JD 690 excavator engines

[TD-5]

Greetings, I have been looking at JD 690 model excavators with the idea of picking one up for some clearing work on the ranch. Several engines were used across the model series & i have no hands on experience with any of these engines. The early 690A/690B series used the 6404T rated @130hp @ 2400rpm, The 690C switched to the 6466T rated @125hp @1900rpm, The 690D then switched to the 6414T engine rated @ 125hp @ 2000rpm.This is also when they made the change to hi pressure variable displacement axial piston pumps for the hydraulic system. Finally the 690E used the same 414 cu.in. engine but it was designated the 6068T. I believe this engine was electronic control?.
Any comments,opinions, or experiences with these powerplants would be much appreciated.
Thank you

 

[Jonathan in MA]

I'd stay away from any 690D or E for hydraulic reasons... The engine is NOT the weakest link in those machines.

 

[TD-5]

I looked at an older 690B but it was just to far gone for the money they wanted. If I had my choice I'd like to find a 690C, I like the idea that the 466 runs at 1900rpm, vs the 404 in the B cranked up to 2400rpm. The C still has the lower presure open center tandem gear pump system for main hydrailics, but has the pilot controls vs the manual sticks in B( although late B's did come with pilot controls). I like the idea that there are no electronics & the system is fairly simple. I don't think the travel motors in the B & C models were as strong as the later models with the axial piston motors, but then I don't need to be in a big rush to get where I need to go.

 

[Heat Houser]

Yes, the weak link was using HyGard oil in the hydraulic system. HyGard will etch copper if it has water in it and anything brass takes a hit. A better choice would have been AW46 hydrauilc oil. Most have been running with HyGard so the damage is all ready done.....