99 Executive M11 Low Boost

[Scott Smith]

99 Executive with a cummins celect plus M11 450hp on the valve cover but it says 500 on the back?  I bought it in 2018, we use it to haul our racecars to the track and stay in while we are there, love it.  The most boost I have seen on the gauge is 18 when going up big hills but checking into it I think it should be more like 25-28 but this is the first diesel pusher I have owned so I didn't know.  It does pretty good at that boost level when going up big hills with the trailer but this past summer we were going to the track up Clinch Mountain and I noticed it was really struggling and look at the boost gauge and it was like only about 10-12.  So I have been trying to find the boost leak or issue with no luck.  It doesn't smoke, run hot (always gets about 220 when going up big long hills but quickly goes down once you top it), and really seems fine on level ground and sometimes when the pull isn't really bad the boost will go up to about 15 or 16 but not on a hard pull only 10-12 then.  The odometer doesn't work and it had 184,000 when I bought it and I think that is close to what it actually had looking at old paper work and the mileage they had written down.  I log every trip I make and I have put 20,000 on it in the 5 years that I have owned it so I would say it doesn't have more than 250,000 on it.  I change the oil and fuel filters every year.  It has a small exhaust leak that at the block that I need to fix also.  I haven't pressure tested the CAC put I have looked all the piping over good and I really don't think it is leaking anywhere.  I think it might be the turbo?  I checked the air filter and it looks fine, I have changed it once a couple years ago.  There is no wastegate so can't be that, I found a video from Terry Chron about the boost sensor was a big problem on the m11 celect plus and I got one from them (Heavy Duty Powertrain) that said it fits all M11s but it is a 3 wire sensor and the one on mine is a 2 wire sensor.  There is no waste gate on these and apparently they use fuel to control boost, so I don't think its the sensor if it is reading low, I could see if it was reading high it would drop down but not sure.  I don't think there would be a different sensor for the gauge, I only see the one sensor on the back of the intake.  Just looking for any ideas and how much boost should this engine be making?

Thanks

[Craggar]

Fix your exhaust leak before doing anything else and see what that does.

[jacwjames]

I live in E TN, Welcome

When was the last time air filter was changed

Exhaust leak could contribute for sure

Pretty easy to check all the air intake, turbo connections.  

CAC is also suspect, spray some  soapy water on it then start rig and have someone get RPM's on engine and look for bubbles.  Back in 2015 my radiator was damaged and had to be replaced.  While it was out I had the CAC checked, they plugged the connection holes, put an air line to it, dropped it in a large vat of water and turned on the air>>>> looked like a jaccuzzi.  So I had it repaired $1650>>>   But it only gained me 1-2 psi in boost, I now get 24 psi occasionally. 

 

I use the Cummins Quickserve site,  https://quickserve.cummins.com/qs3/portal/service/index.html

I looked at the Symptoms for low boost and they have this posted.  There are links within the document to other documents but the only way to get access is to open an account.

 

Intake Manifold Pressure (Boost) is Below Normal.pdf

[Scott Smith]

Yes I will fix that exhaust leak, that could be it. I will check out that site as well.  Thanks for the replies!

[PeterSchweizer]

First Get engine serial number off engine contact Cummins n get info on it manufacture date, HP etc. It may have been changed by previous owners.

Fix exhaust leak, varify boos pressure gauge is correct, by installing a in line "T" n a manual gauge in eng compartment with a longer line so it can be temporarily located inside coach so someone call look at it on the rode to verify pressure. 

If you have to replace exhaust manifold if it's cracked or you break off a bolt? Soake all bolts for several days several times per day with penetrating oil "PB BLASTER" before attempting to lossen n retighten (Torgue) them

.  Might as well replace turbo too, verify turbo part # from Cummins per your installedengine's serial number. 

Turbos Direct is a good source for a factory Holset rebuilt turbo.

Keep site updated on your progress n solution.

[timaz996]

When you have a boost leak you will also have high exhaust temp. I would recommend anyone with a turbo diesel to have a pyrometer. With low boost you will see very high exhaust temp. Be careful. 

[Scott Smith]

I think I will get one of those as well.  Thanks

[Venturer]

This is a bit late to the discussion, but I see about 32# of boost under full load. I thought that was pretty normal for the ISM 500, however, I'm   seeing lower numbers from others. I do have the Ugly Fix now, but it was similar before it was added. I'm very pleased with the performance and fuel mileage.  

