GEN 4 Jimny undersealing wearing off

Can't grumble at that service. Sounds like they know what they are doing and are as surprised as us that it came off. Fair enough avoiding pressure washer, but it should withstand similar to water spray from wheels, so just stand back a bit if you do.
Hope it stays on and thanks for update.
Mike

I picked up my Gen 4 Jimny last Friday, first one I've ever owned. Is undersealing something that's recommended?

My take on this is that given the pretty terrible reputation of Jimnys for rust and the likelihood of the Gen4 being no better (mine seemed to have an endearing random style of rustproofing underneath and was already showing some rust signs under a year old) it is probably good to have it done. However my dealer said it would invalidate any bodywork warranty (probably worthless anyhow) - other dealers have said the opposite - from an earlier thread. My concern with the undersealing is how durable it it, see above. I think you will be commiting to annual re-application (Preserve and Protect in Paisley do this free except for the material). Power washing is not advisable and this is awkward given so many of these machines get covered in mud. At the end of the day if you did not underseal it and cleaned it scrupulously every week and more often in salty conditions, perhaps with one of those specialist underbody spray machines it might be just as effective but who is going to do that. I would do it when fairly new, I wold never buy a secondhand car that has been undersealed mid life: this is a favoured way to conceal terrors in Landrovers, you see them advertised all the time.

I think we need to differentiate between the term Underseal and Protection wax for those joining the thread.

Underseal is a generic term for a rubberised paint that is applied to potential impact areas to provide some level protection from stones etc. Suzuki have made an art of only applying underseal to the absolute minimum of areas that could be subject to this type of damage, it's a way of saving cost. So on all Jimnys it's normal to see the underseal in patches, other areas will just be painted steel, so it's not actually coming off as it was never there in the first place.
The Jimny's tend to rust first on chassis welds and internal box sections, this you can see easily as they are usually just painted areas. Rust can form under the Underseal but it's difficult to see as the flexibility of the covering prevents it showing.

So what can you do?

One method is to get the underside of the vehicle treated with a wax formula. This product never fully sets and has good creep properties when applied to get between metal components. It can also be injected into box sections to prevent rust developing, a common practice in premium vehicles, but sadly not by Suzuki. As the wax will never fully dry it will need a top up every few years, particularly in high splash areas.

Geezerdan
I firmly believe that if you intend to keep your Jimny it's well worth the cost and effort of getting the underside treated with a WAX product, be it DIY or a professional as per Micheal.
NEVER get your vehicle sprayed with underseal, it's a good way to hide rot and trap rust, as Micheal said it's common on rotten Land Rovers etc.

So WAX = yes
Undersealed = no

You do have the body warranty issues at the dealer's, but they tend not to do anything on the underside, usually it needs to be a hole before it's a warranty claim. You are not treating the paint work above so it's going to be hard for them to claim it's had an impact on the bodywork.

Of course this is just my opinion and only wishing to highlight the difference.
All the best
Mike

Before we picked up the Jimny I phoned Suzuki GB and was told if you want to get car undersealed that's fine would not void warranty I got the dealership to waxoil it before I collected it I think they said bring it back every 2 years.

Fat would be a 3rd type of product in addition to wax and underseal. The main differences to wax are:
- does not dry out after 3+ years
- is somewhat weaker against mechanical damage
- stays soft and on the next warm day the fat will get softer and re-cover areas with mechanical damage
- whenever you work at your Jimny, the fingers get fatty (ughh!)
- cannot easily be done by yourself because you need to spray hot liquefied fat.

I had fated my Jimny and so far I can recommend it. Definitely in areas without mechanical damage, e.g., inside the frame, .... . The product I used was Mike Sanders, 8kg of it.

The picture shows, what the jimny looked like directly after. The yellow color means that the there is air from hot spraying inside the fat. After a month, this was all glossy, fatty as can be seen in the second picture.