question about boost leak detecting
 

So I built the boost leak detector because the boost readings on torque seemed a little off to me (mostly zero boost, stays pretty low the rest of the time). I dutifully pulled the little hose that goes into the doghouse off and plugged it then started pushing air into the system at about 15-20 psi. But I couldn't get the system to hold any appreciable pressure, nor could I hear it leaking away, it was coming out so fast. I finally figured it out. I was trying to stuff some plastic into the hole entering the doghouse just to keep the soapy water from getting in since I was spraying like crazy while my son was holding the air on ... and low and behold there was air coming out of the doghouse. So, what does this mean? I didn't think that was supposed to happen ... am I doing the test wrong? Air doesn't seem to leak out anywhere when I plug the doghouse hole as well, although the plug wasn't very good, so it was a little hard to tell. Thanks!

Bad valve seat/guides worn out piston rings or cracked piston. Its also better to do a pressure test directly from the Turbo.

Ah, I was afraid it might be something like that. Is there a next step?

Make sure you are connecting to the intake of the turbo side AFTER the CCV tubing. Otherwise, it just comes out there! Ask me how I know :o

Here's a thread with some pics :https://www.ford-trucks.com/forums/1...ctor-pics.html

This is what I was thinking as well.

Connect your cap to the hose that is directly attached to the compressor housing on the turbo. If you pressurize before that, you are just pumping air into the CCV dog house.

Agreed, this sounds like the CCV is still in the system while testing. You can't plug it - you need to completely bypass it.

It sounds like he REMOVED the CCV hose and plugged the plastic outlet and then pressurized the system. Then he noticed air coming out of the CCV vent from the motor. I think this is fine. You might get air coming out of the oil filler hole too if the cap is off.

For leak testing you just need to maintain some pressure in the system. You can check pressure with an external gauge or you can use the pressure sensor on the turbo. If you use the pressure sensor on the turbo the truck might throw a code related to a bad EBP sensor though. Also don't leave the key on for long periods of time. I found the alternator would get hot if the key was left on with the engine not running.....

Bumping this because mine will also vent out the doghouse when I have the CCV adapter and hose removed and connect directly to the turbo intake. I believe the way I'm connected is basically the same as the OP.

Sounds like he removed the hose from the doghouse and plugged it at the CCV vent adapter, leaving the doghouse house nipple open, and that if where the air leak shows up.

Agreed.

Any body else seen this and know why, besides Freaky's theory??

I have not tried with the oil fill cap off.

if the turbo has a worn shaft seal then air will go into the turbo oil return line and out the CCV

Sorry for being out of the loop for a bit ... the day job heated up. Yes, I removed the CCV hose, plugged it, then pressurized, and got air coming out of the CCV hole (the one the hose would have been plugged into). DND58 seems to have had the same symptoms. It could be a bad shaft seal on the turbo, although I did just rebuild the turbo 3 years ago. I didn't have an EGT sensor, for two of those years and was wont to drive up to a place and just turn the engine off even when towing ... until a friend of mine cringed as I did it ... I said "what?" and he explained ... Brighty is my first diesel truck. So do I need to test/replace the shaft seal (and can one do this without rebuilding the whole turbo)?

Oh, and I should mention that first time I tried checking for leaks I did not cut out the CCV ... back to the forum to check proceedure and discover that many others seems to have made this mistake ... so perhaps that plays into things now?

My engine only has about 7500 miles on a new build. I won't go to far into the build, but it is a very extensive one. Well I recently built a boost leak detector, and when applying pressure to the system I noticed air coming out of the dog house as well. I put a plug in it ccv/Dog house with a worm clamp to hold in place, I then pressurized the system again and it held pressure alot better but was still leaking off, some at the dipstick and I imagine that in any position, a valve will be open and bleed off out the tailpipe as well. I know my engine is in perfect condition with no mechanical issues, so it must be normal to have some bypass here at the CCV/ dog house. Maybe plugging the tailpipe, which I did not do would help hold air. I put an air regulator at my compressor outlet to maintain 25psi and chucked in to the boost leak tester I made to keep constant pressure while I sprayed down the entire engine with soapy water. FYI, I found leaks at the both ends of the map hose at around 10 psi, as well all the green and red vac hose rubber boots that were dry rotted, and where my boost gauge ties into at the top of the Y pipe (AIH removed) boost gauge port here. I bought the rubber replacement Vac boots at Oriellys, they came in a pack of 4-6 or so and worked great to seal these areas. When I pushed the psi up to 25 lb, it did leak at these red and green Vac line points, but I don't think they were designed to hold a constant 20+ psi either, so you will see some leakage here the higher you pressurize the system. I did not have my 38R rebuilt at the time of my engine rebuild 8 months ago, but I don't believe there's a problem with a leak with in the turbo shaft etc , because my gauge will hit 45 psi no problem when I nail the throttle. So as far as my diagnoses goes, it's all pretty tight at this point. Also, at the map line ends I used fuel line with worm clamps to make all nice and tight. I also noticed that air would come out of the Dipstick when I accidentally bumped it. Other than these areas I found no other leaks..Just some info in your search for leaks. I hope this helps you in your search to tighten up your system.

I may need to look in to this. As I mentioned before my turbo hits hard with no apparent issues, but I'm also currently having some issues with smoke and high egts. I suspect it's more due to the fact that my 38R is just not able to keep up. A conversation for another time, but now you got me thinking that I might have to check this one out. Thank you.