Heat exchangers (83)

Mercedes Ponton heat exchangers during the final assembly of the car 2018

The heat exchangers during the final assembly of the car 2018

The heat exchangers were dismantled. When I blew them with compressed air I had a large pile of yellow/black crud on the floor. They had probably not been restored since new. The radiator guy wanted almost 200USD (year 2002) for cleaning and pressure test them. Since there isn't a shortage of used heat exchangers on the market I decided to try do this restoration myself. A failure wouldn't cause an expensive problem (for once...).

  • Ponton heat exchanger before restoration
  • Ponton heat exchanger before restoration

The workshop manual says to pour 5% P3-Lye into the cooler and then drive around for a day. I haven't found out what P3-Lye is or where to get it so I went for caustic soda instead (100% Sodium Hydroxide). To drive around for a day was something that I really would have liked to do - if it had been possible. Instead I boiled the heaters for four hours in a mixture of caustic soda, shaking them each 10-15 minutes and changing the caustic soda three times. The first time I was afraid of the consequences of boiling the heaters in lye so I took only 2-3%. Nothing corrosive happened so the two last times I used a mixture of 5%. Between each time I rinsed them thoroughly, shaking them to get all the oil and crap out (and that was a lot) etc, etc...

Do not forget to use protective glasses and gloves! And if you decide to try my method; note that the caustic soda is highly aggressive/corrosive to aluminium, the material that is used in for example the Ponton's cylinder head!! So rinse the heat exchanger thoroughly before connecting them to the coolant system again! Above all, you follow my procedure on your own risk!

After all the travels and work the car got a total wash 2016

After all the travels and work the car got a total wash 2016

Now when they're clean it was time to go for the limestone. First they had two water baths with vinegar to neutralize the lye and then I let them lie in a new, fresh mixture of water and vinegar over-night. Observe, it's no use doing this before having cleaned the heaters. Vinegar can't get to the limestone under layers of fat, oil and crud. I probably had 3-4 table spoons more of limestone gravel loose from each unit during and after this process!

  • Cleaning Ponton heat exchangers with caustic soda
  • Removing limestone from Ponton heat exchangers with vinegar

After this they were like new when I looked down the regulating valve. Of course, I can't say anything about how the elements look like further down but I doubt - based on everything I got out of them - that there is anything wrong with them now. So, time for the next activity; pressure check. 

I bought a set of rubber hoses (actually hydraulic hoses which made the purchase unnecessary expensive). The set consists of two hoses, fitting the lower connection and the regulating valve respectively. One of them got a nipple for a bicycle pump with an air pressure gauge. The other one was open so that I could check if the regulating valve was air tight (the hose is of course supposed to be under the water in contrast with what the second picture shows). With a bicycle pump the test is of course rather inexact but I don't think it matters. If I remember correctly, the system is to be able to be tested at 1,6 bar, I used 2-3 bars. I found only one leak, one of the lower connections was bent which obviously had caused a crack. I bent it back and soldered it = fixed. Beside of that everything was 100% tight! So, instead of paying the equivalent of 200USD I reached 30USD - the hydraulic hoses taking most of that cost - and a couple of interesting hours. The following picture shows you the rest, cleaning, painting and assembling.

  • Pressure check Ponton heat exchangers
  • Pressure check Ponton heat exchangers
  • Solder leaking heat exchangers
  • Cleaning the outside of heat exchangers before paint
  • Heat exchangers painted with semi gloss black
  • Completely restored Mercedes-Benz 219 heat exchangers