Pagoda SL Group

W113 Pagoda SL Group => Research & Development => Topic started by: waqas on June 23, 2009, 05:47:16

Title: Copper for heater pipes?
Post by: waqas on June 23, 2009, 05:47:16

One of my heater/coolant pipes is really starting to rust through. This pipe runs around the lower front of the oil pan, and is used for routing coolant from the oil/water heat exchanger on the side of the engine (M129).

Can I simply use copper pipe from my local hardware store and bend it into the correct shape? The commonly available 1/2" ID pipe is about the right size as it has an OD of 5/8", which is only a bit larger than the original pipe (original=15mm, this pipe=15.88mm). I can probably flare the ends to receive the heater hose.

Does this type of copper withstand the heat/pressure/chemicals from the coolant running through?

What about the soldered joints used with these pipes?

Title: Re: Copper for heater pipes?
Post by: lurtch on June 23, 2009, 18:56:56

Hello Waqas,   I have been running a copper replacement cooling pipe for several years now. There is typically only 12 PSI in the cooling system (depends on which radiator cap you are using) so no worries about pressure. Copper is the best heat sink there is, so no worries there . The 250F you might see when you over heat the engine is still too low to  effect the temper of the metal. ( it takes 650 degrees F to melt copper) . Be sure you use soft drawn refrigeration grade tubing, because you will not be able to bend the hard-drawn version (common in home construction). Solder joints should be done with silver solder , not low-melt soft lead solder.

See you at PUB?     Larry in CA

Title: Re: Copper for heater pipes?
Post by: waqas on June 23, 2009, 20:24:58

Larry, thanks for the reply.

Don't we need to worry about galvanic corrosion of the water passages in the aluminium alloy head? I suppose this is less of a concern if the electrolytic property of the coolant is minimized by using only distilled water. Also, the clamps around the lower oil-pan can be modified to electrically isolate the pipe from the engine.

For reference, this chart (referenced from http://www.corrosionist.com/Galvanic_Corrosion.htm (http://www.corrosionist.com/Galvanic_Corrosion.htm)) shows that copper and aluminium alloy are approximately 500-700 mV apart on the galvanic scale (and aluminium is on the wrong end of it):

(http://www.corrosionist.com/Corros1.gif)

Quote from: lurtch on June 23, 2009, 18:56:56

See you at PUB?     Larry in CA

Looking forward to it!

Title: Re: Copper for heater pipes?
Post by: mdsalemi on June 23, 2009, 21:07:29

Waqas,

Are not the radiators brass?  Or, at least the tanks?  You thus have dissimilar metals in the system anyway.

That's one reason why the glycol coolant used is inhibited; to prevent corrosion...

Title: Re: Copper for heater pipes?
Post by: Shvegel on July 12, 2009, 01:49:54

I was on a 1946 Trumpy yacht tonight. The engines were replaced in 1986 and the cooling lines were plumbed in copper. Looked good to me.