, and use a vise grip to draw the flanges together enough to start the 2nd bolt. the springs are completely compressed.

[msmithmmx]

Just my two cents.  If you are not leaking exhaust I would not touch that connection.  It looks fine.