Seeking Turbo advice

[Robert92867]

Since I am changing the head gasket on my 2001 Cummins ISB 5.9 24 valve at 128,000 miles, I pulled the turbocharger for inspection.  I have no complaints, other than the fact that the boost guage has never pegged higher than 18 psi, whereas many others have stated they get up to 30 psi boost readings.  I know very little about turbochargers, the blades spin smoothly, there is very little axial play in the shaft.  There is a strange scratch pattern on the compressor vanes, but it doesn't look serious.  So I'm inclined to reinstall it as is.  Any advice or input?

[DavidL]

Boost max pressure, if not to spec (what spec is yours supposed to be?  Makes no difference to what other forum users say - look up the technical specs) is more typically regulated by the wastegate system used.

But, I suspect your is just fine.

If it were mine, I would decarbon it (using carb cleaner, wire brush the exterior and give it a shot of heat paint to make it pretty 😉

Then shoot some fresh clean oil into the oil supply to "prime it" before installing.

Most important is to ensure all dirt is certainly not in the oil supply, and also in the air tract before assembly.

You could also bring it to a turbo rebuild shop.  But there is something to be said for "don't fix what's not broken".

 

 

[BradHend]

Be extremely anal about keeping all the fittings clean.  That shaft is basically floating in the retainers and is fed oil through 4 small holes.  Clog them up and you’ll be in rough shape.  
 

[96 EVO]

I don't know what is normal boost for a 5.9L, but if yours is low, it could be a leaking charge air cooler, or the associated plumbing.

[jacwjames]

The intake side seems to be pitted quite a bit or is this just the casting.  I found a decent picture of a similar turbo and the intake side is pretty darn smooth. 

What do all the air intake pipe/hosing look like, is there any significant signs of dirt??  Have you ever had oil analysis done? 

 

 

I'm paranoid with my intake system, check it specifically for holes, loose clamps, etc.  When I managed a mine back in ~1986-92 I had cases were operators would cut holes in the back of an air intake elbow to make it through a shift when air filter got clogged up.  Needless say eventually the engine would be dusted.  I had several hissy fits with employees threatening to fire anyone I could prove that did it.  Never could prove but I know it happened. 

[Robert92867]

Thanks for all your input.  You got me thinking in the right direction.

Since this is the same motor they put in a 2001 Ram 3500, I got a quick answer: "around 20 psi".

img_2948 gives a closer look at the compressor side. Dirty, yes. But for 22 years I think not excessively so.

img_2943 zooms in on the intake boot and discharge tube.  Thankfully no sand.

img_2944 is the exhaust side.  A shot of compressed air blew the soot off, not really carbonized at all.

 

[Old Dog]

Cummins/Holset put different waste gates on based on the customers specs for full rated hp/torque. Waste gates were frequently used to de-rate engines to protect transmissions. Dodge did it for their auto transmissions on the 5.9L. You can go higher but will most likely damage something else. First step is to id what it should be, chances are it's 18 for a reason if everything is functioning correctly.

 

[Robert92867]

Point taken on de-rating..

In the case of my 2001 Cummins, the 260 hp 450 torque rating pushed the limit of the Allison 1000 (rated 450 max torque input).  I put water/methanol injection on the engine and the red transmission light came on, so I took it off.  Also, I should have realized that the air compressor input tube comes off the intake manifold and was in essence feeding my air compressor with a fuel/water mixture.

[Jim McGarvie]

The book says max boost on our 2002 5.9 ISB (built in 2001) is 22.5 psi, and I consistently see that or almost that at full throttle.

[Robert92867]

What book?

[Rikadoo]

One other question when you were driving did ever notice periods of black smoke from the exhaust? Low boost will not only cause low power but will increase smoke, mostly due to the amount of fuel going into the engine doesnt change (givin the driving conditions) like heavy accel or driving up a hill. 
Or the other scenario is low fuel injection pressure can also cause low boost pressure in that the turbo is not getting the heat from the combustion process which in turn relates to turbo NOT spinning fast enough to build the required psi going into the intake… So then you need to look at the fuel filters, or plugged injectors.

[Robert92867]

Runs clean, no black smoke.  18 psi max boost since the day it was new.  When I get the head off I will check out the injectors.

[Rikadoo]

Hey Robert question, why are you removing the head?

[Robert92867]

Coolant leaking out the exhaust side of #1 cylinder. Very common for the 2nd gen 5.9. No oil in coolant, so I caught it early.

[Jim McGarvie]

On 7/29/2023 at 6:27 PM, Robert92867 said:

What book?

I thought I saw it in the owner's manual that came with the coach, but looked and can't find it. I checked the Cummins 5.9 ISB manual and it says to look on the engine dataplate. I will do that the next time I get the chance. I'm pretty sure I didn't just dream it....

[BradHend]

Max boost on my Cayman with the 5.9 ISB and VGT turbo was always in the 25-30 PSI range.   Bluefire gauge and instrument cluster  guage were same, so I assume it’s correct. 

[Sjholt12]

You could try a good stop leak and that may solve the minor leak there.

My 5.9B head gasket started leaking there when I was on a trip and I stopped mine by cleaning out that area as best I could, scraping out in that seam as good and in as far as I could get in there. then I cleaned the area with brake cleaner and being parked at a deluxe site at Walmart, I got a roll of tank sealer epoxy, mixed it up real good then put it in the crack and used a screw driver to drive it into there as much as I could and let it cure overnight,

Some might say this is Mickey Mouse, but I was on a 6,000 mile trip. That was ten years ago and it hasn't leaked since.

Oh ya, after the trip, I re-torqued the head bolts to 125 ft lbs by taking one head bolt out one at a time, cleaned oil lubed the threads.

HTH