How to find a boost leak

[djuosnteisn]

Here's a copy n paste of a how-to i wrote eons ago. I still find it useful to show people how to find boost leaks. There are other methods as well, like spraying joints with carb cleaner, or smoke testing. But this one has always worked well for me.

One note i should have mentioned in the how-to, is to remove the valve cover breath tube from the turbo inlet, and block off the inlet side hole. This will prevent you from pressurizing the whole crank case, etc. I've done it many times without removing the tube without issue, but imo it's best to remove it.

Here's the how-to:
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Okay, here is a great way to test for boost leaks. Very simple, and only costs about 14 bucks, plus it's a tool you can use forever.

So here are the parts you'll need, you can pick them up at your local hardware store in the plumbing department:

You need a 3in to 2in rubber coupler w/ hose clamps. My intake pipe is actually more like 2.75in, but this piece will clamp down sufficiently to seal. You'll also need a 2in pvc pipe plug, this should fit perfectly into the coupler. You'll need like 4ft of 1/4 plastic tube. Lastly, you'll need a threaded 1/4in barb fitting and a 1/4in nut, all still found in the same plumbing section with the brass fittings etc.

Drill out the PVC plug and put the barb threaded end through, and secure with the nut on the other end. I covered all the threads with JBWeld just to be sure it would seal sufficiently.



Put the plug in the 2in end of the coupler.


Hook one end of the 1/4in tubing to the barb, and the other end up to a compressor hose.


Put the other end of coupler onto your intake inlet pipe.


Pressurize the system and listen for leaks.


You can mix up some soap and water if you really need to and smear it around looking for bubbles, but i found it was sufficient to just feel around with my fingers. You can literally feel the air blowing out of the hole if there is one. And DON'T just susupect the couplers, cause it could be a weld, like in my case!

Look at the lil hole in the weld:



It was very surprising how much air flowed out of this dinky hole. I would pressurize the system, and this lil hole would bleed it all off in only a couple seconds.



Another good idea is to T a boost gauge in line with the pressure tester so you have an idea of how high your testing too. You can alternatively turn the key on (leaving the motor off), and use an AP or dash hawk to indicate how much boost is in the IM. Just be careful if you have meth injection, cause it'll turn on while pressurized if hooked to the map sensor.

[djuosnteisn]

Just wanna add another thing to keep in mind, courtesy of Alan Jackson....

You may want to pull off the recirc tube from the bpv (if your not vta), and block it as well. That way if your BPV is leaking and opening under boost, you'll be able to detect it. If the recirc tube is left in place, it'll pressurize both sides of the valve, and you'd never know if you had a leaky bpv.

[YokiMazoku]

Thanks for posting this i have a high pitched whistle going on under boost so im sure i have a boost leak now to find it!

[event]

How do you know how much you are pressurizing the system and how much is too much pressure?

[djuosnteisn]

Originally Posted by event How do you know how much you are pressurizing the system and how much is too much pressure?

Excellent questions.


You do NOT want to over pressure the system, just up to the boost you intend on running, or a lil over. So if you plan on running 20 psi, pressurize it up to like 22 psi. Too much pressure can break things.



There are a couple ways to monitor the pressure. Normally i just "T" in a mechanical boost gauge i have laying around in the garage. Then i simply stare at it as i fill the intake tract. Works great.


Another method (cause most of us don't have boost gauges laying around)... is to use the map sensor on the intake manifold. Turn the key on, but don't start the car (motor off)... and that will power up the ECU and an AP or Dash Hawk. Then you can just place the AP or DH somewhere in the windshield where you can see it from the engine bay, and set it to a screen that monitors boost. As you pressurize the intake tract, you can see how much boost is in the intake mani.

******* CAUTION WHEN USING THIS METHOD IF YOU HAVE WMI *******
Even with the motor not running, if the key is on, the meth injection pump will be powered up. And as you pressurize the intake tract, it will turn on, filling your intake manifold up with water. So it's extremely important to make sure the WMI is switched off or disconnected from the power source.

