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Old 04-03-2011, 11:22 PM   #31
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At the risk of sounding stupid and acting like captain obvious, from what I'm getting out of your theory is that pretty much the problem lies within the ECU not knowing when the manifold passage is blocked, since it only looks at the EGR sensor for comformation.

So if you could "switch" off the EGR maps (not saying that you should, just throwing a "what if" situation out in the open). Wouldn't there be less of a chance the HG's to blow since the "Compensating Maps" are not there to kick in, meaning that the timing will not advance and fuel mixture will not lean?

Just thinking outloud here..
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Old 04-03-2011, 11:30 PM   #32
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Originally Posted by Homeboyx View Post
At the risk of sounding stupid and acting like captain obvious, from what I'm getting out of your theory is that pretty much the problem lies within the ECU not knowing when the manifold passage is blocked, since it only looks at the EGR sensor for comformation.

So if you could "switch" off the EGR maps (not saying that you should, just throwing a "what if" situation out in the open). Wouldn't there be less of a chance the HG's to blow since the "Compensating Maps" are not there to kick in, meaning that the timing will not advance and fuel mixture will not lean?

Just thinking outloud here..
Yes... and yes.

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Old 04-04-2011, 10:07 AM   #33
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Quote:
Originally Posted by Vic Cardenas View Post
I have a crappy Haynes manual sitting in front of me.
It says firing order is, 1-4-2-5-5-3-6
it literally says this with two 5's
I just went out on my engine simulator and spun the pulley by hand - I got 1-4-2-5-3-6. Kind of weird, it fires from one bank to the next from front to back. I always thought the legend might have a weird firing order due to the strange plate they put in separating the two bank's exhaust down pipes in the y-pipe merge.

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Old 04-04-2011, 02:54 PM   #34
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Originally Posted by sr5guy View Post
I just went out on my engine simulator and spun the pulley by hand - I got 1-4-2-5-3-6. Kind of weird, it fires from one bank to the next from front to back. I always thought the legend might have a weird firing order due to the strange plate they put in separating the two bank's exhaust down pipes in the y-pipe merge.

-Matt
I don't know any v6 that has a different firing order than that. I find it to be the easiest one to remember because you take 1, add 3 to it ( for 4) and then just add 1 to each number continuing. Also, I've always noticed that cyl 5 is at TDC (tho wrong stroke) when cyl 1 is at TDC.

(there are a couple v6s that use a different firing order in that they label the cylinders differently, but the overall firing order is the same)


Anyway, fantastic job by you (and Q if he helped with this part) of finally proving via EGR modifier what many of us (including you obviously) have been suspecting for years.
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Old 04-04-2011, 03:47 PM   #35
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A trick I picked up from my engine class is you take the numbers 123456 and split them in half 123/456. Put the last three numbers underneath the first three and count them one from the top and one from the bottom.

Ex.
123
456

1,4,2,5,3,6.

Hope this helps.
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Old 04-04-2011, 05:43 PM   #36
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OK > I printed off Vic's cylinder numbers from post #19.

I remember when I asked the guy who rebuilt my engine which cylinder / head gasket blew out, he pointed to #6. I'm assuming drivers side are cylinders 4-5-6 and passenger side is 1-2-3.

This would make sense to me for I had pools of coolant on the garage floor at driver's side rear cylinder.

Not a surprise that Tyson is staying out of this thread.
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Old 04-04-2011, 06:20 PM   #37
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Not trying to be a jerk and prove you wrong, considering I know nothing about engines or how they break, but:

BHG #1: ~130,000 miles. Engine repaired.

BHG #2: ~195,000 miles. Engine swapped.

ALL scheduled maintenance was done (doesn't say EGR was cleaned, but says 30K, 60k, 75K, etc. services were performed), so unless the dealership was incompetent/ ripping me off, the EGR was inspected/cleaned as it should have been. Or maybe I just had a bad engine? Any other ideas as to why my HG's kept blowing?

Edit: Also, let's say someone has a 250,000 mile Legend that hasn't had BHG before, but the EGR had never been cleaned or inspected. If they were to clean their EGR and nothing else was about to cause BHG, would that prevent a BHG, or would the damage already be done?
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Old 04-04-2011, 06:40 PM   #38
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Quote:
Originally Posted by BluBrett View Post
Not trying to be a jerk and prove you wrong, considering I know nothing about engines or how they break, but:

BHG #1: ~130,000 miles. Engine repaired.

BHG #2: ~195,000 miles. Engine swapped.

ALL scheduled maintenance was done (doesn't say EGR was cleaned, but says 30K, 60k, 75K, etc. services were performed), so unless the dealership was incompetent/ ripping me off, the EGR was inspected/cleaned as it should have been. Or maybe I just had a bad engine? Any other ideas as to why my HG's kept blowing?

