Dealing with old Under Seal

Hi Guys, the PO of my 1977 Bay had undercoated the van and it is now cracked and bubbling in places also with some rust showing through.

Any suggestions on how to deal with this?

Do I:

1) Clean up the loose bits, deal with any rust patches and re under seal it all?

2) Clean up the loose bits, deal with any rust patches and re under seal it all?

3) Scrape back all of the underseal, deal with any rust patches and paint a new without underseal. Possibly with a modern high endurance paint?

4) Any other suggestion?

Thanks in advance.

 

I'd go with 1 & 2 as they are the same..!!?? Just clean back the bits that are loose and fix rust if any found and re-apply under seal is what i would do.

But if you have hours/days/weeks to kill you could strip the lot..!!!

 

I'd strip the lot as it may be hiding things you cant see!

 

Hi Alex, that's what I am leaning towards but I am concerned that I will do loads of damage with a scraper to the original paint underneath that mainly looks sound.

Is a scraper the only way to get the old underseal off?

 

You are correct @Gar72

On 2) I meant to say clean off all, deal with rust then re underseal..

 

I have heard of people using diesel on a rag to get it off?

Sounds sketchy to me though.

 

Personally, if there're any clean areas of the original underseal, I'd leave them. The soft VW wax was actually pretty good stuff - you'll find nice shiny paint underneath, which you could damage if you scrape it.

WD40 should dissolve it, if you must.

 

I took the worst areas of mine off with a metal scraper and used lots of white spirit and turps with a more gentle plastic scraper for the salvageable areas. It took forever and a really cricked neck to do it, but was well worthwhile. Even areas that seemed okay hid rust and I was able to treat and repaint.

 

Not as much damage as water and rust will do to the original paint. If there's some patches showing, there's a good chance there will be others just below the surface, thick schutz/underseal hides a multitude of sins. I'd strip it all off, and depending on how bad it is, maybe paint with something new, stonechip the wheel housings and then waxoyl everything.

 

I removed all mine, just so as I knew that i caught all the hidden rusty bits,
A scraper and white spirit or thinners worked for me.
It seemed to take forever but well worth the effort.