SOLVED! Ringing whistle? HVAC disruption during servicing? Or?

[Elizabetty]

I don't think this is electrical so I'm starting a new thread. You guys are going to know me well around here LOL I am determined to make this my truck for a lot more miles.

Yesterday I had all fluids checked, general service of oil change, checked transmission fluid, mentioned differential fluid looked good etc and a new fuel filter put in my 2002 trailblazer ls. If I need to be giving more details that matter, it's a 4.2l. 159,000 miles.

Is there anything touched / moved that could affect vacuum? Maybe something is common to be bumped if care isn't taken or maybe something connects to something else I should look at that they may have disrupted? I'm definitely not blaming the shop but since then, I've lost cruise control and while not a common explanation on google, I do see information that HVAC and cruise are somehow related. Additionally, there's a new very very high pitched ringing or whistle over 45 mph. At first I thought it was bearings or ball joints since they mentioned that is service I will need by the next oil change, but it reminds me more of a tiny hole where air is pushing through so hard it makes a sound that would probably be inaudible if I were 80 but still audible if I were a dog. Hope that helps explain what I'm hearing. It is super high-pitched. Almost sounds like someone was running their finger around the rim of a glass of water and making the highest pitch sound a human can create LOL it's not incredibly loud. I had to really focus to hear it. In fact if the window is down a little too far, road noise will overpower it. I don't hear it from the cabin at all with the window up all the way.

Thanks in advance.

 

[TJBaker57]

checked transmission fluid, mentioned differential fluid looked good etc

Hopefully checked not only the rear but also the front differential. That gets overlooked all too often.

I do see information that HVAC and cruise are somehow related

In very old vehicles I could see this. Back in the day when the HVAC and cruise systems used engine vacuum to operate air duct doors and such. Your HVAC system has absolutely NO physical connections to any vacuum system, engine or otherwise. It is entirely operated by electronic devices.

Off hand I can think of only two connections to engine vacuum. One is the power brake booster and the other is the PCV system.

edit: Ooops! I meant EVAP not PCV, though there is a PCV connection as well but it is buried where it is hard to see let alone disturb.

 

[TJBaker57]

 

[Mooseman]

Also check the plug at the front of your intake manifold as per this pic:

It can go missing or get damaged with age and leak.

Does the noise change with engine speed or vehicle speed? If you can do this safely, when it starts to make the noise, throw it into neutral and let the engine drop to idle. If it still whistles, it's not the engine.

If it is the engine, another place to look for a vacuum leak is on the intake manifold as the bolts can sometimes become loose. If you want to check for vacuum leaks, you can use brake cleaner to find them as per this video:

 

[TequilaWarrior]

There's one more vacuum port... sort of. It goes from the bottom of the intake plenum on the right to a connection between the intake runners below it. It's like a hose from the intake to the intake (if that makes sense). This hose can dry out and crack but most people never even touch this hose. It's a major PITA to get to, too. I believe it provides vacuum to the crank case as part of the sudo-PCV system in these engines. It also has a tendency to gum up with blow-by oil. This is not likely the source of your noise.

 

[TJBaker57]

There's one more vacuum port... sort of. It goes from the bottom of the intake plenum on the right to a connection between the intake runners below it. It's like a hose from the intake to the intake (if that makes sense). This hose can dry out and crack but most people never even touch this hose. It's a major PITA to get to, too. I believe it provides vacuum to the crank case as part of the sudo-PCV system in these engines. It also has a tendency to gum up with blow-by oil. This is not likely the source of your noise.

That's the one I mentioned as being "hard to see let alone disturb".

 

[Elizabetty]

View attachment 105981

Oh this is awesome! Thank you so much!

 

[Elizabetty]

Also check the plug at the front of your intake manifold as per this pic:

It can go missing or get damaged with age and leak.

Does the noise change with engine speed or vehicle speed? If you can do this safely, when it starts to make the noise, throw it into neutral and let the engine drop to idle. If it still whistles, it's not the engine.

