Solved: Hard vacuum leak under DECELERATION

[AntleredRuin]

Yeah you raise a good point.

My booster DOES work and no obvious leaks. I just cling to it since it's the only thing I can do without ripping into the intake manifold. Lol
I am missing that bracket that pressed against the check valve. I'm gunna try and scope tht up at the junk yard.

I do have an oil leak I think it's coming from the half Moon on the driver side. But I could never see if anyone had a leak bad enough to have an audible leak coming out of there.

I'm trying to hold off on the valve covers for weeee bit. Starting my timing belt job tomorrow, I got a laundry list of stuff to do. Gunna take me at least a week to get it done.





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Yeah if you have a valve cover gasket leak so bad you can hear vacuum while in the car, and freeway driving no less, then I'd think you'd have bigger problems than that.

That being said, curious as to why replacing the oil fill gasket mostly fixed the noise for a short period of time. I wonder if the valve covers (and maybe the intake manifold) really are that loose, and the pressure you exerted while pressing the new fill gasket on slightly sealed the valve cover down a bit more into the current gasket? Then after a few miles it lifted again?
For shits and giggles, try just getting in there and tightening all valve cover and intake manifold bolts you can find. Be careful, though, the valve covers wings are weak. Those bolts need to be barely more than finger tight.

Have you replaced the PCV?

The intake is a bit of a PITA, but much less work than it seems. Or well, easier than it looks at least. Just a lot of little steps. Just don't break an injector off in it while taking it off. I had to use some super long forceps to get the tip out of the valves. That was a pucker moment :wow:

 

[STI_MECE]

For shiggles, I ordered the valve cover gasket parts lol all parts including half moon plugs 178 from my local dealership. Parts arrive tomorrow.

Took the plenum off in about ten minutes lol started cleaning it up getting grease off .

One interesting note. The runners have pitting?

These valve covers definitely were repaired at some point. I see white sealant and a blue gasket def not OEM.

I think there was a leak on driver side half moon

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[STI_MECE]

Oh and I finally got a garage at my work place apartment [emoji16][emoji3060][emoji3060][emoji3060][emoji3060]

I work alot faster now that I can stop mis mid way into repairs

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[STI_MECE]

So the oil cap gasket was not the issue. Nor is it related to the brake booster. I just put another 5VZ-FE engine in, used OEM brake booster, and a new OEM master cylinder and I still have the noise.

Which tells me it might be coming from the Evap canister or one of the sensors that runs in line with it.

I had a stethoscope and found at idle there is one that makes a ticking noise at idle. It sounds like some type of regulator with a ball inside or or something. It has two hose connections, one from the eval canister at the bottom of it, and the top hose runs along the firewall and into the intake manifold

The fun never ends

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[Dieselchessy]

In all this work have you replaced the fan clutch?
Usually when my Toyota’s have had the odd whistle when letting off the throttle it’s bean the fan clutch.


That intake plenum isn’t pitted, it’s a cast part. They all look like that.

 

[STI_MECE]

In all this work have you replaced the fan clutch?
Usually when my Toyota’s have had the odd whistle when letting off the throttle it’s bean the fan clutch.


That intake plenum isn’t pitted, it’s a cast part. They all look like that.

No I have not. I ended up just buying a new OEM canister. Can you have a bad fan clutch and still have cooling temps within spec?

 

[Dieselchessy]

I don’t know what spec is for temp. My 3rd gens have all run with the temp needle just below level. I’ve replaced a few fan clutches but never due to a temp indication, just cause they made noise or were looser than I liked.

I’m just guessing. Your title says “ vacuum lleak”, but you don’t offer your reasoning for thinking it’s a vacuum leak.

I suspect your real issue is “a whirring or whistle type sound at deceleration”.
That’s a whole lot different than a “vacuum leak”.

 

[Dieselchessy]

Do this; in the am when the engine is cold drive it and listen. Listen for the noise to be more prominent and happen with milder deceleration when cold, and then get less prominent and take harder deceleration to make the sound when warmed up.

If it does that, then replace the fan clutch. And then don’t blame me when it doesn’t work. LOL

I use aftermarket fan clutches. Last time I looked Toyota ones were spendy.

 

[LittleCaesar]

Do you have a scan tool that reads live data? I would be curious to know what the long term fuel trims are when under deceleration.

Possibly the EVAP solenoid. They can get lazy and stick, depending on what type of crude has built up in the tube over time. I know other members have had the canister leak but usually throws the usual lean po171.

The intake manifold is cast like such by the way.

 

[STI_MECE]

Do you have a scan tool that reads live data? I would be curious to know what the long term fuel trims are when under deceleration.

Possibly the EVAP solenoid. They can get lazy and stick, depending on what type of crude has built up in the tube over time. I know other members have had the canister leak but usually throws the usual lean po171.

The intake manifold is cast like such by the way.

I am running -12.5% LTFT cruising at 65 mph. Then WOT it's -15%. Idle it's -2.3%

A while back I remember having a code about a bad evap canister and then it magically disappeared and it never came back.

I'll update if the new canister solves the noise. I think it might be cracked like borderline hair line and it requires a good deal of vacuum to pull through it.

