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Engine Air Leaks

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Monkey Wrench

Monkey Wrench

My last words will likely be, Crap that didn't wo
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Is there a tip or trick to pinpointing air leaks? I'm thinking something along the lines of the soapy water method to find a leak in a tire, though I know I can't use that trick on a nitro engine. Additionally, should I see bubbles in the fuel tank from the line connecting the muffler to the fuel tank? I've never noticed it before on my other trucks (this is a T-Maxx, Pro. 15 mill I just rebuilt), but it could be me.

Thanks for the advice in advance! :shrug:
 
The best way to prevent air leaks it to use some rvt sealant on the base of the carb and on the back plate. This usually eliminates all air leaks on the engine.
 
I would say high temp rtv to be safe. I've always used that and never had a problem and I'm sure others will agree with that.
 
Yes, you can.

You can also take a can of compressed air or wd-40 with the nossle extension on it. Get the engine running off the ground so you can set the trim on the remote to make it run a a decent RPM, not WOT, just so it's a little higher than idle. Spray the wd-40 around the carb neck. If you notice a change in the engine or the engine dies, that's your leak. Doing this around the backplate is kind of annoying since it's hard to get at, but it's worth a shot. Also around the fuel inlet of the carb.

Regardless, I always seal my engines with RTV anyway.

There are a bunch of places for air leaks, not just the engine. If your exhaust header gasket is bad, it will cause bad pressure and leaks. A pin hole in the fuel line, a crack in the tank, a bad sealing tank lid can all be a leak.

Take the tank off the truck, empty it of fuel, fill a sink with water, blow some air into the pressure line while pinching the fuel line as it's submerged. If you get bubbles, you have a leak to fix.

By the way, this is the sealant you should use: http://www.permatex.com/auto/autouh.asp?automotive=yes&f_call=get_item&item_no=81878
You can find it at Napa, autozone, pep boys...
 
Go to Autozone or an autoparts store and pick up [Sensor Safe] RTV.

Get the copper stuff if it's availble, I think it's the best.

If not, the blue or black stuff will work.

Just make sure it's sensor safe.


After, seal the backplate and carb throat with it and your done.
 
WEll, they told you how to stop the air leak, Here is how you diagnose where the airleak is.

If you don't know what's leaking or if there is an airleak, here's what you do.

1. Start the engine.
2. Spray some Nitroblast around the LSN, HSN, Base of the carb, Around the head, behind the collet, back plate ... basically everywhere. Just do one section at a time.

Do one area at a time, of course. Where ever you spray and the engine dies, that's where your air leak is.

My brother spent a couple of days looking for an airleak on one of my engines and this was the only way for him to find it. Happy hunting!

IF the airleak is around the base of the carb, of course seal the carb after replacing the o-rings BUT also make sure that your particular engine doesn't have an o-ring in the hole that accepts the carb as well. Nova based engines have this O-ring. I'm not too sure about OS and the other various brands but Nova based engines, in general, have this o-ring. Replace it as a precautionary step so ou won't have to remove the carb again. This will not necessarily be a "leak spot" but it can change the tune of the car if the rubber frays and has a thread that goes in and out of the throat, causing turbulance. It will idle fine all day but in the higher rpm's it will cause you nothing but headaches.
 
Diver6127 said:
WEll, they told you how to stop the air leak, Here is how you diagnose where the airleak is.

If you don't know what's leaking or if there is an airleak, here's what you do.

1. Start the engine.
2. Spray some Nitroblast around the LSN, HSN, Base of the carb, Around the head, behind the collet, back plate ... basically everywhere. Just do one section at a time.

Do one area at a time, of course. Where ever you spray and the engine dies, that's where your air leak is.
Click to expand...

Umm.... I already posted most of that.
 
olds97_lss said:
Umm.... I already posted most of that.
Click to expand...
Yes you did olds. All I did was cut and paste from the original thread that I first posted that method. Sorry ... I just added the part about the O-ring in he neck since that's what I went through this seaason ... :cheers:

Monkey, use the search function next time. Lot's of your questions can be answered in that fashion.
 
I didn't even know my Nova Based engine's had that o-ring till I started to have issues. That's what gave sl0eg1n so many headaches. We had no idea there was one in there. How many times have you looked down the block with the carb out just to check? I don't know if all engines have that o-ring but ll our nova engines had it.
 
a quick note

First of all great info on the vacuum leaks . This to me is one of the biggest problems a Nitro engine has. And is also the #1 thing that causes flame outs and I agree with the advise that has been given but just a few things that will help: Hightemp RTV o2 safe is what I use but be very carfull on how much you use .If you put to much on the neak of the carb. it will bond to the engine making it very difficult to get the carb back off! Another thing is that there is a chemical in RTV that screwes up glow plugs. So when you use RTV remove the glow plug first then seal your engine and let it set overnight before you put the glow plug back in. Another trick to help is to not tighten the screws all the way untill its dry. Above all make damn sure that the surfaces are all clean and dry from any fuel ,oil,dirt before you add any RTV. As far as O rings go I like to use a film of white greese . This not only helps with the seal but it will aid in assembling with out damaging the o ring again acessive is bad use just enough to get the job done
 
No Probs here either but I guess it's good to know and will do that as a precautionary measure.
 
That's why the sensor safe is better but it still can screw up glow plugs . It does not really damage them that I know of but introducing the RTV vapers to the coil on the glow plug makes them inefficient. I myself am not a expert on this but the captin showed me some test results on this that I thought where intresting
 
Sorry about posting on the old thread, here, but when "backplate" is mentioned, does this refer to the actual plastic casing that the OWB is inside of? I did not seal this, but maybe I should...

:)
 
No need to do that. Some engines heed the actual al. backplate sealed to the block though.
 

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