dan26aus posted:

Hi hl
from EGR to the inlet manifold.

hl posted:

Hi,

On blocking the EGR valve. It would certainly be illegal to do that, but who is to know. However, the effect of hot (oxygen poor) exhaust gas being fed into the combustion chamber, is actually lowering the temperature, so disabling it may not be such a good idea.

Cheers

Member - Glenn D (NSW) posted:

Hows it going Bob,

I reckon the only reason the EGR valve is there is for emission control after all it is a European engine.

It was pretty common for the emission control to be disabled on older cars. I have been wondering the effect of blocking this off but have been way too busy to check it out .

The fact that it closes on full throttle tells you what its doing to your performance.

Would you be able to email me the name of said mechanic : gwdixon at tpg dot com dot au.

Thanks . Glenn.

hl posted:

Hi,
True, it is part of the emission control system, but then, the whole engine is a bit of a maze of different sensors and gadgets, not like the diesels of the past at all.
In all respect to your mechanic, he is probably not an engineer and may not realize the full repercussions of tampering with what is a complex engine management system. You will note that the EGR setup in that engine is rather different from older ones, where just a small tube fed a bit of exhaust gas back into the inlet. This one uses large amounts of EGR under various operating conditions.
Blocking it off might just do more harm than good.
Just my opinion, if anyone knows better, please let's know.

Cheers

Member - Phil G (SA) posted:

I'm with Bob - EGRs cause more problems than they are worth on diesels.
79 series EGR problem

Member - Jeff M (WA) posted:

Bloody oath, I disabled my EGR by unplugging the vacume hose that opens it. Almost immediatly it produced less smoke on hard accelleration and it has been running fine for over12 months like that. As far as pollution goes, they can shove it up there asses, I'm running B100 and am producing less CO2 than my brother's barina. EGR's are only there to try and lower combustion temps by flooding the combustion chamber with CO2 from the exaust when the engine is under load in order to produce less CO2 overall. It's a stupid bloody idea that's at least 30 years old and surley could be updated wtih somthing a little better by now...

Bob on Patrol posted:

I'm no expert in engines or diesels so I based my decision on the advice I received and it all sounded plausible. Given that Nissan remain tight lipped on the true cause of the engine failures we are left to take whatever advice we can get. I cannot remember everything the mechanic said but part of the explanation is as mentioned above the EGR is closed at "full" throttle however when you back off the EGR immediately opens and remains open for seveal seconds before closing again under acceleration. For this period super hot exhaust gases are pumped into pistons 3 & 4. The load of this hot air in some vehicles is spread over all cylinders in some 4wds but the design in the patrol targets 3 & 4 pistons. As I said previously this is only one factor and a combination of other factors would contribute to engine problems like very hot weather, working the engine very hard etc etc .... I'm not the expert but this mod appeared to me to be a worthwhile investment aginst the cost of a new engine. There are risks in everything we do but all you can do is get advice and make informed decisions. As for the legality.... I consider illegal to be a sick bird.

Regards

Bob

Member - Jeff M (WA) posted:

You now what, I reckon this is the most plausable explanation for the ZD30 problems I've heard so far, especially as we all know that a common fault on the ZD30's (espeically the series II's) were the EGR valves.... Perhaps EGR valves are staying open over heating cyl. 3 and 4 causing wholes to be burned in pistons. This maybe why some die and some don't. I reckon if I were a ZD30 owner I would immediatly be blocking off or disabling the EGR as it has been proven many times over that it causes no detrimental effects to diesel engines. At least that way you are plugging one more hole (so to speak) that could potentially be the cause of massive engine failure.

sajiie posted:

if they are staying open, what would be the cause of this and how exactly does the egr operate(mechanically)?? Is there a way of checking it and or cleaning it every now and then to perhaps prevent it from happening.

hl posted:

Hi,
In the ZD30 they are a computer controlled stepper motor. They are also water cooled. I guess the mechanism could clog up with soot and make it stuck but I believe there is some feedback to the computer and it would set the engine check light if it were stuck. It would probably result in sluggish performance if it is open.
As for the post below, a diesel engine does NOT "lean out". High exhaust gas temperatures are usually caused by overfueling and this is usually indicated by lots of black smoke, something you don't see very much on ZD30's. Also, the exhaust gas that comes back into the inlet is ALWAYS much cooler then when it leaves the exhaust port, it can't be "superheated". And as I said in the previous post, feeding exhaust gas back actually LOWERS the combustion temperature, that's the whole idea. If you read about the M-Fire combustion system in the ZD30, you will realize that the EGR system is integral to the engine management. It is not an afterthought that can be left off for different market, as is sometimes done.

