4106 Fresh Air Intake - Cowl Vent Question
 

4106 Fresh Air Intake - Cowl Vent Question

Started by richard5933, September 24, 2017, 02:19:22 PM

Previous topic - Next topic

richard5933

I've been studying the manuals trying to understand the ventilation system on our 4106. Stumped right now regarding the front cowl fresh air vent. i see the vent on the outside (1/2-wide slot underneath the sheet metal on the front with the GM logo). I see in the manual where there is supposed to be a lever above the driver's right knee to open and close the vent. Problem is, on our coach there is no lever.

I looked in from the driver's area best I can, and I see no lever. I don't even see anything that remotely looks like it used to be a lever or a lever mounting place. I don't even see a mechanism for opening/closing the cowl vent.

Any chance that there was a change in the design somewhere along the way and this vent became permanently open? Or, is this something that was common to remove during conversions?

The whole reason for this endeavor is trying to figure out why the hot air coming from my Webasto is not making it from the driver's side of the coach to the curbside of the coach. I have two theories, first that there is a blockage, and second that the hot air is just escaping through either the fresh air intake on the side or through the cowl vent on the front. The Webasto pumps air into the floor duct on the driver's side, and I assume that it's supposed to somehow make it to the matching vents someone installed on the curbside by attaching flex ducting from the floor duct behind the closet going to at Webasto air vents on the wall between the closet and bedroom.

Richard

Any information anyone has about this would be greatly appreciated.
Richard
1974 GMC P8M4108a-125 Custom Coach "Land Cruiser" (Sold)
1964 GM PD4106-2412 (Former Bus)
1994 Airstream Excella 25-ft w/ 1999 Suburban 2500
Located in beautiful Wisconsin

chessie4905

If it is the same as the 4905, don't recall on our 4104 anymore, but there should be a round vent with mesh covering the outside to keep bugs out. It is mounted behind center emblem. The vent has a flap in it with weatherstripping. The flap is controlled by a knob sticking straight upward on top of dash or maybe a lever or a choke type cable in yours. You may be able to see it with a flashlight if you open the panel on the front side of entrance steps and look towards the front and underside of dash. That felt seal can deteriorate over the years. Some have plugged it with rags rather than replacing seal. I like it for the fresh air aspects.
GMC h8h 649#028 (4905)
Pennsylvania-central

OneLapper

My 4106 has the fresh air vent lever, but when I removed the front panel on the nose to refurb it, I found out that there was no fresh air opening!  Looks like it was never there.
OneLapper
1964 PD4106-2853
www.markdavia.com

chessie4905

GMC h8h 649#028 (4905)
Pennsylvania-central

richard5933

Quote from: chessie4905 on September 25, 2017, 05:16:29 AM
It may have been panelled over at some time.

You are correct. I apparently didn't look deep enough into the nose of the bus on the outside. I'd only seen the opening where air was supposed to enter. What I didn't see till just now is that someone closed in the vent with sheet metal. They did such a good job I had to really look to see where the opening was supposed to be.

Guess that removes the cowl vent as the problem getting the heated air from the Webasto to flow through the coach.

Richard
Richard
1974 GMC P8M4108a-125 Custom Coach "Land Cruiser" (Sold)
1964 GM PD4106-2412 (Former Bus)
1994 Airstream Excella 25-ft w/ 1999 Suburban 2500
Located in beautiful Wisconsin