[Scott Smith]

Thanks for the info, I'm working on fixing the exhaust leak, got 7 of the bolts loose the top 4 in the middle are worrying me, I keep soaking them every day.  The heat shield that covers part of the turbo was broke and rubbing on a hose.  I felt the turbo and it has a little play, probably end up changing it.  

[jacwjames]

Are you soaking using WD40

I used PB Blaster and didn't have any problems, I soaked for 2 days and got all of the studs out.

There are other concoctions that people use also

[Ivan K]

I have the same manifold and none of the penetrant (atf+) made it into the threads but there was no sign of rust in them either. The only rust was inside the spacers. Once the bolt head broke loose from the spacer, it just came out easily.

[Scott Smith]

I used all my wd 40 up so got some pb blaster and was able to get them all broke loose except for the 1 bottom one by the turbo but I don't think that one will be an issue after I get the turbo out of the way.  I think I am going to straight pipe it too.

[Ivan K]

I couldn't get the oil feed hose out of the turbo and had to pull it out with the hose, easier that way if you run into it too. That thing is heavy and deep in the hole.

[Scott Smith]

Finally got all the bolts out and the stuff off, the turbo had a quite a bit of play so I got a Holset reman from Turbos Direct like in one day, fast shipping.  New bolts should be here today, got all the exhaust gaskets, I cut one of boots going to the intercooler because I couldn't get it to come loose so I need to order that.  

[cbr046]

Are you replacing exhaust manifold also?   Look for cracks and / or pitting.

- bob

[Scott Smith]

I wasn't going to but I think I probably need to.  I got new bolts but was going to reuse the spacers but when I went to clean them up I noticed that 4 were shorter and two had extra parts and two someone had shorten the bolts at some point... I definitely need some more spacers.  I got new bolts where the turbo mounts to the manifold and had to cut them down a little the studs I bought were too long and just kinda test fit the manfold to the turbo and it looked crooked?  I checked it with the old turbo and it was the same way and I got to looking at the manifold and it's like core shifted or something, check the 5th pic.  I didn't see any cracks but the flanges look pretty rough.  I think I will just order a new manifold and spacers.

[jacwjames]

If you can't find any cracks it might be worthwhile to take the manifold to a machine shop and have it trued up and surfaces cleaned up, several look pretty rough.  That way it would mate to the block better. 

[Ivan K]

That turbo mounting flange looks weird but looking at my picture, the one stud is also off center in the ear and it is an OEM manifold.

 

Edited Saturday at 03:55 PM by Ivan K

[Dean Bennett]

Good Luck. Just an FYI - I have a 1999 Exec with the M11 Select Plus. It has 127,000 miles. The boost tops out at 29.5 on mine.... You will really like the rig when yours has that much boost! 

[Venturer]

We are on our way back to WI for the summer. I noticed something in the boost today for the first time. At 500 to1000' elevation, I get close to 40# of boost under full load. When we were at 4500' elevation, the boost maxed out at 32#. Is this normal for elevation changes? I also have the Ugly Fix on the EGR valve. The engine runs great and pulls hard. 

[cbr046]

OK, I'll bite  . . . What is the EGR Ugly Fix and why would someone need it?

- bob

[Chargerman]

The Ugly Fix is a module that replaces the altimeter module. It makes the engine think it’s alway at high altitude and therefor keeps the EGR valve closed. The benefits of this are slightly better fuel mileage, very slight. To me the bigger benefit is keeping soot out of the crankcase. I installed one a couple years ago and the difference in the cleanliness of the oil is amazing. Now my oil is still translucent after thousands of miles. So good to keep that abrasive soot out of the motor

[Venturer]

We're on the road till tonight. Just wondering if others see a change in boost with altitude changes.

[Ivan K]

I don't watch the boost so closely to notice a difference, I just ease off a little when it starts bouncing but it is expected to loose some percentage of power with thinner air, less oxygen per volume at elevation and lower turbo RPM even with density altitude change at the same elevation. 

[Venturer]

Thanks. That's kind of what I thought happened with altitude. I sure am pleased with the power this ISM has compared to my 450 ISL in our previous Bus. It sure tamed the hills north of Truth or Consequences, NM today.