Cheers

Leroy posted:

hl,

You say the EGR valve is a water cooled, computer contolled stepper motor? Yo're kidding, right?

Leroy

hl posted:

Well... just have a look at it and look how it is connected to the ECU..........

and, for good measure, here is the Nissan blurb on that engine... I would definitely not mess with the system based on the advice of a bush mechanic:

The measures adopted to accomplish M-Fire combustion include:

optimisation of fuel injection timing;
application of heavy exhaust gas recirculation (EGR); and
generation of strong fuel swirl.
In diesel engines, fuel has traditionally been injected at a point considerably before the piston reaches top dead centre (TDC) of the compression stroke.

In the ZD3O engine, the injection timing has been changed so that the fuel is injected closer to TDC of the stroke, allowing compressed air to enter the expansion stroke, thus combustion occurs after the pressure has started to drop meaning lower pressure at the onset of combustion.

As well, injecting fuel at this point allows ample time for fuel to evaporate — because it is not ignited immediately after being injected — making it possible to accomplish premixed combustion.

In designing the ZD3O engine, Nissan engineers substantially increased the Exhaust Gas Recirculation (EGR) rate. This results in a gradual combustion process in which the mixture does not burn instantaneously following ignition which keeps the combustion temperature from rising.

And a newly-developed helical port is used to generate strong swirl motion to improve mixture formation and promote stable combustion.

Member - JohnR (Vic)&Moses posted:

I see that most of the Patrol posts are about ZD30s here, but the recent TD4.2I has an EGR valve too that is also for the same reason even though it isn't an European designed engine. The EGR valve really is pretty easy to disable with a screw into the control port or a bearing in the control line, assuming of course you aren't in an area where your pollution controls are likely to be checked.

Makes you wonder why things like that are especially set up to reduce your engine efficiency.

hl posted:

Hi...
The EGR system in the 4.2 is very different. It is basically an add-on and simple as you describe. I think it could be disabled without adverse consequences.
Cheers

Leroy posted:

hl,

That's a nice blurb on the engine but you still haven't clarified the statement

'You say the EGR valve is a water cooled, computer contolled stepper motor'

You sure you're not getting confused with the turbo?????

Leroy

hl posted:

Hi Leroy,

Have a look at the service manual and you will see.
It is watercooled and it is a motor, presumably a stepper because there are 6 wires to it. It is called an EGR volume control valve and it does more than just opening and shutting. That's why I think it is maybe not a really good idea to go around "re-engineering" things without fully understanding what is going on.
I don't profess that I do, but looking at it rationally, you would have to think tinkering with a complex, interactive system requires more knowledge then the average mechanic is blessed with.

Cheers

Member - Jeff M (WA) posted:

"I believe there is some feedback to the computer and it would set the engine check light if it were stuck"

HL, one of the problems with early ZD30 was the engine light constantly comming on and a loss in power rectified by replacing the EGR!

Mind you the Series III that we drove on a daily basis at my old work with these symptems had it's EGR replaced and spent over 2 weeks in the local nissan workshop trying to rectify these symptoms. Yes, changing the EGR did stop it almost stopping when the light came on, howerver the check engine light still came on after heavy acceleration and the car would be sluggish until switched off and re started.

Member - Jeff M (WA) posted:

I'd also like to add that these starting problems in the morning before these engines go bang could also be EGR. Trying to start a cold diesel with the EGR valve open would be quite difficult...

hl posted:

Quite a discussion, eh?
Re the post above, I can't see how the valve stuck open would make the slightest difference in how the engine starts.
Cheers

Member - Jeff M (WA) posted:

"I can't see how the valve stuck open would make the slightest difference in how the engine starts. "

Ok I'm happy to be wrong but I know sure as bleep that the EGR is closed at idle to prevent the CO2 from the exaust gas from causing a rough idle, I would asume that this would also cause a rough start. Just and assumption, but it makes sense to me...

