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#1
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advice needed - weird temps
Hi
I have a newly rebuilt 0300-D. It is running hot - at OAT 93F, 2 cylinders are exceeding 400F on climbout and oil exceeds 200F. (BUT EGT's are perfect - less than 45F spread on my EI Monitor) On runup, no rise in RPM prior to drop on leaning! All baffling is brand new and installed correctly. I have been told that I need to increase fuel flow to improve cooling. I don't like going to my A&E without knowing what needs doing, why and how (it's a long story So - how do I increase fuelflow on my engine? Also - Cylinder 5 is too cool - running less than 300F CHT - which means it isn't scavenging lead - a recipe for sticking valves. I have been told it's because it is out front - but so is cyl 6 and that is one of the hottest. I am running TCP in the 100ll and Avblend in the oil - the engine is smooth as silk and has 30 hours on it. All suggestions highly appreciated. TIA Tony -- Tony Roberts PP-ASEL VFR OTT Night Cessna 172H C-GICE -- Tony Roberts PP-ASEL VFR OTT Night Cessna 172H C-GICE |
#2
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In article nospam-97F34F.08333904092005@shawnews,
tony roberts wrote: Hi I have a newly rebuilt 0300-D. It is running hot - at OAT 93F, 2 cylinders are exceeding 400F on climbout and oil exceeds 200F. [snip] All suggestions highly appreciated. recheck baffling check oil temp probe for accuracy check CHT probes for accuracy (all of them) Is 400F a temp redline or isn't it 500F? For my Lycoming O-320, the manual discusses having cruise CHT temps at or below 400F, with 500F redline. btw - EGT spreads aren't meaningful (the EI engine monitor manual should have some discussion of this). Have you talked to anyone at the shop that rebuilt the engine? -- Bob Noel no one likes an educated mule |
#3
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I am not an A & P (nor have I played one on TV) but it sounds like a
normal occurance in a newly rebuilt engine. I think that once thigs break in a little more (and loosen up) you'll see a drop in temps along with oil consumption. At least this is according to the rebuild books I have read. That being said, If I just spent up to 20 AMU's for a rebuild I certainly wouldn't hesitate to ask the rebuild shop questions. Good luck!! Jon Kraus '79 Mooney 201 4443H @ TYQ tony roberts wrote: Hi I have a newly rebuilt 0300-D. It is running hot - at OAT 93F, 2 cylinders are exceeding 400F on climbout and oil exceeds 200F. (BUT EGT's are perfect - less than 45F spread on my EI Monitor) On runup, no rise in RPM prior to drop on leaning! All baffling is brand new and installed correctly. I have been told that I need to increase fuel flow to improve cooling. I don't like going to my A&E without knowing what needs doing, why and how (it's a long story So - how do I increase fuelflow on my engine? Also - Cylinder 5 is too cool - running less than 300F CHT - which means it isn't scavenging lead - a recipe for sticking valves. I have been told it's because it is out front - but so is cyl 6 and that is one of the hottest. I am running TCP in the 100ll and Avblend in the oil - the engine is smooth as silk and has 30 hours on it. All suggestions highly appreciated. TIA Tony |
#4
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Jon Kraus wrote:
I am not an A & P (nor have I played one on TV) but it sounds like a normal occurance in a newly rebuilt engine. I think that once thigs break in a little more (and loosen up) you'll see a drop in temps along with oil consumption. At least this is according to the rebuild books I have read. That being said, If I just spent up to 20 AMU's for a rebuild I certainly wouldn't hesitate to ask the rebuild shop questions. Good luck!! What Jon said! You should be flying at 75% power and full rich until the temperatures stabilize. |
#5
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john smith wrote:
: What Jon said! : You should be flying at 75% power and full rich until the temperatures : stabilize. Probably at least. From what I've read, the initial hour or two should be at a very high power... more than 75% (and of course full rich). Definately sounds like you've got a couple jugs whos rings haven't seated. Chrome jugs (like mine) are notoriously hard to get to seat.... particularly if someone put chrome rings on as well (a no-no). -Cory -- ************************************************** *********************** * Cory Papenfuss * * Electrical Engineering candidate Ph.D. graduate student * * Virginia Polytechnic Institute and State University * ************************************************** *********************** |
#6
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But it does sound like he may be running too lean based on the no RPM rise