I was gonna go for sensors, but after seeing the price of them and then the price of the canister with sensors I thought what the hell, go full bore. And with my luck if I replaced the sensor, it would have been the canister causing the issue or vice versa.

I'll kill two birds one stone here.

And the fan clutch is working properly.

I titled the as a vacuum leak kind of to provide a description of the noise im hearing.

I'm more impressed with the fact I'm the only one on interwebs with this specific issue....loll something is definitely up.

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[Mackalicious]

I am running -12.5% LTFT cruising at 65 mph. Then WOT it's -15%. Idle it's -2.3%

A while back I remember having a code about a bad evap canister and then it magically disappeared and it never came back.

I'll update if the new canister solves the noise. I think it might be cracked like borderline hair line and it requires a good deal of vacuum to pull through it.

I was gonna go for sensors, but after seeing the price of them and then the price of the canister with sensors I thought what the hell, go full bore. And with my luck if I replaced the sensor, it would have been the canister causing the issue or vice versa.

I'll kill two birds one stone here.

And the fan clutch is working properly.

I titled the as a vacuum leak kind of to provide a description of the noise im hearing.

I'm more impressed with the fact I'm the only one on interwebs with this specific issue....loll something is definitely up.

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How about a video of the noise?

Your fuel trims show you don't have a constant vacuum leak.

Maybe have someone else ride with or drive so you can stick your head out and listen from different seating positions to try to pinpoint the location better. Potentially even remove the hood if need be.

How slow can you get this to happen? I've rode under the hood of a car in a parking lot for a diag before... Just sayin.

 

[STI_MECE]

How about a video of the noise?

How slow can you get this to happen? I've rode under the hood of a car in a parking lot for a diag before... Just sayin.

I tired a video before but the noise is pretty hard to pick up on my phone. It consistently happens above 40 mph. Then it will sometimes happen below 20 mph.

Duhhhhh.....u just reminded me that I was planning on putting the rear on jacks and having someone drive it up to 50 mph. I've been doing other crap for a month and completely forgot about that.


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[Mackalicious]

I tired a video before but the noise is pretty hard to pick up on my phone. It consistently happens above 40 mph. Then it will sometimes happen below 20 mph.

Duhhhhh.....u just reminded me that I was planning on putting the rear on jacks and having someone drive it up to 50 mph. I've been doing other crap for a month and completely forgot about that.


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If you do that. NEVER step in front of the car. be off to the sides at all times. I'm sure you knew, just wanted to remind you. I've watch someones leg get pinned and crushed between a murano and a toolbox.

 

[STI_MECE]

I replaced the EVAP canister with an OEM one the noise is sitll there. :wtf:

It's a challenge now. going to jack it up in the morning and get to 50 mph and find out what it is.

Its a challenge now. I am so stumped lol

I can hear the thottle body plate oopen and close when i give it gas. it just sounds like a subtle woosh. Videos dont help. I tried.

 

[Dieselchessy]

How long is the sound? Is it short or does it continue for 15 seconds or more as RPM's slow down?

Based no your earlier description I'm still thinking it sounds a lot like the issue I had with a fan clutch. It stumped me for quite a while.

What a mystery.

 

[plcfcng]

Could the noise your hearing coming from the heater core? it some times happens when air get in there it sound kind of vaccum but it more of a watery sound.:juggle:

 

[brillo_76]

See if you can pinpoint the exact location of this sound. See if a mechanic stethoscope or a hose like the cold war kid suggests to find that exact location. No reason to be changing things that are good. Once you have the source you can come up with a solution.

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[Dieselchessy]

If his issue is like my fan clutch issue, then it will only do it when driving and only when slowing down. And only for the first 15 to 30 seconds of the slow down. Maybe longer if conditions were just right. I think higher speeds.

I never put the rig on jack stands and ran it, but I spent lots of time with the hood up manipulating the throttle by hand trying to get it to repeat the noise, or make any noise that would hint to the issue.

It seemed like it needed the wind through the radiator, or maybe just momentum, to cause the fan to spin faster than the engine for it to make the noise. Engine faster than the fan or same speed and it wouldn’t make any noise.

But likely I’m just inserting my own experience into this guys situation.

 

[STI_MECE]

Could the noise your hearing coming from the heater core? it some times happens when air get in there it sound kind of vaccum but it more of a watery sound.:juggle:

You know I never thought about that but I don't think it would be the case now. But the watery nosie is the interesting part because it does kind of rumble more than anything but its just the tone of it.

Best description of the noise, go order a sulshi from Sonic and you are almost done with it trying to suck the final bit of slushi out. But replace the liquid sound with air trying to be drawn around something or thru something.

I had a thought that it might be the fact that I have an araid intake tube on....I don't have the OEM intake elbow and I know it has those silencers on it. If I go back to when I remember hearing that noise those two kind of cross paths.

Gunna jack it up tonight and give it ago.

I wish the devil would show its head by pulling the throttle Body back but it's not. It has to be driving at least above 40 mph.



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[plcfcng]

I have a noise coming from my header core I have not taken care of it yet I think the easy way to fix it is get a cooling system pressure tester from orelley auto parts put a slignt pressure on the system then remove a clamp from the heater hose near the control valve then pull the hose part ways off and exhaust the air. It would cost 0 dollars....:zoom: