TR4/4A To Undercoat or Not. That is the question

[Scotsman]

This question has come up before but am asking it again as new "and improved" products come on the market and am interested in feedback regarding using Bedliner or similar products to undercoat and treat the interior of our cars. My experience with traditional undercoat is that it tends to peal off over time, trap dirt, moisture, and salt underneath and be a cause of severe rust rather than prevent it. I am doing a body off restoration with the car sandblasted and epoxy primed. The painter is recommending I use bedliner both under and in the cockpit saying that the product wont fail like the old stuff. My concern is that shops have been saying this about undercoats since they first came on the market, and they love to charge to put it on. Once on it is next to impossible to detect rust, very difficult to remove, make repairs, and remove body panels.

A classic car mechanic friend of mine recommends using no undercoat materials and touch up any paint chips that may appear as you go.

I live in western Oregon where it rains a lot and they don't use salt on the roads. The car will primarily be driven in fine weather but expect to drive it in the rain on occasion. I am leaning in the direction of not having it applied

 

[Darrell_Walker]

I can't give any advice about bed liner and such, I do know lots of folks use it. But when I did a full restoration on my TR4A years ago, I went with just paint on the underside, with the same theory, I can see (and fix) any issues. I probably live in a similar climate as you, and have not had any issues. Now my car does (despite my best efforts) leak a bit of oil, and that generally keeps everything underneath well protected.

 

[Rut]

I’ve used Raptor Liner on several cars and sticks great, can be tinted and helps with noise, heat and vibration. The pictures are of a Bugeye in process of being sprayed with tinted bedliner over epoxy primer and I had the floor sprayed as well. I’m going to spray the underside of a 75 Scout II in the next week or so and I’ll probably put 3 coats on it since it’s an off road vehicle.
Rut

 

[RGK]

No undercoating on any vehicles. I live in the northeast, drive the cars year round. In winter I use Salt-Away, which I used on my boat, good stuff.

 

[NutmegCT]

Seems there are many types of epoxy primer, and one of those types has already been applied to your car. Depending on the type, and how thick it's applied, an epoxy primer will serve as an undercoat itself.

Just my two cents.
Tom M.

 

[Scotsman]

Seems there are many types of epoxy primer, and one of those types has already been applied to your car. Depending on the type, and how thick it's applied, an epoxy primer will serve as an undercoat itself.

Just my two cents.
Tom M.

I am not referring to primer, but to what is sometimes called underseal. This was originally a tar based compound, and now there are products like bed liner, etc.. The two cars I have both had the the earlier tar underseal/undercoat, and in both cases the underseal has lifted off in places in large chunks, with dirt, mud etc under it.

 

[charlie74]

My daily drivers have been treated with Woolwax which is a lanolin based undercoating. I applied it myself with a gun bought from amazon. It isn’t terribly difficult to do but it isn’t fun when using jack stands. A hoist would have been much easier, but then most jobs would be… It goes one clear but of course it does attract dirt. The nice thing is is that it never hardens, is somewhat self healing and if done in warm weather it creeps so coverage is good. The TR6 has an oil based undercoat inside the frame and many of the body panels but the outside is red oxy-primer and painted. It’s been like this for years and there is no rust. It is not a daily driver and only comes out when the roads are clean and free of salt, no gravel and fair weather only…

 

[glemon]

charlie74 wrote "It is not a daily driver and only comes out when the roads are clean and free of salt, no gravel and fair weather only…"

This...most all of us restore cars with some degree of rust and swear we are not going to let the rust take gold again. However, when we re do the bodywork we apply primer more carefully than the factory ever did using better paint products, then the cars lead sheltered lives after that. I don't think extraordinary measures are needed for rustproofing other than described above. Have also kept a couple cars I have repaired epoxy primered for over ten years with no rust issues. The underseal may even detract from resale value as people speculate it may be hiding something and it may hide the good quality of your clean up and paint of the chassis .

I am not suggesting some sort of underseal is a crime against nature, and it may have some sound deadening qualities, but don't think it is needed for rust protection in a hobby car.

 

[NutmegCT]

" ... The underseal may even detract from resale value [or resale potential] as people speculate it may be hiding something ..."

The dubious "old car with a shiny black undercoat". Agree 100%