It was my second turbo, factory one snapped the shaft at 387k miles and it wasn’t violent – 2 hours later (before it even had a chance to cool down) I was back to the road with reman from Cummins. That updated VGT lasted exactly 50% longer, which is kinda nice increase but… not really. Problem is, they don’ t explode nearly as often as old, non-variable turbos were and keep spinning beyond it’s own lifespan despite being out of whack and robbing you from fuel for who knows how long.
I was dealing with elevated by 100-200 F EGT (Exhaust Gas Temperatures) for at least half a year. At first I was blaming hot summer air (nonsense but thats when it started anyway) then I was suspecting my still original mufflers possibly being stuffed with soot buildup (they were, just a bit though and replacing them didn’t help). Then over time my pyrometer started creeping up to 900 F and when it started hitting 1000 F I went to talk to Ray Righetti, North-California Cummins guru to talk about it. He asked me how many miles on the turbo I got – 583k I said. He made a sound like something stabbed him in the back and said “come, I need to show you something” And being good friend of mine he took me to his engine room where they X-Ray blocks for whole Bay Area and pointed to two open ISX turbos: „they wore out those nozzles and can’t be properly positioned by ECM anymore. With the miles you have put it’s not even worth diagnosing, you need new turbo, there is nothing that could have more bad influence on ISX EGT than worn turbo”
Then doing oil change at Speedco I have met a produce hauler from TN who at 810k miles still had his original turbo (no kidding, I checked the part number) and not complaining – he actually loved his 530 ISX for being almost troublefree. I hate replacing things that still work but then… I got under lighter load and still was hittin 1000 F on pyro and seing some inconsistences on Insite (like occasional 56,000 rpm pulling hills) – I decided I’m fed up with this.
Below are pictures of that turbocharger – Ray was absolutely right about the nozzles being worn and sticky plus the shroud late was loose from its housing (could be the latest development) and the sliding nozzles base was cracked from high temperatures probably or maybe how it all started – from that crack. All this mess must have been causing not only higher drive pressure but boost problems aswell since it didn’t really close nor fully open but max boost reamained almost unaffected. Its actually quite interesting it didn’t blow being the sad junk it was for months and the only gauge to reflect that was pyrometer because Insite software was showing Turbocharger Control Valve being actuated – problem is there was no feedback from turbo on actual position until 2007+ motors (with electric turbo actuation and DPFs) so ECM didn’t even know how far off turbo was from where it wanted to be.
Another culprit of dying variable geometry turbo is weak jake-brake performance. It was working but you’ll be seeking higher rpms, up to 2000 instead of usual 1700 and then, over time you still have to use air brakes to compensate for its under-performance. Which is obvious sign of turbo not being able to close fully – I used to be able to run coast-to-coast fully loaded without touching brake pedal (I’m still on original brake shoes on drives). Thing is… weaker jake started… 200k miles ago. It wasn’t nearly that bad as lately and fairly OK for long time – but it means that wonderful piece of modern diesel technology started walking out of specs at around… 400k miles. In other words you need 2 of them for the miles of non-variable turbo which used to be also 3 times cheaper.
Now, here is another kicker – I have lost probably around 7% of fuel mileage last year and that means I paid for that turbo 3 times compared to what it could’ve cost me if I knew what I know now year ago: placing moving parts in stream of diesel exhaust is poor engineering idea and works for everyone but the truck owner
One of the very many ways ISX motors can start running less-then-perfect is when this sensor start malfunctioning. I experienced it myself and it was quite interesting… It started with lower max turbo boost at hard pulls (26-28 PSI instead of 31-33 PSI) but it wasn’t steady, coming and going plus engine seemed to be still able to build power but it would take longer and thus took me to downshift early and more often. When I connected INSITE first thing I saw was turbo not closing like it used to, it was “working” up and down but seemed to be more likely to stay wide open in the “20’s”. Such difference in operation is hard to see immediately because that’s exactly the nature of the beast – ISX is constantly adapting turbo, EGR and fuel to whatever it wants to be. Then I figured why my jake brake is weaker – turbocharger would go only to about “55” position instead of “70” (which is turbo’s closed position with biggest restriction on the exhaust). This is sure way to confirm turbo actuation problem – when it is not closing completely during hard jake-brake operation. Started looking at the rest of the readings and… Exhaust Gas Pressure was jumping out of range and back – which was giving ECM bad idea about exhaust temperatures being to high and… apparently this was the engine computer answer to this situation… to keep turbo more “open” to help evacuate hot fumes? I guess thats is something many people describing as a “derating”.
