Mystery hissing sound - 300Tdi - Defender Source
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  #1  
Old September 27th, 2016, 09:44 AM
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Unhappy Mystery hissing sound - 300Tdi

I have been trying to track down a sound with my 300Tdi and am running out of good ideas.

Background: replaced manifold gasket and the sound (or a sound just like it) went away for 2-3 minutes before coming back. I assumed it was a blown manifold gasket. When replacing the gasket again, I saw two of the threads in the head are worn so I had new threads put in by the nearby shop. Starting the engine back up with a new gasket and threads, the hissing sound is still here... or there is a new sound which sounds almost exactly the same.

I am starting to think there were two hissing sounds... one coming from the manifold gasket (which is now fixed) and one from somewhere else. Perhaps the sound of the manifold gasket was loud enough I couldn't hear the other sound.

If I can get videos to upload and process, you can hear the sound is coming from the back of the engine near the bulkhead. A little bit of the head gasket is sticking out in that area, but the engine is completely dry there. There is only a little oil seeping from the side under the air filter and up front under the alternator, but its very minor. The attached photos show the location of the seeping oil as well as the back of the engine where a small part of the head gasket is sticking out (and completely dry there).

I took the 110 to a shop and the mechanic believes it is the head gasket, but I am not getting any other symptoms of that. The engine still pulls very strongly, only a little gray/black exhaust when accelerating a little hard which goes away immediately for clean exhaust, the oil looks clean, and it's not losing/burning any coolant. I'm stumped...
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  #2  
Old September 27th, 2016, 09:55 AM
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If you really think there is an exhaust or head gasket leak, take a squirt bottle with dish soap and water and squirt it on everything (when cold) and you should be able to quickly see if there is an gas escaping from a gasket.
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Old September 27th, 2016, 09:57 AM
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Quote:
Originally Posted by TELOS View Post
I have been trying to track down a sound with my 300Tdi and am running out of good ideas.

Background: replaced manifold gasket and the sound (or a sound just like it) went away for 2-3 minutes before coming back. I assumed it was a blown manifold gasket. When replacing the gasket again, I saw two of the threads in the head are worn so I had new threads put in by the nearby shop. Starting the engine back up with a new gasket and threads, the hissing sound is still here... or there is a new sound which sounds almost exactly the same.

I am starting to think there were two hissing sounds... one coming from the manifold gasket (which is now fixed) and one from somewhere else. Perhaps the sound of the manifold gasket was loud enough I couldn't hear the other sound.

If I can get videos to upload and process, you can hear the sound is coming from the back of the engine near the bulkhead. A little bit of the head gasket is sticking out in that area, but the engine is completely dry there. There is only a little oil seeping from the side under the air filter and up front under the alternator, but its very minor. The attached photos show the location of the seeping oil as well as the back of the engine where a small part of the head gasket is sticking out (and completely dry there).

I took the 110 to a shop and the mechanic believes it is the head gasket, but I am not getting any other symptoms of that. The engine still pulls very strongly, only a little gray/black exhaust when accelerating a little hard which goes away immediately for clean exhaust, the oil looks clean, and it's not losing/burning any coolant. I'm stumped...
Sounds like the head gasket is blown on cyl 4. Blowing out the compression ring on a tdi wouldn't mix oil and water or cause a loss of either.
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  #4  
Old September 27th, 2016, 10:10 AM
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Also , take of the oil cap. If it sounds like exhaust noise in the valve cover, then it is probably the head gasket. They tend to leak into the push rod gallery.
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Old September 27th, 2016, 10:14 AM
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hissing sounds for me have usually been associated with turbo boost leaking. did you lose the bolt in your intake manifold port? on a 300 tdi and 2.8, it's in the back of the manifold.
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Old September 27th, 2016, 10:23 AM
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Check the intake hose; there are a few ports on the rubber intake hose that could be loose or punctured. You can take an air compressor on low psi and push air into it to see if it's just a loose hose
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Old September 27th, 2016, 10:31 AM
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Quote:
Originally Posted by Red90 View Post
Also , take of the oil cap. If it sounds like exhaust noise in the valve cover, then it is probably the head gasket. They tend to leak into the push rod gallery.
I took off the cap, and it didn't really sound that different. I can still hear the hissing sound loudly, but it sounds like it is coming from the back of the engine and not as much from the valve cover.
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Old September 27th, 2016, 10:33 AM
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Quote:
Originally Posted by Overlander View Post
hissing sounds for me have usually been associated with turbo boost leaking. did you lose the bolt in your intake manifold port? on a 300 tdi and 2.8, it's in the back of the manifold.
The bolt is still there and secure. This is what you're referring to, right?
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  #9  
Old September 27th, 2016, 10:34 AM
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Quote:
Originally Posted by NPT90 View Post
Check the intake hose; there are a few ports on the rubber intake hose that could be loose or punctured. You can take an air compressor on low psi and push air into it to see if it's just a loose hose
I don't have an air compressor unfortunately (but here is yet another reason why I need to buy one) but the rubber hoses look okay. I started the engine again and listened for the hissing sound. I think it is coming from lower down than the hoses, if that makes sense.

