Strange Question? Need Help!

[gnilsen]

I have a Gulfstream Crescendo Class A Diesel Pusher 2007, I noticed something strange and need help identifying what is going on.

When driving at almost any speed, I can feel and hear something engage it almost feels like the exhaust brake, but the RPM's do not change and I am not slowing or breaking I am driving and accelerating. I have tried shutting off the exhaust brake and it still does it, I have tried Shutting off the Generator thinking it might have been a change in RPM on the Generator. And it still persists.


The transmission does not downshift the RPM remains steady
The generator is not the sound I am hearing
I used both Economy mode and regular mode on the transmission No difference
IT is a freight liner chassis if this helps
Engine Oil just replaced, Generator just serviced
Chassis has about 47k miles

Other weird things that could be related????
Air filter suction thing in the engine bay keep showing I need to replace the filter, Had camping world look and they said I do not need to replace but if I reset the vacuum sensor it keeps showing replace.

Fuel economy seems a little lower than I would expect I average about 6.7 per the dash computer


I do not know if this is completely normal but I am trying to identify it I will be taking for 2000 mile plus trip in about a month and want to be sure nothing is wrong.

Thanks in advance for the help???

[Yankee29588]

Sounds like the air pump is engaging to charge up your air-brake system. Next time you sense the noise, check your front and rear brake pressures and see if they are low or building back up. If so, you have a brake air leak somewhere.

As for the air filter sensor, sounds like a spring issue at the sensor.

[RayChez1]

Not sure on the engaging noise, but on the vacuum gauge I used to have the same problem since new. To solve the problem I changed brands of air filters from the original which was a Farr filter. I got on the internet and started buying air filters from Racor and man what a difference in power, economy and the vacuum gauge works the way it is suppose to. I get around 8-9 miles per gallon. I have the 3126-E Caterpillar engine which is the same as the C-7.

Just thought of another thing that might be making the noise you are talking about. Have you checked the oil on the differential? Also lube the spline gear and U-joints on the drive shaft.

[gnilsen]

Thanks for the replies, I thought is possible it was the air pump, The air pressure gauge does not seem to fluctuate at all when I am driving and it holds air when parked. How can I find out exactly what air filter to order for the coach. I was going to remove it and look for a part number? but I wanted to have the new one in hand so I didn't have to do the job twice...

Thanks again

[RayHarkness]

I have had good luck contacting Freightliner. There have been recalls on things like the computer box in the back rear compartment. Mine was bad. My gauges would jump around. New box was around 400 bucks, but fixed the problem. I had replaced ONE air gauge, which was good after all. It was common and they were aware of it.
If you call them, have your VIN number, which should be the chassis number. You would be suprised how much they know about your chassis. It may mean something to them. I think you can google for their number..think it was in South Carolina or something. Good staff there.........worth making the call and explaining what is going on.

R

[RayChez1]

Thanks for the replies, I thought is possible it was the air pump, The air pressure gauge does not seem to fluctuate at all when I am driving and it holds air when parked. How can I find out exactly what air filter to order for the coach. I was going to remove it and look for a part number? but I wanted to have the new one in hand so I didn't have to do the job twice...

Thanks again

First of all, what engine do you have? Is it a Caterpillar or Cummins? I am sure they would be different. But If I was you, I would crawl under the coach and if the filter is located where mine is, you should be able to read the part number and manufacturer. Then get on the internet and cross reference with the Racor air filters. They will even show you a picture of their air filters and the measurements. Like I posted: I have a Caterpillar engine which is the same as the C-7.