Loctite on heads

by Roger Lee in General Tech Discussion 8 years ago

Hi Rob,

Have you ever used or heard of someone sealing the heads on a 912 with Loctite if they are leaking?

I know leaking is usually caused from overheated heads or oil migration up the head studs.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

Re: Loctite on heads

by Rob Seaton » 8 years ago

Rob Seaton

3 1.32k 240

using 243 loctite between the head and cylinder used to be an approved method but it was removed from the manuals many years ago. I am not completely sure why (we did have 1 shop who put too much locktite on and fouled the combustion chamber)

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Re: Loctite on heads

by MARK JACKSON » 8 years ago

MARK JACKSON

12 332 11

Could this be the miracle cure I'm looking for to seal my heads?

Please say "yes"

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Re: Loctite on heads

by Roger Lee » 8 years ago

Roger Lee

126 5.13k 4.56k

This leakage is usually caused by two things. The first would be from an overheated head which caused warping. This can't be fixed and needs new heads. The real way to test for this is to send heads in and have them hardness tested.

There is no oil in the head to leak.

Second:
The huge majority of people that think heads are the problem are wrong. It is the head studs that are allowing oil seepage to migrate. This leakage is from the crankcase compression and causes oil to migrate up a stud. If you remove the head and then the stud you will find oil on the stud and there shouldn't be any.

Last is that lapping can make a difference, but if you have a soft head it will eventually leak again after about 100 hours.
Rotax factory assembles the heads and applies a VERY thin film of the silicone heat transfer paste to the head sealing surface. As the heads get tightened down this allows the head to move ever so slightly to find it's happy position and not bind up from the metal to metal surface seating.

Bottom line is if it hasn't been overheated then replace the stud "O" rings. There is an SB on this for earlier engines.

Here is a little more background. Many years ago Rotax did have in the manual that adding a VERY thin film of 243 was acceptable. Then it was taken out of the manuals. Allowing people other than the factory may have caused more issues than it solved. That's just speculation on my part. If the mechanic or owner used the wrong type or didn't apply a VERY thin film then the Loctite ended up in the cylinder and it caused issues. A thin film can be a little subjective. Then we have people that believe they know more than Rotax (who would have known) and they figured if a little was good more is better. Then you have expensive repairs. Rotax doesn't use any Loctite to seal a cylinder any more.

If you try this be careful, but I would look at the studs long and hard first.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: Loctite on heads

by MARK JACKSON » 8 years ago

MARK JACKSON

12 332 11

Thanks for your time Roger. I'll whip the heads off tomorrow and let you know what I find.

Cheers Mark

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Loctite on heads

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