Underseal

[mrb]

My chassis had been undersealed prior to ownership ! just wondering if it is necessary or advisable to redo it periodically ?

have not needed to disturb it for any reason - and just wondering if it has to be removed ? or just recoated ? due to holidays it as been stood in dry storage all winter and not been subjected to salt etc - so now seems a good time to consider !

Regards Dave

[panky]

I would check for any loose or flaking underseal and remove it back to good material, make sure the metal is sound and treat and paint as required and re coat. Underseal goes hard over time so a coat of wax oil will help make it supply again and less prone to cracking and flaking.

[mrb]

Thanks very much - that sounds easier than under sealing too !

Thanks again

[biomed32uk]

Ordinary old fashioned underseal really is not the best as above, it cracks and flakes, then allowing water behind it and to become trapped.

Dinitrol and the likes are the much better option, they do different types depending on where its going. Inside cavities and box sections are really important, the nice runny cavity wax desgined for this purpose get everywhere, especially with 100psi behind it blowing it in.

When I did the underneath it was first coated in cavity wax and then gone over with the black, makes a very complete job of it.

The black dinitrol underbody wax never really sets, and self heals, great stuff. Its a really filthy job though.

[panky]

Agreed, but if it's already coated in an 1/8" of black bitumen. and you don't fancy stripping it all of, a good dose of wax oil wont do any harm
I spent a week under my camper chipping and scraping and found that the metal under the sound underseal was like new, still with the original coat of paint on it( especially where it was soft from gearbox oil leaks ), but where it had degraded was another story I repaired where necessary, treated any surface rust with Aquasteel (after a good wire brushing) priming then a good couple of coats of chassis black - then wax oil. I guess it all depends when the coating was applied and what it was applied over - on new metal then brilliant, but splurged on in an attempt to cover up a load of rust then not so good I would suggest having a good prod around and make sure the underseal isn't hiding anything.

[biomed32uk]

I would second that approach, definately not fun scraping it off when it is sound. i was going more for the dont put another coat of ordinary underseal on, waxoyl, dinitrol, dynax are all way better, and can be sprayed on which makes a much better job. I personally like the last two, but anything under there is good.

I have pumped the stuff in everywhere I could find, it was running out of all sorts of places, if I could get the spray gun probe in then in went cavity wax.

If you have a compressor then a proper wax injection gun is well well worth it.

That the good thing about old cars with oil leaks, its not an oil leak, its the inbuilt corrosion prevention system working perfectly

[mrb]

Thanks for all advice

car was under sealed from new and had a full restoration in 2010 including a underseal according to invoices have had it on a ramp at the local garage and we have had a good prod round and found nothing that jumped out as us ? just thought that a top up would be an advantage ?

and yes agree that the g/box oil leak does look after a small area ha ha

Regards Dave