Sensor happened to be cracked and getting water in it, replacement is simple. Looking into its pipe is also important diagnosing procedure as you want to see how heavily sooted it is inside (and clean it then). Contrary to common belief properly working ISX does not built the soot all that much…
Before we get further into EGR guts lets jump into Variable Geometry Turbo for a sec. This is pretty amazing piece of modern technology which started living under our hoods right with EGR system back in Oct-2002 and till Jan-2007 was actuated by… air. The actuation itself was causing a lot of problems so they went to electric actuation by then. VGT is the mother of ISX power and efficiency unfortunately married to EGR who is the smoking father – so it gets screwed and whole family have problems. Theory of the operation is perfect though as when turbo gets closed (they call it 70% position) it builds boost momentarily so we have no turbo lag and no smoke from the stacks (EPA is glad) but next thing we want right after it hits its speed limit at 90,000 rpm (which doesn’t take very long, maybe a second) is to have it open (all the way to 20% position, mostly around 34% though) so the restriction on exhaust gasses is down – that’s where the sliding nozzles are doing their job, in the hot part increasing/decreasing backpressure. These turbos are greatest improvement on diesel motors since DDEC but like I just mentioned they get screwed by soot that make them blow because all this stunt with super-fast actuation only works when it works perfectly and having quater pound of coal all over the precise mechanism make it not so perfect anymore. Anyway, if you noticed your boost/pyro started acting strangely here is first, simple and inaccurate but totally free way of testing your VGT:
1. This is normal position when engine is shut down. The turbo is “open” by the power of spring inside of the actuator.
2. Now if you put some force and turn the wrench up you should be able to overcome the spring and manually “close” the turbo. The trick is to figure out if there is some additional (beside the spring) friction coming from the soot or whatever else that shouldn’t be there. I was never able to feel it taking this shot coz my turbo was and still is good so no further advices. I was told about this method by mechanics from a reasonably big ISX fleet.
There is a growing number of people asking the question: “where is this damn EGR Valve located?” It is located just a few inches away from the first cylinder exhaust and that is also the reason why everyone with smoking ISX wants to find it – It works right in the stream diesel fumes leaving the cylinder: up to 1,500 degrees Fahrenheit (850 degrees Celsius) under hard pulls which is obviously killing it. These are temperatures existing on the sides of erupting volcano but thing is, EGR Valve greased (!) mechanism is there to withstand it for years and hundreds of thousands miles. I think the reason why it sits there is… to save EGR Cooler from that heat – EGR Valve isn’t always open and often is opened partially seriously limiting the flow of hot exhaust thru its route and thus limiting exposure. When they moved it to the “cold side” in 2007 – EGR Coolers started failing even more often and it is way worse failure since leads to coolant intrusion into engine oil. Here is the situation on 2003-2006 ISX:
This is one of many sensors on ISX engine but it has one interesting feature – it is built like potentiometer on you old skool car audio. There is no way you can turn it to change the bad valve position – just forget this idea. But there is another one and possibly interesting. If you want to know if your valve is closed, like it should be every time the engine is shut – but you suspect that it is not closed since you are getting CEL (Check Engine Light) and/or you’ll see all the other symptoms (like rolling black smoke from your stacks)… Well, there is probably way to learn about the inside situation without taking it apart from the engine yet. Here are two pictures with EGR Position Sensor unscrewed from the EGR Valve body. That is the bottom, shinning little shaft I promised you will be familiar with if you ever pissed off your father loosing that stereo knob on his Fiat 126p or Chevy Bell Air. Taking that sensor off should not be complicated, all it takes is turning those two little screws. Problem is the rotary movement form back to back is not much – just about 20-30 degrees, thats all. You can’t really be sure, you are not going to register small, milimeter-like diffrence in the Valve position (and its’ enough to start screwing things on ISX). But – if you smart enough to take a look at it when your EGR is still performing well (preferably new), snap a picture of it like I did below – you will have reference for future problems on the side of the road. And remember – The Judgement Day is coming this way or another
Since October 2002 when Cummins started selling their first EGR engines the Exhaust Gas Recirculation Valve pictured below is just never ending fiasco. There is few things I have learned about its ways and here is the first observation. It doesn’t really open all that much for what it’s able to be doing with every single ISX engine. When starts malfunction it can cause anything from slight smoking from the stacks to sudden truck owner bankruptcy. Now, there is no way to save the planet by having this piece of lousy engineering and everyone who buys this dumb idea is ignorant jerk brainwashed by some really powerful lobbies running things. But there is sure way to save the engine. We are going to start some more or less serious discussion about it under new category called “ISX”
Here is the look of the 2006 EGR Valve, the first one – installed on 2002-2006 motors referred often as the one mounted on “the hot side” (exhaust manifold) of the engine as opposed to next generation valve on 2007-2009 ISX-es which was mounted on “the cold side” (air intake). What we learn from this picture is that the thing is cooled with engine coolant and it has EGR Position Sensor mounted on itself. That’s right, it is capable of self-check on its very own performance and reporting that to the ECM (engine computer) so it can do anything from Check Engine Light to seriously derating engine by putting it into limp mode. That’s what happens when desired by ECM position is commanded by sending electrical impulse to EGR Actuator (which is nothing but small electric motor) but such position is not reached according to EGR Position Sensor. And unfortunately it is very popular scenario.