1991 International 9670 Cabover Air Leak-Help Needed

1991 Intl 9670 COE

Air leak was discovered when holding tractor with foot brake down hill at a stoplight using more than usual brake pedal force.

When pushing brake pedal down, air leaks from the small hose (photo attached) in my hand under the floor pan. The harder the pedal is pushed, the more it leaks.

I checked to see if this hose was broken loose from any fittings in the floor, and could not find anything it would attach to.

-All brakes work normal.
-Leak is not influenced by the position of the red tractor brake valve.
-Leak is not influenced by the position of the yellow trailer brake valve.
-Leak is not influenced by the position of the trailer hand valve.

I am mechanically skilled, 15 years on the road, and I have only owned this old truck for a short time and still learning.
Is it possible the hose was plugged or capped from the factory many years ago and blew said plug out?
Is it possible this hose is supposed to flow air? (...I highly doubt it...)

All pros please advise, thanks and God Bless.

Boneytrucker

 

Hey that's something I did not consider. I do not have that gauge on my panel and it would make since to have that line on standby in-case one was installed. I did find a cylindrical piece of metal in the floor pan when I was cleaning up the mess shown in the pictures. I have a feeling that's probably it. Thanks for the reply Dino!

 

Yeah she gets a lot of looks, smiles on peoples faces from the memories of old time road trips when they were kids. Its fun to drive and easy to back. It's got a Cummins L10-330E in it. Not a hard puller but she gets along fine and sips the fuel compared to today's motors. Give $9500 for it down in South Texas last year. Just needed oil change and a thermostat. Interior is all original 1991 light blue everything. All lights work no electrical problems either. I'm glad to have her.

 

haha mine gets along. Starts and runs dependably, easy to work on. Its not a hard puller by any means, I do know what you are talking about with that. I got 7.62 mpg for all miles driven back in February. So far i've only have up to 36,000 in the box, and it pulled okay. It got 6.4 pulling that. i'm usually loaded between 12,000 and 30,000. 70 mph is about as fast as I go when I am loaded. Its got 4.10 rears and a 9 speed eaton overdrive. I would love to put a 13 speed in it so I could have a ratio between .74 and direct. In due time, i due time. Good tires will be my next investment.

The truck pulled carnival rides around the southwest USA and SoCal for 21 years. Only worked from spring to fall, then maintained and put away in south texas until it was time for the season to start again.

I found a Miller Genuine Draft bottle cap under the driver side floor board and a bunch of old Nascar signs under the bunk mattress when I was cleaning it up.

Boneytrucker

 

haha mine gets along. Starts and runs dependably, easy to work on. Its not a hard puller by any means, I do know what you are talking about with that. I got 7.62 mpg for all miles driven back in February. So far i've only have up to 36,000 in the box, and it pulled okay. It got 6.4 pulling that. i'm usually loaded between 12,000 and 30,000. 70 mph is about as fast as I go when I am loaded. Its got 4.10 rears and a 9 speed eaton overdrive. I would love to put a 13 speed in it so I could have a ratio between .74 and direct. In due time, i due time. Good tires will be my next investment.

The truck pulled carnival rides around the southwest USA and SoCal for 21 years. Only worked from spring to fall, then maintained and put away in south texas until it was time for the season to start again.

I found a Miller Genuine Draft bottle cap under the driver side floor board and a bunch of old Nascar signs under the bunk mattress when I was cleaning it up.

Boneytrucker

 

A few thousand miles after replacing the blown out plug with a good size screw, I can confirm that this line was indeed the culprit and no other issues have sprang up related to it. Thanks again for the help Dino.

Boneytrucker