Rotax Radiator Cap

[Runtoeat]

Is there any aftermarket options for replacing our 1.2 Bar "mini" mradiator cap or must we buy "Rotax".  I note these cost about $84 at LEAF and Aircraft Spruce.

[Anticept]

If the cap fails, will your aftermarket supplier back the damage they caused?

Trust me. Buy the rotax one.

[Runtoeat]

if I knew it was made by Stant or a reliable manufacturer I would trust it.  The cap on our CT's doesn't show the manufacturer.  I'll follow your advice and order one.  Thanks.

[FlyRatz]

Tip: Check for the Motorbike Yamaha RD 350. It has the same cap.

Recently I bought this one: https://www.moto-deluxe.de/verschleissteile/motorteile/kuehler/4915/kuehlerdeckel-kuehlwasser-kuehler-deckel-fuer-rieju-mrt

 

[Runtoeat]

Thanks for the info.  I bought one @ LEAF this morning. 

[Tip]

Hi Dick,  I recently needed a cap for my Polaris Ranger & it was $32. When I said , wow, the dealer said that some are as high as $80. 

[Runtoeat]

Hi Tip.  I guess it's the same for all the ATV's, snowmobiles, boats and airplanes but it still hurts to pay this much.  After posting, I found that I needed some "O" rings for my engine.  I  ordered two 19 x 2 mm "O" rings.  These cost $13 each.  It's crazy to pay this much for a simple part like this but metric "O" rings aren't available where I live.  Lucky for me that I called back in time to include these in my radiator cap order at LEAF or it would have cost another $7 to have these shipped!

Update:  I was at my local hardware that's still got all of the "good stuff" that the Big Boxes don't have.  I found 19 x 2.5 metric "O" rings that would have worked.  These cost $3.59 each.

[Roger Lee]

Use Viton and not neoprene. 

I get "O" rings from Maryland metric.

[Anticept]

It's critically important to get the right o-rings. O-rings in hardware stores are neoprene. They are only good at sealing water. Buna-nitrile (buna-n) or viton is what you want. Viton lasts a lot longer but doesn't seal very well at freezing temps (22 F or lower if I recall) because it gets stiff, and are expensive. Still, viton is best if possible.

[Runtoeat]

Good info on "O" ring materials.  An update on the coolant "weep" being working on on my CT.  Once the cylinder coolant inlet tube and plate were taken apart, it was apparent that the weeping was probably not due to the "O" ring but caused by coolant getting thru the threads of the aluminum tube and the plate it screws into.  Roger indicated to me that failure of the loctite seal at this threaded joint is the cause for leaks in the majority of cases and not the "O" ring.   I'll reseal the joint with Loctite and also install a new (Rotax) "O" ring.  Removal of the intake manifold was required to remove this cylinder coolant inlet tube.  The tube had to be heated slightly to allow the loctite to soften and unscrew it from the plate.  Not a 15 minute job.  Especially when the threaded joint needs to sit overnite to allow the Loctite to set.

 

[Mike Koerner]

Dick,

Was the weep under the plate in the photo or between the plate and tube?

I have occasionally seen evidence of a leak that I thought was from under the plate on the front left cylinder. I had assumed there was a gasket under the plate, not an O-ring.

Mike Koerner

[Roger Lee]

99% of the time they weep out the tube. There is an "O" ring under the plate. They have Loctite 243 on the threads. It's better to use Loctite 648 and it will never leak again.

[Mike Koerner]

Thanks Roger.

[Runtoeat]

Mike, if you see coolant bubbling out from the joint between the tube and the plate only and not coming from under the plate, it is probably due to the failure of the loctite to seal the threads.  If you only see the coolant coming from under the plate, I would say that the "O" ring needs replacing.  Roger may correct me on this but after taking this  Now that this has been taken apart, I see that the plate has a sleeve that the tube screws into and this sleeve goes down into the hole in the cylinder head.  This sleeve has a bevel on the bottom which compresses the "O" ring against the hole wall at the bottom of the hole and seals the plate only.  The "O" ring does not seal the threads so the loctite is there to keep the coolant from leaking thru the threads. The Rotax website has a informative video on all of the types of Loctite used on the Rotax engine.  243 can be used on this type of joint but, as Roger says, 648 is best to use here.  It will actually glue the joint and should be the last time one will need to repair it.  You mention your leak is at the front left cylinder and I think you should be able to remove the coolant inlet without removing the intake.  There is a 19 x 2 mm orange "O" ring at the bottom of the hole. Rotax part #950-180. This little beauty costs $13.46.  Grainger has Loctite 648.  Page 144 in the Rotax parts catalog give a good view of all of the parts. 

[Roger Lee]

Here is where I get most of my sealing and glue products.

 

http://www.rshughes.com/c/Adhesives-Sealants/2000/

[Runtoeat]

Thanks Roger.  I'll add RSHughes to my list.  I've got a Grainger about 15 minutes from my house so this is my "go to" for unusual or hard-to-get stuff that is top name brand.  

[Runtoeat]

My leak is fixed.  The new cap is now sealing the accumulator bottle.  The Loctite 648 did a nice job of sealing the coolant tube to the flange.  Using this Loctite product was interesting.  At first,  the liquid which doesn't go into the threads is visable and remains liquid even when left overnite.  There is very little color to the 648 and in this thin application, it is virtually clear.  The product which did go into the threads, where there is a "no oxygen" environment (648 is anaerobic), does set up.  Visually, there was no indication that anything was applied to the threaded joint.  After installation back onto the engine and attachment of the coolant hose, there was no movement of the parts.  The tube/plate joint was solid.  Run up of the engine verified the joint is totally sealed.  The 648 is also a high temperature product.