flash59 Posted May 3, 2005 Share Posted May 3, 2005 Yes this is a 92 2.2L installed on an experimental aircraft. It has always operated at about 198 degrees but the other day it spiked to 245 degrees. Radiator coolant temperature was about the same as outside temperature and the engine was hot. I replaced the thermostat (OEM subaru) and refilled the system and purged air from the system at the heater pipes on top of the block. This has worked well for me in the past. I operated the engine on the ground for 20 minutes and the temperature held steady at 198 degrees up to about 3500 rpm. But when the rpm was advanced for takeoff (5060 RPM) it immediately spiked to 245 again. I repeated this purge cycle several times, always with the same result. Thinking head gasket did a compression test (170 cylinders 2 & 4, 150 cylinders 1 & 3), prior to this compression readings were 170 cylinders 2 & 4 and 165 cylinders 1 & 3. I pulled the heads and had a machine shop check them out. The only thing obvious found was a slight warp on the 2 & 4 head between the cylinders and nothing on the 1 & 3 head. Although they did mention that it looked like someone had used a belt sander to surface them. Any thoughts would be of help Quote Link to comment Share on other sites More sharing options...
Subarunation 713 Posted May 4, 2005 Share Posted May 4, 2005 Are you using avgas or auto fuel or switch from one to another? Did you carburate the engine or leave FI? What I am getting at is that somehow the engine may be leaning too much? What about timing, could that have been bumped by accident? If you are to advanced or retarded you might get some extra heat at higher RPMs. More than likely you will have fixed the problem with new headgaskets and machined/resurfaced heads. If the timing belt had jumped a tooth, when you put it back together you will have remedied that possible problem too. Good luck, Greg (an envious pilot) Quote Link to comment Share on other sites More sharing options...
flash59 Posted May 5, 2005 Author Share Posted May 5, 2005 Thanks for the reply Gregg. I am using 92 octane auto fuel (Union 76). I have heard of some folks using 100LL AVGAS during cross country flights and auto fuel at their home field, but I have not tried this. It is fuel injected. I decided to pull and inspect the water pump, seemed like the smart thing to do since the timing belt was off anyway. Everything looked great. Alot of time was spent on timing. The engine sets quite close to the rotor mast so you cant get the balancer and center timing cover completely out of the way. It paid off though since the timing is spot on, at least by what the service manual outlines. I searched through the posts and found some nice info about filling the cooloing system. With any luck I wont have any problems purging air pockets this time around. Quote Link to comment Share on other sites More sharing options...
blitz Posted May 5, 2005 Share Posted May 5, 2005 I. These will be accompanied by a change in exhaust note and a drop in power. A. Really late timing (make sure your knock sensor isn't telling the ECU to yank timing under load). B. Lean fuel (check your fuel pressure & TPS). C. Restricted exhaust. II. The only other thing that comes to mind would be a reduction of coolant flow. A. Restriction/blockage. B. Water pump impeller erosion. I don't see what else could possibly be causing it. You are getting adequate air-flow through the radiator? Fans? Quote Link to comment Share on other sites More sharing options...
fujiyama Posted May 13, 2005 Share Posted May 13, 2005 II. The only other thing that comes to mind would be a reduction of coolant flow. A. Restriction/blockage. B. Water pump impeller erosion. Do you have antifreeze in your cooling system? If the rad freezes at the bottom then the engine temp will rise very rapidly. This happened to my engine once, it was so bad that a head bolt had unscrewed completely and was bouncing around! Quote Link to comment Share on other sites More sharing options...
TheBigJ Posted May 13, 2005 Share Posted May 13, 2005 Have you verified that the newly installed thermostat is operating properly? If engine temp is up to 245 and coolant in the radiator is still the temp of outside air, something has got to be blocking coolant flow. Either air pockets or a defective thermostat. Easiest check is get a temperature probe (eg your hand) in/on the upper radiator hose and see if it heats up with the engine. Quote Link to comment Share on other sites More sharing options...
