426 /301

Question for the gurus , the 301 motors nearly always need rebuilding because of liner cavitation/electrolysis ,how often do the 426 get cavitation/liner pitting water in pan problems.? I haven’t seen as many allis motors as some, but out of all my time fixing stuff i have only come accross 426 motors with conrod out of the block as there main issue.

Edited by JPG AUSTRALIA - 29 Jan 2024 at 5:04pm

Thanks doc, i have never come across a 426 with a liner pitting problem ,interesting that you havent either. Have Seen the 516 motors pitted badly . I only use fleetgaurd DCA4 coolant,and have done for over 20 years,does a good job.

Cavitational erosion or electrolysis is the general term.  Wet sleeve engines  suffer from sleeve vibration at the bottom.  The vibration causes tiny 'bubbles' or cavitation that contact the sleeves or originate from the sleeves.  Now pistons/rings move up and down at high speeds and cause and slight electric charge. As the air pockets contact the sleeve there is a micro 'lightning strike' as each air gap leaves or contacts the sleeve. This moves molecules of metal from the surface of the sleeve - thus the 'pitting'. Keeping the coolant at a PH of 7 will make H2O a non conductor and mostly eliminate the issue of electrolysis. Cavitation erosion will still occur but takes longer in this environment..    The SISU or Agco Engine has a sleeve mid mount point that virtually eliminates the sleeve vibration and exponentially reduces electrolysis.  I have listened to  and read theories for decades and on this issue - this is our take - some say the electrical part is false - to which I ask then why does the pitting only take place where the sleeves are closest between the liners and less on the outside ends?  .   I have noticed the higher the HP and RPM the faster the pitting occurs.  as in 7020's and 7080's.

Edited by tbran - 29 Jan 2024 at 8:25pm

Some engines more likely to have trouble than others. Direct injection engines. More injection timing. More HP output per cubic inch. More RPM's. The cooling system is thee most neglected system on any diesel engine. Using the correct type coolant will see to it the problem NEVER arises.

As Dr Allis pointed out, cooling system maintenance is key. Speaking from experience with Caterpillar, Cummins and Detroit heavy truck engines, the use of red extended life coolant rather than conventional green ethylene glycol, is the single biggest prevention tool against liner pitting and cavitation. Upon tearing down an engine that has used ELC it’s whole life, I have (rarely) seen minor cylinder liner pitting, but never catastrophic damage. With conventional green coolant, a whole other story…. You’ll still have liner (sleeve) seals fail and put water in the basement after years of service sometimes, but again, not as often. Only bad thing is, the red ELC doesn’t seem to make your oil as milky and sludgy when it’s leaking into and mixing with engine oil, so it’s more difficult to spot the problem happening as compared to conventional coolant….

I personally wouldn’t worry too much about a small amount, but you could flush it once or twice with plain water before refilling. If there is a drain cock or pipe plug in the lower portion of the block and/ or oil cooler, remove it to get the most of the old stuff out first before putting it back in and refilling with new coolant.