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Turbo boost loss

Yahoo Message Number: 74547
Recently I have noticed that boost pressure is not holding on long inclines. The boost will go to 23psi as I start up the incline and within 8 seconds will drop to 12psi and then up to 14psi which it will hold the rest of the way up. This information is coming from a Cummins Road Relay 4 [simular to a Silverleaf ]. IF it had a catalytic converter I would think it was pluged up. Have checked all of the rubber connectors and they all seem to be good and the air filter is new as of January. Doing up hill I am keeping the RPM betweem 1800 an 2000 so should have full boost. The coach now has 164,000+ miles on it. Any thoughts what might be the cause of this problem?

Bill Dane 99 Allure 30326

Re: Turbo boost loss

Reply #2 –
Yahoo Message Number: 74554
Sounds like you have a defective charge air cooler, as I had on my 98 Allure and 2004 Intrigue. I also had a leaky sensor base on the crossover pipe from the exhaust manifold to the turbo on the Intrigue, that supplies the info you are seeing decline on your road relay. I would take the coach to Cummins and have them pressure check the system.. It takes about an hour and a half.
TWI 2004 Intrigue 11731 and former Allure 30255.

Re: Turbo boost loss

Reply #3 –
Yahoo Message Number: 74555
Bill, I agree with Arthur, have the Charge Air System pressure tested at Cummins, with the loss of Turbo Boost PSI, the Tech's will hear where the air loss is coming from.
A few weeks ago I had my tested and it was a failed Charge Air Cooler, upon removing the Radiator, Charge Air Cooler & A/C Condensor I had them send the Radiator/Oil Cooler & Condensor sent out for cleaning, rodding out and pressure test. All came back good, now awaiting the CAC to come in this week.
If you have CAC replaced and not check the other components you'll be subject to double labor if Radiator goes out soon after.

Thanks, Mike 03 Allure 1st Ave. #30898

Re: Turbo boost loss

Reply #4 –
Yahoo Message Number: 74567
Bill,

When the boost pressure declines, does the speed decline as well or stay the same?
If the speed stays the same, the engine is cutting fuel back, as the power required does not require full boost. These engines use what is known as a constant speed governor, meaning they will try to maintain a constant RPM. Thus they adjust fuel up or down to maintain the desired RPM, based on throttle position. They now do it electronically, but the concept is the same. .

If the speed is declining, the fuel filters may need changing.

If it were a leaking CAC, it would never get up to 23 psi.

Mikee

Turbo boost loss

Reply #5 –
Yahoo Message Number: 74568
Thanks to all that responded to my boost problem. The coach runs fine on regular grade roads and it acclerates fine if I need to speed up to pass a slower vehicle. But going up a long up hill incline, the coach may slow to about 40 mph. The thing that really had me stumped was that fact that it would go to 23 psi, than drop. Thank I will try Mikees suggestion and change the fuel filters first. If that does not work, I will have it pressure tested.

Bill Dane

99 Allure 30326

Re: Turbo boost loss

Reply #6 –
Yahoo Message Number: 74570
Mikee says you'd never see 23psi with a CAC leak.
I have my CAC getting replaced right now. It would hold 19-21 psi. Had a previous (repaired) leak and would hold 17psi with the previous leak.
So it is possible for a leaking Charge Air Cooler to still hold a boost pressure in that range.
However I never saw boost pressure get to a certain point and then drop, that's a pretty interesting scenario that doesn't sound like just a simple CAC leak. Could be CAC leak combined with something else (fuel pressure, pressure sender, etc.)

Mine is with a single-turbo Cat C15.

Jim Walsh
2003 Lexa

Re: Turbo boost loss

Reply #7 –
Yahoo Message Number: 74572
Bill

it's probably a crack in your CAC...... Look at the left side on the flat end piece where it joins the core. You will probably have a 4-6" crack running vertically. I just had mine repaired at Premier in Junction City, Or & Russ is having the same thing done next month.
My indication it was bad was only 10-12 lbs of boost & more black smoke on acceleration.

Terry

99 Magna 5703

Re: Turbo boost loss

Reply #8 –
Yahoo Message Number: 74575
I had one of my dump trucks with the same symptoms just last week. Replaced to tubo and runs fine. Just a thought.

Rod

Re: Turbo boost loss

Reply #9 –
Yahoo Message Number: 74580
Friend having a 99 Allure I agree with the above Posts but also have the Turbo Waste Gate checked at Cummins also laptop to check codes and FUEL PRESSUE, Ken Retired Caterpillar Power Systems Tech. Please bring your findings to the table! 99 Allure 30356

Re: Turbo boost loss

Reply #10 –
Yahoo Message Number: 74596
I am at Cummins NW right now getting a quote re CAC and exhaust manifold replacement. Advice? Thoughts? Meet to cry in our beer? Seriously, any advice would be appreciated.
Terry

97 Intrigue 10392

Re: Turbo boost loss

Reply #11 –
Yahoo Message Number: 74598
Terry,

Before you get the expensive news......You might as well take care of the radiator while you have everything torn apart. In other words.........." Clean-house".
Unless you have had the radiator worked on recently before. Go with a copper core radiator if its possible.
.

Good Luck!

I might be in your shoes some day.....let us know what happened.

Don't be hasty..........If possible....Try to get at least a couple more bids from others before you decide. If they are pretty close at least you'll feel better of your decision if the bids are somewhat close together in price.

Scott Jones, 2004 Allure 33'. # 31094

Re: Turbo boost loss

Reply #12 –
Yahoo Message Number: 74600
Scott,

Having radiator and A/C done at the same time as previous posts suggest seems prudent, though the mention of copper made my wallet float right outta my pocket! Will let you all in on the results.
Terry

97 Intrigue

Re: Turbo boost loss

Reply #13 –
Yahoo Message Number: 74602
I think you could do better price wise by heading to Oregon Motorcoach in Junction City. If you are a member of CCI or NorthWest Country Coachers you can get a 10% discount on parts and labor.

Don

'02 Intrigue #11427
'02 Intrigue #11427

Re: Turbo boost loss

Reply #14 –
Yahoo Message Number: 74610
Hi Friend, Last Spring in Yuma had our Exhaust Manifold replaced at Yuma Diesel the Cummins dealer here in Yuma. I did an inspection and found the crack! A fellow CC Owner of the same 1998 model C-8.3 shared info that this was normal for our older cummins. Also have the laptop applyed to the ECU and check for codes and FUEL PRESSURE! The first thing I noticed was more power and our Mileage at the sweet spot of 1800 rpm was 8.25 mpg up from the higher 7's! Have the turbo checked and pressure check the turbo waste gate! Cummins charged me under 900 dollars Parts and Labor. Keep us posted! Ken Retired Cat Service Tech. In Yuma. 99 Allure 30356