Yak Driver
Joined: 09 Mar 2012 Posts: 34
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Posted: Mon Sep 17, 2012 3:54 am Post subject: Yak-List Digest: 2 Msgs - 09/14/12 |
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Hey Andrew,
I recently had a similar problem with my 18T. It was leaking air just inside the firewall from one of the non return valves. I ended up overhauling a couple of
them. Very simple process and the parts I got from Jill at M14P, cheap too. Just remember to ask for the Yak 18T kits. When you dismantle the valve there is a small piston, a rubber seal, spring and a crush washer. Note: be careful not to lose the spring. I cleaned the piston and bore, replaced the rubber seal and
crush washer and re-assembled. No more problems since.
Yak Driver.
________________________________ Message 2 _____________________________________
Time: 08:37:32 PM PST US
From: "Andrew Park" <andrew.park(at)xtra.co.nz (andrew.park(at)xtra.co.nz)>
Subject: Yak18t air leak
I realise this topic is probably worn thru with you all but Im relatively
new to the Yak and a little hesitant to go rushing in. When I went up to
the plane a couple of days ago I did the usual start up procedure and
noticed a hissing sound coming from the front somewhere. I also noticed the
air pressure dropping very slowly. Opened up the cowls and on the left-hand
side of the firewall is a device Approx 250mm long, grey in colour and I
presume it's a blow off relief valve for the compressor. It has 3 pipes
connected to it, one from the compressor, one exhaust which exits to the
bottom of the fuselage and another pipe which disappears thru the fire wall.
The hissing sound is coming from the exhaust at the bottom of the fuselage
and when I put my finger over it, the air then escapes from around the plate
which is screwed to the grey device (I suspect the relief valve for when the
compressor exceeds the required pressure). I started the engine to let
pressure build up and its stays up to where it should be in flight, however
after engine shut down the pressure drops away after about an hour. I
presume this valve assembly is the problem, what do you all think? If I
dismantle the unit, what am I likely to find and what is the likely fix? Is
it an O ring failure, seal etc? Your help would be much appreciated..AJ
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