PQ35 Underbody Protection

Hello everyone,

Today, I took a close look at the underside of my new 1Z (Octavia 2 station wagon, but I suspect the other cars of the PQ35 platform, such as the Golf 5 and 6, look the same from below) and was quite shocked by the cost-saving compromises made in the last 12 years. My 2001 Ibiza came from the factory with a thick layer of underbody protection covering the entire surface, which held up perfectly for 12 years and 218,500 km. Even one or two minor impacts didn't change anything (which I checked each time). There was absolutely no rust down there (except for the bolt heads of the suspension components, but that's probably normal).

Below the 1Z, there are four different things to see.

Underbody protection applied in the usual way at the transition to the sills and on some exposed areas (e.g., the edges of the spare wheel well).

Large plastic covers, including "air deflectors," are located primarily on the left and right sides, between the front and rear wheels, and between the rocker panels and the centrally located exhaust system.

Heat shields above the exhaust system.

Bare, unpainted metal everywhere else.

That last point is really giving me pause... Are they seriously banking on the fact that there will never be any stone chips damaging the paint? Or are they hoping that the galvanization of the metal sheets is sufficient and that stone chips won't be able to damage the galvanization? Or have they calculated everything so precisely that stone chips can only hit the protected areas?

At least there's a 12-year warranty against rust, so they must have thought something through.

Since the PQ35 has been on the market for quite some time: Has anyone had experience with this type of "protection" for the PQ35, or would it be more reasonable to completely cover the unprotected areas with underbody sealant? However, this would likely cause problems with the warranty, because if it's done improperly, it could have the opposite effect.

Best regards,

Jan.

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Or are they hoping that the galvanization of the sheets will be sufficient and that stone impact will not be able to damage the galvanization?

Cost savings is the key word .
It should last for 10 years, assuming the rest of it lasts that long . If rust appears, it will be visible and not hidden under the coating, so that an intervention can be carried out before it is too late.


In the past, thicker and more extensive coatings were used to counteract booming noises. Nowadays, the focus is more on sealing.

It goes even further. For example, in my Golf IV and my van, the areas "under" the hood and in the engine compartment are also painted (not perfectly, but you can see the exterior color there). In many newer cars, these areas are only primed. However, I believe that besides the visual aspect, there are no other disadvantages (advantage: less paint and labor, which translates to €€€ savings for the manufacturer).

Many newer vehicles have a significant amount of plastic underneath, compared to my old car. This is certainly good as a stone chip protection, and it can also help to easily identify any defects. In the "middle" of the car, stone chips should not cause much damage. It is important that no dirt nests form there (like the ones found in the front wheel wells of the Golf IV, which extend into the interior).

I wouldn't be worried about the lack of a protective coating on the underside, especially since the existing plastic covers effectively shield the area vulnerable to stone chips.

After seeing some alarming pictures of the undercarriage of a G VI, especially the axle components, I applied an additional protective coating to mine immediately after receiving it. I used a spray-on wax from Teroson. If I ever want to remove parts after a few years, this will definitely have been worth it. Not to mention the visual appeal when reselling the vehicle. I check it every winter, and once I had to apply a little more protective coating, but overall it looks good, even with the daily exposure to road salt in the winter.

There was even a TPI (Technical Problem Information) report for the platform, which mentioned extensive rust in the area behind the rear axle and on the underbody, specifically in the area of the fuel tank. Unfortunately, a colleague experienced this firsthand with his Golf.

Hi,

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I applied a protective coating to it immediately after receiving it, using a spray wax from Teroson.

Sounds reasonable...

There, I have a whole bundle of questions for you .

Do you have a more specific product name for that, or is there only one type of spray wax from Teroson?

Did you spray all the metal parts, including the suspension components, with paint (of course, excluding the exhaust system and the heat shields)?

Does VAG (Volkswagen Group) have anything to say about this regarding the warranty, or have they completely ignored it so far?

Best regards,

Jan.

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Right away, I have a whole bundle of questions icon_smile.gif.

The problem with spray foam is that it can dry out, crack (develop shrinkage cracks), etc.

Although - with repeated use, these remedies tend to work better.

Reading material:

http://www.oldtimer-markt.de/sites/default/files/oldtimer_markt_rostschutz-test_teil_1.pdf
http://www.oldtimer-markt.de/sites/default/files/oldtimer_markt_rostschutz-test_teil_2_1.pdf

While this specifically refers to cavity sealing, the underlying principle is essentially the same.
The best affordable long-term protection would be an oil-based product.

I primarily sprayed all the axle parts, the shock absorber housings, the control arms, and the exposed underbody components. Not much is actually exposed. I paid particular attention to the vulnerable area around the rear axle.

Rust tends to form quickly on the edges of the control arms, and the wax doesn't adhere as well in those areas. However, a small amount of edge rust will be acceptable when selling a product with a 5-year warranty.

After two maintenance visits, there have been no comments (I purchased a 2-year extended warranty).

Teroson is available in a colorless and clear form, and I'm not aware of any other variations. My uncle got it from a wholesale supplier, and he also provided the lift. A 500g can goes a long way. The only downside is covering the parts you don't want to spray. However, if you have someone hold a piece of cardboard in between, it works well without much effort or masking.

So far, there are no cracks, but it is recommended to apply a second coat of sealant after the first winter.

Hi,

Quote:

I primarily sprayed all the axle parts, shock absorber housings, control arms, and the exposed underbody components. Not much is actually exposed. I paid particular attention to the vulnerable area around the rear axle.

