So I thought I'd do a boost leak test, as I'm having a low boost issue with my truck. Wanting to keep it simple I took a PVC cap (4") and drilled/tapped it twice for 1/8 npt. Then I threaded in a 0-30 psi gauge, and a Schrader valve. This way I could put it in, and use a tire valve to apply pressure.

Well, I haven't done a ccv mod or anything, and I'd read to make sure it wasn't applying the pressure to the ccv. So I just took off the boots to behind the ccv junction (I'll post some pics to make it more clear in a second).
​​​​​​When I got the tester put in, I put on pressure. I could only reach about 5 psi (and I could hear it just flowing straight out) and as soon I let off, it dissipated. Well, as I was doing this, I was feeling around my tester to make sure I wasn't leaking air there. Then I felt air coming out of the open ccv (which, recall, is not connected currently as I went past it for the boost leak test).


What's up with that? Have I messed something up for it to be coming through the block and out the open ccv? I've read a number of things about the boost leak testing, and haven't run across that problem having happened before.

Thanks guys. I gotta figure this out soon today, because I have to button the truck back up tonight to be able to get to work tomorrow. The truck has been driving fine, just felt underpowered with a trailer on it, and Torque Pro showed really low boost, so I thought I'd start looking into any leaks.

 

The air is coming out following that blue arrow. Thoughts?
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I don't know...my thoughts are that the only way that can happen is if it's blowing by a piston somehow, have you checked your blow by with the oil cap on top of the oil fill tube recently? But you say she runs fine.

 

Yeah... I'm thinking check the blow-by.

 

I haven't personally checked the blow by. Soon after I got this truck, I took it to a diesel shop, and he popped the oil cap off held his hand over and said "blow by ain't too bad"

Although, I took it to the shop, paid them to diagnose my low boost, and they replaced one hose, said it was good, and it didn't change at all on the TorquePro boost gauge... So idk how much to trust them...


But yes, day to day driving, I don't really notice a large lack of power. When I put a loaded two horse trailer behind it, it did seem a little laggard, that's why I'm looking into again now.

 

I'm thinking that if you had some worn or broken piston rings they shouldn't necessarily cause low boost. Can you somehow cap off that CCV and see if it helps any? Or would building pressure in the crank case cause bigger problems?

 

That's part of what I'm here to find out, lol. I'm not sure. I've seen conflicting stuff about whether or not it's bad to do such.

At this point, I think I'm gonna button it all back up for the day, and take a look at the blow by. But if possible I'd still like to make sure I don't have any serious leaks, but I'm worried about building up pressure I'm the crank case. Can I block off the turbo system before it hits the crankcase?

 

When driving the truck what boost level could you reach?

You were logging boost via TorquePro right?

What boost levels were you seeing before they dropped, or have they always been low?

Are your manifolds and up-pipes in good condition?

 

Do you have an EGT gauge? If not be careful, if it's fueling but not getting air it will get hot. You could cap off you CAC return line where it gets to the turbo and check the system to that point. That will leave your spider, plenums (and the engine) out of the mix. However, the boots from the spider to the plenums are a hot spot for leaks. I suppose that you could rig something up onto the spider and check from that point on.

 

If you have a broken piston ring you dam sure are going to have high egts with low boost #'s hopefully not your case.

 

You forgot the duct tape?
When I did this test, I used duct tape to seal that green tube from inside the boot prior to installing the boost test adapter.

 

Alright, after some more working, etc.

I found several leaks, one major one was the red boot, right near the ccv. That was part of the air I was feeling, and thinking that it was coming from the ccv.

So, after fixing several other leaks, I can build up to 20 psi with the boost leak tester, but it bleeds back down fairly quick. There is some air coming from the ccv, if I cover it with my thumb, and let it off, there's a slight puff of air.


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Results of the Blow-By test. Never done one before, but this doesn't look too bad? Especially considering the mileage.

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Blow-by looks good and air does leak through somewhere. I didn't really pay attention as to whether it was the crankcase or out the exhaust.

 

This is a video I got of TorquePro several months ago while running down the road in the truck. At this point I was trying to compare to my dad's truck (I have a video of TP on his too). It's on the longer side, but you can scrub to the end, and see the max psi I hit on the boost. It was something like 12 psi, at approx 3000 rpm.