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Model Forum / Radio Controlled / Air Models / April 2004Help with TT .46 fuel leak/bubbles
I have started noticing my TT pro .46 is leaking fuel, and what appear to be air bubbles, somewhere around the left rear bottom of the engine. I have included a pic if that helps: http://www.mparkes.com/ttpro.jpg I had crashed it last week (nose in) so I wonder if the rear seal or something is now leaking? The engine seems to be running fine otherwise. Is it fixable or can I just ignore it? thanks On 4/12/2004 12:23 PM Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge: I wouldn't ignore it. Try find/fix it now - it is only going to get worse and possibly become not repairable. I would try the following: 1. Try removing the inline fuel filter and bench run the engine. You might get lucky :) 2. If it still bubbles, pull the engine out of the plane (if you haven't already) and THOROUGHLY clean it. I mean use a toothbrush and/or a small stainless or brass brush along with some lacquer/paint thinner or carburetor cleaner. Do this outside and DO NOT SMOKE OR HAVE ANY OPEN FLAMES AROUND WHILE DOING IT. Wipe off any residue and let it dry. Then get a magnifying glass and start checking the general area at the MOST FORWARD AREA OF THE BUBBLES for cracks. Any suspected cracks check with the point of a #11 exacto blade or "T" pin. If/when you find a crack clean that area with some acetone to remove any oil/grease that may be in the crack and JB weld the area. The hardest part will be to get the area free of oil. The "proper" way to repair the crack (to keep it from growing) is to find both ends of the crack and drill a small hole all the way through. Then make a "V" groove between the holes and clean the area. Then fill with JB Weld. The "proper" way will require disassembly of the engine. If you decide to go this route (instead of a surface patch), make sure you mark the piston/liner so you don't reassemble it backwards. I doubt it is the rear seal. The bubbles are too forward of the backplate (the prop blast is going to push the bubbles back). You want to start at the most forward area the bubbles are showing. In the photo, it "APPEARS" that the bubbles are starting in the general area of the fuel filter or the rear bolt hole on the mounting lug/back part of the casting for the schnurle porting. Hope this helps. > I have started noticing my TT pro .46 is leaking fuel, and what appear > to be air bubbles, somewhere around the left rear bottom of the [quoted text clipped - 5 lines] > otherwise. Is it fixable or can I just ignore it? > thanks When you say I might get lucky (with number 1), the fuel filter might be at fault somehow? As in its leaking? >On 4/12/2004 12:23 PM Ted shuffled out of his cave and grunted these >great (and sometimes not so great) words of knowledge: [quoted text clipped - 44 lines] >> otherwise. Is it fixable or can I just ignore it? >> thanks On 4/12/2004 1:52 PM Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge: Yep - it might be cracked. I doubt it, but it is easy to rule out. > When you say I might get lucky (with number 1), the fuel filter might > be at fault somehow? As in its leaking? [quoted text clipped - 47 lines] >>> otherwise. Is it fixable or can I just ignore it? >>> thanks Ted, I gather that just using JB weld over the crack (option 2) the crack will grow? Thanks for your help! >>>2. If it still bubbles, pull the engine out of the plane (if you >>>haven't already) and THOROUGHLY clean it. I mean use a toothbrush [quoted text clipped - 6 lines] >>>a crack clean that area with some acetone to remove any oil/grease that >>>may be in the crack and JB weld the area. On 4/12/2004 2:16 PM Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge: It can. Unless a crack is terminated smoothly (drill a hole), the fracture line can increase. You have probably seen this in a car windshield - it gets a chip or small crack, and 2 weeks later the crack goes across the whole thing. A lot will depend on the size of the crack and the amount of stress and vibration to that point. I would suggest seeing if it is a crack first (although I do think so), and if so how big it is and where it is. Items such as the mounting lugs are under a lot more stress and vibration than say, the back plate. Another option (if you have a crack) is to have it MIG welded. That is probably going to cost in the neighborhood of $10 - $15. I don't know how old the engine is or if there is an emotional attachment to the engine. You may want to consider replacing the engine or you may just want to go over the crack and run it until it dies. While I would not consider it hard to disassemble an engine and do a repair like that, many people do not want to tear into their engines because they lack the necessary equipment and/or skills. Hey, not everyone can be an astronaut, some of us have to fuel the thing :) TT engines are relatively inexpensive compared to something such as an Irvine, Rossi or Jett, however, everyone's budget and available funds are different. > Ted, I gather that just using JB weld over the crack (option 2) the > crack will grow? [quoted text clipped - 10 lines] >>>>a crack clean that area with some acetone to remove any oil/grease that >>>>may be in the crack and JB weld the area. Ted After taking the engine off the plane and cleaning it up (there was oil film pretty much all over the motor), I discovered the gasket between the muffler and the motor was cracked - so maybe that is where the oil is coming from? I tightened the bolts holding the the backplate on. I looked closely over the area where the bubbles were forming and can find no indication of a crack or damage. My thought now is that the maybe (hopefully!) the oil was coming out from the leaky muffler gasket, the prop wash is pushing it around the engine to collect around the mounting lugs, and there just happened to be a little air leak from the back plate gasket at some point causing the bubbles. Does that sound plausible? I will try to bench test the motor and see if a new muffler gasket fixes things. >On 4/12/2004 2:16 PM Ted shuffled out of his cave and grunted these >great (and sometimes not so great) words of knowledge: [quoted text clipped - 39 lines] >>>>>a crack clean that area with some acetone to remove any oil/grease that >>>>>may be in the crack and JB weld the area. >Does that sound plausible? Very plausible. The slipstream will blow the oil all over the place. One backplate bolt might have been slightly loose. It doesn't take much. Dr.1 Driver "There's a Hun in the sun!" The backplate would be the first point of contact by the crank when it hits. If it went that far, it has likely damaged teh front bearing as well as that is what holds the crank in position. Remove the back plate and look for the impact point from the connecting rod or crank pin. If you don't see anything there, take the engine apart and have the crankcase checked with dye-penetrant NDI. A local machine shop should be able to do that quickly for you. You may also be able to get the stuff to do it at a good auto parts store. -- Paul McIntosh http://www.rc-bearings.com > I have started noticing my TT pro .46 is leaking fuel, and what appear > to be air bubbles, somewhere around the left rear bottom of the [quoted text clipped - 5 lines] > otherwise. Is it fixable or can I just ignore it? > thanks |
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