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Air bubbles building up in fuel feed line.

Discussion in 'Traxxas T-Maxx' started by svecobrar, May 8, 2012.

  1. svecobrar

    svecobrar RCNT Member

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    Hey guys I need help. I have classic tmaxx with a 2.5, and the truck runs pretty good but it runs a bit too hot and i've tried sealing the engine and all thr basic stuff. One thing I have noticed is that the fuel feed line is constantly full of air bubbles.

    Ive put a brand new gas tank in it and ive tried a few different fuel line routings to try and keep the fuel as cool as possible but I feel that the heat is still getting to the fuel and causing vapor lock.

    I have three other nitro monster trucks so I'm not a beginner by any means but am not a expert either.

    Thanks in advance
     
  2. REVO-5309

    REVO-5309 Hardcore RCNT User

    there isnt enough back pressure going through the exhaust to push the fuel through the line.... check the header seal
     
  3. 2revo1maxx

    2revo1maxx Hardcore RCNT User

    Is it a brand new tank? Are all the screws in it and tight? A loose or missing screw can cause foaming.
     
  4. Phins Fan

    Phins Fan Hardcore RCNT User

    Do you have anything else in the fueline like a filter or a finned cooler? Those extra breaks in the line can cause airleaks as well.
     
  5. svecobrar

    svecobrar RCNT Member

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    I don't have anything else in the fuel tank or on the line. I guess my next step would be to check the header seal. Can i test it for leaks with soap and water while it runs?

    Also does the stock pipe on the tmaxx make it sound like the idle is high compared to, lets say a revos? My stock piston and sleeve are out getting repinched so i put my revo 2.5r in it for the time being, same fuel line systems by the way, and it seems like the 2.5r idles a lot higher in the tmaxx then in the revo.

    Thanks again.
     
  6. REVO-5309

    REVO-5309 Hardcore RCNT User

    just blow into the exhaust pipe. if pressure doesnt build up then there is a leak somewhere. if u blow into it and when u stop the air rushes back out then its tight...
     
  7. 2revo1maxx

    2revo1maxx Hardcore RCNT User

    So the screws are all in and tight then?
     
  8. svecobrar

    svecobrar RCNT Member

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    Ya the screws are in and tight. Its alot easier putting the tmaxx header on compared to.the revo one so I know its on there good. Ill be checking the exhaust for leaks in the morning.
     
  9. 2revo1maxx

    2revo1maxx Hardcore RCNT User

    I meant the fuel tank, make sure it's secure.
     
  10. svecobrar

    svecobrar RCNT Member

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    Ya the fuel tanks secure, i've removed it a bunch of times and its solid. I'm going to try the suggestions about the header gasket tonight or tomorrow, whenever i get my parts in from rcrenew and amain so i can do everything at once.
     
  11. svecobrar

    svecobrar RCNT Member

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    I replaced the exhaust to fuel tank fuel line and it helped with the air bubbles but they were definitely still happening and causing some problems although the idle went down very noticeably. I didn't have time to swap out the tank as it was because i was racing my buddy's lrp .30 savage x and didn't want any down time.

    I did check the exhaust for leaks and none were found. And i did notice that when i fill the tank full i get fuel that goes into the pipe to tank line. Is that normal?
     
  12. Pope

    Pope RCNT Talkaholic

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    Replace all fuel lines and check all seals on header and fuel tank. You may have a clogged in tank filter and need to replace the tank.
     
  13. 2revo1maxx

    2revo1maxx Hardcore RCNT User

    Just get a new tank, it obvious that your problem is with that.
     
  14. svecobrar

    svecobrar RCNT Member

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    thanks i'm going to swap it after i swap the springs on the mgt 8.0 i just bought.
     
  15. svecobrar

    svecobrar RCNT Member

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    swapped tanks but still having the same problems. The car runs pretty good with the newly repinched motor but it tends to run hot so i bought a golden horizons cooling head and we'll see how that goes.
     
  16. 2revo1maxx

    2revo1maxx Hardcore RCNT User

    Still getting air bubbles? It must be something to do with tank pressure then. What exhaust are you running?
    That cooling head might make it run cooler, but if it's lean it's lean, no cooling head can fix that.
     
  17. svecobrar

    svecobrar RCNT Member

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    I'm running the stock tmaxx 2.5 exhaust. I was tuning mu buddies tmaxx yesterday who has a sirio .18 in his with xtm exhaust and his was doing the same thing. I put all new fuel lines on it and it still had the same problem. Ill try to get a video today and post it tonight.

    Also, I thought the 2.5s were known for overheating and running hot, thats why I bought the new head for it.
     
  18. Metalhead Matt

    Metalhead Matt RCNT VIP

    Traxxas engines like to run on the warm side. Mine liked 280-290. Old 2.5.
     
  19. Fish

    Fish RC Newbie

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    It's ok to run the 2.5 at 280 F?
     
  20. tmaxxfreek

    tmaxxfreek Hardcore RCNT User Supporter

    thats the range i used to run mine at 240-280
     
  21. Fish

    Fish RC Newbie

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    We have been running at 160 to 180...time to lean them babies then! thanks!!
     
  22. 2revo1maxx

    2revo1maxx Hardcore RCNT User

    Svecobrar, is that a plastic pipe? I'll bet it's melted inside.

    ---------- Post added at 7:30 PM ---------- Previous post was at 7:28 PM ----------

    LOL fish don't burn up your engine. Tune for performance, not temps....and don't let it hit over 260-270.
     
  23. svecobrar

    svecobrar RCNT Member

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    Yes its a plastic pipe. But what does it being melted internally have to do with the bubbles?
     
  24. 2revo1maxx

    2revo1maxx Hardcore RCNT User

    If the baffle is melted inside you won't have enough fuel pressure.
     
  25. svecobrar

    svecobrar RCNT Member

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    I solved the air bubbles problem. I turned the fuel feed needles direction so the fuel line doesn't have to pass by the exhaust to get to the carb. I also installed a GH cooling head. My problem is that the thing still over heats. I run it without a body and i've tried 20% odonell, traxxas top fuel and cool power 25% and it still over heats. I rebuilt the carb, sealed the carb and the backplate and it still over heats and runs slow as hell.

    I regularly see over 280 with poor performance. I've searched google for overheating answers but there all the responses are the same and i've tried them all. The only other thing i can think of is to replace the engine bearings, as the flywheel side seems sensitive to brake cleaner (checking for leaks), but only sometimes. Sometimes it kills the motor, and other times it does nothing, holding the engine at roughly the same rpm.

    Any help is appreciated.
     

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