HELP!! QUICK!! IP BELT PULLEY MARK???

[mbtech208]

I'm in the middle of replacing the IP belt, I can see the mark on the crank, but not the mark on the IP gear. What does it look like?? I see three marks on the IP gear, but none are even close to where they should be!

[mbtech208]

Never mind. FYI, it's the "B" mark. Whew, I thought I was walking home tonight.

[asavage]

There's a link to the FSM page that shows the "A" mark (NEVER TO BE USED) and the correct mark, in the FAQ. Really, there is.

[mbtech208]

Once I finished the job, I took the car outside and held it at about 2,000 rpm to warm it up. While I was doing that, the engine bogged down and started billowing black smoke. I couldn't believe how much smoke came out of that little pipe. Then just like that, it disappeared and ran normally. What was that all about?

[goglio704]

Sounds like it ingested a chunk of intake fouling. Some of the other threads mention it in detail. Take a look at the "intake grunge" thread here in the LD engine forum. It doesn't seem to do any damage - to the car anyway. Air quality - maybe.

[mbtech208]

That doesn't damage the engine? I would think it would damage the valves and cylinder walls at the least.

[TheDieseliminator]

Just yesterday I decided to go out in the garage and clean my intake manifold that has been removed off the car for a good month or two. I seperated it into the two halves and now I have a good idea of how dirty and oily that sucker gets inside. Plus I've learned you can't physically clean the insides of the two pieces because your hand can't fit inside (which is really needed). Within about 10 minutes the rubber gloves I had on were "pitch black" diesel oil, haha. Yesterday I also decided to give the FAQ a visit because I remembered that there was some advice on cleaning the intake manifold. Al, I think I'm going to go the same route and have my local machine shop clean both parts of the manifold. In reality you need to submerge the two manifold halves into a bath that has a liquid that can free up the oil and sludge inside the pathways of each cylinder. I was able to get some handfulls of caked grease out though and I really can't even see how you can get decent air flow to this engine! I guess I really don't think too much of the EGR system because it will always do this to your manifold no matter what. And man I think I could gain about a solid 2-3 mpg in my car after I put on the fresh clean manifold. What do you all think?

Salvy

[83_maxima]

Does anyone have any pictures of the LD28's manifold before cleaning?

I never realized that this was much of an issue. I have been communicating with a couple that have a 285,000 mile diesel max they may be selling come fall and it sounds like this "grunge" may be a real issue in a car that has that many miles. I also begin to wonder about how much a 285,000 mile motor has left...

[goglio704]

For pics go to the FAQ section under "intake grunge"

As far as damage to the engine from this my biggest worry would be if a valve actually closed on a piece of this stuff. Even then I don't know that it would do damage.

I wouldn't be scared of 200k plus on a diesel Maxima if it has had good maintenance in terms of oil changes and the like. Depends really on what you want to do with it.

[asavage]

Does anyone have any pictures of the LD28's manifold before cleaning?

I have some fuzzy pics in the FAQ under Intake Manifold Grunge.

I never realized that this was much of an issue.

The VW TDi folks have been battling this publicly for a while, which is where I first heard of the issue.

The problem may be compounded in our case by the EGR system being active at idle (yeah, really). Other EGR systems I've seen are only active with a moderate load and RPMs above idle.

At any rate, it's not all that big of a problem, it just needs to be cleaned periodically. I venture that most of our engines have never had this service, in over twenty years, so I don't consider the system, overall, to be a problem waiting to happen. It just needs to be cleaned every so many miles/years.

[83_maxima]

For pics go to the FAQ section under "intake grunge"

As far as damage to the engine from this my biggest worry would be if a valve actually closed on a piece of this stuff. Even then I don't know that it would do damage.

I wouldn't be scared of 200k plus on a diesel Maxima if it has had good maintenance in terms of oil changes and the like. Depends really on what you want to do with it.

I read the Intake Grunge thread, but not the FAQ on it. 'Preciate it.

When the owner of a diesel max doesn't know what an IP is or that there is a belt that needs to be replaced and has had it for over 5 years, it kind of puts up a red flag.

[asavage]

Cleaning the intake tract is not in the Scheduled Maintenance section , but it ought to be. I don't think that anyone knew that it was going to be a problem, back in 1981. Diesel + EGR was new then. VW's TDi is a different story, EGR had been around a while by then and diesels had been running them.

GM's 5.7l diesel didn't seem to crap up like the LD28. Then again, how many 5.7l diesels made it to 200k? Many had potential, but few made it I'd wager.

Keep in mind that cleaning the intake manifold is the easy part: cleaning around the intake valves is far more work, IMO. You can farm out the intake cleaning (which is what I did), but you have to do the intake valves yourself, and you can't used compressed air or you'll have it all over you, the car, the neighbor's hedge . . .

I used the ShopVac method, and I'd do it again. Makes a mess of the 'vac, but my 'vac is already pretty messy. Even so, it took a while.

[mbtech208]

Is it really the EGR that's the main culprit for the sludge? Judging by what I saw when I pulled my intake, it looks more like the PCV system that caused the majority of it. The first three cylinders (before the PCV valve, but after the EGR valve) didn't have any wet goo in them, just a bit of dry residue that was easily scraped out. The rear three cylinders after the PCV is where all the nasty gooey mess was, and that's because the crankcase vapors mixed with the soot from the exhaust that the EGR introduced. Vent the crankcase to atmosphere (bypass the PCV), and I bet you wouldn't have anymore sludge. Not good for the environment though.

[asavage]

Precisely. It's the mixture of the blowby vapours and the EGR PM that form the goo. Venting crankcase vapours isn't a good idea, as there is an exchange that occurs -- unfiltered crap gets back up the vent and into the engine, plus the usual unburned HC that goes out the vent.

If I was to modify the system, I'd disable (remove completely) the EGR system. The throttle valve could go, with all its plumbing and solenoids. The EGR valve and feed tube, of course. The EGR speed sensor and part-throttle timing advancer. All of it could go. On the car that gets the turbo, I may go that way, as trying to make this particular EGR system work well with boost will be problematic.

Normally, I advocate for retension of OEM emissions control systems (and I plan on adding a diesel NOx catalytic converter eventually), but this one I may have to make an exception for.

Does anybody see the point of EGR operation at idle? I think it may actually be designed to make the idle quieter as a primary function, rather than as an emissions control -- at idle.

[goglio704]

A crankcase vent filter that would remove the oil vapor prior to the intake would be a good way to go. These are a pretty common modification to the VW TDI's and the Jeep CRD's.