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Boost Leak, Hissing Sound?
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=90336		 Page 1 of 1
Author:  jagster936 [ Thu Aug 15, 2019 8:39 am ]
Post subject:  Boost Leak, Hissing Sound?
Is it normal for these CRD's to have a hiss upon acceleration? I had a low boost code and cleared it, then I replaced the boost hoses with the fancy silicone ones

I drove it around sounds exactly the same. It did not generate a code at all now. And still makes the same sound. I'm unsure the correlation here.

I also held brake and applied throttle to make boost while sitting still and did not hear any hiss, strange. I did it fairly aggressively but don't wanna stress torque converter too much.

I heard this same hiss from a TDI I have and there was a loose boost hose. Thoughts?
Author:  iakj11 [ Thu Aug 15, 2019 9:21 am ]
Post subject:  Re: Boost Leak, Hissing Sound?
I dont think a hiss is normal. It would be relevant for the people here that can help you to know if the egr system is installed and functional on your jeep.
Also, not entirely sure, but with a stock tune the system may not allow boost with the brake applied...
Author:  jagster936 [ Thu Aug 15, 2019 9:57 am ]
Post subject:  Re: Boost Leak, Hissing Sound?
2005 crd 72k miles. Egr exists but GDE tuned so it’s turned off.

That’s interesting about brake thing never heard of that.

I also did a boost leak test with compressed air and was only able to get about 10psi because wrong size fittings. Anyways there was no noticeable leak or hiss at 10 psi. Since hoses are new they are only thing that would expand and fail. The intercooler is rigid I’d think it would show the leak under any pressure. I didn’t hear any leak!

I do plan to remove egr system at some point and see if it helps. I wouldn’t think you could hear it leaking past egr valve if it was.

The hiss is kind of subtle not super loud. But no codes so far?
Author:  jagster936 [ Thu Aug 15, 2019 9:59 am ]
Post subject:  Re: Boost Leak, Hissing Sound?
On your Jeep is there any noticeable hissing type sound?
Author:  TKB4 [ Thu Aug 15, 2019 10:27 am ]
Post subject:  Re: Boost Leak, Hissing Sound?
The only engine sound I hear with acceleration is a slight turbo whine. The EGR can still leak boost with the electrical turn off with a tune but I don't think it would make much of a hissing sound without a code and doubt it would even with a code.

Since it isn't showing a code now I would take a close look at the turbo to air hose which could suck air in and make a hissing sound and wouldn't hurt to check it anyway. See this topic that covers that hose etc and at end there is a silicone hose available now from Sasquatch. This hose of course does not carry boost pressure.
viewtopic.php?f=5&t=60636
Author:  jagster936 [ Thu Aug 15, 2019 11:30 am ]
Post subject:  Re: Boost Leak, Hissing Sound?
Hmm, as far as I can see it looks pretty good, some seeping and it's pretty nasty would be hard to see much of a tear or hole.

I'm not sure it would hiss like that either, the vacuum isn't very high like -1psi or whatever?
Author:  TKB4 [ Thu Aug 15, 2019 12:29 pm ]
Post subject:  Re: Boost Leak, Hissing Sound?
I don't think its real likely but the vacuum is higher than you would think try undoing the hose from air filter top and put your hand over it. Of course if you do and can feel the vacuum and its doubtful it has a significant leak.

I can't think of too many there sources though . Maybe a leak in vacuum system somewhere and that would likely also affect boost.

Remember a relatively small leak makes more noise than a large leak. Just like barely opening a faucet versus opening it wide open.

Another thought would be an exhaust leak but I would think that would also cause an odor or smoke etc.
Author:  jagster936 [ Thu Aug 15, 2019 12:39 pm ]
Post subject:  Re: Boost Leak, Hissing Sound?
GDE mentioned exhaust leak also. Seems it would make a lot of noise though not just a hiss. Weird

Yea I can try the air box hand thing it should kill the engine if it’s sealed up
Author:  iakj11 [ Thu Aug 15, 2019 1:12 pm ]
Post subject:  Re: Boost Leak, Hissing Sound?
jagster936 wrote:
On your Jeep is there any noticeable hissing type sound?

