Underseal type?

[Carman35]

I have been using Hammerite Underseal but have been advised that bitumen based underseals are not good in the long run because they dry out and water can get behind them.

BMW (I have E30s) recommend polyurethane. What is the difference please and is it worth the extra cost for the polyurethane type?

Thanks in advance for any helpful advice.

 

[Burnerman]

I use a spray body schutz by 3M, which seems to work well enough.
One things for sure, if its painted over rust it won't prevent further corrosion at all - irrespective of what material you use.
John

 

[Carman35]

Thanks, John. Very helpful. So, what about Waxoil first (let that dry) and then underseal?

 

[Mursal]

Not sure about the sealer over the Waxoil. might not take/grip.

Best to descale using a hot water pressure washer or grit. Let it dry thoroughly and prime rust spots and paint. Several coats of both on untreated areas. Then reseal using the best you can afford, especially if you intend keeping the motor. If you are not keeping it, just Schutz using the application gun after washing. Yes it does dry out, you see it coming off as you hit it with the washer.

Not an easy job, especially hand painting the recesses, we tape a long piece of timber onto the brush handle, but its difficult and time consuming.

 

[Burnerman]

Waxoyl underseal has waxoyl in it (!) so the claim goes, but you cant put the wax on first and the underseal on top.
Personally I'd go for the body schutz on all of the area which will get spray and grit abrasion, and then a good body wax on what remains.
Bilt-Hamber claim to be market leaders in products such as this.
John

 

[Carman35]

Many thanks, again, John. Looks like Bilt Hamber is it then.

 

[Belle427]

check out dinitrols products, they do a specific underbody wax. All quality stuff from them.

 

[Carman35]

Many thanks, ch427. Will do that.

 

[Nige F]

I use a spray body schutz by 3M, which seems to work well enough.

3M - Minnesota Mining + Manufacturing - made the original Underseal - but like Hoover it became a generic name . So their schutz should be good

 

[Carman35]

Many thanks, Nige F. Much appreciated as well.