My EGR is as simple as a billy on the campfire... All it is, is a vacume operated valvue that opens a connecting pipe from the exaust into the inlet manifold. ie When you rev the motor, the vacume is increased and the valve opens, when the revs drop the vacume is not as strong and the valve closes.

hl posted:

Hi Jeff,

That's the point I was trying to make... The EGR you have on your car is easily disabled and I for one would be happy to give it the chop.......
The ZD30 is a different ballgame as the engine is designed to run with very heavy EGR. The valve is controlled by the computer and at various conditions it will either be fully open, fully closed or somewhere in between. Only the engineers who designed the engine could answer whether there are no adverse effects in disabling it. I guess in a few years from now when the chaps who have closed it off post that they have just passed the 500,000 clicks mark, we'll know it was an ok thing to do.
Cheers

Member - Jeff M (WA) posted:

Yeah I here you HL, but what are the owners of ZD30's supposed to do? Replace 5 engines at less than 100,000k's each while you wait for someone who blocked their EGT to get to 500k with no problems? Seems like a loose loose for ZD30 owners. I reckon if I owned one I'd be doing it, looks like some guys below have done it and had reasonable success so far. There is obviously a risk factor involved, but I guess you gotta way it up. Personally I would think that if it was effecting the engine managment system badly the light engine light should be comming on and there should be a drop in performance as the ECU goes into safe mode, if this doesn't happen that it's a pretty good guess that the ECU doens't give a crap that you blocked it.

Leroy posted:

'like a loose loose for ZD30 owners'

Jeff,

What on earth are you going on about. 5 engines. I have never heard so much rubbish. Yep we all know to death (and really are over it) that the early 3.0l had issues. Like any engine with probs in early life the manufaturer will look at fixing them which Nissan has done. You just don't hear the problems with the late model engines that the early ones had.

Leroy

Member - Jeff M (WA) posted:

Leroy, do a search on this forum, there are reports of series III (the later ones) starting to fail too.
Also when we are talking about faulty EGR and air flow sensors potentially causing these failures, the fore mentioned series III I drove for work also experienced these issues. If it is the EGR and Air flow sensors causing these failures then it is safe to assume that engines such as the series III ZD30 will also be likley candidates for engine failures.

I hope that cleared it up for you.

Leroy posted:

There was one that was posted recently that was an '03 model. Series III's came out in 2002 so yes you may get the odd one. You have to remember that's 4 1/2 years ago. You're stuck back in 2001/2002 when there were lots of early failures. They are not failing like that anymore. MAF sensors failures you see seem to be on those early engines also. And you go on to say
'If it is the EGR and Air flow sensors causing these failures then it is safe to assume that engines such as the series III ZD30 will also be likley candidates for engine failures'
This being the case, we would have an absolute epidemic of series 3 patrols blowing engines. It's just not the case.

Leroy

Member - Jeff M (WA) posted:

I'd say the reason you don't have an "epidemic" is because they have worked out what the problem is now.

ie. When the work patrol started coughing and spluttering, they blaimed us for not changing the air filter reguarly (even though it was a company car that had done ZERO off road or dusty driving and was always service by them) and sent us on our way.

It took TWO weeks over many months for them to work out the EGR AND Air flow sensor were both bung and it was only after alot of fuss kicked up by us that they went to that much effort.

How many patrols owners just got sent away with faulty components burning holes in their pistons because Nissan had ZERO customer service and NFI what they were doing?? That is probally why there were so many to start with and why it has tappered off now. They probally check these things on regualr services to ensure that they are not malfunctioning.

IF this is the case, the best option would be to block the EGR. No matter weather you have a series II or a series IV IMHO.

Leroy posted:

I think initially their mechanics had no idea on diagnosing problems with the 3.0l. Especially MAF sensors. These may of contributed to the problems as well many other factors including high sulfur fuel.
EGR has been used on engines for many years (20?). I don't see this as being the main reason for failures though.

