Proper Loctite for Rotax Water Pump Elbows

Brandon Peterson or anyone,

What is the proper Loctite number for sealing and locking the fine threads on the Rotax 912 water pump housing elbows when they are repositioned? I know Kitfox factory does this for customers, but they are closed now. Actually I need to reseal an upper coolant elbow that goes into the cylinder head to fix a leak, but I know its the same Loctite that is used on the water pump elbows.

I have been all thru the Rotax Heavy Maintenance manual, but there is a confusion between Loctite 243 and 648.

Jim,


I understand that 648 is the correct item.


648 has the ability to fill small voids and hold parts that aren't completely mechanically tight. The locktite spec says 648 is good for filling voids up to 0.15mm. 648 is also a bit stronger than the other.



Here is an article by Phil Lockwood - check the part on "cooling system"


http://www.ultralightnews.ca/rectifi...stallation.pdf


Also be aware that when you pull the fitting, there is a red silicon O-ring in the head. Jerrytex on the list got me a spare O-ring and saved the day on that. Maryland metrics which Jerry referred to in his reference is no longer in business. I later got additional O-rings in metric sizes and correct material from McMaster; so, if you end up needing some - let me know - Mcmaster sells packs of 30 or 40 for little difference than Rotax proudly:rolleyes: wants for a single O-ring.

from a 1015 version of the 912iS illustrated parts manual ,water pump section, shows Loctite 243 for "bent socket fittings item 8 and 9"where they slide into the water pump housing. I do not know if this information is valid for 2018 or your particular engine.

Jim,


Part of the confusion in the Rotax Heavy Maintenance Manual is the fact that the cylinder head coolant elbows are not treated in the "Cooling section" of the manual - it's in the cylinder head section. Logical deficiency of the manual.....:rolleyes:


(The water pump section does say 248)



Here is a cut and paste from the manual cylinder head section:



".......When replacing the coolant elbow, mark its position, heat the area with a hot air
gun to max. 120 °C (248 °F) and unscrew the fitting. Remove residues of
LOCTITE means and check threads. Apply LOCTITE 648 to the thread on the
cylinder head and to the new coolant fitting and screw the fitting into the cold
cylinder head. Leave cylinder head to harden for approx. 10 minutes at 100 °C
(212 °F)........"




I believe the reason for the difference between the application for the water pump and the cylinder head flange has to do with the higher operating temp on the cylinder head flange compared to the water pump. (also the reason for a silicon O ring in the cylinder head fitting). Top of the cylinder is the hottest part of the cooling system.



For what it is worth, I don't have much faith in the traditional field fix of heating a cured joint and moving the fitting to align the hose - it will likely leak sometime in the future. Best procedure is to unbolt the flange - heat & disassemble it, clean it up and apply new locktite with the connector pointing in the correct direction. I don't even like the Rotax method of resealing without removing flange - stuff can crumble down the hole to contaminate the cooling system and it is not as easy to be sure the threads are clean with the flange stuck in the head.

On the water pump, I meant 243 not 248:o

I did use 648 during the assembly of that water pump housing. It is what Rotech in Canada recommended. It is also what Roger Lee recommended. I clocked all of the elbows to minimize the stress on tubing at both the pump and on the cylinders.
I galled one of the elbows during disassembly but didn't damage the housing. I simply didn't keep the heat on the part long enough to turn out the elbow. Aluminum will do that. I decided to buy a complete housing and new elbows to make sure I didn't have any damage in the housing.
I still have the undamaged housing on my shelf and an assortment of elbows. I would use 648 due to its heat resistance and its compatibility with the coolant. Once its on, it won't leak. I can't work on that section of the engine with the engine installed. IVs just don't have the room. So I decided to go for the long haul. I don't ever intend on removing that part again.

Thanks Dave, just the info I was looking for but having a hard time finding.