Seam sealer not setting

[Rollin]

There's an area on my old Mercedes where 2 panels meet that was filled with some sort of sealant. This had started to break down and causing a water leak. I have the workshop manual for the car and it states that the area may need to be resealed occasionally. I cleaned out the decaying sealant and I've used some seam sealer to refill the joint. The stuff is filling a space of about 15mm deep and 5mm wide. Problem is, it's not set fully after 24hrs. The surface has skin over fine though.

Car is outside and it's been a bit chilly since I did the work. Is this why it's not set or is it because it's the wrong material and too thick?

[V8covin]

If you've used a pu sealer like sikaflex or tiger seal it skins over in a couple of hours but takes upto 24 to fully cure

[Rollin]

It was some Upol Grey Stripe that I already had. Dunno if that's PU or not

Think I should have used Tigerseal but hoping it's the cold temps and thickness that's delaying the setting.

[V8covin]

Brushable seam sealer is meant to go on thinly so it'll probably take a while for it to harden the way you've used it

[227bhp]

That gap is huge and you've used a sealant which is only supposed to be brushed (clue is in the name on the tin) on an already tight welded joint.

[Rollin]

So does that mean I just wait until it sets or dig it all out and use something else?

[Matt_E_Mulsion]

Leave it for a few days to see if it hardens off a bit more before doing anything drastic.

[paintman]

The U-pol is intended for overcoating welded seams, not filling deep holes. Put on in that quantity my concern would be shrinkage as it dries & possible loss of adhesion to the panels allowing water ingress.
https://www.u-pol.com/uk/en-uk/product/upol/coatin...

[Rollin]

paintman said:

The U-pol is intended for overcoating welded seams, not filling deep holes. Put on in that quantity my concern would be shrinkage as it dries & possible loss of adhesion to the panels allowing water ingress.
https://www.u-pol.com/uk/en-uk/product/upol/coatin...

That's what I'm thinking. What would be the stuff to use? Tigerseal?

[paintman]

As per V8covins post I would be inclined to use either tigerseal or one of the sikaflex mastics.

[227bhp]

Strange a car manufacturer has left such a huge gap which requires periodic refilling? It sounds like something a house builder would do.

[Rollin]

It's a W123 Mercedes.

[anonymous-user]

Mercedes should be able to supply the right stuff, might be a better option than just using whatever is to hand and redoing it several times.