Yes... the same applies to the Octavia, it's completely bare. Even on the spare tire well, only the edges are finished, not the center.

However, there isn't much else that's similar to the Octavia, so your choice is probably a good one there.

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Rust tends to form quickly on the edges of the control arms, and the wax doesn't adhere as well in those areas. However, a small amount of edge rust will be acceptable when selling a product with a 5-year warranty.

My goal is for the car to structurally last for at least 12 years or more. The Ibiza probably had a little bit of rust on the edges of the suspension components towards the end, but it wasn't really that bad. I'm aiming for something similar.

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After two maintenance visits, there have been no comments (I purchased a 2-year extended warranty).

After two years, everything down there will be quite dirty anyway, so you probably won't even notice it unless you're specifically looking for it.

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Teroson is available in a colorless and clear form, and I'm not aware of any other variations. That's the product.

I'm just wondering what the difference between colorless and clear might be .

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"My uncle got it from a wholesale supplier, and he also set up the scaffolding. A 500g can goes a long way. The tricky part is covering the areas that shouldn't be sprayed. But if someone holds a piece of cardboard in between, it works without much effort or taping."

I imagine the most challenging part will be protecting the rubber bushings of the suspension, but I think that should be manageable with a little bit of cardboard and/or tape.

From your words, I understand that you might be able to get by with a 500g can, but two would be better?

Best regards,

Jan.

The Kia Ceed SW, which is almost the same size, used about 4 cans of that Teroson product. After one winter, the same amount was used again, and since then, for about 3 years, it has mostly just required minor repairs. There's some chipping from stones, a few dents, but nothing else.

P.S.: The cavity preservation in the doors, sills, etc. was almost perfect. I have treated the hood (painted but not sealed) and the water reservoir in front of the windshield (primed, but not sealed) afterwards.

Note: The exhaust system still looks chrome-plated to this day, as it is made of stainless steel. We replaced the heavily rusted screws and springs, and since then, nothing has rusted there anymore. These are truly impressive cars in terms of quality, although the interior finish could be better in some details.

Jan6K wrote:

I'm just wondering what the difference between colorless and clear is

You really shouldn't post from your smartphone... it should obviously be colorless and black.

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From your words, I gather that one 500g can might be enough, but two would be better?

Okay, I only started the second can and used about half of it when I began the second pass for the final touches.

Hi,

Quote:

The Kia Ceed SW, which is almost comparable in size, consumed about 4 cans of that Teroson product.

Does it also have very large plastic parts that cover almost the entire surface? As Roger already wrote... the critical, "exposed" areas of the underbody are around the rear axle and the axle components. I didn't want to remove the plastic covers, and I suspect that Roger didn't either, considering his consumption of stone chip protection. It's not necessary to remove them anyway, because the metal is painted, and the plastic part protects it from stone chips. Of course, you should check it after hitting something, but that's generally a good idea.

Best regards,

Jan.

Jan6K wrote:

... and, given Rogers' consumption, I suspect he didn't do that either.

No, he didn't .

Hi,

I thought so.

Teroson also has "UBS Wax Spray" and "Multi Wax"... according to the description, both should be suitable for the purpose. I'll see if I can find out more about them. In any case, you should use a wax that is free of bitumen (which the first one definitely is, and it's not mentioned for the second one).

Best regards,

Jan.

Jan6K wrote:

Hi, I thought so. Teroson, by the way, has "UBS Wax Spray" and "Multi Wax"...

It was a UBS product. However, in 2010, it was only available in black.

The lower engine bay cover is engine-dependent; the smaller 1.4 16V model doesn't have it. Instead, it uses small metal strips to reinforce the front wheel arch liners. These are sometimes already corroded or rusted through in cars just three years old – they were only primed and are located in the direct splash zone of the wheels. If corrosion is detected, they are replaced without complaint with plastic supports, which, however, break immediately in winter, either due to snow buildup in the wheel wells or if the car hits a bump. Even the authorized dealership doesn't know which solution is better.

Parts of the underbody are covered with plastic panels. The brake and fuel lines are located in larger plastic areas, but are actually exposed. While it prevents direct stone impact, it also allows for good ventilation. However, the area underneath was only thinly primed, so we removed the plastic panels and thoroughly coated the metal with sealant. The rear wheel arches are completely covered, but like the lower edges of the A-pillars at the front, a lot of sand and vegetation debris accumulates in the cavities. Since the A-pillars in the area covered by the fenders only had a primer coating, the area around the fuel filler cap inside looked similar, and the rear panel underneath the rear fenders was also only primed, we applied a generous amount of Multiwax in those areas.

The fuel tank area is also covered with plastic, but only from the front and sides. I suspect these are more air deflectors than underbody protection. The fuel tank is made of either steel or plastic, depending on the engine. The 1.4 16V model has a steel tank. The sides and bottom edge were covered with rubber protection, and the rest was simply painted matte black. Matte black is porous, so a lot of wax ended up on it as well. The wax used is approximately honey-yellow, and you would be able to see any corrosion quite clearly within it.

Hi,

Quote:

It was a UBS product. However, in 2010, it was only available in black.

Based on my research yesterday, it seems that's more likely to be the case for the Multi Wax.

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A very generous amount of Multiwax was used there. ... The color is approximately honey-yellow, and you would definitely be able to see mold in it.

...because that's exactly what I think too.

@Janek: Did you check back then if it's free of bitumen?

Best regards,

Jan.