If it is the engine, another place to look for a vacuum leak is on the intake manifold as the bolts can sometimes become loose. If you want to check for vacuum leaks, you can use brake cleaner to find them as per this video:

Thank you. I put this on my list to return to!

 

[Elizabetty]

Hello again. Still working on vacuum issue. Question is about short hose in center of air intake manifold. There's a split in the rubber where it slides onto the manifold but it goes on far enough the opening on the plastic nipple is past the split. Can this be part of a HVAC symptom or is this hose something that doesn't deal with pressure; meaning as long as it's on past the split it's ok?

 

[TequilaWarrior]

Cracked/Split hoses should be replaced. Hoses are generally inexpensive (with some exceptions). It's not clear to me which hose you're referring to, but none of these should be expensive to replace.

 

[Elizabetty]

Cracked/Split hoses should be replaced. Hoses are generally inexpensive (with some exceptions). It's not clear to me which hose you're referring to, but none of these should be expensive to replace.

Funny because I'm not clear on what hose it is either. When I look at pictures of what I believe is the manifold for this trailblazer, I see pictures without the hose on the nipple so I'm struggling to figure out what it's called.

 

[Mooseman]

Can you take a pic of it and point it out? Is it the one in the pic I posted above?

 

[Mathoran]

Probably this

 

[TJBaker57]

Probably this

View attachment 106020

That hose does not connect to any manifold. That part looks like the hose that connects th intake resonator to the engine valve cover as part of the PCV system.

 

[Elizabetty]

Hey guys. It's a crankcase breather hose from what I found. I have a picture of what mine looks like from ebay. I have no clamp and where the clamp would go, I have a split from the top where it would butt uptight on the nipple and it's about an inch long down the hose. There is a second split from the top also about an inch long. If the hose were not on, I would basically have about a half inch wide piece of rubber between the two splits that can flex back and forth. When it is on the nipple, that half inch piece of rubber doesn't appear to be lifted off or pulled back but of course there are two inch long seams of splits which doesn't allow it to be a solid hose piece. The nipple is longer than the split so the opening is down into the hose further past it. I don't feel or hear any air around it but I would assume that could be a problem and obviously I can't put my fingers around it or my ear to it when I'm driving. I can only test while idling. I have posted a link from a guy on YouTube explaining how the system works and he points to it and talks about it again with a clamp that I don't have. Between the fact it should be clamped and it shouldn't be split, I would assume there's some compromised integrity of a seal there.

 

[Elizabetty]

Hey everyone. I'm applying everything I've learned between this thread and others and I'm making definite progress on my vehicle. In addition to what I've listed here about a cracked hose I need to handle, I'm branching off just a bit into another potential vacuum problem I am finding. I remember from a comment about my cruise control that the brake booster would be a starting point. Knowing I could potentially have a vacuum issue there, even though cruise has been working since the day it didn't work, I'd like to make sure what I'm finding with this hose is correct. The brake booster hose is very soft. I can easily pinch it with my finger and thumb. There's also a little bit of play where it attaches to the brake booster. The actual clamped area of the hose on it is tight but there is some swivel behind that on the brake booster. I may have to take a video to show you what I mean. Should this hose be as soft as it is? All other hoses seem to be really firm so it's surprised me to have this one be as pliable as it is. This definitely looks like a hose replacement I can handle if a soft hose is a potential problem. I understand cracks and holes are obviously the worst problem but perhaps pressure in that hose can be compromised if it is too soft? This is definitely an easier cheaper solution then jumping right to the assumption the brake booster itself is a problem.

 

[Mooseman]

The eBay hose you posted looks like the one that goes between the two parts on the intake manifold on the other side, like the one with the X in this pic:

The one the video pointed to is the one that @Mathoran posted above with two bends.

More Information for DORMAN 46062

It could cause a whistle if it's under pressure or vacuum, both of which are possible.

 

[Elizabetty]

The eBay hose you posted looks like the one that goes between the two parts on the intake manifold on the other side, like the one with the X in this pic:

The one the video pointed to is the one that @Mathoran posted above with two bends.

More Information for DORMAN 46062

It could cause a whistle if it's under pressure or vacuum, both of which are possible.

