Outback Rusted Exhaust Stud Broken New Exhaust

[msmithmmx]

98 OBW w/ 2.2 240K miles

 

The back story. Three  years and 5K miles ago I performed significant exhaust repair. I replaced the rear catalytic converter, O2 sensor, center pipe and muffler all due to rust.  I purchased the parts off the internet.   All of them were aftermarket.  I could not get things bolted together tightly so I did end up at a local exhaust shop that tightened things up for me including extended the center pipe for a $100.  I am writing this up to provide some encouragement when things go bad and to provide all of the parts that will fit perfect without any trips to the shop.  If I had to take this to the shop I probably would have sold the car as-is due to the cost of the repair

Present day Nov 2015. I thought this would be a 5 minute $5 fix.  I had a leak where the Y-pipe meets the head.  I proceeded to unbolt the y-pipe with the impact wrench and snapped an exhaust stud.  I was able to remove the other three with nut and stud as one piece.  They were fused together due to rust. Now I needed the exhaust out of the way.  Unbolting the y-pip from the front cat is not worth the pain of working on  your back so I pulled down the entire exhaust for a good inspection.  Things just got worse from here. 

 

1. One broken exhaust stud in the block. Rear stud driver side. (worst one to snap)
2. The y-pipe head flanges where rusted out.  I could see black exhaust trails flowing down the head.
3. The three year old non-oem replacement catalytic converter (Walker 16090) had advanced rust issues on the flanges and the hanger was half rusted out.  (I purchased this off Amazon and it had a 5 year warranty).  They replaced it without any issue.
4. Unable to remove generic O2 Sensor (BOSCH 15726)  from the catalytic converter
5. The three year old non-oem center pipe had a huge hole on the top of the resonator. Could not find any receipts for this one.

Removing the exhaust stud

There are many tricks to get this done.  I had no access to welding equipment.  I did not even bother with the EZ out tools
because there was no way I was getting more torque then what was available before the bolt head snapped off. 1) Get a new hack saw blade and wrap one side with a towel so you can hold it comfortable. Use oil and cut the stud flush with the head if it is not already thatway. 2) Center punch the stud 3) Drill a pilot hole using a ¼ Colbalt drill bill.  Drill to the depth that the other empty stud holes are at.  You can measure this by dropping in the drill bit in an empty hole and wrapping tap around the bit as a marker. DO NOT DRILL TOO DEEP. 4) Now drill the hole for a second time using a 5/16 Cobalt drill bit. I used a DeWalt DWA1220 and it cut like butter. 5) Now it is time to tap the hole.  I used an IRWIN 10mm – 1.25 that picked up off eBay.  THIS IS A CRITICAL TIME. You need to do this by hand. Since I broke the stud located in the worst spot I had to put the tap into ¼  12 inch extension and then insert the extension into the hand tool.  I will include a picture of this.  At most I was able to turn the tap 1/16 of an inch before I had to pull it out and blow the metal shavings off with compressed air and re-oil the tap.  This entire process from step 1 took me 6 hours over the course of a week to complete.  Do not lose faith here. This  is very slow going.  If you break the drill bit or the tap in the stud hole you will need a new head.  Careful work here is worth it. Do the math.  I also chased the other three holes.  I was very surprised to see all of the shavings that came out.

Cover everything in anti-seize

 

I went with new OEM studs and nuts instead of the old fused stud/bolt that I pulled off.  For $20 I thought it was worth going new. The exhaust will go on exactly as it was taken off.  When it comes to exhaust parts I am generally ok with aftermarket except the gaskets used between the y-pipe and the head. Use OEM. This is just my experience.

 

This parts list worked perfectly for my 98 Subaru Outback with 2.2 engine.  The 2.2 engine is a single port exhaust.  If you have the 2.5 you have dual port exhaust on the head and will need a different Y-pipe and head exhaust gaskets.

Parts List

 

• (1) Y-pipe  Part# 2100-58201-2.  Manufacture: AUTOPART International  - eBay
• (2) Gasket between Y-Pipe and Engine. Part#  44011AC020. Manufacture Subaru  - eBay
• (1) Gasket between Y-Pipe and front catalytic converter. Part# 2107-00288. Manufacture: AUTOPART International – Came with the y-pipe
• (2) Gasket between front and rear catalytic converter. Between center pipe and muffler Part# 31388. Manufacture: Walker - Amazon
• (1) Flex joint donut gasket between rear catalytic converter and center pipe. Part# 31697. Manufacture: Walker - Amazon
• (1) Spring Bolt Kit used to connect center pipe to rear catalytic converter. Part# 35412. Manufacture: Walker - Amazon
• (1) O2 Sensor for rear catalytic converter. Part# 15726. Manufacture BOSCH - Amazon
• (1) Rear catalytic converter. Part# 16090. Manufacture Walker.  (Warranty replacement for me) - Amazon
• (4) Exhaust Studs. Part# 800910550.  Manufacture  Subaru - eBay
• (4) Exhaust Stud Bolts. Part# 902370029. Manufacture Subaru - eBay

The parts total was $255. I have 10 hours labor in this job.  If I had a shop complete this work I am guessing the total would have been $1,000 to $1,400. 

Edited December 5, 2015 by msmithmmx

[Rooster2]

WOW, you have far more patience then me to spend so much time and effort doing that tap work. Congrats! on a job well done.

[DaveT]

Never use impact on steel bolts in aluminum.

 

I got fed up with the aftermarket exhaust stuff rotting out, and oem too spendy. So I fabricated all stainless systems for my 2 wagons. Anti seize on everything. No more exhaust hell. I have not done the mufflers yet, since the ones I have were still good.

[keith3267]

Did you use zinc oxide anti-sieze this time?

[msmithmmx]

I did use anti-seize on everything.  I also did three years ago. In PA the salt is bad.  I have removed 4 or so engines in the past and I have never had an issue using a impact wrench to remove exhaust studs until now.

[Stelcom66]

Thanks for taking the time to post this, very good information and to include part numbers is a big help. I remember years ago breaking a bolt when replacing a thermostat on an '89 Plymouth Voyager V6. I had to make a new tap, but it wasn't that bad since the thermostat was easily accessible on top.