Leroy

Phil12345 posted:

EGR's are designed to cool cylinder temps, and they do when working correctly by returning CO2 back into the engine. However when another faulty componet (MAF sensor) effects the fuel ratio large amounts of hot exhaust gas containing high ammounts of O2 are injested causing the melt down (more fuel, more heat, meltdown). The ECU doesn't have the abillity to detect a faultly EGR on a 3lt patrol, EFI petrol motors do as they have an oxygen sensor in the exhaust and a fault can be logged due to the excessive ammounts of O2 present. These motors recycle huge amounts of exhaust just to keep emissions low. As for the water pipe going into the EGR, this is not for water cooling, its to warm the valve when the motor is first started, allowing for emisions to be controled earlier. In my opinion the EGR combined with a faulty MAF is the cause of the meltdowns. Proof enough is the fact 3 & 4 pistons are the ones being melted and these are the ones directly fed by the EGR. Nissan can not and will not endorse the blocking of the EGR system due to emision laws, I suggest the EGR was updated by Nissan when the problems were identified, however an EGR valve is not designed to last the life of a motor, earlier vehicle manifacture's recomended 80000kms replacement, no one ever did as the mechanics just blocked off the useless things. I suggest the thoughts expressed on the "Bush mechanics" "tampering with" are totally misguided as the "Experts"(nissan) have had their turn to fix this problem and so far have been more concerned in covering their own arses, rather than identifying a problem with an otherwise terrific vehicle. Block those valves boys and bring on 500000kms!!!!!!!!

Outbacktourer posted:

I'll just add one factoid to the mix. My service manual has a supplement issued in July 2001 saying "EGR cooler has been added to ZD30 Engines".

OT

hl posted:

Hi Outbacktourer,

You will find that this applies to the european spec. It is in fact a water jacket around the pipe that comes out of the exhaust manifold. I have not seen it on any aussie spec ones so far.

Cheers

Outbacktourer posted:

hl, on closer inspection I find you are absolutely correct. Wonder why only Europe? Also while we are here, do you know if faulty MAF Sensor will show in boost or EGT figures?

OT

hl posted:

Crikey.. this thread is getting big, eh?
Yes, I wondered about that too, but, contrary to popular opinion, the europeans flog them harder.....160 clicks for an hour or two in 35C would warm things up nicely.
My theory is that a faulty MAF sensor that shows more airflow than there actually is would probably increase fueling and also boost because that is also controlled by the ECU. So, it could greatly increase performance (and stress). In fact, one of the fellows that had his engine blow up mentioned that the day before he was towing a car trailer up the hume highway and his truck went unbelievably well.. Next day when he started her up in a Sydney carpark...... it bit the dust.
Increasing the fuel and boost at the same time would not necessarily produce a lot of smoke, so it would just make you happy that it goes so well.......

Cheers

David from David and Justine Olsen's 4WD Tag-Along posted:

I haven't read all the post, as the thread is a bit long.

Some comments-

EGR lowers combustion temperature, disabling it will raise combustion temperature and damage valves and possibly pistons- early EGR systems were disabled on pertol cars and this resulted in burned valves in the long term.

We recently disabled EGR- 3 weeks ago- on a Rodeo that was on our Simpson trip, because it couldn't pull the skin off a custard from a standing start, let alone pull the Kimberly camper it was towing. Fully open EGR will significantly decrease power particularly at low revs.

Difficult starting could well be due to damage sustained (low compression) from low oil levels. My information from Nissan people is that the cause of failures is due to oil breakdown and usage and not regular enough (for this vehicle) checking of the oil level particularly when lots of highway or towing work is involved.

Dave O

Bob on Patrol posted:

Phil,

Good points, as I said in my original comments the EGR is one factor but it is a combination of events that eventually causes the engine failure hence the difficulty in saying if or when an engine may fail. The mechanic who did my job is certainly no mug mechanic they are very experienced and specialise in diesels, they do nothing else, so I put my faith in their advice. It is reassuring to know that others have done similar things to their patrols.

I also question the cooling effect of the EGR gases as the original comments in this posting were about the warping of the pipes associated with the EGR. How hot would things have to get to cause this? Doesn't sound very cool to me but I will leave that to the experts whose advice I am following.

Regards

Bob

Member - Jeff M (WA) posted:

I think there's probally some confusion over heat regarding the EGR.