Yes. I've been able to locate it, feel the splits, and have confirmed it needs to be replaced. However, I have not been able to find any way of doing this without removing the entire manifold. I'll keep digging but if that's the case, that sucks because apparently it's many hours of labor to get this thing off and that is something I would have to pay for. I was hoping it was something I could get my hands under at the bottom to take off after removing the top where it connects even if I had to move some things around and unplug some things etc, but it doesn't sound like I'll be that lucky.

 

[Mooseman]

What are you calling a manifold? The one you see in my picture is the intake manifold where that one bend hose goes. It does NOT have to be removed to replace that hose.

The thing on top of the engine that says "Vortec 4200" is resonator or plenum. The hose with the two bends on that one also does NOT need to be removed to replace however may need to be lifted up to allow enough space to remove the hose. There are two bolts that holds the resonator down.

 

[Elizabetty]

What are you calling a manifold? The one you see in my picture is the intake manifold where that one bend hose goes. It does NOT have to be removed to replace that hose.

The thing on top of the engine that says "Vortec 4200" is resonator or plenum. The hose with the two bends on that one also does NOT need to be removed to replace however may need to be lifted up to allow enough space to remove the hose. There are two bolts that holds the resonator down.

Apologies. I guess I call it the manifold because in this picture, and when I watch videos, everybody calls this big giant thing with 10 bolts a manifold. When looking through GM manual, included in pic attachment, they also discuss it as a manifold that this hose attaches to. I guess I don't know what I'm not explaining well or what I'm stating incorrectly because I understand what the hose is, I understand the crankcase ventilation it contributes to and everything I see and read says it's a crankcase breather hose and on other sites with the same exact shaped piece it's referred to as PCV valve hose that attaches to nipple on this manifold in images. In the attached photo, where it's disconnected at the top is where I have splits in my hose. I don't know another way to state it correctly so please point me in the appropriate direction. In the screenshots, the hose is seen and the nipple on the back of the "manifold" is where I have the hose split. To refer back to my question, I was stating that replacement of this breather hose is noted to be a pain if I find any information at all as far as videos or walkthroughs. When I do find something, people are removing the manifold, taking off the hose, cleaning out the nipple it attaches to, and then putting things back together. I was hoping I could simply remove and replace the hose. I'm not meaning to be frustrating or irritating but I'm literally teaching myself how this engine works so I am going to use incorrect terminology but I don't know where I'm off track with this one. *Confused*

 

[TequilaWarrior]

Yes. I've been able to locate it, feel the splits, and have confirmed it needs to be replaced. However, I have not been able to find any way of doing this without removing the entire manifold. I'll keep digging but if that's the case, that sucks because apparently it's many hours of labor to get this thing off and that is something I would have to pay for. I was hoping it was something I could get my hands under at the bottom to take off after removing the top where it connects even if I had to move some things around and unplug some things etc, but it doesn't sound like I'll be that lucky.

If you're referring to the hose on the right side of the engine with a single bend and a single clamp, it's a major PITA to get to. BUT, @Mooseman is right. You don't NEED to remove the manifold to replace the hose. IT HELPS, but it's not necessary. You will need to remove the PCM, however. It may even help to visualize the hose through the driver's wheel well. This hose will be under almost constant vacuum as it is between the throttle body and the cylinder head - a zone of almost constant vacuum. The hose from the resonator to the valve cover (two bends, no clamp) is under virtually no vacuum. It routes "fresh" air to the engine. Anything from the throttle body to the filter experiences little to no vacuum but has been filtered... hence the positioning.

