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Older 5K Waste Gate Diaphragm fix/substitute
I've already explained that I'm not a regular subscriber in
an earlier email.
Like many other turbo owners, my waste gate diaphragm
deteriorated severely due to condensate collecting in the
upper bell housing. The last time I had it off, about 18
months ago, it looked so bad that I simply couldn't put it
back. So, I looked around for a substitute, even contacting
Bendix Air Brake, trying to get some air brake diaphragm
material. It probably would have worked but I couldn't con
anyone into giving me a scrap to try. So, I took a piece of
an inner tube(from an old truck tire), used the upper cover
of the waste gate as a template, drew it out and cut a
diaphragm out of the inner tube. The only tricky part was
to draw lines through the 6 mounting holes with a pencil and
a straight edge, which established the center point and the
placement of the mounting bolts. I provided for some slack
material for the flexing of the piston by extending the hole
marks outward by about 1/4". I used a leather hole punch to
punch the center hole and the mounting bolt holes.
When I installed it, I expected it to tear up, burn up, or
just die a premature death. I ran it for a while, opened it
up and looked at it and it looked none the worse for the
wear. I tried several fixes for the condensate; my 5K
turbo came with the upper bell housing vented to the engine
compartment which I thought to be causing the condensate. I
tried venting it to the turbo inlet, and later to the inlet
of the air filter; neither of which reduced the condensate.
I also tried turbo feedback by venting the pressure from the
large tube that contains the over pressure cut off switch(it
grounds the fuel pump relay under normal usage). Turbo
boost feedback provides amazing boost and a real burst of
power. However, I wasn't too eager to exceed my BMEP or
blow oil so I removed this after trying it for a short time.
I suppose that one could become accustomed to the extra
boost and drive prudently and accordingly.
On May 17, 1998, I opened up the waste gate to inspect the
diaphragm expecting it to be in shreds and it seemed just as
intact as it was when I installed it!! Except that it
literally contained about 8 ounces of condensate which ran
out as I opened the housing. That prompted me to remove the
vent to the air inlet which had caused more, not less,
However, my trial shows that almost anyone can replace their
waste gate diaphragm with a little time and effort and a
scrap of inner tube.
Direct any questions to me at email@example.com.
MCSE, MCT, MCP+Internet
81 5K Turbo/290K