Rotax 912 Coolant Elbows and Hoses

[Dermot McD]

I thought I would put some information up here about Rotax 9xx coolant hoses and elbows because I have not found anything suitable elsewhere. I'm doing an engine swap and of course found that the coolant elbows were pointed directly at the engine mounts and that while Rotax recommend heat shielding over the cylinder head coolant lines, they don't fit this on new engines. The 17mm Continental hoses are a really tight fit and one had to be cut off to remove it.

 

The coolant elbows are a bit of a fiddle to remove so they can be clocked properly. The recommendation is to heat the elbow to 120ºC and using a dowel or drift, turn the elbow. I don't fully understand the logic here since the type of Loctite used on the elbow still has 90% strength at 120º and that's about the working temperature of the elbow. Anyway, some public notes on stuff I found below.

 

The current Bert Flood price on nominally 17mm ID coolant hose is $178 per metre but I only needed 200mm and would have to buy a full metre. Mackay rubber do a nominal 17.5mm hose. The Mackay hose I bought measures 17.3 ID. From memory, the BF Continental hose is closer to 16mm ID than 17… though measuring rubber is not a precise art. Both types of hose have a yellow, possibly Kevlar reinforcement. The Mackay hose fits snugly over the elbows and given the right hose clamps should work as well as the Conti version.

 

The elbow is 18 OD - 19.1mm over the pip at the end. The ID is about 13.85 some something less than this is the right diameter for a rod to turn the elbow once it is hot. Using a hot air gun is fairly slow since heat is conducted away almost as soon as it is applied. I wonder whether a cartridge heating element in a 13.8mm plug inserted into the elbow would be a better option and it's something I will try after getting one. Something about using a propane torch on a new engine offends me!

 

The elbow thread is M18 x 1. Good luck in running a tap or die over the mating parts to clean up the Loctite without wrecking the thread. A 1mm thread file will do better than a wire brush. 

 

If only BRS had supplied the parts loose instead of this rigmarole. 

 

D

 

[facthunter]

Why use a high temp loctite?  Sheild near parts with Copper or Al sheet and use a small propane torch on the inside of the threaded fitting. Watch out for heat  going through the Pipe and exiting the other end. Make sure there's NO accelerant about. (Thinners etc). Vent the place and have a CO2 extinguisher and be aware the shield gets very cold when you pull the trigger.. CO2 is not poisonous or corrosive It just excludes oxygen by displacing it. NEW threaded parts could be Lapped with Brasso so they seal better  and stop where you want them to, Don't mix them once Lapped. Nev

[Blueadventures]

2 hours ago, Dermot McD said:

I thought I would put some information up here about Rotax 9xx coolant hoses and elbows because I have not found anything suitable elsewhere. I'm doing an engine swap and of course found that the coolant elbows were pointed directly at the engine mounts and that while Rotax recommend heat shielding over the cylinder head coolant lines, they don't fit this on new engines. The 17mm Continental hoses are a really tight fit and one had to be cut off to remove it.

 

The coolant elbows are a bit of a fiddle to remove so they can be clocked properly. The recommendation is to heat the elbow to 120ºC and using a dowel or drift, turn the elbow. I don't fully understand the logic here since the type of Loctite used on the elbow still has 90% strength at 120º and that's about the working temperature of the elbow. Anyway, some public notes on stuff I found below.

 

The current Bert Flood price on nominally 17mm ID coolant hose is $178 per metre but I only needed 200mm and would have to buy a full metre. Mackay rubber do a nominal 17.5mm hose. The Mackay hose I bought measures 17.3 ID. From memory, the BF Continental hose is closer to 16mm ID than 17… though measuring rubber is not a precise art. Both types of hose have a yellow, possibly Kevlar reinforcement. The Mackay hose fits snugly over the elbows and given the right hose clamps should work as well as the Conti version.

