How to underseal a vehicle yourself with Lanoguard or Bilt Hamber. If you have a limited budget or you are glutton for punishment the following guide will explain everything you need to know about undersealing your car, van or motorhome. For most people it is simply not worth even buying equipment and spending 2 days doing hard dirty work (Don’t say I didn’t warn you 🙂  You will need a bare minimum of a jack, 2 axel stands and other equipment. So if you want us to do it for you in the comfort of your home REGISTER Below we come to you anywhere up to 2 hours from N19 North London and in the Midlands and North West. Prices start from £350.

Underseal is a liquid that forms a barrier to oxygen and displaces moisture it is PLACED ON SURFACE rust and bare metal after loose and excess rust has been removed. 

We recommend Bilt Hamber Dynax UB it finishes in a touch dry matt black or clear coat which makes your vehicle look new. For D.I.Y. use without an air compressor you can by aerosol cans on the website BILT HAMBER WEBSITE. Bilt Hamber can be expected to last 3 years whereas Lanoguard only lasts 1 year. In 2 separate tests I carried out lanoguard test strips of metal started to rust in a few days and Bilt hamber remained rust free and was impervious to hose water.

[start-read-more]In more scientific laboratory salt spray tests (ASTM-B117) Bilt Hamber totally out performed a lanolin based sealant which is widely believed to be lanoguard. Other products also perform well like LPS3 and waxoil by Jenolite but for me Bilt Hamber Dynax is the best underseal on the market. You can buy Bilt Hamber Dynax in clear or black HERE  and it costs £16.95 for a 750ml aerosol as of 2025.

The 5 litre tubs offer much better value but you can only use them if you have an air compressor and spray gun in which case you can dilute it with 500ml/750ml of white spirit because Dynax in tubs is much thicker then the aerosol version.   I do not get a commission by the way its just the best product according to our research and own tests, Go to this page to see compilation of test videos of different products from around the world. 

[end-read-more]

• Lanoguard washes off ALOT easier than Dynax.
• Dynax is half the price of Lanoguard 
• Lanoguard only comes in clear Dynax comes in black and clear
• Dynax needs be washed of with white spirit.
• Lanoguard can be washed of with water.

[start-read-more]

• dries to a semi hard wax which looks amazing.
• Lanoguard stays wet looking and sticky attracting dirt.
• Dynax will last 3 years or more without needing a recoating.
• Lanoguard must be applied every year. 
• Dynax comes in an easy use spray can.
• Lanogaurd is applied from a manual trigger spray bottle.
• Lanoguard has a pungent smell of sheep Dynax does not.
• All clear coats like lanoguard lend themselves to inconsistent finish because you cannot gage the evenness and thickness of the liquid applied.

[end-read-more]

You will need a minimum 2 axel stands and a jack to work on your vehicle.

• Car 5 cans – Van 7 cans of Bilt Hamber Dynax UB 1 can of Dynax s50. £100
• Tarpaulin 6 – 4 meters.  £15
• 2 axel stands and a jack.  £60 amazon/Ebay
  
• White spirit to clean the Dynax if required from you hands or vehicle. £5 500ml
• Disposable gloves get good ones or they will break all the time. £7.99 box amazon
• Protective dust mask. £5 – £10 get a few 
• Protective Goggles. £10
• Balaclava is useful for face protection. £10
• Large flat head screwdriver, wire brush and air can.  £15 to £20
• Hammer, Stiff Dustpan Brush and Long Pipe Brush.

[start-read-more]
Around £220 for everything you need assuming you do not have axel stands or a jack.  Even if you are amazingly frugal it will cost a fair bit of money things like eye protection and a tarpaulin must be purchased. When you add the 2 days it normally takes a beginner doing a decent job it is easy to see why its actually easier to get us to do it for you.

