View Full Version : GMC Cab Lights Leaking

10-31-2008, 15:11
Does anyone have the new GM part number for the improved cab light lens or good after market lens.

10-31-2008, 15:23
You don't say what year or model truck you have, but I fixed my leaks by taking the lenses and rubber seals off, applying a bead of silicone sealant around the perimeter of the seal between the seal and the cab, and then reassembling. I tightened the lenses down enough to hold things firmly in place and then tightened them down completely after things had a chance to cure.

10-31-2008, 18:22
I'll do one better. Here is the whole bulletin. As I remember, this affected the 2003 - early 2007 C series trucks. ;)

Subject: Water Intrusion into Cab (Inspect/Replace Roof Marker Lamp Lens/Bolts)

Models: 2003-2006 Chevrolet Kodiak C4500-C8500 Series

2003-2006 GMC TopKick C4500-C8500 Series

2005-2006 Isuzu HTR/HVR/HXR Conventional Models


This bulletin is being revised to change the torque specification. Please discard Corporate Bulletin Number 05-08-57-004 (Section 08 -- Body and Accessories).


Some dealers/customers may comment that there is water leaking into the cab after a rainstorm. Water may be present on the headliner and/or the cab floor.

The retaining screws for the roof marker lamp lens may have been overtightened, causing the lens to crack. This may allow water to enter the cab through the lens or the gasket around the retaining screw.

Inspect the lens and the screw/gasket assembly of all the roof marker lamps. If any screw/gasket is damaged, replace the screw(s). If a marker lamp looks cracked, run your fingernail across the top of the crack to determine if it's cracked all the way through. If the marker lamp lens is cracked all the way through, replace the lens. After replacement, tighten the screws to 1 N·m (9 lb in). Do NOT overtighten. Refer to Marker Lamp Lens Replacement - Roof in the Lighting Systems sub-section of SI.

Parts Information
Part Number

Lens, Roof Clearance Lamp

Bolt/Screw, Roof Clearance Lamp Lens

10-31-2008, 18:51
Thanks for the information, it seems from the Bulletin the cab lights are not leaking between the metal roof and light housing.
It seems GM is saying the leak is from a cracked lens or gasket between the lens and light housing.

If this this is correct I will not have to pull the headliner down and remove the complete cab fixture / housing.
It is a 2007 Topkick

11-01-2008, 00:01
No just look on top of the cab at the lenses. You will probably see that the lenses are cracked.