Michael Christmann Posted May 9, 2012 Report Share Posted May 9, 2012 I recently observed a slightly higher reading on the right CHT indicator. In cruis it is about 12 to 15 degrees higher but during pattern work it can be 30 degrees higher and exceed 270 degrees. I exchanged the right and left probe with no change in readings. My next plan is to check compression. Any other ideas? Link to comment Share on other sites More sharing options...
Roger Lee Posted May 9, 2012 Report Share Posted May 9, 2012 Hi Michael, These temps are way too high and you shouldn't be there. (I take it we are talking about a CT?) The prop pitch being too course can easily cause this on a warm day. You need to see in flat and level WOT 5500-5600 rpm. If you unload the prop the engine will run cooler. If you are down around 5200 there is your problem. How is the oil temp and EGT's. temps are hotter in mid range throttle at 4500-4700 and you shouldn't be there in prolonged cruise. If it isn't the prop you need to make sure the radiator is square in the front mount to get all the air. You need to check all coolant lines for any crimping and then check the oil lines. I live in Tucson, AZ and it was 90 degrees today and yesterday. Flew in the pattern and CHT's are 210-215 but can be as high as 230 during a hot day. Link to comment Share on other sites More sharing options...
Michael Christmann Posted May 9, 2012 Author Report Share Posted May 9, 2012 My WOT is right around 5200. How and how much do I adjust the Neuform 2 blade? Link to comment Share on other sites More sharing options...
Roger Lee Posted May 9, 2012 Report Share Posted May 9, 2012 Hi Michael, There's your heat problem not to mention poor performance. By reducing the pitch you will gain better take off roll, climb, you will gain cruise speed at a reduced throttle, you will have more speed and you will save almost 1.5 - 2 gph depending on the cruise throttle setting, not to mention 5200 WOT prop pitch settings can and has cracked crankcases. There is a Rotax bulletin about this and a couple of people on the Rotax owners forum have reported the problem (no FD CT's). The 5200 WOT rpm setting cause too much stress on the engine and it wasn't designed for that. People think they will go faster with this course prop, but it is just the opposite. We don't have the HP and torque to turn the prop efficiently at the setting. Reduce your pitch by 1.75 degrees and that should put you between 5500-5600 WOT rpm. Then test fly it. It is possible you may need 2 degrees, but 1.75 should be good. That is the rpm you want to be at for WOT at your average cruise altitude. I'm sure once a few read this that have experienced the difference between 5200 and 5500-5600 WOT rpm they will chime in and tell you what a big difference there is in performance and temps. Link to comment Share on other sites More sharing options...
Michael Christmann Posted June 28, 2012 Author Report Share Posted June 28, 2012 Well, here is the follow up. We changed the pitch and got 5200 static and 5560 dynamic rpm. Still high CHT. We decided to continue with the hose replacement for the ROTAX and had the same results. Next we had the carburators overhauled. No change. We replaced the ignition, because the right o e had failed. No change .next we replaced the thermostat and got slightly better results but noticed that the temperatur dropped, when we switched off the master avionics. We recleaned the ground contacts and got rid of that problem, vut still experienced 230F on the left and 250f on the right, which Lockwood considers to high even in 96F. Any comments? Link to comment Share on other sites More sharing options...
Roger Lee Posted June 29, 2012 Report Share Posted June 29, 2012 250F is too high for 96F. 215F-230F would be more in line. So you replaced the coolant hoses. The carbs should not have made any difference. The ignition should not have made a difference. Since you replaced the coolant hoses are any kinked, even slightly? The hose they have been using kinks easier. You can drop the temps by making sure the rubber piece under the radiator is faced forward and not backward. Make sure the radiator is square and not even 1" off to one side. Are you using 50/50 coolant? I hope not Evans. It is possible that the thermostat is the issue by not opening all the way. Personally I see no reason for the oil or coolant thermostat in most US states. If these have any restricted flow at all the temps will rise. Are the other temps up across the board as well? Since you rebuilt the carbs are the needle clips in the #3 position? What are the EGT's? If they are high too then you are a little lean and the needle clip could be move to the #4 slot. (Last resort, do the other things first) If these items above are all okay then I would suspect a slight restriction in the thermostat. Yank the thermostat itself out of the body and just do a test run to check the temps. If they are down you have your answer. Link to comment Share on other sites More sharing options...
