Corrosion inside the coolant return pipe?

[DrJeff]

Since I had some surprises finding corrosion pitting on the aluminum components of the water pump, y-pipe, flanges, back plate, and thermostat housing - I wanted to look inside the coolant pipes just adjacent to these components. The goal was to determine if the corrosion problem extended further or was limited to just the aluminum connections under hose and clamps.

Here are a few snaps of the coolant return pipe (small pipe running out of the back plate of the water pump and across the valley.

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[Full Disclosure: These photos may have been enhanced during preparation for publishing.]

Most of the corrosion or deposits are limited to within about 1 inch of the end of the pipe. The central runs show little sign of corrosion.

I checked the two main water pipes that run to the LH (where thermo sensor is located) and RH (located under the tank) and they were boringly clean.

Phew.

[NightFlyer]

Since I had some surprises finding corrosion pitting on the aluminum components of the water pump, y-pipe, flanges, back plate, and thermostat housing - I wanted to look inside the coolant pipes just adjacent to these components. The goal was to determine if the corrosion problem extended further or was limited to just the aluminum connections under hose and clamps.

Here are a few snaps of the coolant return pipe (small pipe running out of the back plate of the water pump and across the valley.

24591245922459324594245952459624597
[Full Disclosure: These photos may have been enhanced during preparation for publishing.]

Most of the corrosion or deposits are limited to within about 1 inch of the end of the pipe. The central runs show little sign of corrosion.

I checked the two main water pipes that run to the LH (where thermo sensor is located) and RH (located under the tank) and they were boringly clean.

Phew.

Can't remember if you addressed this before or not, but were you running standard reinforced rubber or silicone hoses?

[DMCMW Dave]

Typically that means the system was leaking a bit and that particular area was exposed to air for some time rather than good coolant.

Often the corrosion at the ends like that is actually going from the outside in where there was coolant past the clamp and exposed to air, and there are microscopic holes in the aluminum. In that case you either need to weld up the holes (hard to do), replace the tubing, or use longer hoses and clamp them well into the "good" part (perfectly functional but doesn't "look right").

[DrJeff]

Can't remember if you addressed this before or not, but were you running standard reinforced rubber or silicone hoses?

It was the stock hoses. I doubt they had ever been opened.

[SS Spoiler]

Didn't DMCMCO? offer a full set of stainless steel pipes? Josh needs to add them to his catalog.

Paul Cerny #2691
Kalispell, MT

[DMC5180]

Didn't DMCMCO? offer a full set of stainless steel pipes? Josh needs to add them to his catalog.

Paul Cerny #2691
Kalispell, MT

Yes, and they were nothing to right home about either. Very poorly made. The bends were NOT done with a mandrel tube bender (the type that maintains the ID through the bend) and a lot of the sharper bends had crushed inside radii. Also stainless tubing is rather expensive material to start with. That's before bending costs and additional welding (header bottle pipe) and (Air bleed nipple right side front). I just don't see the need for Stainless Coolant pipes on the D. This isn't to say that after 30 plus years the aluminum pipes couldn't stand to be freshened up with replacement Aluminum stock.

[David T]

My theory is the coolant was in the car for a very long time and not circulating. It became acidic and with electrolytic action because of the dissimilar metals the aluminum dissolved. The same thing happens to the pipes under the car and they are always full of coolant and no air.