Exhaust Woes

[zak99b5]

The flex pipe in the Previa cracked. It's part of the "mid pipe," which also includes the cat. So I had to buy a replacement part. Price wasnt too bad, considering. Plus, it just bolts on with flanges at either end.

So I went to install the new cat today. Rear nuts were all corroded, so I ground them off. Front nuts are in great shape. Start loosening one, and SNAP the stud (in the flange at the end of the manifold) twists apart.

Replacement pipe


rear end bolted back together temporarily


snapped stud. You can see what it should look like on the left. There's a third on top in the middle.

[TheMAN]

the "nuts" are part of the hanger bracket... you don't ever touch those, only take the bolts off those
as for the studs that broke, you can just replace them.... that's what I did when I replaced my manifold

[zak99b5]

The bolt heads on the back side of the rear flange were too corroded. So I followed a YouTube video from a guy in New Zealand (I think) in grinding off the nuts. I figured I could tack some washers onto the bracket if needed.

I think ink I will need to fine someone with a blue wrench to help get that broken stud out. I do have Irwin bolt-outs. Maybe I will try melting a little wax in the threads of the remaining nuts with my pathetic MAPP torch. Can't break it more, can I??

[zak99b5]

I couldn't make any real headway in the driveway, so I contacted a guy I know who's a tech at a shop. He offered to do it for $50 after hours. It should be a quick job with a lift, a torch, and air tools.

Well, it wasn't. Both the other studs snapped, and since they are stainless, they were a pain to drill out. Took a loooong time. Then there was the issue of removing the O2 sensors. They were basically fused/welded to the old pipe. He did eventually get them out (rear one separated), but I'll put new ones in shortly.

I tried to to pay him more, but he honored his original "worst case" price. I was able to give him extra money for hardware and supplies, though.

He even welded up an O2 flange that was leaky on the new pipe.

[TheMAN]

those studs aren't stainless, if it did, there wouldn't be any rust

but even if they were stainless, you should've used antiseize anyway to prevent galling, which will cause damaged threads or seizing if you tried to loosen them without antiseize

[tbkilb01]

I got lucky with mine. But I soaked them fir days and days and days...with PB blaster! Come to think of it I dont recollect using antisieze...oops! I'll have to revisit them sooner than later since its been 2years since. I recently parked my BlooDog anyway. Been driving the Fj and Prius allot. I really put some miles on the PREVIA these past couple of years. I really miss her tho. Runs perfectly and has a full tank of gas!

[zak99b5]

those studs aren't stainless, if it did, there wouldn't be any rust

but even if they were stainless, you should've used antiseize anyway to prevent galling, which will cause damaged threads or seizing if you tried to loosen them without antiseize

Well, I wasn't the one who bolted the cat/flex pipe section to the header in Japan sometime in 1991, so I'm not sure how I was supposed to use anti seize on assembly.

And the studs weren't rusty. In fact, I thought the nuts would come off with little issue since it all looked so good. But the factory used lock nuts, and the heat cycling over 25 years had them stuck fast.

[tbkilb01]

So you got her all together? Back on the road are ya?

[zak99b5]

Yes back on the road. I need to replace the O2 sensors, but the exhaust is now fine.

[timsrv]

Stainless steel is awesome regarding rust issues, but can be a problem with machine threads as it has a tendency to grab & strip. It's usually not an issue when assembling, but when you try to take off, the threads tend to strip. Sort of a snow-plow effect. If just one part of a thread catches, it digs in and starts tearing out the remaining threads . I have also found anti-seize compound effective in combating this issue. For exhaust, I use the high heat anti-seize. Tim

[celeron55]

I'm replacing my exhaust (which is totally falling apart after 260 miles) with a somewhat less used one (170 miles) so I might as well post a photo here. This is the one going in.

Specifically, this originally was one of the single-cat models, but someone has welded a second cat in place of the middle flange. As a result of that, I had to cut the entire thing in half to get it out. It also seems that the muffler has been replaced at some point.

scale_P1200280_crop.jpg

[TCR10]

After 301,000 miles, my front pipe (17410-76012) cracked. It is a credit to Toyota that a replacement is still available, but it costs almost $1200 retail. In my experience of replacing exhaust components on various makes of vehicles, I’ve never found an aftermarket part that is comparable to OEM. Their fit, finish, appearance, and durability are always disappointing. I looked at all that RockAuto offered. The prices were great, but nothing struck me as a quality part. My solution was to pull the OE front pipe out of a Previa we own that wasn’t intended to be a parts car, but with this step is closer to becoming one. This pipe had “only” a quarter million miles on it, but having spent most of its life in AZ, it was solid. I did have to cut and weld in a new flex section.
So, I have two questions: Can anyone recommend a quality aftermarket front pipe? Has anyone bought Toyota parts from PartsOUQ.com (they’re also on eBay) from UAE?
Thank you.

[buzz2401]

I bought a aftermarket one from a big name in exhaust systems and the flex portion of it failed after 50K miles so i just cut flex out and welded solid been working good since.