reducing the mixture from full rich. If that is the case, I would suspect a miss-adjusted carb or an intake manifold leak. "tony roberts" wrote in message news:nospam-97F34F.08333904092005@shawnews... Hi I have a newly rebuilt 0300-D. It is running hot - at OAT 93F, 2 cylinders are exceeding 400F on climbout and oil exceeds 200F. (BUT EGT's are perfect - less than 45F spread on my EI Monitor) On runup, no rise in RPM prior to drop on leaning! All baffling is brand new and installed correctly. I have been told that I need to increase fuel flow to improve cooling. I don't like going to my A&E without knowing what needs doing, why and how (it's a long story So - how do I increase fuelflow on my engine? Also - Cylinder 5 is too cool - running less than 300F CHT - which means it isn't scavenging lead - a recipe for sticking valves. I have been told it's because it is out front - but so is cyl 6 and that is one of the hottest. I am running TCP in the 100ll and Avblend in the oil - the engine is smooth as silk and has 30 hours on it. All suggestions highly appreciated. TIA Tony -- Tony Roberts PP-ASEL VFR OTT Night Cessna 172H C-GICE -- Tony Roberts PP-ASEL VFR OTT Night Cessna 172H C-GICE |
#7
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Another non-A&P -
Of the two O-300s overhauled among family and friends both had lean operation problems. The first one others thought might be a little carb ice (it would smooth out when carb heat was added, a sure sign of lean operation) until it disassembled itself at about 50 hrs. The cause was never found. The second one (a 172H) appeared lean on first annual after OH. We drilled out the carb jet ever so slightly. I now know that was both illegal and gauche. But it ran well then to TBO for whatever reason. I also had lean indications with my 172M (Lycoming) after the one piece venturii mod - especially on autofuel in the winter. You might want to make up a test fitting epoxying a 6 inch length of 1/8 inch dia clear plastic hose into a 1/8 inch pipe plug to screw into the 1/8 inch pipe port in your carb bowl. Using that rig on the ground, you can find out just where the fuel level stabilizes in the bowl. Make sure there are no intake leaks (the gaskets on each cyl adapter tend to suck in) & that all baffles are in place AND rigid enough that air pressure doesn't force them away from the fins. Is the baffle to direct cooling air around the crankcase properly spaced too? We added a couple of small rubber foot grommets to space that baffle out from the crankcase. Previously it rubbed on the casting. Might your Cyl number 5 thermocouple be miscalibrated? You might consider the use of the autofuel STC to minimize the lead contamination. High oil temps and oil that quicly becomes black are a symptom of piston ring blowby. Lead of course will make it turn gray. |
#8
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Hi Tony;
I also had problems with my 0-300D running at those temps. Turned out that the ignition timing was 10 degrees over advanced. I found this out by accident when I had to replace a failing mag myself. Both were overadvanced. My A&P sweares he checked them at the last annual. Note that the correct timing mark is a pain to find so some people may be tempted to pencil whip checking it(If I remember it is on the underside of the crank when it is at TDC). The two mags are also timed to different settings. When I reset the timing the engine ran exactly the same just 100 degrees CHT cooler. Now I can't get it over 400F almost no matter what I do. Full power cruise is about 375F. Note that the advanced setting eventually raised hell with my rings and I had to replace them later on. On the same engine, some time later, I had a sucked intake gasket that made one of the cylinders run cold along with a lousy idle. Jim |
#9
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Ignition timing is so fundamental to the proper operation of a piston
engine that it should never be taken for granted. Serious owners should really learn how to check it themselves. Theoretically they are not permitted by FARs to adjust it, but they are certainly able to check it. The Continental O-300D is about the smoothest running engine in aviation. It has the torsional damper masses on the rear of the crankshaft that the earlier O-300s don't have. |
#10
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Thanks for all the suggestions - you have given me a few things to look
at. To clarify a couple of things - The engine now has 30 hours on it - cylinders are new ECI's. We switched temp sensors around and got the same results (except oil temp sensor as we didn't have another one to test with). Baffles are new - were installed by and A & E and I have had another A & E inspect them - both say they are good. There is no excess lead problem - the TCP is doing a great job (Highly recommended) - the only lead I worry about is on cylinder 5 as it is running below 300 degrees which is the temp at which the lead scavengers start working. Cyl 5 and Cyl 6 both hang out front but there is consistently about 70F difference between them. Some of your suggestions I already checked. Possible causes that I hadn't considered that I got from your responses: - Timing, - miss-adjusted carb - intake manifold leak. Thanks to everyone - this is one great group - I'll report back when I find the cause. Tony -- Tony Roberts PP-ASEL VFR OTT Night Cessna 172H C-GICE |
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