That said, i prefer the T'd mechanical boost gauge. You can get a cheapy one at vatozone or something.

[Dano]

LOL i think the WMI caution should be in a bright red color....

[One2poo]

Thank you for posting this! Will be hitting up the plumbing section soon!

[silvapain]

I built my tester just a little differently, using a schrader valve. With the threaded fittings I can add a brass tee and put in a gauge later if I want.


Tapadatass

[Ace Protege]

^^ same
and I used my Matco digital gauge to know exactly how high I was getting the pressure. mine cost me all of $3. Pipe cap and schrader valve from work.

[silvapain]

Another reason to pull the valve cover vent and cap it on the intake side: if your PCV valve is leaking, you'll see it in the form of air blowing out the valve cover vent when you try and pressurize the system.

I had it happen to me today when I was pressure testing.

[event]

Originally Posted by silvapain I built my tester just a little differently, using a schrader valve. With the threaded fittings I can add a brass tee and put in a gauge later if I want. Tapadatass

Where did you find the shrader valve? I couldn't find one at menards...

[silvapain]

Ace Hardware. Lowe's and Menards didn't have them here either.

brady schrader air valve - STNDARD PUMP REPAIR ITEMS

[8.5MS3]

@silvapain are you sure its the pcv valve? i just tried to leak test mine and Im losing air thru the valvecover as well. I have MD's kit with an additional check valve in the line

[djuosnteisn]

OEM pcv valve is known to leak. Some more than others. A check valve however (if installed correctly) shouldn't leak unless it's real shitty.


And many of them are :-/

[8.5MS3]

@MATT DAMOND

dj be callin you out

[djuosnteisn]

Lol, i love matt, and IIRC he uses the best option for check valves.

I just think some of them randomly leak.

[Fatguy729]

Wow... Shows how much of a msf celebrity you are! You've gotten more love in a week than I've gotten in awhile LOL

How-To NATOR A Boost Leak Tester for $15

[silvapain]

Originally Posted by 8.5MS3 @silvapain are you sure its the pcv valve? i just tried to leak test mine and Im losing air thru the valvecover as well. I have MD's kit with an additional check valve in the line

I have a MD setup as well.

I pulled the line from my catch can to the IM and checked it this morning; the PCV is working fine.

It could be blowby or leaky valve guides... Can't think of any other sources off the top of my head. My car runs fine, but I'll be doing a compression check anyways.



Tapadatass

[8.5MS3]

im going to hook it up to a few local speeds this week and report back. it may be a common thing....idk

i did a comp check a few months ago and was at 190 across the board

[Fatguy729]

I was trying to diagnose an issue I was having and I got air from my valve cover hose... Didn't remember that happening before. Perhaps that was the issue I was having that prompted this thread!?

http://www.mazdaspeedforum.org/forum/foru...-my-car-88861/


What would your trims be if it were a pcv valve issue?

[8.5MS3]

wanna know something hilarious

i just threw in a dp 2 weeks ago hahaha, before that i made this thread

why cant it just work

[8.5MS3]

seeing as the valvecover breather is after the maf, in theory there should be no change to the maf calibration

but if 10% of the air is simply flowing from the intake mani -> crankase -> the intake and around again, then the fueling would be rich since that portion of the air is running around in circles

whats worse is that potentially means that the turbo is spinning like a fucking lunatic trying to hit boost targets with a bypass in the system....and your pressurizing the crankcase

or im absolutely 100% wrong....idk im gonna go drink and mow this over in my head

[djuosnteisn]

Lol. I did lots of drink thinking this weekend too....

[8.5MS3]

so ive done a lot of drinking

its either what i said before or a bent valve or a dropped cylinder

thoughts?

o and i revved my engine in neutral and saw 22.7 degrees of KR hahahahaha hopefully just a fluke

[dougefresh_]

^You just have a minor boost leak. Refer to OP.

[djuosnteisn]

Originally Posted by 8.5MS3 so ive done a lot of drinking its either what i said before or a bent valve or a dropped cylinder thoughts? o and i revved my engine in neutral and saw 22.7 degrees of KR hahahahaha hopefully just a fluke

Lolwut?

[8.5MS3]

Originally Posted by dougefresh_ ^You just have a minor boost leak. Refer to OP.

see below

silvapain are you sure its the pcv valve? i just tried to leak test mine and Im losing air thru the valvecover as well. I have MD's kit with an additional check valve in the line

Originally Posted by djuosnteisn Lolwut?

yea im srs i just laughed. but if im losing air thru the valvecover vent that means only a few things

2 pcvs in series are both shot (seems like a low likelyhood)
air going thru bent valve stem into head and getting thru valvecover
air going past rings into crankcase and then back up thru oil passages to head and out

i couldnt get the system over 5psi, the air leaving the valvecover was the same amount as my pussy pump could put in. i need to get a real pump and get the system up to pressure quickly

[silvapain]

Just stick your finger over the hole, or don't unplug the valve cover breather.

My car is running great - holding boost fine, and makes good power (see the Virtual Dyno thread). I just don't know why it leaks air out of the valve cover during a boost leak test.


Tapadatass

[djuosnteisn]

Probably a combination of leaky pcv / open valve and blow by / magic.

Originally Posted by 8.5MS3 see below 2 pcvs in series are both shot (seems like a low likelyhood)

The stock PCV does leak, and 2 in series would still leak. Maybe you need to trade the pussy pump in for a penis pump?

[8.5MS3]

Originally Posted by silvapain Just stick your finger over the hole, or don't unplug the valve cover breather. My car is running great - holding boost fine, and makes good power (see the Virtual Dyno thread). I just don't know why it leaks air out of the valve cover during a boost leak test. Tapadatass

did that, 2 quarts of oil in my eye via the dipstick

go ahead guys, have a field day

[LuczOr]

KR of 22 seems like it would be a problem... But I dont know shit about revving motors in neutral.

[djuosnteisn]

I think the 22 was a joke. At least i hope to god it was.... i'm still not sure.

[8.5MS3]

unfortunately its not

i get kr (less than 1.5) when i rev it in neutral and let off, according to the DH

but ive seen that the reproducible kr in the dh is not recorded in the ap, so maybe it was a timing change as i let off the pedal....idk

you gonna be in NYC anytime soon? lol

btw im blaming all this on phillyb touching my fucking car

shit ran great until he touched it

[djuosnteisn]

I have just the sticker for you.....


There's a difference between 22.7 and <1.5 lol. What bpv are you using? Do you really think the motor is sick? Anything weird while driving or has this all started from the boost leak check issue?

Does your clutch pedal vibrate when you just barely press it in?

[8.5MS3]

that 22 was only once last night lol

stock bpv

vibes have increased since i switched to the jbr dogbone

could be part paranoia, but the car just doesnt feel right, idk its hard to put my finger on

my wot afrs are beginning to fluxuate, seeing as high as 12.5 at times when they used to be rock solid at 11.8, running rich at shifts, rich spots when the maf changes tiers etc

clutch vibrates same as the rest of the car, ill check again when i drive home tonight.

[djuosnteisn]

A local here (knarfles) would see like 20's KR with his sound system lol. Always part throttle. Used to scare the shit out of him, hahahaha. So this isn't the first time i've heard of it.

It sounds like some hardware has shifted or something has changed. I can help you troubleshoot if you want, just shoot me an email and maybe a maf cal log, and i'll see if i recognize any common indicators from it.

I bet it's 80% paranoia, but 20% something changed.

[8.5MS3]

lol ill send you a log if the weather clears up, ill just do some typical driving with a wot or 2 in it so you can see both loops

thanks dj

[djuosnteisn]

Yeah man, no problem.

[dougefresh_]

8.5 I thought you were joking about the whole thing earlier :/ Hope you get it sorted and it's something simple.

[8.5MS3]

Originally Posted by djuosnteisn I have just the sticker for you.....

met up with the locals tonight for a get together. i run into the pizza place......come back to find this on the back of my car from one of the miata guys

irony at its best....