Coolant leak

[Dorsal]

Anybody rebuilt one of these? you can see a little drool just over the spark plug. After a week the well at the base of the plug fills up, slow but annoying.

[Dave S]

Dorsal,

My plane/engine is pretty much the same vintage and model as yours including the 912ULS........on one or two of the fittings I get an occasional bead of moisture (coolant) showing up. There are two places where these leak...one is at the threads between the flange and pipe (which is sealed with threadlock) the second place is the O-ring between the flange and cylinder.

I don't think your experience is unheard of.......I don't get a pooling of coolant....just an occasional bead and no measureable loss @ the supply bottle.

I haven't fixed one of these; however, I believe Rotax shows the method in their maintenance method...It involves heating the joint with a propane torch to free up the threadlock (after removal from the cylinder) cleaning up the threads on both parts, renewing the threadlock with the specified k\material & using a new O-ring. Shouldn't be too complicated.

Sincerely,

Dave S
KF 7 Trigear
912ULS Warp Drive

St Paul, Mn

[Steves142]

Hi Dorsal, I replace 3 or 4 elbows when I installed my engine because they faced the wrong direction. They’re installed with the green loctite so it may be possible but hard to believe that the threads would start leaking and if they did it would be above the flange. My guess would be the o ring.

[Slyfox]

Dorsal,
something tells me that you should try heating up the screws and see if they tighten, even a little might stop that leak.

steve

[Dorsal]

All, thanks for the tips, agreed it is likely the o-ring not the threads. Will try tightening them first and see what happens.

[rockyrim]

Hey,
Mine came factory new missing one "O" ring, did the tightening thing for a little too long. Good luck.
Rocky

[Dorsal]

rocky, Good to know, will look for that. What was the result of tightening too long?

[Dorsal]

Replaced o-ring, will check after she has been sitting for a week and post results.

[Dorsal]

Just to close out this thread, no more leak :) after several weeks the area is consistently dry as a bone. In the end an easy fix, 1 hour start to finish and a $20 O-ring :eek:

[Dave S]

Dorsal,

Thanks for posting your results.....I can possibly see some O rings in my future now.

Dave S

KF7 Trigear
912ULS Warp Drive

[Jerrytex]

$20 for an o-ring! That's that Rotax inflation. If anyone needs o-rings for a 912 you can order them from Maryland Metrics, alot cheaper. I ordered all that I could cross reference from them, (I think they had all but 2) and I quadrupled the order to get to their $10 minimum order. I have a list of their part numbers and they all fit perfect. PM me if needed.

[Dorsal]

Jerry, that would be great information to post in the reference section. I will certainly be looking for it next time.

[Jerrytex]

Good idea. I didn't even think about doing that. I'll get it posted as soon as I can.


This is a list of o-rings for a 912 UL that I compiled when putting my 912 back together from it's partially disassembled state when I got it. These are NOT all the o-rings in the engine but it is the majority needed and the ones that are the hardest to get to when the engine is assembled. If other o-rings are needed, I attached links to the parts pages and a link to Maryland Metrics so you could find the one needed, cross reference it to Maryland Metric's part number and order it. Like I mentioned earlier, you will have to triple or quadruple your order to get to their minimum order amount. These are NOT rotax parts, but they worked in my engine and thus far, no leaks.


Quantity p/n size brand name description Location Rotax #

> 4 R398-20744 34x2 N/A O-ring Intake to Head 230-910
> 4 R398-20660 19x2 N/A O-ring Coolant socket flange 950-180
> 2 R398-20559 5x1.5 N/A O-ring Starter bolts 950-420
> 1 R398-20736 32x2 N/A O-ring Water pump 90 230-020
> 1 R398-20724 30x2.5 N/A O-ring oil pump 950-410
> 2 R398-17597 11x2.7 N/A O-ring oil pump 250-460
> 1 R398-20849 57x3 N/A O-ring oil pump 430-405
> 1 R398-32557 24.4x3.1 N/A O-ring starter to block 250-140
> 2 R398-20811 47x2 N/A O-Ring Carb Socket to intake 230-300

Made from Viton

Link to Lockwood to find the o-rings. The size is in the description.
http://www.lockwood.aero/c-3-rotax-four-stroke-engine-parts.aspx (http://www.lockwood.aero/c-3-rotax-four-stroke-engine-parts.aspx)

Link to Maryland Metrics. Find the size and their part number.
http://mdmetric.com/or/fpm80oringsizelisting.htm (http://mdmetric.com/or/fpm80oringsizelisting.htm)

[DesertFox4]

Jerry- I added your o-ring information to the reference section for future use then added the same info. back into your last post for easy archive locating.

[Dorsal]

Leaks developed again this time on the #3 cylinder and, I believe, one hose fitting. Replaced all 8 hoses and the other three O-Rings as well as the 4 O-rings on the intake manifold. I was not foresightful enough to order these from Maryland Metrics, the good news is no drips at all after test flight :)
I am planning on ordering more of these from MM as it is clear to me that these will need to be replaced every few years and I want to have them on hand. Also FWIW the replacement coolant hose was far more supple than the stuff I removed (I assume from aging).

[mcomeaux53]

What type of lock-tite is used on the threads to the pipe To flange?

[Dorsal]

I believe Loctite 648
http://www.lockwood.aero/c-151-cylinder-head-intake-manifold.aspx