Piston Slap: Feelin' Rotten Sans Seam Sealer?

Sajeev Mehta
by Sajeev Mehta
piston slap feelin rotten sans seam sealer

TTAC Commentator Calgarytek writes:

Hey Sajeev,

I enjoy reading your posts on TTAC. This one is a chassis related question and concerns rear quarter panel rust issues on old school Hondas.

I’ve got a 2000 Civic SiR and I’ve poked around the rear wheel wells to figure out why that may be. It seems that Honda didn’t seal the rear quarters well enough. There is no sealant present on the inner skin of the outer portion of wheel well. The outer skin just tends to ‘fold’ into the inner well and just ‘sit there’ as exposed metal.

The question is – would applying seam sealer to the above mentioned locations protect the quarters? If so, can you recommend a brand?

If you’re wondering, I’m helping my younger cousin buy a non-rust-belt-based 2000 Acura EL. We’re planning to winterize the vehicle during the summer time when he eventually gets it.

Sajeev answers:

Thank you for your note, and for reminding us Americans that cooler Hondas are available outside of our borders.

Before answering, one point of clarification: what you see isn’t “exposed metal” waiting to rust. As part of the assembly line process (all?) manufacturers dunk their cars into a rustproofing bath to minimize corrosion. Peep this vid:

Also note how BMW’s machine applies seam sealer after the rustproof dunk. But in the case of Honda rear wheel arches…well, I wonder if any manufacturer uses seam sealer there. It’s gotta be a messy proposition.

On to your question: if you are positive you’re applying seam sealer to a rust free, dirt free, dry and solid meeting of two panels, by all means go ahead! My big concern is trapping dirt, water or anything else that can cause the panel to rust under the seam sealer. Hence why the rustproofing “dunk” at the factory is so cool.

A company called POR-15 makes a host of products for the pre-seal, I do not know of an alternative that works as well. OTOH, seam sealer is available from a host of manufacturers sold by even more vendors. Not being a body man by hobby or trade, I’m offering this as a guide instead of making a recommendation.

There you go, Best and Brightest.

[Image: Shutterstock user Sirinn3249]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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3 of 57 comments
  • Jgwag1985 Jgwag1985 on Mar 09, 2015

    POR15 waste of time. Used it per directions (all steps correctly followed) and it peeled off after a year. I had the Krown process performed on a car and was impressed. It is a yearly process though...............but I could not stand the car and after a year I got rid of it. But I will use Krown (Carwell same thing) on my Jeep when out of storage......Hagerty insurance did an article on undercoating, and recommended Krown/Carwell products. Again it must be done annually, but it's worth it.

    • DeadWeight DeadWeight on Mar 10, 2015

      POR-15 was the be-all, end-all, miracle solution to rust prevention 3-4 years ago. Fast forward to today, or even a year or two ago, and horror stories abound regarding the crap just coming off in sheets - even when metal/surface prep directions were adhered to religiously, on everything from truck beds, to frame rails, and on everything from trucks, to passenger cars, to tractors and combines.

  • Gzuckier Gzuckier on Mar 10, 2015

    Just wondering; might the rust through not be worse if the steel is thinner, because of using high strength steel?

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