Trans Cooler

[Divedaddy]

I just finished three weeks of engine and mechanical work on my newly acquired '97 330 DA w/ 7.4L v-drives, Hurth transmissions, raw water cooled. Part of the plan included changing trans fluid. Just when we thought we were about done, when we drained the port trans the last bit came out milky (starboard was fine). Getting to the point, the port trans cooler was found pin-holed due to corrosion - luckily my mechanic believes it had just happened (we caught it right away) - starboard was okay but showed a lot of corrosion too. He also felt they had failed way too soon.

What we noticed was surprising was the coolers had no bonding connection, leaving them very susceptible to electrolytic corrosion. They just "float" in the cooling line. My mechanic found this and installed two new coolers modified with bonding straps.

I highly recommend anyone with trans coolers check theirs for a decent bonding connection. If there isn't one, add it.

Related, the engine oil coolers were also checked and found to be in good shape. They are bonded to the engine via a clamp and bolt.

 

[fwebster]

...........and what about sacrificial zincs?

If there were 2 drain plugs in the ends of the old oil coolers, take the plugs out and see if one or the other has a threaded hole in the end that is full of white chalky metal, if it does, that is where the zinc was that should have been changed.

If the new ones do not have a sacrificial zincs, I'd add one. Replacing the $1.50 zinc twice a year is a lot cheaper than replacing oil coolers and transmission clutches and bearings.

 

[Divedaddy]

We looked - neither the old nor the new had any anodes,