If you like longwinded posts and rambling threads, check out this one.
It details my (mis)adventures replacing the gaskets on my valve cover, intake manifold, exhaust manifold, VVT solenoid and cam position sensor. ~might~ be worth a read. As an extra bonus, there's pictures of my kid getting stitches....

https://gmtnation.com/forums/threads/exhaust-manifold-replacment-input-requested.21156/

 

[TequilaWarrior]

Apologies. I guess I call it the manifold because in this picture, and when I watch videos, everybody calls this big giant thing with 10 bolts a manifold. When looking through GM manual, included in pic attachment, they also discuss it as a manifold that this hose attaches to. I guess I don't know what I'm not explaining well or what I'm stating incorrectly because I understand what the hose is, I understand the crankcase ventilation it contributes to and everything I see and read says it's a crankcase breather hose and on other sites with the same exact shaped piece it's referred to as PCV valve hose that attaches to nipple on this manifold in images. In the attached photo, where it's disconnected at the top is where I have splits in my hose. I don't know another way to state it correctly so please point me in the appropriate direction. In the screenshots, the hose is seen and the nipple on the back of the "manifold" is where I have the hose split. To refer back to my question, I was stating that replacement of this breather hose is noted to be a pain if I find any information at all as far as videos or walkthroughs. When I do find something, people are removing the manifold, taking off the hose, cleaning out the nipple it attaches to, and then putting things back together. I was hoping I could simply remove and replace the hose. I'm not meaning to be frustrating or irritating but I'm literally teaching myself how this engine works so I am going to use incorrect terminology but I don't know where I'm off track with this one. *Confused*

Your terminology is fine. Our understanding is sometimes... lacking. While these "boards" make a great platform for the exchange of information and ideas, sometimes the simplest things are the hardest to communicate. REPLACE that hose. Whether it's the source of your noise, it needs replaced.

 

[Mooseman]

Yep, you had it right, it is the intake manifold. And you don't need to remove it for that hose. Follow @TequilaWarrior 's advice for replacing it but yes, it should be replaced as a leak there can cause major headaches, lean codes, poor running, bad MPG and possibly that whistling noise.

 

[Reprise]

I'll jump in to add... your truck is about the mileage (and definitely the age) where the int. manifold gasket can deteriorate and require replacement (the seal fails, and lets extra air in -- remember what was mentioned about vacuum in this area.) When that happens, the air-fuel ratio gets out of skew, and the PCM increases fuel to compensate.

Don't worry about this yet, though, as I don't want you to suddenly make plans to replace the manifold gasket. If you get your hose replaced, and notice you still have a whistling sound in that area, we can come back to this as far as how / what to check. You'll get a chance to use your scanning tool again, as well.

With regard to the hose -- since it carries vacuum, you don't necessarily need to get the molded GM replacement. You can get a suitable replacement at a nearby hardware store, along with a couple of worm gear clamps, if needed. Just measure the inside diameter of the old one, for comparison. If you go this route, a little extra length on the new hose is just fine.

If you don't have vacuum hose about, but do have some fluid-rated hose of the proper diameter, it's OK to use that, in a pinch. Overkill, yes -- but if you want to avoid yet another run to the parts store...
I'm using a section of that right now in my own pickup's PCV system, as it turns out. Beat the hell out of paying $60 for the GM replacement, too.

(just don't ever use vac. hose in place of fluid / pressure-rated hose -- that never ends well)

 

[Elizabetty]

I replaced the PCV valve hose which is the l-shaped short one that was split. I have the slightest whistle in front of the driver's side firewall area when I lean my head in so I thought it was the brake booster but after further investigation, when I push slightly on the manifold, the whistle-tone changes so I'm pretty sure that needs to be torqued correctly. Once that is done, I'm hoping that is the rest of my vacuum issue. Yay team!

 

[Mooseman]

It's a common occurrence for the intake bolts to loosen. Fair warning, it's a b!tch of a job to get to all of them. It may be easier by removing the PCM bracket. If I can do it with my giant hoofs, you should be fine.

Don't overdo it when torquing these down. Manual calls for only 89 INCH pounds.

 

[TequilaWarrior]

SWIVELS... and... believe it or not... 1/4inch drive ratchet/sockets will be your friend in this....

It sucks a little... but it's not terrible. Definitely remove the PCM... and take your time.

Like @Mooseman said, don't "ape" these bolts down....

Depending on your proclivity for torture, consider removing the intake and replacing all the gaskets....
It's a bit of a timesink though.

 

[Elizabetty]

SWIVELS... and... believe it or not... 1/4inch drive ratchet/sockets will be your friend in this....

