Perry Mick wrote:
What is the best sealant to use between the oil pan and the engine?
I have an oil leak between the pan and the engine, especially when
parked nose down. I used the Mazda gaskets both above the 1/4
aluminum plate and below.
They are squeezing out in places, so I think next time I will not
use
the gaskets, but want to use a good sealant so I don't have to do
the job twice. I know RTV won't last a minute near fuel, and
probably is not oil resistant over time either.
Perry
Hi Perry,
I haven't used gaskets for many years. It's usually the gaskets
themselves that leak. Mazda have been using direct bonding on
sumps for the past 15 years. They still supply sump gaskets in
the kits, but I never use them.
The trick is to make sure that the surface is perectly clean and free
from ANY oil and grease. I usually just use good old methylated
spirits (denatured alcohol to you guys). Acetone or MEK.
If you want the sump to come off easily, (handy when doing
development work) a LIGHT SMEAR ONLY of a rag dampened with
WD-40 (or other de-watering fluid) will act as a release agent. But
for best results, perfectly clean and absolutely dry.surfaces are de
rigueur for leakless sealing..
As for sealants, Dow RTV Silicone is excellent on sumps (I've
used it for 30 years and rarely if ever had a leak). Not affectd by
oil, but it's not happy with fuel.
Loctite make neutral cure sealants like BlueMax and Hi Temp
RedMax Silicone (it's actually an orange colour) (I use the red stuff
on exhausts - it's safe for Lambda sensors).
Wurth make a grey sealant which is excellent on sumps as well as
the joins in transmission casings where gaskets cannot be used.
It remains semi-soft and allows for a bit of flexing.
I've even used black Sikaflex at a pinch when nothing else was
available (the polyurethane sealant used for sticking windscreens in
place) but it makes it a bugger to get the sump off next time!! But
it's guaranteed NOT to leak!!
One final tip. Down the back of the engine, there is a brass plug
that blocks off the bottom of the oil pressure gallery to the oil filter.
These are known to weep on a regular basis. Looks for all the
world like a sump leak. The plug is visible as te sump only covers
half of it.
I'd suggest that when building an aircraft engine (or a competition
engine for that matter), all these brass plugs be drilled out and
replaced with tapered plugs liberally coated with loctite. As always
when using sealants of any type, cleanliness is next to Godliness!
Cheers fellas,
Leon
Best Wishes & Kindest Regards,
Leon Promet
Aerota.com
leon@aerota.com
0408 223 675
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