EGR Codes (P0401, P0403) and Cooling system

rgorke

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I began getting a periodic P0401 EGR Insufficient Flow code in my 2004 LS V8. I pulled the EGR valve and cleaned the insides with carb cleaner and reinstalled. Fortunately I had an extra metal gasket. Of course I dropped one gasket and it slide under the intake manifold. I tried to retrieve it with one of those long grabber snake things and managed to get it securely lodged somewhere in the bowels under the intake. The other "of course" is that the vacuum harness between the EGR, throttle body and fuel pressure sensor cracked in several places during removal. I was able to reconstruct the harness with vacuum line from the local NAPA.

Once i got the EGR reinstalled, I then got a P0403 and P0108 code. The fix was disconnecting the EGR electrical connector and cleaning with Deoxit cleaner and reconnecting. I'm not quite sure if it was the Deoxit or I didn't have the connector fully seated but now no codes after 300 miles of driving. I do have a new EGR coming from Rockauto. Debating whether to put the new one in or return it.

Now to the cooling system...when I removed the EGR, I had a clean line of sight to the 9N499 neck that had coolant stains on the base. I cleaned off the coolant stain and after I drove the aforementioned 300 miles, I can see a line of seepage coming from the under side of the 9N499 neck starting at where it connects to the 8548 main crossover pipe body. I did a full cooling system replace about 4 years ago including all the plastic parts, thermostat, hoses, degas, etc. I am thinking the O ring between the 9n499 and the main crossover body has failed and/or is not seated properly. I'll start by replacing the O ring rather than replacing both the 9N499 and crossover pipe.

The car is NOT overheating. On the freeway it stays under 205 (which is the norm) and occasionally up to 210 sitting in traffic with the AC blowing.

Thoughts on if replacing just the O ring is a fools errand. I am one of the first to advise a full replacement of cooling system parts but since it has only been 4 years, I'm not sure that is warranted.
 

joegr

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Thoughts on if replacing just the O ring is a fools errand. I am one of the first to advise a full replacement of cooling system parts but since it has only been 4 years, I'm not sure that is warranted.
I can't answer that, but do be aware that either of those two parts may break during the process of replacing that o-ring. I wonder how long the new parts that you put in four years ago sat "new" on the shelf in a warehouse somewhere?
 

rgorke

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I can't answer that, but do be aware that either of those two parts may break during the process of replacing that o-ring. I wonder how long the new parts that you put in four years ago sat "new" on the shelf in a warehouse somewhere?
Right, that's the problem with an 18 year old car...and I should have added that they were Motorcraft. I may just replace everything. the most expensive part is the crossover pipe.

Unrelatedly, I looked in the manual and didn't see a normal replacement interval for coils. Spark plugs are 100,000 miles. Maybe the coils don't need to be changed as long as they are good?
 

04_Sport_LS

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If you replace that large o-ring on the neck... you "should" be good for a few more years.

Just lube the o-ring with a little coolant before installing the neck in the back of the crossover pipe.
 

rgorke

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If you replace that large o-ring on the neck... you "should" be good for a few more years.

Just lube the o-ring with a little coolant before installing the neck in the back of the crossover pipe.
Thanks, I was just looking to see if the O ring "could" be a source of potential failure. With 271,000 miles, I need to make sure I nip issues in the bud.
 

joegr

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What I saw was that the o-ring would flatten out over time. While it works well when everything is correct, it is (in my opinion) a design weakness. Also, a little caution here. I once chased a leak that I was certain was that o-ring, and it turned out not to be.
 

joegr

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In my case, it was actually spraying from where the crossover tube assembly met one of the heads, spraying back and hitting the tube rising from the top, so it looked like it was leaking at that o-ring. That said, that hose is a good suspect too.
 

rgorke

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What I saw was that the o-ring would flatten out over time. While it works well when everything is correct, it is (in
... like the throttle body heater hose behind the gooseneck... that when leaks... the coolant flows toward the rear of the block???

my opinion) a design weakness. Also, a little caution here. I once chased a leak that I was certain was that o-ring, and it turned out not to be.

In my case, it was actually spraying from where the crossover tube assembly met one of the heads, spraying back and hitting the tube rising from the top, so it looked like it was leaking at that o-ring. That said, that hose is a good suspect too.
Thanks guys! I'll be sure to inspect everything closely to ensure that the leak is from the o-ring or from somewhere else. Even though the existing EGR seems to be functioning correctly, I have decided to install the new Motorcraft EGR I got. With my luck, as soon as I returned it, the codes would come back.
 

rgorke

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Since it annoys me (it doesn't take much these days) when guys don't give updates on repairs...here we go!

I replaced the O-ring between the 9N499 neck and the crossover pipe and the O-ring was completely flat. When I used my handy dandy SO O-ring pick (those things are awesome!), the O-ring just snapped in half and part of it crumbled off. Also, the end of my thermostat housing cap crumbled off after I removed it. The O ring on the cap still stayed in place but I will be replacing it.

The end of my ordeal dealt with putting the EGR valve back on. Of course the threads into the throttle body got a bit crossed, so I carefully used an M8 tap and chased the threads and was able to successfully get the EGR mounted. The EGR is a huge pain to get lined up correctly with the stiff EGR tube not allowing much maneuvering. One thing that helped tremendously is the MAC 27mm thin profile wrench I picked up a few years back. I think it is an S157A. It has enough of an offset so that you don't come near the fuel pressure sensor hose connector as you turn the EGR tube connector.

Everything buttoned up, bled the system and now running at the low 190s. Strangely, as I was doing the bleeding procedure, I wasn't getting any heat/defrost for quite a while even with the coolant temp in the 200s. I turned the heater on and off and gave the DCCV valve a few gentle taps to see if something was sticking and then the heat came on. Not sure if it was just turning the system on and off or a few gentle raps on the DVVC valve. It was changed in mid 2016. I'll keep an eye on that...
 

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