In the list above I have suggested 6 cans of Bilt Hamber Dynax for car which are £17 each. With an air compressor you can buy the 5 liter (£50) can and dilute it with 500ML of white spirit because it is rather thick for most spray guns. 5 liters would be ample for 1 car but that is coating every square inch metal and non metal and also coating the wheel suspension and inner arch. You could use a lot less cans if you simply covered metal. I however normally put a thick even coat all the way round for aesthetics as well as rust prevention. Lanoguard per liter is around the double the price of Bilt Hamber Dynax the company suggest you only need a small amount but that is by using a thin uneven coating which is not ideal and could be achieved with any undercoating. Also lanogaurd is simply not as good as Dynax and must be applied every year compared to every 3 years for Dynax.[end-read-more] 

Doing this on your own it us assumed you will not have 4 axel stands or ramps. So a hard job will be made even harder but having to raise the vehicle twice with 2 axel stands giving access to one side of the vehicle at one time.

• Lay tarpaulin
• Lift the vehicle 
• Wheels at least 10 cm from the ground or more.
• No outer protective sheet is needed.
• A bin liner cover for the cambelt.
• A bin liner for the brake discs. 
• Exhaust cover optional underseal marks will quickly burn off without harm.

[start-read-more]
Some people do suggest that you can lift the vehicle sideways and that could give a good access however it depends how comfortable you are doing that. There are resources online to about lifting a vehicle but the wheels should be a good distance from the ground atleast 10cm and preferably more. I do not mask around the vehicle it is a wasted step. It is easier to quickly wipe away marks with a cloth dapped in white spirit when you have finished. A protective sheet attached to the vehicle can cause a mark at the point where masking tape is used to attach the sheet 

[end-read-more]

In its simplest form preparation amounts to removing loose dirt, debris and scaly rust.  A basic tool set for this would be a wire brush, Hammer and heavy flat head screwdriver.

 

Remove all undertrays these are normally held on by 8 – 10mm bolts and or plastic fasteners. 

• Remove the wheels and plastic wheel lining these usually have plastic fasteners or small bolts.
• When the trays and wheels liners have been removed put a bin liner over the brake disks of each wheel and over any engine belts visible through the wheel arch.
• It is not necessary to cover over the car or exhaust. Any marks on the exhaust will burn off and marks rarely go on the paint work if they do you can quickly wipe them off afterwards with a cloth and white spirit.
• Remove all plastic covers under the car these are normally 8-12mm bolts or plastic fasteners which can be removed with a flat head screw driver or dedicated tool with a U head.
• Make a video of the rust describing the location clearly. You cannot know how well the sealant is working in the future if you have not documented the rust properly.

[start-read-more]

• First start by removing loose and crusty rust. Its impossible to reach every part but remove what you can with you wire brush using sweeping motion back and forth until no rust or debris is loose. 
• The hammer and screwdriver can be used for heavy scaly rust. 
• Ask yourself is the surface solid without flaking? There is a common misconception that to stop ongoing rust that you must remove all rust. That is NOT the case the underseal is designed to adhere to stable surface rust and displace moisture so it stops ongoing rust (removing all existing rust is not necessary to stop more rust forming). 
• Check spots of rust in some cases spots of rust can work there way under factory rubber underseal or paint so you need to peel away surface around the spot. 
• When you have finished removing loose rust move onto general cleaning. 
• I will assume the car is bone dry if not you can put a cover over the vehicle if it is raining otherwise there will be water leaks in some places.
• Not having an air gun is a major disadvantage which I would normally use with a brush to remove a lot of mud a debris. However you can try a hoover or air can. 
• Now use the 2 brushes: dustpan and longer brush and cleaning wipes if obvious dirt on surfaces needs to be removed but generally speaking the idea here is to brush away loose mess so the surface is solid and stable.
• It is physically impossible to remove some marks and serves no purpose whatsoever. Remember you are not painting the underside you are applying a heavy waxy product which will displace moisture as long as the surface is not sopping wet or caked in mud it will adhere and form a barrier to moisture and oxygen.
• Some people will insist on a Jet Wash and can often be heard mumbling “its all in the prep” and “a fair days pay for a fair days work” and “Never put off until tomorrow what you can do today” These are often the same people using Lanoguard which is very poor product.
•  You can jet wash a car but NEVER do it first which most garages do. Why because if salt irons are present they will be under the rust you remove and under the debris.  So its always best to remove most of the debris by hand. However be aware a jet wash is very limited. I remember once undersealing a Toyota 4×4 the owner told me he had washed the vehicle twice and yet it was caked in muck. A dirty car can never really be washed with a a hands free car wash and the dirt under a car is ALOT heavier. 
• If you do wash a vehicle use AUTO WASH from Bilt Hamber as the main cleaning agent this has anti corrosion properties and as a rinse use Atom Mac also by Bilt Hamber diluted in distilled water as a rinse. Leave everything a few days to dry and do this all in the summer.
• Many vehicles will have mud in the chassis and in the sills washing with normal water will make the mud soggy and repel the underseal. 
• Bilt Hamber will work brilliantly on a stable surface a small amount of adhered dirt WILL NOT stop it working in the same way dirt in surface rust does not stop Bilt Hamber working. No matter how much you try unless you remove all parts from a vehicle and use a dry ice blaster your car will always have dirt you cant reach.
• The main thing to avoid is loose up mud or wet surface. Mud can often be found at the end of the sills near the wheels if you pry back the plastic trim.