Tad Olmsted Posted June 30, 2012 Report Share Posted June 30, 2012 Have you slaved in a (known good) mechanical gauge to rule out the instument? Sounds like it should be running in the normal range from what I have read. Link to comment Share on other sites More sharing options...
airhound Posted September 1, 2012 Report Share Posted September 1, 2012 250F is too high for 96F. 215F-230F would be more in line. So you replaced the coolant hoses. The carbs should not have made any difference. The ignition should not have made a difference. Since you replaced the coolant hoses are any kinked, even slightly? The hose they have been using kinks easier. You can drop the temps by making sure the rubber piece under the radiator is faced forward and not backward. Make sure the radiator is square and not even 1" off to one side. Are you using 50/50 coolant? I hope not Evans. It is possible that the thermostat is the issue by not opening all the way. Personally I see no reason for the oil or coolant thermostat in most US states. If these have any restricted flow at all the temps will rise. Are the other temps up across the board as well? Since you rebuilt the carbs are the needle clips in the #3 position? What are the EGT's? If they are high too then you are a little lean and the needle clip could be move to the #4 slot. (Last resort, do the other things first) If these items above are all okay then I would suspect a slight restriction in the thermostat. Yank the thermostat itself out of the body and just do a test run to check the temps. If they are down you have your answer. I guess it probably got resolved somehow.....Could plug gaps influence CHT? Link to comment Share on other sites More sharing options...
FlyRatz Posted September 1, 2012 Report Share Posted September 1, 2012 If the temperatures are real high and it is for sure that it is not a sensor, electrical or gauge problem, then I would assume that the radiator became clogged. This happens sometimes due to chemical processes with the coolant. If you have access to another radiator, it would be worth to change and test. Markus Link to comment Share on other sites More sharing options...
Jim Meade Posted September 1, 2012 Report Share Posted September 1, 2012 If the temperatures are real high and it is for sure that it is not a sensor, electrical or gauge problem, then I would assume that the radiator became clogged. This happens sometimes due to chemical processes with the coolant. If you have access to another radiator, it would be worth to change and test. Markus Markus, Can you expand on this idea? Which coolant? What processes? What conditions? How much time does it take? Thank you. Link to comment Share on other sites More sharing options...
airhound Posted September 1, 2012 Report Share Posted September 1, 2012 Anyone---can mis-gapped plugs cause heat problems? Link to comment Share on other sites More sharing options...
Roger Lee Posted September 1, 2012 Report Share Posted September 1, 2012 Plugs slightly off gap won't cause over heat issues like you are talking about. Overly wide gaps may cause a little cooling. Both these would usually be too small for you to see or notice. They usually just cause hard starting, internal vibration due to poor firing and run characteristics.,You can see theses in a mag drop with a good digital instrument. Case in point. Had an engine not too long ago that had a 70 mag drop on one side and 180-200 on the other mag. Found a plug with the electrode tip smashed down. Link to comment Share on other sites More sharing options...
FlyRatz Posted September 5, 2012 Report Share Posted September 5, 2012 Markus, Can you expand on this idea? Which coolant? What processes? What conditions? How much time does it take? Thank you. Hi Jim, I have such a glogged radiator in my workshop. I sent it to a radiator manufacturer for a capacity test and they attested a performance of 35 %. This means, that this particular radiator has lost 65 % of its original cooling capacity. To identify the chemical processes, I need the help of a expert. I found a laboratory which is willing to do the diagnose for me. But this takes time. I expect a result at the end of this year. The radiator was used with 50:50 coolant (G48) and regular water from the water-cock. If I have details about the chemical process, I will post it here. Best to you Markus Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted September 5, 2012 Report Share Posted September 5, 2012 ...The radiator was used with 50:50 coolant (G48) and regular water from the water-cock... Is it a tame water-cock? Link to comment Share on other sites More sharing options...