The ZD30 is a high performance turbo diesel engine creating what I would imagine to be very high EGT (exaust gas temps). Now it's not the exaust gas that's "cooling" anything as it's probally the hottest part of the engine. It's the CO2 in the exaust gas that is "cooling" the combustion tempeture. It's not really cooling anything, but it's the simplest way to describe it, it's making the burn temperature of combustion lower as there is less oxygene in the combustion chamber on ignition. The heat from the exaust gasses could well and truely be enough to damage pistons and valves and may even be what is contributing to all of these cracked heads we here about IMHO.

But as I said before (and I agree it's probally not doing the damage by itself, there are most likley other contributing factors) this is the most reasonable explanation that I've heard for the "hit and miss" statistics of ZD30's blowing up. Esepcially as we know air flow sensors and EGR valves are common parts to fail early on in ZD30's engine's lives.

I think it's very interesting and IMO I reckon this is really a breakthrough in helping work out exactly what is causing these motors to crap themselves.

Interestingly as has been mentioned before, the ZD30 motor in the Navaras has suffered little from these problems. I wonder if it's EGR valve is electronic or vacume operated? I wonder if it has lower boost on the turbo creating lower EGT's. It would make sense that the boost was lower as it has no intercooler.

More peices to the puzzle I reckon...

hl posted:

and again,

One thing I can't quite work out and maybe someone knows. When the EGR valve is fully open it is like a completely open path between the exhaust and inlet manifolds. In fact the pipes are quite large, about 1" diameter. Now, the turbo produces say 10 psi into the inlet manifold.... how come the exhaust gas will flow from the exhaust to the inlet? One would think it would get pushed straight out the door again.....

Anyone know how?

Phil12345 posted:

The EGR will only open when there is no boost pressure, (when you take your foot off the the pedal, or cruising along). This is in an effort to stop the black smoke when changing gears or on overrun etc, the EGR is a stepper motor controled by the ECU and is electronically variable on how much exhaust gas is let into the inlet. Its totally a pollution device and doesn't effect performance as under accelleration the valve is closed and fresh air is going into the motor. Unfortunatly the laws of today require these things to be fitted and when other compnents fail damage can occurr. My theory is the air flow sensor fails, high temp/oxygen exhaust gas is then taken thru the open egr into the motor, causing the meltdown. Drivers do not detect the open EGR as a diesel motor is quite different from a petrol and a rough idle is not detected when the valve is open. The first of the ford falcon EFI's were regular rough idlers from leaking EGR's and ford took the step of providing a factory made blank off plate, no one would be game to do this today!!!!!

hl posted:

Thanks for that, Phil.....
Now, where is the best place to block it.....?
Cheers

sajiie posted:

So we don't or we do get a warning light on dash when a air flow metre or egr valve is not working correctly??. I do remember earlier on that i asked nissan to check my air flow sensor when it was in for service and they ended up checking it with another one and said there was some difference in the two( being electrically i think), but i had no warning light come on. I do know it comes on when the cable to the air flow metre is disconnected.

hl posted:

Yes and no...
If the airflow meter fails completely, i.e no output or stuck at one level you will get an error code. If it is producing incorrect output but within an acceptable range, no.. So, it could be overfueling without a code being set.
Don't know about the EGR valve. There is an error code for it, but I don't know how it is generated.
Cheers

David from David and Justine Olsen's 4WD Tag-Along posted:

I agree in part

In my experience, disabling the EGR will eventually (in the very long term) result in burned valves. It may in this engine contribute to piston damage (assuming combustion temperatures are as high as some report)- I just don't know.

As far as the Nissan error codes go, I wouldn't trust them to report an overfueling situation. Best to learn how to check the MAF yourself in my opinion.

Phil12345 posted:

hl
I sandwich a plate in the upper end of egr pipe between the inlet manifold. As for the above post "disabling the EGR will eventually in the long term result in burned valves" this was the argument when unleaded was introduced many years ago. Mechanic's were wary of disconecting the egr's due to the fear this would occur, however in my experence I didn't see any more burned valves from disconnection, rather damage caused by the new fuel with poor design/materials used. I feel the the fact that 1. 3 & 4 pistons are getting melted 2.the egr dumps into these pots. I can live with the "risk" that a valve might burn out "in the very long term".

cheers

hl posted:

Hi again, Phil

Well, I have tried blocking it and the result is quite surprising....
It got rid of an annoying flat spot between 1800-2000 rpm and also the slight shake that happens just after pulling up at the lights is gone. SO maybe my EGR valve is a bit sticky. Will have a chat to my trusty dealer. Also noticed some soot on the injector pipes behind the EGR valve, so the bottom gasket seems to leak too.

