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Exhaust manifold problems.

GreatOdin'sRaven

NAXJA Forum User
Location
Las Vegas, NV
1999 limited - 6cyl/4.0.

Had a rusted freeze plug - causing slow leak and over heating.

Removed valve cover, head cylinder, fuel injectors, intake manifold, exhaust manifold.

Took head cylinder to shop. No cracks. Had it Cleaned it up, new valve seals installed.

Inspection of parts:

1) Cracked intake manifold: purchased this: Dorman 615-610 Intake Manifold https://www.amazon.com/dp/B009ZBQDUG/ref=cm_sw_r_cp_apip_k5jkTmoTHLENu

2) cracked/corroded fuel injectors - purchased these: http://m.ebay.com/itm/271530798451?_mwBanner=1

3) Exhaust manifold cracked in multiple
Places - purchased this: DNA Motoring HDS-JC9140-BK Stainless Steel Exhaust Header Manifold https://www.amazon.com/dp/B00QKJGKIQ/ref=cm_sw_r_cp_apip_i5VWULFX5P5xy

I followed the installation of everything to the T.

Installed head cylinder, new exhaust manifold (with loose down pipe), new intake manifold with new hardware.

Here's what I noticed: the exhaust manifold and the intake manifold flanges were not the same thickness.

This new exhaust manifold flanges is thinner than the stock one.

The bolts go in straight but since the flanges are different in thickness, the washers go on a little slanted.

40517e727c4b74a4ec2b63716ee7690a.jpg


I torqued down new harware in the correct sequence following the Haynes manual and put everything else back together.

When I started the Jeep, it sounded like it was trying to escape from hell.

The first few attempts it sputtered and died. After that it seems as if its trying to commit suicide by RPM death, instantly climbing to 4 or 5k before I promptly shut it back off.

Since the engine has only been on for a few seconds, it's hard to investigate much, but I know for sure there's an exhaust leak

What I tried so far to fix the problem:

1) checked all vaccume lines, sensors and plugs
2) cleaned the IAC sensor
3) cried
4) googled this sh**

After searching, I found that other people have had the same issue as me after replacing exhaust gasket or exhaust manifold

My question is: has anyone else ever seen such a thin aftermarket exhaust manifold flange? what would you do in my situation to fix this? Do you think the difference in thickness is causing the problem? Should I shave down the intake part?




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i would bet that you now have an intake leak.

X2 on that. You could fix the different thickness manifolds with some custom washers, you'll need a lathe and mill and some bar stock for that. A machine shop could make those at a reasonable cost, they wouldn't have to be close tolerance.
I would check the new injectors for proper sealing to, maybe re-install the factory ones. Mine are cracked, but I think that's more of a cosmetic thing.
And codes in the short time it ran?
 
i would bet that you now have an intake leak.
No doubt, there is a serous leak. Nothing else would allow engine to rev so high, so quickly.
He may just have the top or bottom manifold bolts unevenly tightened or it could be a gasket problem.
Might try loosening all the manifold bolts and then evenly retighten them.
If that doesn't work, cut your losses and remove the manifolds and start over, after inspecting the gasket for damage.
To address the differences in the flanges, I would make thick, custom washers, with cut steps, to deal with the difference flange thicknesses, helping to evenly tighten them.

I bought one of the aftermarket, 99+ intake manifolds and found the ports to be way off, requiring a lot of work, with the die grinder, to better match the manifold's ports.
 
The high RPM's indicate an intake manifold leak. The manifold is likely not flat and flush to the head. Check it for flatness, and make sure it is not getting hung up on the dowels in the head.

Have a machine shop mill the intake washer flats to the necessary thickness.
 
Thanks guys!

Did not run any codes. But good idea.

Will loosen everything and retighten.

If it doesn't work, I'll remove everything, have custom washers made and try again.

Thanks for the help!




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I would return it back to Amazon as new defective and replace with a used intake manifold.

Many Dorman products are of exceptionally poor quality.
 
Is it just me, or can you physically see a gap between the intake mani and the head in that picture?

Make sure the manifold isn't stuck on one of the dowels!
I see gasket between the head and manifold.

I agree, if the fit up is not perfect, it is time to "stop the job" and find out why.

This new exhaust manifold flanges is thinner than the stock one...

My question is: has anyone else ever seen such a thin aftermarket exhaust manifold flange? what would you do in my situation to fix this? Do you think the difference in thickness is causing the problem? Should I shave down the intake part?
If you have verified the difference in thickness by measuring both exhaust flanges, send that new junk back as sub-standard.

Hopefully you had the intake fully seated before trying to tighten any bolts. If not, you could have messed up the intake. I hope this learning experience is not too costly for you. :(
 
Yeah, I'll have to look through all of this.

I may send the exhaust back if this doesn't work out. It's definitely thinner. I still have the stock one and can put my caliper on it and send them a pic for a refund.

But still gonna try to make this work out with what I have. First time doing this kind of engine work. Fun stuff. Get a jeep they said...


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Re-reading this thread, so the exhaust is thinner than the one you removed and the intake is the same as the one you removed?
 
Make sure the headers aren't interfering with the intake. Installed some APN headers on a 2001 a while back and the header tube for cylinder 5 interfered with a cast "gusset" (no idea what else to call it) between runners on the intake. Had to cut some of it to clear it and get them fully seated. The thickness difference shouldn't be an issue (mine was more substantial).
 
But still gonna try to make this work out with what I have. First time doing this kind of engine work. Fun stuff. Get a jeep they said...

Yup, you purchased an adventure.

Myself, I would send that thin-flanged pile back in a heartbeat.
 
Make sure the headers aren't interfering with the intake. Installed some APN headers on a 2001 a while back and the header tube for cylinder 5 interfered with a cast "gusset" (no idea what else to call it) between runners on the intake. Had to cut some of it to clear it and get them fully seated. The thickness difference shouldn't be an issue (mine was more substantial).



Thanks! You give me hope! I'll have to really inspect everything really well.



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I just went through this with DNA motorsport. I emailed them before I bought the manifold to ask what the flange thickness was. Their response was that the manufacturer didn't specify that measurement but it was guaranteed to fit all oem measurements. My DNA manifold measures 0.39" and a stock is 0.493". I'm guessing they both start out with 0.5" flange stock but grind more off to compensate for warpage. Again just a guess. I filled an informal complaint. They gave me back $20 and I got to keep their POS manifold. I contacted speed_daddy and emailed "Nikki" the customer service rep.
 
The Banks('98 on a 2000) I just bought was a perfect fit! Love the fit from the header to the existing downpipe, simple splice!
 
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