Rust Eradication- Heat Exchangers

[Whaanga]

I was able to find an original set of heat exchangers for my 73 bus from a local source today. While they are dirty, and there is some surface rust, they are very solid.

I did an initial cleanup with wire brushes mounted in my drill. I've made descent progress but still have a lot of work to do. I'm also concerned about rust that I cannot access inside the box. Is there a procedure or chemical that I can run through the inside of the box to work on the rust inside the box?

The photos show the clean up process... any advice would be appreciated.

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Late 1973 Bay w/a transplanted 914 Engine

[dodger tom]

white vinegar.
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1978 Champaign Edition 2 Westfalia
Would never find the time to keep up another classic air-cooled.

[Bnanwel]

Ospho, do something else for 20-30 minutes, wire brush/wheel, repeat
When you a finished or sick of it, ospho and leave it overnight. Come back the next day and repeat the process. If not media blasting, I’ve found this method works well. There is a lot of time involved, but a lot of it is not “hands on”!
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‘72 Karmann Ghia Conv.
‘73 Karmann Ghia Coupe
‘74 Karmann Ghia Coupe
‘70 Deluxe
‘72 Deluxe

[69BahamaYellow]

Those are very nice-looking heat exchangers. The rust appears to be just surface stuff. I'm not sure if the '73 has this, but on my '78 exchangers, there's a heat shield between the finned aluminum block around the pipes and between the outer shell. I'd bet these were made of asbestos, but they could have been fiberglass. Over time, these get saturated with engine oil, and you can never get it out (think about how all air-cooled VW's have that stinky oily smell, when you turn on the heat). The only way I've found to really clean out the inside of the heat exchangers is to remove the shells (and just replace the oil saturated heat shield with fiberglass). You can then clean and re-paint everything else for a lasting repair. It's extra work but having heat that does not stink is well worth the effort. Keep your valve cover gaskets and pushrod tube seals leak free to prevent a repeat of the problem.

[Wildthings]

If you split the heater boxes open then find someone with spray welding equipment and have them spray galvanize them for you.

As for stink, I have found that long western grades will get the boxes hot enough for long enough to burn out the oil. If I get oil into the heat exchangers, I just remove the accordion tube(s) and block off the ducts going into the cab and after a few mountain passes have been crossed the stick will be gone.

I have thought about coming up with some way, should one get a pushrod tube leak or valve cover leak, to deflect the oil to keep it from getting into the boxes. Maybe just some high temp silicone weirs where the tubes go through the sheet metal.

[orwell84]

Get them sandblasted. Doesn’t have to be special. Some guy who does truck frames in his yard. Shouldn’t cost much.

[aeromech]

I did a 1974 last summer. I took the exhaust system to a powder coating place that used Cerakote ceramic coating after sand blast. The owner was pleased

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Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[Whaanga]

Thanks for the comments and suggestions. Once I get them cleaned up, can someone recommend what kind of paint color is close to VW factory?
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Late 1973 Bay w/a transplanted 914 Engine

[Ry-dog]

[Busfixer]

Regarding the oil smell and residue inside the heat exchangers - I had the same problem on a leaky orange & white '73 Bus when I dropped the engine to re-seal it around 1989. Solution - went to a truck diesel engine shop and they put my heat exchangers in a steam tank for 3 days. Then I had an experienced welder weld the exhaust runners to the heat tin to stop further oil entry. In hind site, sealing them with silicone would have been easier and cheaper. There is a tiny weep-hole on the bottom of the heat exchangers that you don't want to seal up. It lets condensation escape and prevents further rust on the inside. Summary - steaming, sealing and painting the heat exchangers fixed them right up and the heater never stunk again.
Cheers, Busfixer

[aeromech]

Radiator shops can hot tank them for you. I take fuel tanks to Ace Radiator is San Diego.
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound