Boost leak at downpipe question
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Boost leak at downpipe question
So I noticed I've been having a boost leak for a while and decided to replace my up-pipes with some Dorman bellowed up-pipes whenever I swapped in a new 38R turbo. Afterward, I still had the damn leak and I can't seem to fix it. I pressurized the system using an air compressor and found a leak coming from the downpipe. I also think there may be one coming from the up-pipes but it is hard to tell. Also, there is no leak at the connection between the header and the up-pipes nor on the intake/intercooler side.
So my question is, would a leak at the downpipe cause boost pressure loss? It doesn't make a whole lot of sense considering it is downstream of the turbo, but I don't know enough to tell. Also is it possible that there is a leak coming from the headers? Lastly, what would be the best way to get both the up-pipe and downpipe to seal? Becuase I think I can get one to seal but not the other.
Thanks for any advice
So my question is, would a leak at the downpipe cause boost pressure loss? It doesn't make a whole lot of sense considering it is downstream of the turbo, but I don't know enough to tell. Also is it possible that there is a leak coming from the headers? Lastly, what would be the best way to get both the up-pipe and downpipe to seal? Becuase I think I can get one to seal but not the other.
Thanks for any advice
Fleet Mechanic
Joined: Aug 2006
Posts: 1,465
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From: Jacksonville, FL
A boost leak would not show on the downpipe, once the exhaust gasses hit the down pipe they have finished doing their job. On the up pipes, it's not a boost leak per se, more a lack of pressure in the exhaust stream to turn the turbo efficiently.
If you think you have no exhaust leaks then it is time to move into the charged air portion of your system. Boots are a common leak point, if they are original it would probably be prudent to change them out. Riff Raff has an excellent set for sale, along with new hose clamps from there and the plenum inserts. Another potential point of leakage is the intake plenums themselves. The sealant used can deteriorate over time and cause leaking.
You should not be getting any leaking whatsoever from the exhaust if you are externally pressurizing your intake system, they are two completely different parts of the same puzzle. How exactly are you testing for boost leaks?
If you think you have no exhaust leaks then it is time to move into the charged air portion of your system. Boots are a common leak point, if they are original it would probably be prudent to change them out. Riff Raff has an excellent set for sale, along with new hose clamps from there and the plenum inserts. Another potential point of leakage is the intake plenums themselves. The sealant used can deteriorate over time and cause leaking.
You should not be getting any leaking whatsoever from the exhaust if you are externally pressurizing your intake system, they are two completely different parts of the same puzzle. How exactly are you testing for boost leaks?
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I've already replaced the boots with some different ones, they're pretty good but are not RiffRaff boots, I'm forgetting the name right now.
The way I pressurized the system was by removing the intake filter (afe stage 2) and then hooked up an air compressor to where the filter was using a piece of PVC cap, a quick hose connector and some gorilla tape to hold it all on. I did the same for the this for the exhuast side but instead I hooked it to the exhaust pipe. This seemed to hold the air pretty well. I then sprayed some green clean on the band clamps and boots. It started bubbling up at the downpipe but I couldn't tell if it was at the up-pipe to turbo band clamp. I didn't see any leaks at the boots.
The way I pressurized the system was by removing the intake filter (afe stage 2) and then hooked up an air compressor to where the filter was using a piece of PVC cap, a quick hose connector and some gorilla tape to hold it all on. I did the same for the this for the exhuast side but instead I hooked it to the exhaust pipe. This seemed to hold the air pretty well. I then sprayed some green clean on the band clamps and boots. It started bubbling up at the downpipe but I couldn't tell if it was at the up-pipe to turbo band clamp. I didn't see any leaks at the boots.
Fleet Mechanic
Joined: Aug 2006
Posts: 1,465
Likes: 17
From: Jacksonville, FL
If you are trying to pressurize the system before the CCV then you are just blowing air into the crankcase. This is the little tube that goes into the intake before the turbo.
Your best bet is to search the forum for pressure testing, there is a simple diy tool that can be made with a PVC cap an air fitting and a pressure gauge.
Your best bet is to search the forum for pressure testing, there is a simple diy tool that can be made with a PVC cap an air fitting and a pressure gauge.
Hotshot
Joined: Mar 2014
Posts: 10,750
Likes: 1,065
From: Douglassville, PA
. ^^^ Rikster beat me to it.When you perform that boost leak test you need to eliminate the crancase vent (CCV) from the equation and affix your adapter to the turbo inlet tube, not just at the filter tube.
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