I needed to start a new Discussion for this based on some other discussions for 8 series and another similar problem.

The Problem: We have a fleet of Toyota 8 series LPG forklifts, they are all 4 Tier Masts, and all but the clamp trucks are configured with sideshifters and double forks. The hours vary from 1200-2900, purchased April 2008. We now have begun to see a series of lifts that at first appear to be the safety down valve is malfunctioning.

The operator takes a load from the rack system at the third level, which is approx. 15 feet up, and weighs around a ton at the max, they take it, pull out, and then even if they feather the controls, it trips the down valve safety and the mast will come down very slowly, and can take more than 45 seconds to hit ground. This does NOT occur while unloaded. Also, this occurs at any tilt angle, from any height EXCEPT the first tier. Although we have another lift today where it DOES occur at the first tier.

Our lifts are managed by a maint. program that covers periodics...oil changes and so on, I am responsible for everything else, including damage, unusual wear and so forth.

For an example, this problem persists despite checking and adjusting mast wheel bearing tolerances, greasing the tracks, after cleaning them, checking the pressure with a gauge, replacing the safety down valve, bleeding the LH rear mast cylinder of air ((from the safety down valve change)), adjusting all electronics to factory specifications, and insuring that no other system such as SAS is tripping this down function to behave as it is.

Also for what its worth all lifts have the mini lever controls. My personal conclusions include the electronic hydraulic control selenoids have an internal part/spring failure, the safety down valve is incorrect despite being packaged with the correct Toyota PN.

This is NOT operator error, I have observed the operators while they are unaware of my presence and the lift is being operated as designed. If anyone has input or ideas on this complicated subject I am all ears, and thanks in advance.