 

The elbow is 18 OD - 19.1mm over the pip at the end. The ID is about 13.85 some something less than this is the right diameter for a rod to turn the elbow once it is hot. Using a hot air gun is fairly slow since heat is conducted away almost as soon as it is applied. I wonder whether a cartridge heating element in a 13.8mm plug inserted into the elbow would be a better option and it's something I will try after getting one. Something about using a propane torch on a new engine offends me!

 

The elbow thread is M18 x 1. Good luck in running a tap or die over the mating parts to clean up the Loctite without wrecking the thread. A 1mm thread file will do better than a wire brush. 

 

If only BRS had supplied the parts loose instead of this rigmarole. 

 

D

 

Flylight in UK will sell a full 17mm Silicone hose kit with clamps for about $170.  Do you still need 200mm of 17mm hose.  I could spare that in 4ply 17mm id silicone as I bought an extra meter of the 17mm hose.

[facthunter]

I used stuff from Purple PIG years ago  They had a wide selection of products to pick from ALL straights which suited Me.  Mid engined race cars have similar problems. oil coolers and radiators are up the front  You can lobster Back stainless tube or get sharp preformed bends from good exhaust  system suppliers or makers of 2 stroke Expansion chambers. I've cut and pasted a few banana's  and cross over extractor systems that don't look as good as sand filled and bent pipes. Many Pipes Are too thick. Stainless is thinner and can be mandrel bent. 

[Dermot McD]

Quote

"Why use a high temp loctite?"

You don't want to deviate too far from the Rotax maintenance manuals with a new engine or they can void the warranty. Personally, I am not 100% happy with gluing parts together like this but who am I?

 

For those who don't know, the coolant elbows are screwed and glued directly into the water jacket of the cylinder head and coolant pump. Making something up from stainless isn't really an option. Loctite both secures the elbows and fills gaps in the threads. The original recommendation from Rotax was to use 243 (which softens about 165º) but now they recommend 577 which is a fairly standard thread sealant but has better gap-filling properties (about 0.25mm) which is the main point. However this softens at 250º.

 

Having used a hot air gun for heavy soldering etc. I am a lot happier with that than a naked flame with its endemic oxidation and corrosion problems.

 

D

[IBob]

Unless Rotax have changed it, the elbows into the water pump take Loctite 243, while the elbows into the heads take Loctite 480.

 

I repositioned the elbows into the water pump using a dowel and a propane torch, as you describe. But I did it with that part of the water pump off the engine and held lightly in the soft jaws of the vice. It felt a bit amateurish, but it worked. 

Due to an error not of my making, I ended up having to replace one of the elbows on the underside of the heads......and that wasn't easy. As I recall, I ended up using acetone and one of those gun cleaning brushes to clean out the threads in the head.
As noted, those elbow threads are very fine......and they are also 'soft as butter'.

Edited Monday at 09:14 AM by IBob

[IBob]

Okay, just saw your above post, Dermot. Are they now using 577 all round?

[Dermot McD]

Quote

Are they now using 577 all round?

Yes it appears to be the case only on the coolant elbows since at least the 2022 manual. Other Loctites used elsewhere. My guess is that this might be something to do with the gap filling and reduction in strength with temperature but that's only a guess. A few years ago, I think it was 648. I found this on the Rotax-Owner website:

 

"I started some research and found that the rotax-owner video calls for "Loctite 648", which is pretty expensive and not rated as a thread seal either, plus, the data sheet indicates that 648 looses strength over time in Glycol. So I contacted Loctite customer service and they were adamant in recommending "Loctite 577" for this application. I have now done 2 of the elbows with "648" and will do the last one with "577". Curious to know what other people's experiences are. I can already tell you that excessive and hardened 648 is very difficult to remove from the aluminium flange sealing surface."

 

So there you are. Typical rabbit hole! I think any of these would work OK but since I have 577, then that's what I will use.

