Hydraulic pump cycling / Replacing dump valve/ UPDATE

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From: Erik Larson <asw20747 [at] aol.com>
Sender: <marv [at] lancaironline.net>
Subject: Hydraulic pump cycling / Replacing dump valve/ UPDATE
Date: Sun, 30 Jun 2013 12:12:11 -0400
To: <lml [at] lancaironline.net>

First.... thanks to Danny, Skyhawk, Andy and anyone else that responded to our hydraulic pump cycling issue.  


We took your collective advise, isolated each cylinder, then the pump and finally the DDV (Dumb Dump Valve) and like Danny said.... it WAS to be found in the.....Dumb Dump Valve.

Changing the valve was VERY difficult.... the only access was blind, with no less than 5 connections that had to be clocked precisely to mate up again with the hard lines.  The thought of upgrading to a "High Quality" valve was considered, but if it wasn't the exact same dimensions, the hard plumbing would have to be changed....we'll save that project for another day....or year.

Thanks again for the help..... my only advice to anyone else with these symptoms..... G.D.V.E. = Go Dump Valve Early!

Erik Larson
Legacy/N74FX







I have a Legacy, 6 1/2 years, appx 650 hours, we started experiencing momentary hydraulic pump cycling averaging now every 6-8 minutes for a micro second.

It's time to start trouble shooting to find the leaky bypass and following some previous postings on the issue, it seems that the best place to start may be the dump valve, then the cylinders and finally the pump.

At first glance it looks like getting the dump valve changed out could be quite a job.  Anyone that's done it recently care to share some Helpful Hints?

It looks like the only way to get to it, is by disassembling the throttle quadrant, even then it looks tight?

Thanks for any advise you may have.

Erik Larson
Legacy/N74FX


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