Exhaust Manifold Cracked (again)

[fixt]

As part of my quest to improve mileage, I was changing plug wires yesterday and saw that my exhaust manifold on passenger side was cracked, again between #2 and #3 cylinder running down toward the collector. No noise to clue me in, as it was only a a crack instead of fully separated. The previous original manifold had broken completely under the insulation. The replacement was Dorman part 674357 at around 129,800 or so. About 17121 miles on the manifold since 4/25/11 when it was installed.

According to Dorman, Manifold flatness should be within .010 before installation.
They do not come flat, at least mine didn't and was almost .030 from high to low. I'll have the new one milled closer to spec because that job sucks due only to the collector bolts.

From my log book, mileage was at 9-10 prior to replacement with unbalanced readings on O2 sensors, with bank 2 voltage offscale. After replacement mileage improved to 14.2 with O2 bank 2 on scale and changing as it should.
I do not understand bank 2 O2 sensor behaving in such a manner when the problem was the bank 1 (passenger side) manifold. Its possible I wrote it down wrong I suppose.

According to Rock Auto it is warrantied as long as you own the vehicle (limited lifetime). I submitted the claim so we shall see. I do have confidence in Rock Auto. I just received email stating return authorized. Pay first refund later as I expected... but its still covered
Still as good as the original Ford manifold which also broke and was priced at $630 bucks.


Looks like it cracked paralell to their crappy Chinese weld.

This is the original manifold taken off 4/25/11

This was Turdles manifold... same break same place between cylinders #2 and #3

Dorman spec was .010 flatness, here's how it came

 

[Accarguy]

I would see if you could get it from another supplier other than dormant maybe from ford?
Norman parts ave not been up to quality.

 

[fixt]

Well, I don't think much of Dorman parts either, but it is covered under warranty and the original Ford welded headers were prone to break as well.
It will cost me shipping the manifold back to them, but still much less than a new full price one. The only other maker available at Rock Auto is ATP... I don't know anything about them either. They talk about being based in Elk Grove IL but say nothing about manufacturing facilities. They might be made by Dorman for all I can tell.

EDIT: After thinking about it a little, I went to Rock Auto and cancelled the Dorman manifold and ordered the ATP manifold instead. Its about $20 more than the Dorman, but maybe it will last. I'll report on initial flatness as well when I get the thing.

 

[SoHK_alumni]

Consider moving to a later cast manifold and simply plugging the EGR port on it.

 

[fixt]

Will the cast manifolds bolt up to the existing exhaust system?
If so, what models or part numbers will work?
A cast manifold sounds really really nice. I'd like that.

Edit: I went and dug through Rock Auto Parts. Looks like sometime in 1998 they changed the welded tubular manifold to a cast looking manifold. It does not look like it will bolt up without changes to the exhaust collector as the angle appears to be different.
A new exhaust system is not in the cards.

 

[delexploder]

They crack too , I have tossed out a few sets , at least with the older tube style you can wield them back together , cast can be welded but it generally doesn't hold on thin dirty cast iron manifolds and actually tends to make them more brittle

 

[SoHK_alumni]

Ford moved to the external EGR port and cast exhaust manifolds the later half of the '97 model year. Any late '97 through '01 used the cast.

No, they're not perfect but they are much less notorious for cracking.

Other than the external EGR port, they are interchangeable, oh and usually less expensive!

 

[fixt]

The welded tubular are made for external EGR and come with a pipe cap for plugging. The cast manifolds look to cost about half of welded tubular, but then I'd have to add in the cost of new exhaust system or at least some method of adapting the exhaust collector angle to the cast manifold.
I guess I'll just continue on with welded tubular and prepare it by milling flat and inspecting welds prior to install.
Maybe I can get it to last or at least outlast me.

 

[delexploder]

Its the same exhaust , they are interchangeable , I have the early style on my 99 motor , I'm setup as a late external egr 97 in my sport , I also have a few sets of each kind as I keep the ones I find that aren't cracked

 

[fixt]

ATP Not so Great Either

OK, I got the ATP brand manifold in and checked it out to see what the differences are. As a side note, Rock Auto considers this a separate purchase and won't warranty the Dorman manifold replacement unless I order the same replacement part. My fault for not reading return policy not closely enough.