Roger Lee Posted September 5, 2012 Report Share Posted September 5, 2012 Hi Markus, You should be using distilled water only. Regular tap water will allow the impurities to cook out and start clogging the small passageways which will reduce the flow. Coolant should be changed every two years. It is only about 750ml. Link to comment Share on other sites More sharing options...
chanik Posted September 5, 2012 Report Share Posted September 5, 2012 Hi Jim, I have such a glogged radiator in my workshop. I sent it to a radiator manufacturer for a capacity test and they attested a performance of 35 %. This means, that this particular radiator has lost 65 % of its original cooling capacity. To identify the chemical processes, I need the help of a expert. I found a laboratory which is willing to do the diagnose for me. But this takes time. I expect a result at the end of this year. The radiator was used with 50:50 coolant (G48) and regular water from the water-cock. If I have details about the chemical process, I will post it here. Best to you Markus Tap water is usually OK to mix, but hard water, with lots of dissolved minerals can give rise to corrosion which can plug up radiators. That's uncommon too. The REAL risk from tap water is obliquely related to hard water and that is if you use SOFTENED water. Water softeners leave quite a bit of salt in the water. At high temperatures that salt will do an impressive job rusting out the thin steel/brass in your radiator first plugging it and then making it leak. You should see the orange/green discoloration in the coolant if that is going on. Link to comment Share on other sites More sharing options...
Doug G. Posted September 5, 2012 Report Share Posted September 5, 2012 Is the two years a Rotax recommendation or requirement, or a Roger Lee practice? Link to comment Share on other sites More sharing options...
Roger Lee Posted September 6, 2012 Report Share Posted September 6, 2012 All my practices come right out of many years of Rotax school and the manuals. I didn't make a single one up. It is recommended by Rotax. (Rotax school) Just like the oil it is recommended and if you want to leave the oil in for ever I guess someone could do that. It does say in one document to change it by at least the overhaul. That would be 15 years or 2000 hours. That's an utter joke and it gets discussed in school. Stay with 2 years. It's only 2/3 of a gal. and won't break anyone's bank and it only takes a few minutes. We don't have a large quantity of coolant that will stay more stable over time like a car or truck. Kind of like anything in life. You have those that keep things new, have every thing done documented and it stays maintenanced and spotless. Then there are the others. We all get the freedom to pick our poison. That's why we have the Darwin awards. I just had two calls just today about two ruined 912 engines. Different issues. Fixes are going to cost $5K-$6K. Maybe they could have spent $100-$200 back then and would have saved the other $5K. That old saying does hold true some times: pay a little now or a lot later. I get 8-10 calls a day from all over the world on the 912 (half that from CT owners) so I get a unique chance to hear a lot of issues and problems and very fortunate to help some along the way. That's the best part for me, the call back saying problem solved. Makes my whole day. Link to comment Share on other sites More sharing options...
airhound Posted September 6, 2012 Report Share Posted September 6, 2012 All my practices come right out of many years of Rotax school and the manuals. I didn't make a single one up. It is recommended by Rotax. (Rotax school) Just like the oil it is recommended and if you want to leave the oil in for ever I guess someone could do that. It does say in one document to change it by at least the overhaul. That would be 15 years or 2000 hours. That's an utter joke and it gets discussed in school. Stay with 2 years. It's only 2/3 of a gal. and won't break anyone's bank and it only takes a few minutes. We don't have a large quantity of coolant that will stay more stable over time like a car or truck. Kind of like anything in life. You have those that keep things new, have every thing done documented and it stays maintenanced and spotless. Then there are the others. We all get the freedom to pick our poison. That's why we have the Darwin awards. I just had two calls just today about two ruined 912 engines. Different issues. Fixes are going to cost $5K-$6K. Maybe they could have spent $100-$200 back then and would have saved the other $5K. That old saying does hold true some times: pay a little now or a lot later. I get 8-10 calls a day from all over the world on the 912 (half that from CT owners) so I get a unique chance to hear a lot of issues and problems and very fortunate to help some along the way. That's the best part for me, the call back saying problem solved. Makes my whole day. Roger, you made my whole day, the Tanis arrived and what a class act....Thank You! What would be a good reference to use when changing radiator fluid? Are there any Cautions?? Link to comment Share on other sites More sharing options...
Roger Lee Posted September 6, 2012 Report Share Posted September 6, 2012 No cautions except don't put your lips on a hot coolant tank to blow the coolant out. Blisters the lips bad. No references. I did make a post here or maybe it was on the Rotax forum on how to change fluid. If you can't find it give me a call. Basically find the low point either on the water pump bottom screw or pull off a low point coolant hose. Blow through the system hard 3-4 times to vacate all the fluid and then just re-fill. Two more Tanis pre-heaters go out tomorrow. They work extremely well in the coldest of climates and heat soak the entire engine.. Link to comment Share on other sites More sharing options...
Doug G. Posted September 6, 2012 Report Share Posted September 6, 2012 Thanks Roger. Makes sense. Especially when I will be doing my own annuals. Doug Link to comment Share on other sites More sharing options...
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