High Air Filter Restriction

[Hunter013]

2025 T880 X15

Driver said inlet air restriction was at 30 when loaded. We changed the filter (Filter was barely dirty and was changed 1 month before that). Driver said restriction was better, but still high around 17. We took apart whole inlet side and didn't see anything abnormal. What else should we check?

 

[Nige]

17” of water restriction for a new filter setup (inner & outer elements) is about right in my experience. Certainly in the ball park.

Question: Even though the elements that were removed were not apparently dirty is there any chance they might have been a bit damp.?

 

[Hunter013]

Question: Even though the elements that were removed were not apparently dirty is there any chance they might have been a bit damp.?

I didn’t see any moisture

 

[Nige]

I didn’t see any moisture

The moisture probably wouldn’t have been visible. Usually you can tell the difference in weight if you hold a brand new element in one hand and a used one in the other.

 

[Hunter013]

Usually you can tell the difference in weight if you hold a brand new element in one hand and a used one in the other.

They felt about the same

 

[Coaldust]

Gents. The Kenworth dash instrumentation indicates %. 30% is normal. We are getting units of measurement mixed up. 30 inches H20 vs 30%.

 

[Hunter013]

30% is normal

I'm sorry, I thought it was H20, but it is %. Why/how is it normal to have 30% restriction? Is it just because of the high vacuum being pulled from acceleration?

I drove both the problem truck and its sister truck unloaded down the interstate and they read the exact same numbers; boost, air restriction, fuel filter restriction, torque %. The driver in the sister truck has no complaints. I will try to test drive it with a load tonight to try to duplicate the issue.

 

[Nige]

Colour me surprised also. I'm used to filter resriction being measured in inches of water.

 

[Coaldust]

I'm sorry, I thought it was H20, but it is %. Why/how is it normal to have 30% restriction? Is it just because of the high vacuum being pulled from acceleration?

I drove both the problem truck and its sister truck unloaded down the interstate and they read the exact same numbers; boost, air restriction, fuel filter restriction, torque %. The driver in the sister truck has no complaints. I will try to test drive it with a load tonight to try to duplicate the issue.

The driver display isn’t very accurate or consistent. If you have a concern, connect a Magnehelic gauge and get some real numbers to work with.

 

[Hunter013]

A few days later the truck came back with a def light on the dash. Ran a forced regen and that seemed to fix everything.