The ATP is made of welded seam tubing, and it looks like enough side clearance to get to manifold bolts easily enough. The tubing seams are not nearly as pronounced as the Dorman above; tubing welds are on the inside. It comes with the EGR plug installed.
But... the exhaust flange for cylinders 3-4 was .020-.024 low compared to the flange for 1-2 cylinder flange, using straight edge and feeler gauges. Label on the box made in China Graywerks by ATP Automotive. It would still require planing to get it flat, an added cost to a more expensive part. So its going back for refund.

Inside the collector viewing the #4 cylinder runner, quite a protrusion for flow restriction

Weld on inside of flange, typical of all four

Conclusion: No net gain by trying different manufacturer for welded manifold.
It looks like cast is the way to go. I'm betting it will flow better.

EDIT: Dorman manifold recieved. Seamless tubing used for runners and the #4 runner doesn't protrude into the collector like the ATP part does. It does have the weld where it cracked; the ATP manifold does not.
But... the bolt flanges are still way out of spec. Measured worst at #1 reading .045 low out from the #3- #4 flange. Again using straight edge and feeler gauges.
From the Dorman install sheet: (No install sheet with the ATP)

(end to end runout should be no greater than .005 for V6 engines, .010 for inline 4 cylinders or V8's and .015 for inline 6 cylinder engines)
Correct mounting runout prior to installing replacement manifold or cracking will recur.

Note that of my three samples, none were bolt on ready parts due to excessive runout on manifold flanges

 

[fixt]

Update

I got the manifold back from the machine shop from resurfacing. A straightedge laid across it looks really good.
$45 to resurface the manifold to .010 or less flatness from the NAPA next town over. No milling as there is no way to fixture the thing for surface milling and it would require building a special fixture to hold it in a mill, not worth the cost in my case. The guy it went to had a sanding table usually used to resurface heads.

So lessons learned are.
(1) Exhaust manifolds do not come ready to bolt on. The Ford manifolds break just like the chinese ones
(2) Next time it cracks or breaks, go to the cast iron manifolds as you can get both for the cost of one welded tubular manifold.
(3) Dorman and Rock Auto stand behind their parts warranty as I will be refunded the cost of the new manifold minus $9.95 Fed Ex return shipping, about $95 or so in my case
(4) Its still a right pain in the arse as I'm replacing it now, the old one is off and I'm taking a break.
(5) I'm very happy I put antisieze on the manifold bolts previous install

I got a pic of the new surface; I'll edit the pic in after I'm done today
Back to work.

 

[masospaghetti]

I would second getting a cast manifold, they do bolt with no major issues, you may need to modify your oil dipstick tube though.

 

[Turdle]

We replaced the above referenced picture with the cast version. The downpipe angle is identical.

 

[fixt]

The consensus says cast from those in the know, so when it breaks again and I'm reasonably sure it will, I will definitely go with the cast from a 1998. That seems to be what most used for the 2nd generations. I don't know if it matters up to 2001. I was all worried about the collector angle bolting up but everyone thats done it says its the same. Good enough for me.

If it had not been under warranty, I would have went with cast this time. That did make the repair fairly cheap though.

Do the cast manifolds come flat or is surfacing required for them also?
I would think they come flat but I don't know. I would check anyway I think
Just finished the job except for torquing lug nuts and putting away tools. Not as bad as last time but I don't want to do it enough to get good at it.

 

[Turdle]

In my case the truck in question was a 98 , the cast manifold used for replacement was from a 2000. There is no difference. Since they are cast, then machined, they remain pretty flat. Also, the ports are larger.

 

[markfothebeast]

I had a cracked exhaust manifold on another vehicle and welded it up. I found that the underlying cause was the movement of the exhaust system pulling on the manifold under acceleration. My first clue was that there was lack of exhaust hangers present supporting the exhaust system. I welded on more hangers to relieve some tension from the manifold being tugged on. My crack appeared at the cyl closest to the firewall where the most pressure would be applied during engine movement. No problems since.