What type of sealer to use for Roof Leak Around AC and vent?

[greg67]

What type of sealant would you recommend to use to reseal around the Airconditioner and non-powered roof vents. I purchased a used 2004 TrailManor and have significant roof water leaks. I plan to remove the AC and roof vent, cut away the old sealant, and reseal and reinstall them.

Thank You,
Greg

[Wavery]

What type of sealant would you recommend to use to reseal around the Airconditioner and non-powered roof vents. I purchased a used 2004 TrailManor and have significant roof water leaks. I plan to remove the AC and roof vent, cut away the old sealant, and reseal and reinstall them.

Thank You,
Greg

I believe that you may find that there is no sealer used on the AC (I could be wrong). The AC units are usually installed with a thick foam compression gasket.

For the vents, a good quality silicone sealer works great. If you use something like 3M 5200, it will do a better, longer lasting job of sealing but if you need to replace the vent for any reason, you will find it extremely difficult (to impossible) to remove without damaging the roof.

After removing the vents, achieving a perfectly clean srface is critical. Use an ample amount of sealer on the vent so that when you screw it down, sealer oozes out of every side. Clean-up immediately with mineral spirits (some sealers only require water for clean-up).

[commodor47]

I believe that you may find that there is no sealer used on the AC (I could be wrong). The AC units are usually installed with a thick foam compression gasket.

We had our A/C gasket replaced this summer. There was a slow leak which was attributed to thick foam compression gasket. According to the dealer, those gaskets can break down over time. Have not had any water infiltration since the repair - and we had an especially rainy summer.

[Wavery]

We had our A/C gasket replaced this summer. There was a slow leak which was attributed to thick foam compression gasket. According to the dealer, those gaskets can break down over time. Have not had any water infiltration since the repair - and we had an especially rainy summer.

This is quite common. The AC unit is quite heavy and mounted high above the axle and is subject to some pretty severe jarring. The foam gasket helps to maintain a seal but gets a lot of hard service. If a sealer is used, it would break down even more quickly unless it was a very aggressive sealer (like 3M5200). If they used 3M5200 to caulk the AC unit, the unit would never be able to be removed without causing severe damage to the roof.

It wouldn't be very peasant if we had to replace the roof each time the AC had to be serviced......:new_cussi

[ShrimpBurrito]

An alternative to 3M 5200 is 3M 4200. Still very aggressive, will hold much tighter than many other silicone sealants/caulks, but is actually removable. Sold in boat stores everywhere.

Dave

[Liberty Bell]

I'm trying to track down and fix a roof leak in my 3124 King TM as well. It is manifesting itself from the center roof trim near the back of the TM, but upon closer inspection, I think it is starting closer to the mid section of the TM. In other words, the main center seam needs to be recaulked along the back side of the trailer. I also noted, however, that one foot of the AC seems to overlap the center seam. So, having not gone up there yet and closely inspected, I'm trying to undersand 1) How do you seal that foot/center seam if it encroaches on the center seam, and 2) how would you know if it is the AC leaking vs the center seam (would the AC leak flow over to the center seam, or leak directly out of unit into interior?

I've read the discussion/debate on various sealers and asked the TM factory last week what they recommened. Current recommendation is a 100% silicone, and clear supposedly adheres a little better than the white. I will probably just use the silicone but I can understand the argument for using somthing stronger as well (fix it once and be done with it).

[Wavery]

I'm trying to track down and fix a roof leak in my 3124 King TM as well. It is manifesting itself from the center roof trim near the back of the TM, but upon closer inspection, I think it is starting closer to the mid section of the TM. In other words, the main center seam needs to be recaulked along the back side of the trailer. I also noted, however, that one foot of the AC seems to overlap the center seam. So, having not gone up there yet and closely inspected, I'm trying to undersand 1) How do you seal that foot/center seam if it encroaches on the center seam, and 2) how would you know if it is the AC leaking vs the center seam (would the AC leak flow over to the center seam, or leak directly out of unit into interior?

I've read the discussion/debate on various sealers and asked the TM factory last week what they recommened. Current recommendation is a 100% silicone, and clear supposedly adheres a little better than the white. I will probably just use the silicone but I can understand the argument for using somthing stronger as well (fix it once and be done with it).

The seal for the AC unit takes place around the (approx) 12"x12" hole that the AC is mounted through. The "Leg" that you are referring to does not seal to the roof. That is just a removable shroud and should not be caulked to the roof. A certain amount of water travels under the AC shroud but should not pass past the foam rubber seal that the AC actually rests on.

If that seal is leaking (which is quite common), the water may enter the interior in different places. The water may run down past the top layer of aluminum, enter the foam core and travel across the bottom layer of aluminum and manifest itself as an interior leak nearly anywhere.

It seems to me that the AC unit should be removed periodically and that seal replaced maybe every few years, if you tow your trailer a lot. The seal is mainly effected by vibration. It's not effected by the Sun. Sitting should not effect the seal other than just drying out and cracking over time.

[ShariW]

Use 100% Silicone. It's messy and had to cleanup but it wears like IRON. Try to be neat when applying it. Wear rubber gloves because it is difficult to get off or skin. I live in Tucson AZ, this is the only think I have found that can stand tremendous heat. And it doesn't rain here, it POURs in terrential down pours we call Monsoons.

[Liberty Bell]

Thanks for the insights on the AC leak. Now I'm thinking it could also be the AC gasket contriubting to the leak, but I'll probably start with the center seam. Does anyone know if there is a post out there somewhere on how to remove a roofmounted AC, or is it a fairly intuitive process? And is the foam gasket something you could pick up at most RV stores?

Thanks.

[Wavery]

Here are the installation instructions for a Carrier AirV. I'm not sure what AC that you have but they all mount pretty much the same.

http://www.airv.carrier.com/Files/AirV/Local/US-en/customer_service/99-00469-02.pdf