------ Follow up post added September 27th, 2016 11:36 AM ------

Quote:
Originally Posted by Uncle Douglas View Post
Sounds like the head gasket is blown on cyl 4. Blowing out the compression ring on a tdi wouldn't mix oil and water or cause a loss of either.
This makes a lot of sense and agrees with what the shop suggested might be wrong. I ordered a new bolt set and complete set of gaskets to replace the head gasket which should be arriving tomorrow. I might just have to drop it back off to the shop and have them take it apart to the head and see how it looks. I'm comfortable doing manifold / exhaust removal and refitting, but the head gasket and everything above it involved are getting outside of what I want to tackle in my garage.
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Old September 27th, 2016, 10:50 AM
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Another video

Here's another video. I recorded this one to see two things... 1) how the sound responds to changes in RPMs and 2) to capture what it sounds like when I turn off the engine. If you listen close enough, you can hear air hissing out when I turn off the engine. This happens every time, but seems more pronounced if the engine has been running for a few minutes instead of a shorter period of time. (video may take a few minutes to process)
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  #11  
Old September 27th, 2016, 10:52 AM
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Originally Posted by TELOS View Post
The bolt is still there and secure. This is what you're referring to, right?
No, not the heater hose. Boost pipes are larger in diameter
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Old September 27th, 2016, 11:09 AM
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You either have a single cylinder exhaust leak or a blown head gasket. Boost leaks do not leak on a single cylinder compression stroke as can be heard on your video's. Boost is appx 16 lbs vs diesel compression is appx 380lbs. That sound isn't boost. Stop looking for a boost leak and borrow a compression tester. A compression test will confirm that it is compression leaking, not boost. The way the sound is pronounced as you moved around rear of the engine locates the sound to the back of the head which is where they usually blow.
If you are comfortable doing the manifold gasket thats half the job, you can do this. A tdi head isn't complicated.

FWIW you can often feel the pulsing air escaping if you can get your hand in the right spot, that would save you the effort of a compression test.
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  #13  
Old September 27th, 2016, 11:27 AM
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Quote:
Originally Posted by Uncle Douglas View Post
You either have a single cylinder exhaust leak or a blown head gasket. Boost leaks do not leak on a single cylinder compression stroke as can be heard on your video's. Boost is appx 16 lbs vs diesel compression is appx 380lbs. That sound isn't boost. Stop looking for a boost leak and borrow a compression tester. A compression test will confirm that it is compression leaking, not boost. The way the sound is pronounced as you moved around rear of the engine locates the sound to the back of the head which is where they usually blow.
If you are comfortable doing the manifold gasket thats half the job, you can do this. A tdi head isn't complicated.

FWIW you can often feel the pulsing air escaping if you can get your hand in the right spot, that would save you the effort of a compression test.
Thank you for the advice. I'll see if I can track down a compression test. If I reach my hand towards the rear RH side of the engine, I THINK I can feel air escaping. I also think it smells a little more like diesel exhaust under the hood than normal, but that could just be that I am focusing more on observations.

If it's a head gasket, I have the parts on their way already. If it is a cylinder exhaust leak, what does the repair look like?
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Old September 27th, 2016, 11:40 AM
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Originally Posted by TELOS View Post
If it's a head gasket, I have the parts on their way already. If it is a cylinder exhaust leak, what does the repair look like?
Exhaust leaks @ the engine would be limited to around the gasket you just replaced, a cracked exhaust manifold, or a leak where the two ears of the manifold join the turbo housing.
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Old September 27th, 2016, 11:47 AM
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THANK YOU everyone

First of all, THANK YOU to everyone who shared thoughts on this. I really appreciate it. It can feel like I'm a little bit alone with my head stuck in the engine bay trying to figure out what's going on and all of your fast contributions help tremendously. In the past 9 months I have been working on refurbishing this vehicle, the sense of community on this forum has been an unbelievable asset. Almost every time I had a question, it was already discussed at length and a quick search revealed the solution.

Secondly, I think I found the leak. If I reach my hand straight to the back of the engine where the gasket is sticking out a little (see first batch of photos), I can DEFINITELY feel air puffing past my hand. I held a piece of white paper there to see if I could visually see the leak on the paper, but the air hit my hand right away and I didn't need to wait to see if the paper would discolor. I can definitely feel it with my hand. I think this confirms it is the head gasket blown?

The parts should be arriving tomorrow and I can get started with removing the gasket to see if the head needs to be skimmed. I have driven it for 100-200 miles over the past few months under the impression my only problem was the manifold gasket. As soon as the gasket was properly fixed and I realized it might be the head gasket, I stopped driving the vehicle. I hope I have not done damage.
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Old September 27th, 2016, 11:54 AM
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Cool. You didn't hurt it.
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Old September 28th, 2016, 06:24 AM
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This might be fun to watch while you wait for the parts to land.

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Old September 28th, 2016, 07:03 AM
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This might be fun to watch while you wait for the parts to land.

I actually just watched that video yesterday! I love the Land Rover Toolbox Videos... so thorough and well done.

I'll post some photos of the disassembled head next week when I can take it apart and see what I have to work with. I have never done a job like this before, so I might be back on this thread with some questions if I get stumped. Quick question first... The four big round holes in the engine... I think they're called "cylinders" or something... are those necessary? Or can I just plug those with something and throw away all the extra parts that are stashed inside those holes?

Just kidding... it's going to be just fine.
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Old September 28th, 2016, 07:14 AM
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You might consider having the head cleaned, checked for flatness and the valves done. $250 in parts and labor was well worth the piece of mind.

Also, I made the mistake of trying to go OE metal gasket. Bad Idea. Composite is the way to go.
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Old September 28th, 2016, 07:18 AM
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You might consider having the head cleaned, checked for flatness and the valves done. $250 in parts and labor was well worth the piece of mind.

Also, I made the mistake of trying to go OE metal gasket. Bad Idea. Composite is the way to go.
I thought oe was composite and aftermarket was MLS
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