Opinions on pressure washing underside

[Smudgemanuk]

Hi all,

I was recommend by a friend of mine (a mechanic) that to clean the underside of my car before undersealing, I should pressure wash it.

Which sounds helpful but I am worried about forcing/ trapping water in places it shouldn't be, leading to rust

I would love to hear your opinions on this

Thanks Chris

 

[z3ddie]

Dry ice cleaning. - getting more popular with restoring unsides - plenty of youtube vids on it - think you may have to find a specialist though

 

[John_B]

Karcher hire-out dry ice cleaners. They say on the website that they're "not suitable" for home use, I asked about whether this was a rule or just a recommendation, they said they would hire them to a home user if someone wanted one, however the compressor requirements are quite high - 120CFM @ 10bar.

Just whatever you do, make sure the underside is BONE DRY before applying underseal

 

[Smudgemanuk]

Oooo interesting, I shall look further into that option

Do you think it would dislodge the very stubborn road crap that has built up over a few decades?

 

[John_B]

Oooo interesting, I shall look further into that option

Do you think it would dislodge the very stubborn road crap that has built up over a few decades?

Yes. Easily!

Watch some YouTube videos of it in action, it's very impressive

 

[Pingu]

Karcher hire-out dry ice cleaners. They say on the website that they're "not suitable" for home use, I asked about whether this was a rule or just a recommendation, they said they would hire them to a home user if someone wanted one, however the compressor requirements are quite high - 120CFM @ 10bar.

Just whatever you do, make sure the underside is BONE DRY before applying underseal

Not many home compressors will be capable of that. Mine is 8bar / 15CFM. The biggest at Machine Mart is 40CFM, and that costs over £2,500.

 

[Smudgemanuk]

Yeah good point, I don’t think our compressor is very powerful either.

I also think that I might aswell leave the original factory underseal, if it is still ok, and underseal over it when it is clean. I think the dry ice might just take it back to bare metal, but maybe that is what I want

 

[ktnez99]

OK. I have to add my 10p worth here.

I had a company clean the underside of my Z prior to sealing it as I was thinking about the longevity of my car. The company concerned pressure washed the underside as the garage closed one night and sealed it the next morning as it opened.

I’ve subsequently learnt that this is a massive no-no! The company didn’t give my car’s underside sufficient time for it to dry and I mean, make certain it was bone dry before sealing it. What the company did was seal in the water. I’ve had to have the rear top arches, inner sills and front arch all replaced due to corrosion.

My advice? If it’s not broken, don’t fix it.

 

[Smudgemanuk]

Good tip on the not sealing the water in !! I think I might pressure wash it one weekend and then seal it the next

I think undersealing it is a good measure of preventative maintenance and peace of mind, but as long as it is bone dry

 

[GZed]

OK. I have to add my 10p worth here.

I had a company clean the underside of my Z prior to sealing it as I was thinking about the longevity of my car. The company concerned pressure washed the underside as the garage closed one night and sealed it the next morning as it opened.

I’ve subsequently learnt that this is a massive no-no! The company didn’t give my car’s underside sufficient time for it to dry and I mean, make certain it was bone dry before sealing it. What the company did was seal in the water. I’ve had to have the rear top arches, inner sills and front arch all replaced due to corrosion.

My advice? If it’s not broken, don’t fix it.

Hi Dawn, could you post your recent pics of your rear wheel arches on this thread as a warning? I was gobsmacked when I saw them

 

[Smudgemanuk]

Now you are scaring me already

 

[ktnez99]

Hi Dawn, could you post your recent pics of your rear wheel arches on this thread as a warning? I was gobsmacked when I saw them

Yes, I shall. They’re a very cautionary example of how not to seal the underside of any vehicle least of all my beautiful Z.

 

[ktnez99]

Now you are scaring me already

Be afraid, very afraid. As I said, if it’s not broken, don’t fix it.

 

[ktnez99]

Hi Dawn, could you post your recent pics of your rear wheel arches on this thread as a warning? I was gobsmacked when I saw them

Here are a few. Passenger rear top arch:

 

[ktnez99]

Driver’s side top rear arch:

On the way, too.

 

[ktnez99]

Cowboy car traders whose only concern is quick money.