Using brake bleader pump for vac leak check

[SnowFox]

So, Ive been fortunate enough to never have a vacuum leak in my life. So I never really learned to check for them. (I could have had one and never knew it I suppose)

I put on my super charger, everything is going great, but having messed about with vac lines I wanna be sure I have no leaks before final tune.

I have a hand held break bleeder/vac pump. What's the best methodology for using it?

I see lots of people doing smoke tests but I really don't wanna try that yet.

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[SheepDog]

It won't work. The volume of air you need to test the entire system at once far exceeds what a little hand pump can generate. If you removed the throttle body and plugged the opening in the intake manifold, you are still going to fight the small inconsistencies in the valvetrain, fittings, Injector o-rings, etc. Even then, you wouldn't know exactly where the leak was unless it was so large that you could hear the air being sucked in.

In order to put the entire intake under a vacuum, you would need a serious vacuum pump and perhaps tap a hole in the intake manifold to install a shraeder valve. Or a valve in the cap that would plug the intake hole

This is why a smoke machine works better. You fill the entire intake system with smoke, and watch for leaks, and even this can sometimes not work very well to find the small stuff.

One thing you can do, is start the engine and let it idle. Hook up a scan tool with live data and bring up short term fuel trims. while watching the data, spray short bursts of brake cleaner or carb cleaner around specific potential problem areas such as the intake manifold gasket, various fittings, ijector o-rings and so on. If there is a leak, the engine will suck in the cleaner, and the fuel trims will go negative for a short time. Your engine is a 5 liter air pump

 

[SnowFox]

It won't work. The volume of air you need to test the entire system at once far exceeds what a little hand pump can generate. If you removed the throttle body and plugged the opening in the intake manifold, you are still going to fight the small inconsistencies in the valvetrain, fittings, Injector o-rings, etc. Even then, you wouldn't know exactly where the leak was unless it was so large that you could hear the air being sucked in.

In order to put the entire intake under a vacuum, you would need a serious vacuum pump and perhaps tap a hole in the intake manifold to install a shraeder valve. Or a valve in the cap that would plug the intake hole

This is why a smoke machine works better. You fill the entire intake system with smoke, and watch for leaks, and even this can sometimes not work very well to find the small stuff.

One thing you can do, is start the engine and let it idle. Hook up a scan tool with live data and bring up short term fuel trims. while watching the data, spray short bursts of brake cleaner or carb cleaner around specific potential problem areas such as the intake manifold gasket, various fittings, ijector o-rings and so on. If there is a leak, the engine will suck in the cleaner, and the fuel trims will go negative for a short time. Your engine is a 5 liter air pump

Copy that. Think I'll give that a try. Also just remember it's prime day maybe find a cheap smoke machine. Thanks for the info and reply.

 

[SheepDog]

Copy that. Think I'll give that a try. Also just remember it's prime day maybe find a cheap smoke machine. Thanks for the info and reply.

Do you suspect a leak?

Part of the issue with very small leaks, is that the PCM will make adjustments to the fuel trims and that tiny leak, will become the new normal when the PCM adds a bit of fuel to compensate. If you take your scan tool or flash device and clear the data, then start the engine and let it idle, the STFT's should hover as close to 0 as possible, but will go + and -. The long term trims should be no more than +/- 10%, but ideally in the single digits and as close to 0 as possible.

Large leaks will cause stumbling, misfires, poor idle

 

[SnowFox]

Do you suspect a leak?

Part of the issue with very small leaks, is that the PCM will make adjustments to the fuel trims and that tiny leak, will become the new normal when the PCM adds a bit of fuel to compensate. If you take your scan tool or flash device and clear the data, then start the engine and let it idle, the STFT's should hover as close to 0 as possible, but will go + and -. The long term trims should be no more than +/- 10%, but ideally in the single digits and as close to 0 as possible.

Large leaks will cause stumbling, misfires, poor idle

I'll go with a solid maybe lol here's why.

For first few days after installing the blower I did have a high idle. It Would sit at 1k RPM while warming up and would stay that way even after warming up while in park (it didn't drop down to 700ish like it usually does after warming up)

I tightened up the charge pipes and that seemed to fix it.

While driving and sitting at stoplight the idle is perfectly fine nice and smooth.

Starts fine, no stumbleing, never feels like it's gonna die.

Part of this might be my OCD just wanting to be doublely sure. I very likely may have none. BUT if I don't confirm my assumption it will drive me nuts

 

[SheepDog]

I'll go with a solid maybe lol here's why.

For first few days after installing the blower I did have a high idle. It Would sit at 1k RPM while warming up and would stay that way even after warming up while in park (it didn't drop down to 700ish like it usually does after warming up)

I tightened up the charge pipes and that seemed to fix it.

While driving and sitting at stoplight the idle is perfectly fine nice and smooth.

Starts fine, no stumbleing, never feels like it's gonna die.

Part of this might be my OCD just wanting to be doublely sure. I've very likely may have none. BUT if I don't confirm my assumption it will drive me nuts

look at your fuel trims

 

[SnowFox]

look at your fuel trims

Would I only be looking at trims while at idle? My guess is I want them at 1 or very very close.

 

[SheepDog]

Would I only be looking at trims while at idle? My guess is I want them at 1 or very very close.

Yes.

Fuel trims at any other engine speed, load, throttle input etc. will be different based on what your tune is targeting. 0 is perfect, meaning that the PCM doesn't have to add or subtract fuel to achieve stoich. The STFT will always fluctuate back and forth. a little bit

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