ShawnW Posted May 14, 2005 Share Posted May 14, 2005 What did you do with the heater lines on the 2.2? They are important in getting the engine to cool right. Quote Link to comment Share on other sites More sharing options...
flash59 Posted May 14, 2005 Author Share Posted May 14, 2005 Thanks for all the input. This time around I was able to purge what little air was in the system with minimal effort. Burped the system at the cap twice and that was it. Temps were fine after that, 192 degrees. All was good for about 4 hours until the lower hose got against the 2 & 4 exhaust stack and that was the end of that hose. Changed it and started over again. 2.5 hours of ground runs later without any overheating I took it out for a flight. Water temp looked good (192 degrees) but the oil temps seemed a bit higher than normal ( 224 degrees @ 5100 rpm). As the flight progressed the water temp started fluctuating between 192 and 210 degrees, but this was preceeded by a rise in oil temp which was fluctuating between 224 and 233 degrees, I havent been able to find any specs to know what the oil temp should be. This high oil temp had happened once after re-installing the heads changed oil (it didnt have coolant in it but looked extremely thin), and filter. Once back at the hanger the oil indicated 1/2 quart over but showed no indication of coolant. It was just extremely hot and thin. In fact the oil pan was still quite hot long after (45 mniutes) the engine had cooled down. Chiltons talks about using the next higher grade of oil (10W40) sustained high rpm use ( I think 4500-5100 rpm would meet that). Any thoughts on that or on what the oil temp should be would be of great help. All I have been able to find about oil temp is 230-300 for turbocharged 2.2 and nothing for a FI 2.2 Quote Link to comment Share on other sites More sharing options...
flash59 Posted May 14, 2005 Author Share Posted May 14, 2005 Shawn The heater pipe from the the water pump and the pipe from the crossflow manifold are connected at the top of the block with a 4" piece of pre-formed , U-shaped heater hose. Anything longer would be to close to the propeller. Quote Link to comment Share on other sites More sharing options...
ShawnW Posted May 14, 2005 Share Posted May 14, 2005 I think it might be time to put an oil cooler on if you havent already. Subaru offered them in turbo model legacy's and some outbacks in the 96-99 era. Quote Link to comment Share on other sites More sharing options...
Setright Posted May 14, 2005 Share Posted May 14, 2005 Or just fit the correct Mocal oil cooler. For sure you should be running a 50 weight oil. Whether it's 5W-50 or 10W-50 or 15W-50. I would not use a 5W-30 as the handbook suggests. Much too thin for all those revs. Quote Link to comment Share on other sites More sharing options...
99obw Posted May 14, 2005 Share Posted May 14, 2005 Oil viscosity is rated at 100°C, so at those higher temps your oil is thinner than its rated viscosity. I would use a 15w-40 or 20w-50. Lower spread multi-viscosity oils are more rugged than higher spread oils when exposed to high temps, and cold-start flow probably isn't much of a concern. Higher viscosity will raise oil temps due to friction in the oil. An oil cooler is an absolute necessity IMHO. Is the engine cowled? Air flow out of the cowl can be an issue as it restricts the air flowing in and through the radiator. Quote Link to comment Share on other sites More sharing options...
blitz Posted May 14, 2005 Share Posted May 14, 2005 I second the oil cooler. Opt for an aftermarket oil-to-air, stand-alone unit rather than the oil-to-coolant, OEM style and be sure to mount it in a place of adequate airflow, but where it's not physically vulnerable. Pick one with a much larger than required capacity in conjunction with a thermostatic valve. This way in the event of a coolant temp rise (or complete cooling system failure) the massive oil cooler will buy you time to find a suitable place to set the craft down. Just be sure to use high-quality stuff (lines, clamps, etc). The 15W-40 is a great idea also. Quote Link to comment Share on other sites More sharing options...
frag Posted May 14, 2005 Share Posted May 14, 2005 And would'nt it be a good idea to use synthetic oil since one of the strong points of synth oil is resistance to breakdown at higher temps? And in your case «higher» temps takes an even more ominous meaning... Quote Link to comment Share on other sites More sharing options...
flash59 Posted May 17, 2005 Author Share Posted May 17, 2005 I would like to express my thanx to all those who replied. Today I changed the oil (20W50) and filter. Took it around the patch a few times and everything looked great. Water temp 192 and oil temp 220 steady @5100 rpm. Planning on installing an oil cooler soon, plumbed into the outlets on the bottom of the oil pump. Just have to work out a design for mounting brackets and air scoop. Anyway its running strong so its time to get out and do some serious flyin. Thanx again Quote Link to comment Share on other sites More sharing options...
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