Best underseal?

[Finto_316]

Hi ,
i am looking to underseal my e30, it is 100% mint, there is a bit of surface rust setting in where the shell scraped on the trailer, i will be grinding these down and zinc priming them, i will be covering the old underseal where its good in places
my questions are:
which is the best underseal for this type of job
needs to come in a big quantity
needs to be easy to apply
i have the use of a shultz gun , is shultz any good?
thanks

[polsta]

Scroll through the 1st few pages if this section there was a thread exact same not long ago, not Schultz you want a polyurethane sealant

[Finto_316]

is the polyurethane flexible ? thanks will check it out

[Finto_316]

dinitrol or dynax is very dear for such a smal quantity, im after a big drum of underseal such as epoxy mastic, anyone ever use that?

[polsta]

Yes it's the flexible stuff, would be wise to maybe remove some of it around the inner arche walls and rust hunt if your going to do it, then re do the lot, surface rust hides under there and around the edges and brackets and is best caught early, have a look through jumbos tech 1 thread he used some boat mastic stuff and lots if pictures and also pics of where issues lurked under the sealant

[Finto_316]

i will be doing a rust hunt , i dont think ill find much as in all the usual spots were they go its mint. just need to was the under side and have a good look



as you can see just on the brackets and spring mounts the surface rust

[polsta]

Yeah looks ok, rear bungs look like they need looking at maybe, like you say around the edges of things- that's where the rust can hide one the inner arch walls under the sealant, it all looks good until you take the sealant back, so it Amy all look great but as you can see you have some surface rust about and cruddy looking bits, chances are there is rust hiding unseen

As you have the car stripped like that you could do a fantastic job , but remove old sealant 1st for good measure and a real rust hunt, rather than just what you can see and re seal over anything hidden and it will be fantastic and good for many years

[Kedge]

Take that surface rust and times it by at least 4 and that might be close to how much surface rust has spread under the underseal. Been there and done it, my car has only covered 70k and looked far better underneath than those pictures. It's a long tedious job!

[Finto_316]

i cann assure yous there is not rot, the only rot was in the front footwell and has been repaired since. Theres not even a bubble on an arch,rust stain in the boot or even a scab underneath, i have prodded the underneath with a metal fork and all solid for what we can see but as yous say once yous strip it , i will try and re seal the arches with new seam sealant and we shall see how could the joins are. thanks for the tips guys

[Kedge]

I'm not saying it'll be rotted through, I said surface rust. Anywhere on mine that had a slight crack in the underseal had large amounts of of surface rust spread under it that was cleaned up with wire wheels, you'll find you'll be taking pretty much the whole underside back to bare metal to do a proper job looking at your pics.

[Finto_316]

well see how bad or good it is after a power wash, the idea of this car was having it daily/show presentable im not one of these ocd boys who buy everything new off bmw , so it will be done the best i can on the budget i have. it will be stripped where needs be and treated and sealed. i know where your getting at and i would love to strip her all down and do a proper job but i just dont have the time and money for all the sealants and under suggested in the other threads

[Rtaylor2208]

The Jotul (i think thats the name) epoxy mastic seemed to work well for jimboe30cab on his tech1 resto. I see its for sale on Ebay and its no where near as expensive as the dinitrol or dynax products.

[Finto_316]

jotun

[polsta]

i cann assure yous there is not rot, the only rot was in the front footwell and has been repaired since. Theres not even a bubble on an arch,rust stain in the boot or even a scab underneath, i have prodded the underneath with a metal fork and all solid for what we can see but as yous say once yous strip it , i will try and re seal the arches with new seam sealant and we shall see how could the joins are. thanks for the tips guys

well see how bad or good it is after a power wash

were only trying to help, i dont think you quite realise how it lurks under the sealant, it will feel solid and no visible rot or anything, but you start taking the sealant back in certain areas (that is very old) and this is what you find.. if you dont find and attend to it , and re seal over it , then it will fester and develop in to rot and holes and go through both sides

these areas were little test ones,and no visible issues or splits etc, is 100% bet money by looking at the underside there, that you will find stuff like this, its not expensive or hard to fix and as you have car on stands stripped like that, you would be foolish not to strip it back

[Finto_316]

i know your only trying to help and i appreciate it, i am going to buy seam sealer and underseal this week due to your advice, i will wire wheel along the seams and see how i get on and report back. i know i would be foolish not to have a proper look

[Finto_316]

brushable seam sealer yeah?