Same a TKB4, just some turbo whine. Wouldn't describe the sound as a hiss.
It likes to whistle when the throttle comes off....:rockon: :JEEPIN:
Author:  jagster936 [ Thu Aug 15, 2019 2:32 pm ]
Post subject:  Re: Boost Leak, Hissing Sound?
I don’t hear any whistle surprisingly. Maybe the turbo isn’t acting right but it seems to run good with good torque and so far no codes after hose replacement. Old hose for turbo outlet had some suspicious tape on it lol. Who knows.
Author:  TKB4 [ Thu Aug 15, 2019 8:40 pm ]
Post subject:  Re: Boost Leak, Hissing Sound?
other than rechecking boost hose connections especially if you have the two piece intake elbow, short of putting it on a DYNO and listening with load while it is still and you could stand beside it with mechanics stethoscope which isn't safe I don't know anything else to suggest. If it runs good I don't think I would worry about it unless it starts running bad or throws other codes

Make sure and tell us what it was if u find cause.
Author:  jagster936 [ Thu Aug 15, 2019 10:46 pm ]
Post subject:  Re: Boost Leak, Hissing Sound?
It does run good and I think I'm not going to worry about it, lol. It has not thrown a code and drove it around all day. Runs great, AC ice cold, I'm happy.

I think the hissing could have been separate problem from the previous underboost code, now it's gone after replaced boost hoses with the silicone ones.

I will definitely post an update if I find something in the future, thanks!
Author:  mrhemi [ Fri Aug 16, 2019 7:55 am ]
Post subject:  Re: Boost Leak, Hissing Sound?
Maybe a long shot but this did happen to on of my CRD's. I chased a suspected boost leak for a long time. Sounded like a hiss coming from the upper passenger side of the engine. Mine never through a code though, nor displayed performance issues, just the hiss. New hoses, etc. rechecked all connections, pressure checked the inter-cooler all with no success. Very annoying. Then one day got a wiff of burning metal and the hiss was louder. The viscous heater bearing had failed and was dying a slow death for quite awhile making the hissing sound I mistook for an intake leak. The viscous heater had been unplugged for years but the pulley still spins basically as an idler. The whole heater assembly is now bypassed and removed, replaced by my design idler pulley assembly so the same size belt remains.
Author:  WWDiesel [ Fri Aug 16, 2019 12:39 pm ]
Post subject:  Re: Boost Leak, Hissing Sound?
mrhemi wrote:
Maybe a long shot but this did happen to on of my CRD's. I chased a suspected boost leak for a long time. Sounded like a hiss coming from the upper passenger side of the engine. Mine never through a code though, nor displayed performance issues, just the hiss. New hoses, etc. rechecked all connections, pressure checked the inter-cooler all with no success. Very annoying. Then one day got a wiff of burning metal and the hiss was louder. The viscous heater bearing had failed and was dying a slow death for quite awhile making the hissing sound I mistook for an intake leak. The viscous heater had been unplugged for years but the pulley still spins basically as an idler. The whole heater assembly is now bypassed and removed, replaced by my design idler pulley assembly so the same size belt remains.

Got any pictures?
Author:  jagster936 [ Fri Aug 16, 2019 1:20 pm ]
Post subject:  Re: Boost Leak, Hissing Sound?
But mine only hisses upon throttle application mostly above 2k. Not just cruising 2k. Definitely boost related or maybe exhaust. Related to throttle and turbo spool.

I’m unsure how this viscous heater works I did notice a pulley not spinning upper left of engine is that what that was? It works by friction heating? Weird
Author:  mrhemi [ Fri Aug 16, 2019 7:24 pm ]
Post subject:  Re: Boost Leak, Hissing Sound?
jagster936 wrote:
But mine only hisses upon throttle application mostly above 2k. Not just cruising 2k. Definitely boost related or maybe exhaust. Related to throttle and turbo spool.

I’m unsure how this viscous heater works I did notice a pulley not spinning upper left of engine is that what that was? It works by friction heating? Weird

Because its speed varies with engine rpm, it can seem it is throttle related. Not saying that is your issue, especially if yours threw a code, but something to keep in mind.
Author:  mrhemi [ Fri Aug 16, 2019 7:25 pm ]
Post subject:  Re: Boost Leak, Hissing Sound?
WWDiesel wrote:
mrhemi wrote:
Maybe a long shot but this did happen to on of my CRD's. I chased a suspected boost leak for a long time. Sounded like a hiss coming from the upper passenger side of the engine. Mine never through a code though, nor displayed performance issues, just the hiss. New hoses, etc. rechecked all connections, pressure checked the inter-cooler all with no success. Very annoying. Then one day got a wiff of burning metal and the hiss was louder. The viscous heater bearing had failed and was dying a slow death for quite awhile making the hissing sound I mistook for an intake leak. The viscous heater had been unplugged for years but the pulley still spins basically as an idler. The whole heater assembly is now bypassed and removed, replaced by my design idler pulley assembly so the same size belt remains.

Got any pictures?

I do. I will try to get them posted later tonight, with a small write up.
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