2nd Gen Non-Engine/Transmission Cab leak

[danadj2]

The cab brake light assembly on my 94 is letting water in. Is there something that would make a good gasket or seal for this without having to get a new assembly?



I just went to the dealer and bought a new gasket for less the $7. 00. I will let you know how it turns out. Seems like it won't stop raining here in NE FL these days.

 

[MBean]

I have heard of others using caulking. Never heard anything about it after that. You might try searching the archives for brake light & leak. That may produce some results with more information, but I know its been here before... FWIW...

 

[Joe G.]

The gasket from Dodge is cheap. It's pretty flimsy so you have to be very careful. I used denatured alcohol to clean around the hole before reinstalling the gasket and light. It's been ok since then for over 150K miles.

 

[Matt42]

You might consider using some of that black mastic goop used to seal pop-in windows. A tiny bead ought to do it. It never really hardens, so will take vibration and heat-cool expansion.

 

[Tardog]

I've always been told not to use the house hold silicone on paint as over time it would melt it off. I've heard of a lot of people using an rtv silicone? Might want to check into this a bit more?

 

[Matt42]

I've used black RTV silicone to seal body parts before, particularly the tail light assemblies on a 1983 full size Wagoneer. The results were mixed. What that means is that it sealed OK for a while, but vibration eventually opened up a small leak. Unfortunately, the 90% or so that was still sealed made it very difficult to remove the assembly to seal it again.



Vibration and differential movement of metal and plastic parts are the reasons that RV manufacturers usually use oil or butyl based strip seals.



YMMV.

 

[Clinton]

I've been told that silicone is slightly acidic and will, over time, corrode paint and sheet steel. I can't verify that. Auto glass places use urethane based adhesives, but it's hard to find urethane sealants.



I replaced my third brake light gasket with a new one from the dealer. The new gasket was thicker, sealed better than the original, and only cost around $5.

 

[Bill Lins]

Silicone is MORE than "slightly" acidic and WILL eat paint & steel. Urethane will degrade over time if not protected from UV. It would also make it almost impossible to remove the light if needed to replace bulbs. I used some 1/4 X 1/8 single-sided foam tape to seal the cab light- it seals to the cab with adhesive, and seals the light by compression.

 

[Bill Lins]

Originally posted by slo-ryde

Silicone is acidic? Are we sure about this?

Yup- you know the "vinegar" smell it gives off? Acetic acid. RTV silicones cure by releasing it. There are "neutral cure" silicones which cure by absorbing moisture, but they are twice as expensive & hard to find (try pet stores or supply outfits- the primary use for NC silicone is for assembling aquariums- RTV solvent release will kill the fish!).

 

[w-cummins]

Originally posted by Bill Lins

Yup- you know the "vinegar" smell it gives off? Acetic acid. RTV silicones cure by releasing it. There are "neutral cure" silicones which cure by absorbing moisture, but they are twice as expensive & hard to find (try pet stores or supply outfits- the primary use for NC silicone is for assembling aquariums- RTV solvent release will kill the fish!).

Well almost, the acetic acid is the catalyst that causes the stuff to cure. It's added to the mix and then after it's has done its job, the water evaporates and concentrates the acid, you then should wash it off the surface. I guess that some might get traped at the bonding interface of the metal and the Silicone.