2 cracked down pipes in a month, anyone had this problem?

[im2bad4ya]

Okay, so here is my conundrum. My BP engine is from a '94 Protege. For those that don't know, the headers and down pipe are unique to this year, unlike the 90-93's which are the same. A few weeks ago, this happened to me while driving: http://www.mx-3.com/phpBB3/viewtopic.php?f=20&t=78681

Lower ball joint popped out the spindle because pinch bolt wasn't tightened. Axle was damaged and the down pipe cracked (where it bends), everything else was fine after inspection. So since these are under warranty, I got them replaced. My replacement down pipe came in and I installed it, and not only 3 weeks later, the pipe is cracked again, same spot....but no accident, just developed a crack...what the hell is going on???!!

The down pipe was a WALKER 52196. I was just wondering if anyone else has had an issue with this down pipe or Walker exhaust parts in general.

If you go to amazon.com, where i bought it, and try to search for it, you'll see it's 'under review' (thanks or NO THANKS to me) http://www.amazon.com/Walker-Exhaust-52 ... 398&sr=8-1


So instead I ordered a BOSAL 751-115. I hope this one doesn't fail me.


When i had the B6 engine, i ordered a front pipe from discountbodyparts on ebay, never had any problems or issues, and as a matter of fact, I hope to put that up with a few other spare parts for sale, sometime in the near future. Reason for replacing THAT down pipe? It was also broken, but NOT THE SHAFT.....the BRAIDING had rusted and fallen out............I'm just saying.

[Daninski]

Bosal makes cheap aftermarket crap as well. Bought my Bosal cross over pipe for my MX6, it broke from the mount twice.

[im2bad4ya]

Well I already put the order in for the Bosal pipe. It's nice to know that it has a 1 year warranty so I can always return it for a replacement or a refund. But I couldn't do that with the ebay stuff, that's why I'm gonna avoid it for now. Unless all else fails, there's another manufacturer that makes the down pipe: http://www.ebay.com/itm/Mazda-Protege-1 ... 180wt_1141

FAP part #60896

I haven't seen it in retail, just ebay. Crossing my fingers this works, I spend more time under the hood of this car than in the cabin!......True labor of love

[Daninski]

Funny, I find Ebay headers cheaper than buying straight up exhaust parts.

[Ryan]

Could you post a picture of the failure? I'm curious.

[wytbishop]

Something is out of alignment and the downpipe is under some sort of stress. Another possibility is that the engine is moving more than it used to since your little ball joint issue. Either way I'd say something changed when the car hit the ground and it's causing your exhaust to be experiencing some strain that it isn't supposed to.

That's what I think.

[Daninski]

The stress-strain curve of a metal will depend on its composition, heat treatment, prior history of deformation, and the strain rate, temperature, and state of stress imposed. Fatigue occurs when a material is subjected to repeated loading and unloading. If the loads are above a certain threshold, microscopic cracks will begin to form at the surface. Eventually a crack will reach a critical size, and the structure will suddenly fracture.
Check your engine mounts.

That's what I think.

[im2bad4ya]

I'll post a pic soon. For now I'm gonna borrow my friends '08 CTS to get around (nice!). But it's not like I had a hard time putting the down pipe on, it bolted without struggle or problems (that's to say the headers line up fine along with the cat). I'd figure if it was under stress that the braided part of the pipe would take the hit, not the pipe itself.

[wytbishop]

The stress-strain curve of a metal will depend on its composition, heat treatment, prior history of deformation, and the strain rate, temperature, and state of stress imposed. Fatigue occurs when a material is subjected to repeated loading and unloading. If the loads are above a certain threshold, microscopic cracks will begin to form at the surface. Eventually a crack will reach a critical size, and the structure will suddenly fracture.
Check your engine mounts.

That's what I think.

Didn't I say that?

[Daninski]

I was just reiterating.

[im2bad4ya]

Here it is:







The blackness around the pipe was my attempt at Puerto Rican welding, AKA duct tape



Anyway, here's a pic of the subframe, new but broken down pipe, new cat, and new resontaor.



If you notice, the driver's side hanger of the cat is not hanging, it's up a little, and this kinda forces the down pipe up a little bit, which may or may not be why the pipe cracked. That's because the cat and the resonator are welded together, not bolted on. But I'm skeptical, because the pipe bolts on with ease, it's not a dramatic amount of force, and my B6 pipe was fine (I did the exhaust when I had the old motor).

Here's a shot of the pipe off the car:




Here's how bad the crack actually was (I was able to bend the pipe where the crack had formed, I didn't break it any further to bend it):




Here's a shot of the down pipes (new BP to the left, damaged BP in the middle, B6 to the right):



Also, notice how the damaged down pipe is ribbed (from Walker). The replacement I got isn't (from Bosal). I'll see if this makes a difference. Hopefully this will be the last I have to deal with this issue.

[wytbishop]

The Walker OEM replacement piece is "Crush Bent". It's just a lower cost way of shaping the tube. The Bosal unit is "Mandrel Bent" which is done on a fancy machine that maintains the smooth ID of the pipe as it is being bent. The Bosal one should be a little stronger assuming the material is similar.

Looking at those pictures it occurs to me that there is probably too much weight on the horizontal pipe. Maybe a hanger is missing or something? it looks like as the car bounces down the road the horizontal section of the pipe is probalby bouncing up and down which will slowly but surely cause that crack regardless of the material or how it's bent. Consider adding another bit of support just ahead of that flange. Not a rigid support just something to absorb some of the motion.

[Daninski]

From the 3rd picture it looks like the exhaust is bolted directly to the structure between the expansion pipe and the cat. That's a big no no. It should be hung via a rubber donut. If that's the case there's your answer, get it fixed.

[Josh]

From the 3rd picture it looks like the exhaust is bolted directly to the structure between the expansion pipe and the cat. That's a big no no. It should be hung via a rubber donut. If that's the case there's your answer, get it fixed.

Not on the 4 banger. they are all like that.

The problem was the downpipe brace you can see part of it there in the first pic. if you had that connected it probably put too much pressure on the pipe pulling it towards the engine and causing it to crack. that is a good reason not to use this type of piping your Bosal pipe is SOO much better quality over the other.

[Daninski]

Good point Josh.