Cheers

Member - Jeff M (WA) posted:

My EGR setup is obviously a lot more basic that yours HL, however, mine had put soot all over the back of the motor where it had also been leaking in several places. I also belive that mine was jammed open (probally due to a build up of carbon on the valve) and that it could have been one of the main reasons for excessive smoke after backing off after heavy acceleration which dissapeared immediatly after disabling the EGR.

Previous to disabling the EGR I would make huge clouds of smoke when I took my foot off the accelerator (auto), even on normal driving I noticed it on the freeway folloing my wife while I was in another car. Each time she'd back off, a puff of smoke would come out the exaust. If you floored it and backed off, massive clouds would come out. My vehicle does not produce any noticable smoke (other than startup) whilst driving now.

Mind you it was fun, I remember some tosser in a saab convertable so far up my behind I could barley see his car in my mirrors! I just stabbed my foot on the throttle and took it off.... He backed off pretty quick after getting envoloped in a cloud of black smoke! LMAO!

hl posted:

Hi...
Yes... really they are nasty things if you want to keep your motor for a long time.
No problem if you're changing every 3 or 4 years. Just wished I knew how those new donks run without it long term....
Cheers

hl posted:

Hi,

The EGR valve is supposed to close on full throttle. It also closes at high revs, but don't know exactly when (somewhere above 3000).
It is open to varying degrees from idle. I blocked it on saturday and went for a drive and the difference is quite noticable. It goes much better and no flat spots..... makes you wonder what exactly the add on thingys like dtronics do. Maybe they just disable it too.... I always wondered how the would work being external to the ECU....
Maybe you would like to stick a plate in there and report you findings, since you have the gauges fitted already. It is very easy to fit (and take out again).

Cheers

Outbacktourer posted:

Interesting factoid. After fitting my Dtronic I noticed an overall drop in EGT, around 50 F, posted here at the time.

hl posted:

Hi Chaz,

I have done a lot more searching on the subject. One of the things mentioned is that EGR cuts peak temperatures during the combustion process, but that does not necessarily translate into lower EGT overall. Since the valve closes at high engine loads, the peak exhaust gas temp is really the same when it is disabled. The maximum EGR occurs at light to moderate engine loads and the EGT is nowhere near peak values under those conditions.
Anyway, I would not be after "performance gain" if I closed it, just don't like the crap that builds up in the intake system. And it DOES build up. I might still come round to "the other side......"

Cheers

hl posted:

Hi, Outbacktourer...

Since you have a Dtronic fitted, I wonder if you could do a couple of simple tests.
Could you just run your engine at idle for a few minutes (warmed up and cold) and then feel the EGR pipe about half way down from where it enters the intake manifold. Then do the same after a short drive. If your EGR system is operating normally, the pipe would be quite a bit hotter than the inlet manifold. I wonder if that is the case.

Thanks

Outbacktourer posted:

No worries...

Chaz posted:

Hi hl,
Thanks for your input on this. On the question of where to block it off, wouldn’t it be better to block it at the valve and stop the heat from getting to the inlet manifold. Perhaps even blocking it at the exhaust manifold would be a better option. Just a thought.
I too have a Dtronic fitted, but unfortunately it was fitted before I fitted the gauges, so I can’t make a comparison but I will have a go at blocking it off in the near future and let the forum know of my findings.
Cheers

Chaz

hl posted:

Hi Chaz,

The easiest place is right at the inlet manifold. If you undo the 2 bolts, the existing stainless gasket just falls out when you pull at the pipe. You can then use that as a template to cut out a blocking plate and slide that in, in place of the original gasket. I just used a small sheet of aluminium since I only wanted to test to see what happens. As for blocking it off closer to the valve, there is little point in trying to do it the hard way. The exhaust gas will not flow into the system at all, whether the valve is open or not makes no difference. There will be no pressure differential.

Cheers