 

D

[skippydiesel]

Dermot McD,

 

Suggest you join the Rotax Owners Forum https://www.rotax-owner.com/en/forum- Your questions will be answered by very experienced people and you will have access to the latest Installation, Maintenance (Line & Heavy), Operator, Manuals.😈

[Dermot McD]

Hello SD,

 

Agreed. However, apart from often using obscure and obsolete measurement units, I was not sure that there was information on Mackay rubber hoses there since it's mainly US. I got that info here. They also don't have to deal with Bert Flood.

 

I'm not sure how they deal with criticism of Rotax. I'm an edge of the bed Rotax fan these days. While the engine etc. is pretty good, they've gone down the Katmandu route where everything is now branded Rotax… Bing Carbs, K&N air cleaners etc.  My original Rotax installation was entirely AN fittings and to replace many of these fittings, you have to either use AN car parts (which is generally OK in my opinion since most Rotax plumbing is automotive) or buy barb to AN fittings from Rotax at a cost of about 14 times the real cost. $175 for a simple brass fitting. That's if you can find a replacement. The current standard oil tank top has metric reverse flare fittings. I haven't found anything which seems to fit these to go to AN.

 

D

[skippydiesel]

"I was not sure that there was information on Mackay rubber hoses "

 

I have never used Mackay hose but am very impressed with their range (see catalogue)

 

I use Gates hoses -  fuel & coolant from Repco  & oil from Hydrolink

 

Go to (this Forum) Aircraft General Discussion - Started A Spare Parts List

A lot of tangential chit chat but the information is all there

 

 

Edited Wednesday at 11:34 PM by skippydiesel

[IBob]

29 minutes ago, skippydiesel said:

...............A lot of tangential chit chat but the information is all there

 

 

Yes....but do we get to shout at each other???........................😬

[facthunter]

 Loctite is a good product. I'd trust  them for the correct one for a particular purpose, or at least question it. Is it to seal OR Lock and is the temp a particular issue? Rotax are getting a bit strange in their insistence of ONE brand and name of product. Why is their engine so critical? Nev

[Thruster88]

3 hours ago, facthunter said:

 Loctite is a good product. I'd trust  them for the correct one for a particular purpose, or at least question it. Is it to seal OR Lock and is the temp a particular issue? Rotax are getting a bit strange in their insistence of ONE brand and name of product. Why is their engine so critical? Nev

We know this works, we only want you to use this produce that we know works. Our reputation is on the line so we want you to use the products that we know work in our engine. It's like fastener torque, 34nm not fairly tight. Rotax 912 is probably the best piston aero engine out there. 

[facthunter]

But Oh so fussy.  Some of that I think is made up to be part of the Rotax CULTURE. It's a Bl**dy Plumbers Nightmare to start with. You'd never get it past the scrutineers on a race car. Too many things near exhaust pipes  unshielded and more. Costs are going through the roof for "special" bits. Carbs are cheap and nasty, unbalanced and dangerously located. Nev

[Dermot McD]

Quote

Loctite is a good product.

Mostly yes. However we have had several unexplained failures with loctite over the years. The manufacturer of a motor we use recommends loctite as the best method of securing a gear or pulley rather than a key, however sometimes they fall off. Loctite has a recommended shelf life (2 years?) so we're better at throwing bottles away than before but either something works or, if it does not, then it's unsafe.

 

Where Loctite is used on the fuel elbows, the recommended temperature to remove the fittings is almost the same as the temperature of the coolant.

 

I'm slightly perplexed by some of the inconsistencies in Rotax engines… some fasteners safety wired, others not. Some with loctite and others not. I'm annoyed by things like barbed fittings as standard and anything else being penalised by over the top prices.

 

I don't envy them having to make recommendations about service intervals etc. Any manufacturer is going to err on the side of caution. However I know from our work that Waddington's principals apply so if a customer wants to know what to service, we say don't. Have a good close look at it and if it is not broken or worn, leave it alone.

[facthunter]

Lapping tapered threads is a good way of helping  them seal and adjusting where they stop when tightened.  Tightened correctly they will lock themselves. Thats the Purpose of using a Tapered Pipe thread.   Nev