ibjet Posted October 17, 2017 Report Share Posted October 17, 2017 I just ordered the earlier version of the Rotax radiator cap, 922-075, which is 0,9 bar (13 psi). The newer cap which Rotax is recommending is 922-070, which is 1,2 bar (18psi). So, I'm wondering what the good folks here have experienced with this issue. Is the original cap, Rotax 922-075 working for you? Discussion: I have had a problem of radiator leaks in the past couple of months. Seems like when I add a new clamp it leaks in a new place. I've done that twice and now I have a 3rd leak which I have not pin pointed yet. My radiator cap is a 1,2 bar (18 psi) and it has a date of 2006 on it. It also had a bunch of coagulated "goop" on the bottom part when I took it off wandering if it was "the problem". I figured it would be easier to buy a new cap than to find a place or way to pressure test it. Ouch, those little suckers are pricy! I ended up buying a Rotax 922-075 from CPS. They do not list the newer recommended cap (that I noted above, ref rotax 922-070). So, after stressing out a while, I ordered their part. I reasoned that, with the milder weather now, I'm pretty sure that cap will be just fine and hopefully will solve my coolant leaking issue. I am using the recommended coolant, Zerox Dex-cool. But, in the summer heat here, I suppose I take a risk of boiling off coolant if I operate near red-line (which I did this summer). I did a post about my oil temp going high. By the way, I found I had oil and dust in my radiator cooling fins which I cleaned out (air gun/solvent, water flush). Seems to run cooler now. I figure I can make a rubber washer and put in where the cap seats if I need to raise the pressure a bit. Then I'd be stuck needing to pressure test, but I could do a spring rate calculation. Link to comment Share on other sites More sharing options...
Roger Lee Posted October 17, 2017 Report Share Posted October 17, 2017 The older .9 bar cap shouldn't even be available any more. You should only be able to get the 1.2 bar (18 psi) cap. If for some reason the cap you get is only .9 bar send it back. I didn't even think they had these on the market for rotax any longer. When the CPS operator pulled up that old part number it should have redirected her to the new one. Link to comment Share on other sites More sharing options...
ibjet Posted October 17, 2017 Author Report Share Posted October 17, 2017 I ordered online. But I searched CPS's parts listing for both parts. The 922-070 showed no search results. The 922-075 showed In Stock! I was pretty shocked myself (because, like you say, that is the old P/N). I'll call them now. Thanks Roger!!! Link to comment Share on other sites More sharing options...
Runtoeat Posted October 18, 2017 Report Share Posted October 18, 2017 I just installed the 1.2 bar cap (18 psi) which I bought from Aircraft Spruce. I believe the Leading Edge Airfoils (LEAF) also had these caps in stock. Some suggestions for things you might check If you're having coolant leaks. One is to see what coolant hose you are using. If you are still using the European DIN hose, this is 25 x 3.5 mm. There is a LOA issued which allows us to use the Gates 1" coolant hose. This is a thicker walled hose. It is 25.4 x 4 mm. The Gates hose, being thicker, seems to provide better sealing from those I've talked to who have used this. The other thing to check is your hose clamps. All Rotax engines now being sold use the " 2 eared" spring clamps. These clamps seem to provide consistent clamping force on the joint they are used on, regardless of ambient temperature. You might consider, if you haven't already done it, to order some of these clamps and try them. I would also use the Gates 1" hose in combination with these clamps. The last thing you might check is to pull the hose off of the leaking connection and inspect the aluminum tube. My personal experience tells me that mechanics can and will put gouges in these tubes by sticking flat bladed screw drivers between the rubber hose and aluminum tube in an attempt to pry the hose off of the tube. This will dent or gouge (or do both) to the tube. You can fix a gouge by filing the tube until the gouge is eliminated. I'm not sure what can be done if the tube is dented-probably a new tube must be ordered. One last thing you should do when installing these hoses is to insure the inside of the hose and outside of the tube is dry and not wet with coolant. Funny as it might seem, if the hose and/or tube is wet, this can provide a path which can allow the coolant to weep past the clamp. Link to comment Share on other sites More sharing options...
ibjet Posted October 18, 2017 Author Report Share Posted October 18, 2017 Update of my quest . . . I called CPS and according to the order desk, the latest Rotax P/N is 922-072. I asked the price and it was $87.xx!!! That really urks me! I told them thanks and left my existing order stand. That one is $47.55, still highway robbery, ha ha. So, I have a winter radiator cap and a summer, ha ha. I went and searched my garage and found my Stant radiator leak and pressure tester. Came back in the house and did an online search for "adapter for testing small radiator caps". Bingo, on order, $14.xx with 2 day free shipping from Amazon. No longer will I have to wonder! Thanks you guys. I'm still wondering how the 0,9 bar cap works. I'll find out and update here. Link to comment Share on other sites More sharing options...
Roger Lee Posted October 18, 2017 Report Share Posted October 18, 2017 An SB many years ago told people to remove that .9 bar cap and not use them any more. Link to comment Share on other sites More sharing options...
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