Edit: Also, let's say someone has a 250,000 mile Legend that hasn't had BHG before, but the EGR had never been cleaned or inspected. If they were to clean their EGR and nothing else was about to cause BHG, would that prevent a BHG, or would the damage already be done?
Removing the intake manifold and EGR pipe to clean them out isn't in the scheduled maintenance and it's not likely something the dealer would do, at least the intake manifold part isn't, maybe cleaning the pipe is. If you failed smog with high Nox then it would probably be recommended by the tech to clean the EGR, but he wouldn't know that the manifold has a chamber that gets completely blocked. There's a very good chance that the dealer was following the guidelines to the best of their ability and didn't address the potential problem Matt is pointing out. Intake manifolds really shouldn't need to be removed for regular maintenance on any car, and to the uninformed it would be the same on a Legend. Matt is trying to say that it's not the case with the Legend.

As to your imaginary scenario, it goes back to what Matt said about the HG seeping very slightly at first and showing almost no effects at first. There could be no damage done or there could be a process that is happening. HG's will deteriorate eventually and if some part of the gasket has already started to fail then eventually it will completely.
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Old 04-04-2011, 06:41 PM   #39
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^ Intake manifold removal just to clean out the EGR is VERY unlikely for a dealer to do as part of regular maintenance. My 98 Accord (J series motor) had issues with the EGR system getting clogged on the earlier intake manifold designs (much like the C32 v. C35 bottom section of the manifold). It's recommended to clean it out but the dealer won't touch it unless an engine code is tripped, you ask for it specifically, or, there is a recall in effect.

Thankfully the J series motor (OBDII) has a code for insufficient EGR flow which senses that there is actually exhaust gasses entering the intake manifold.

Not that I can give any additional credit to Matt's hypothesis as he knows for more than I, but I do know quite a bit about how engines work and it seems extremely likely that he is correct. The main thing that has me convinced is the fire ring "herniation", I mean, you would have to have some high cylinder head temps and huge spikes in pressure to cause that, suggesting long-term detonation damage. That and the EGR compensation maps, which I saw in his earlier thread, it just looks like a recipe for detonation and extreme pressures and temps at the cylinder head; and since the latent heat is going to be the worst on the rear most cylinders, it really makes a lot of sense.

I know one thing is for sure, the next 3.5 I do, or have done (lol...yeah, I'd have to win the lottery for that ), I am going to use the bottom of the 3.5 manifold that I have lying around with my Type II manifold. I actually remember Reboticon's thread a long time ago, when he compared all of the intake manifolds and noticed the baffle for the EGR system in the 3.5...I remember thinking that that looked like a somewhat significant change, though, at that time I wasn't sure how. Of course I have learned a lot since then and completely understand it. Also, the PCV oil catch can seems like a GREAT idea. It's funny, why do I think about such things with my older Cherokee's and older, how should I say, more simple engine designs but never thought about adding one for the Legend.

Anyway, Matt, we seriously owe you SO much for your persistence, time, effort and, well intelligence, to try and figure out why BHG/SHG's happen so frequently. Also, and I know that this is very insignificant, BUT, it may also be why there are so many repeat failures as most people aren't thinking EGR has anything to do with a head gasket job, most jobs would probably just go through the top end, do the HG and seals up top and button it back up, only for the gasket to repeat failure relatively shortly after the job. Thanks again for all of the information that continues to help us in the Legend community

Important Question below:

Ok, going out on a limb here but, other than maintenance of the EGR system and a PCV oil catch can, just wondering if an auxiliary EGR flow detection system could be integrated into the the Legend ECU, something that could trip Code 12 by using a sensor that uses the same range of voltage as the EGR valve lift sensor. Perhaps that could be tied in together or used instead of that particular sensor. That way at least the EGR compensation maps would be bypassed appropriately, to PREVENT damage.

Last edited by soloist; 04-04-2011 at 06:59 PM.
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Old 04-04-2011, 07:44 PM   #40
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Quote:
Originally Posted by 4HondaOwner View Post
OK > I printed off Vic's cylinder numbers from post #19.

I remember when I asked the guy who rebuilt my engine which cylinder / head gasket blew out, he pointed to #6. I'm assuming drivers side are cylinders 4-5-6 and passenger side is 1-2-3.

This would make sense to me for I had pools of coolant on the garage floor at driver's side rear cylinder.

Not a surprise that Tyson is staying out of this thread.
AFAIK, Tyson has had his EGR regularly serviced .

-Matt

Quote:
Originally Posted by BluBrett View Post
Not trying to be a jerk and prove you wrong, considering I know nothing about engines or how they break, but:

BHG #1: ~130,000 miles. Engine repaired.

BHG #2: ~195,000 miles. Engine swapped.

ALL scheduled maintenance was done (doesn't say EGR was cleaned, but says 30K, 60k, 75K, etc. services were performed), so unless the dealership was incompetent/ ripping me off, the EGR was inspected/cleaned as it should have been. Or maybe I just had a bad engine? Any other ideas as to why my HG's kept blowing?

Edit: Also, let's say someone has a 250,000 mile Legend that hasn't had BHG before, but the EGR had never been cleaned or inspected. If they were to clean their EGR and nothing else was about to cause BHG, would that prevent a BHG, or would the damage already be done?
Anytime someone begins a sentence with "I'm not..." I automatically think just the opposite

I think Wes and Soloist answered your question adequately, if you'd like I can go into further detail.

-Matt
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