When I prepare a vehicle at someone’s home I have an advantage of a 50 Liter air compressor. This allows me the benefit of a needle gun which is great for reaching into tight spots and removing heavy rusted scale.

Other tools I will sometimes use is an angle grinder with wire brush attachment, this is only really good for larger flat areas like the frame of a motorhome or van more so then a car.

The single most important benefit of the compressor is for a high pressure air gun as used by professional car cleaning (detailers) The gun removes a huge amount of debris and mud from the inner chassis by pointing the gun tip near open holes.

So with this in mind investing in a air can “might” serve a similar function. I remove a huge amount with the air gun so it is a big loss to a home DIY set up. Although some hoovers or a leaf blower might be able to do the similar. 

You will not be able to do a perfect job without an air compressor and you can’t use the most efficient tools. That said you can still a very good job and put a coating on to displace moisture and oxygen. Bilt Hamber Dynax is so much more forgiving then other Lanoline products because it adheres to the surface and dries. Other Lanoline products like Fluid Film, Woolwax and Lanoguard stay much more wet in consistency and loosen the surface they  are also sticky which attracts dirt. Professionals will simply do a quicker more efficient job this is not rocket science. Apply a Bilt Hamber Dynax to a stable surface and your novice job will be superior to any professional applying Lanoguard.

[end-read-more]

As a rough estimate you will need 5 – 7  Cans of Dynax UB for the average car and 1 can of Dynax s50 which you can use in the sills, wheel arches and the holes in the vehicle body.  These are simply large Aerosol cans somewhat nicer to apply then a manual trigger mechanism which Lanoguard use at the moment. 

 

• Apply the Dynax S50 into all the holes in the visible working your way to from the front to the back. Also Spray into the suspension drain holes using the 360 spray tip which comes with the can. (Check the video above)
• Applying into holes is easy just poke the wand in and when completely inserted press the trigger and withdraw slowly. The 360 tip will coat the whole inner surface.
• Spray into the doors via the drain holes and then into the Sills (rocker panel) running along the side of the vehicle under the doors. The Sills can be reached by removing round bungs under the car and also often by removing plastic trim inside the bottom were the door closes into.

• The Aerosol cans spray will apply the product somewhat lighter then the same product from the tubs which is used with a spray gun attached to an air compressor.
• Just keep your hand moving back and forth at a distance which gives an even coverage without forming a puddle which drips. (You will find your method within a few minutes)
• Don’t worry about applying too much or slight over spray. If you spray too much it will puddle up and drip which can look ugly and mean you will have to wait longer for it to dry.
• The most important parts to avoid are the belts near the engine which must be avoided at all costs. You should avoid the brake disks and exhaust. However masking of the exhaust or brakes is not useful. Overspray on the exhaust will burn off and the brake disks can be wiped down and don’t require being covered.
• Bilt Hamber Dynax recommend 2 thin coats 24 hours apart that said I apply a 1 thicker coat from a spray gun. Even 1 coat will be totally superior to Lanogaurd.
• The vehicle can be used an hour after application but wont fully cure for 24 hours in the summer or up to 4 days in the winter. It is best if possible to allow the vehicle to dry for 1 day if you can.