What is the truth about using foam, such as great stuff

[Buck 5,000+ posts]

I've heard various thinks about using foam.

-it collects moisture and rusts your vehicle from the inside out

-will eventually start to dissolve or break down over time.

My question is what is the alternative? CCF? CCF looks like spongy material, does it not hold water?

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[geonfreaq 10+ year member]

I have used the great stuff pond foam in a few saltwater fish tanks I have built. It does not break down or leach anything into the water so I would assume that ot won't rust anything in a vehicle.

 

[Buck 5,000+ posts]

They make pond foam?

 

[keep_hope_alive Premium Member]

is that more like structural foam? a two-part pourable mixture?

CCF doesn't hold moisture - by name it is closed cell foam. closed cell = no water absorption. but it is soft. open cell foam does hold moisture.

what is your goal with expanding foam?

 

[Rudy 10+ year member]

There are few reasonable uses for expanding foam in this context. I think the rust issue may have been with early versions or with latex foam, which wouldn't be appropriate here. I can't swear there aren't any rust problems, but I did have some in a car for 5 years before removing most of it and saw no evidence of corrosion.

The first important point is that it really isn't removable without going to great lengths. Even then, you won't be able to get the sheet metal clean again without removing the paint or e-coat at the same time. It's meant for weatherproofing and is very durable. It forms a rigid closed cell material that is quite inert - materially and acoustically. It degrades when exposed to UV, so exposed areas may need to be painted. It is very messy stuff to apply.

All of that said, there are two applications where it might be useful. The first is filling voids that would otherwise transmit sound from one area to another. Rear quarter panels are an ideal illustration if they have inner and outer skins. Fill the void with expanding foam and air won't move through any more. If this is part of a noise reduction strategy, it would probably be better to fill the void with an absorbent material.

The second is in reinforcing panels to resist deformation caused by high SPL. Quarter panels are a good example here too - fill the void and you effectively lock the inner skin to the outer skin, strengthening both. Filling the space between the trunk lid outer skin and inner skin may strengthen both. If you're just trying to stop rattles between the 2, a few dabs of RTV silicone is a much neater solution.

 

[Buck 5,000+ posts]

This is to take up the empty space in the rear hatch.

 

[dumple 5,000+ posts]

id.say your safe using great stuff.in your trunk lid

 

[Rudy 10+ year member]

This is to take up the empty space in the rear hatch.

Hatch door? Very difficult to control the stuff around mechanical systems. Pretty easy to think you've applied exactly the right amount - until you see it consuming the locking/latching mechanisms.

 

[Buck 5,000+ posts]

Hatch door? Very difficult to control the stuff around mechanical systems. Pretty easy to think you've applied exactly the right amount - until you see it consuming the locking/latching mechanisms.

I know exactly what you are saying. There are just 2 completely hollow sections on either side of my door hatch. Very large sections.

 

[Rudy 10+ year member]

I know exactly what you are saying. There are just 2 completely hollow sections on either side of my door hatch. Very large sections.

You really don't have to fill the entire thing to get the benefit - if they're really large, you wouldn't be able to do it all at once anyway. Too much in an enclosed space won't cure. What are you trying to accomplish? Not likely to help with rattles and pressure usually releases around the weather seals instead of distorting the tailgate sheet metal. Even if it goes terribly wrong, replacing a tailgate isn't the worst thing that could happen.

 

[Buck 5,000+ posts]

You really don't have to fill the entire thing to get the benefit - if they're really large, you wouldn't be able to do it all at once anyway. Too much in an enclosed space won't cure. What are you trying to accomplish? Not likely to help with rattles and pressure usually releases around the weather seals instead of distorting the tailgate sheet metal. Even if it goes terribly wrong, replacing a tailgate isn't the worst thing that could happen.

I really don't know to be honest. It seems like hollow places like that aren't good. I don't know why, it's a feeling.

 

[Rudy 10+ year member]

I really don't know to be honest. It seems like hollow places like that aren't good. I don't know why, it's a feeling.

Not to be a smart ***, but there are enough areas we can identify as needing work not to start making irreversible changes to the vehicle on a hunch. Might end up being something to worry about later on but I wouldn't make it an early priority. Taking care of the big issues first makes it much easier to figure out where additional effort is required.

 

[Buck 5,000+ posts]

I get you. The reason I say that is because the rear hatch is where my port loads off.

 

[Bumpin' Goalie 10+ year member]

I'd like to take this time to simply say:

I appreciate Don Sambrook.

Carry on.

 

[Rudy 10+ year member]

i'd like to take this time to simply say:
I appreciate don sambrook.

Carry on.

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