It sucks a little... but it's not terrible. Definitely remove the PCM... and take your time.

Like @Mooseman said, don't "ape" these bolts down....

Depending on your proclivity for torture, consider removing the intake and replacing all the gaskets....
It's a bit of a timesink though.

So the intake was removed to be cleaned with gaskets replaced, throttle body removed and cleaned with gasket replaced and that's when the cracked hose was found which has now been replaced. It was hand tightened and not ape tightened LOL which is a fabulous way to explain that

I'm basically addressing the bolts being at a correct torque spec just to be sure all my ducks are in a row as each piece under the hood is out and back in.

If the whistle is not from the bolts loosening after a bad hand tight, what ways do you guys look for vacuum leaks aside from spraying and listening for the engine sounds to change? I'm fairly certain it's not a break booster hose or the brake booster valve or anything in that area but I will be double checking that hose situation. Do any of you use the smoke test? Is this as reliable as spraying around under the hood to listen for those changes in the engine?

 

[Mooseman]

The smoke test is the preferred method but it does require the machine to produce the smoke, which most of us don't have so we use other methods like spraying carb or brake cleaner.

 

[TequilaWarrior]

The smoke test is the preferred method but it does require the machine to produce the smoke, which most of us don't have so we use other methods like spraying carb or brake cleaner.

Cheaper, faster, and works. Virtually no set up. Virtually no downtime.
Can use WD40 if you don't mind an oily residue.
I stay away from using brake cleaner, though.... it's not the greatest thing to run through the engine.
BUT, carb/choke cleaner, MAF cleaner, WD40, SeaFoam are all fine. Some people will even use starting fluid... I wouldn't recommend that, however. It likes to go "boom". Heck, I knew an old-timer that used water in a spray-bottle.
You're looking for a "change" in idle... the whistle may briefly stop as well.

 

[Elizabetty]

The smoke test is the preferred method but it does require the machine to produce the smoke, which most of us don't have so we use other methods like spraying carb or brake cleaner.

ok so hang tight with me here, BUT what about he guys that take a hose off and blow the ol' cigar in? lol half kidding half serious......

 

[Reprise]

Cigars work. But you must use a Cuban cigar. ::j/k::
(If you saw Scotty Kilmer doing this... be forewarned--we don't especially hold him in high regard here.)

But, yeah--the important thing is to introduce something (fairly non-flammable) into the tract / airflow areas that will visibly or audibly be noticed. Cigar smoke works, if you fancy a stogie! 🔥

 

[Elizabetty]

Cigars work. But you must use a Cuban cigar. ::j/k::
(If you saw Scotty Kilmer doing this... be forewarned--we don't especially hold him in high regard here.)

But, yeah--the important thing is to introduce something (fairly non-flammable) into the tract / airflow areas that will visibly or audibly be noticed. Cigar smoke works, if you fancy a stogie! 🔥

I have seen Scotty Kilmer do it but he's a lot more entertainment factor to me than he is a go-to. However, there are times that I do take what he says and run it through additional filters of YouTube Google Reddit etc in case any of them hold value/truth when they feel doable for me.

 

[Mooseman]

That guy has a big X with me. He doesn't use jackstands, just a jack while under a car and lets brake calipers hang from their hoses, as well as other malpractices. If he ever shows up here, I will personally ban him. Take his advice with a grain of salt, more like a block.

 

[TequilaWarrior]

That guy has a big X with me. He doesn't use jackstands, just a jack while under a car and lets brake calipers hang from their hoses, as well as other malpractices. If he ever shows up here, I will personally ban him. Take his advice with a grain of salt, more like a block.

Ah.... a future Darwin award winner...

 

[Elizabetty]

This can be closed out. No further vacuum leak found. Ringing/whistle will be attributed to something else down the road but at this point I doubt I am keeping the vehicle. Appreciate the help. At least it led me to getting that PCV hose handled.

 

[Mooseman]

Sorry to hear that you won't be keeping it after all the work you put into it. In all fairness, this one looks and sounds like it was previously touched by someone who either didn't care or had very poor skills.