Whistling right above engine.

[sly]

How would you check around the tree? Just do the propane test??? I tried doing that, idle didn't surge..

Maybe I didn't hold it close enough to the tree (the propane nozzle)

I would just grab hoses and see if they move easy or actually grab. Any that slide around get replaced. Since it's such a small leak, the propane test probably won't work.

[BigMerc96]

What year is the car in question? I just skimmed thru this thread again and didn't see it mentioned.

There are a lot of things that can cause it, but without the model year it makes it hard to say what should or shouldn't be looked at.

[porschpow]

It's a 1997 Lincoln Town Car Executive

[BigMerc96]

It wouldn't happen to have a Dorman intake manifold on it, would it? Like, one installed since mid-2013. Dorman changed their intake design around june '13. The newer design is defective and causes a vacuum leak on cylinder 4. It is a whistle while running, seems like its coming from the back of the engine. I installed one of these in 2014 on my '97, ended up taking it on and off 3 times before I figure out WTF is going on with it. Its a design flaw that will likely effect each car slightly differently since Dorman can't align a manifold flange to save their own ass. Like you, the normal methods of diagnosing a vacuum leak found nothing, likely because the leak is under the intake and only effects that one cylinder. Simple fix, but it means pulling the intake back off the car.

[porschpow]

Yes, I have one of those Dorman intakes. Cheese I hope it's not that!

What would be the simple fix if it's not aligned on cylinder 4? The shear idea of having to take off the intake again pisses me off, but it is what it is

[BigMerc96]

Yeah. They redesigned the shape of their "gasket" around all of the intake ports, which is fine, except on #4. In 4.6 heads there are 4 little divots on the intake flange surface. On a stock style intake, these were used to align the stock gaskets which have tabs that slot into those divots. They are there by cylinders 1, 4, 5, and 8. The reshaped gasket on cylinder 4 runs directly over top of one of these, which if the hole falls to the inside of the gasket its fine. However, no 2 Dorman intake are aligned the same and on mine and a few others that I'm aware of, it causes a vacuum leak that has a distinct whistle to it as air flows thru the alignment divot an right under the Dorman intake gasket. The solution is to simply fill the hole with RTV, which seals it up just fine, but this is something you need to know before installing the intake and Dorman failed to include that bit of instruction on their install sheet.

I was thoroughly PISSED when I saw what was causing my vacuum leak. The car ran okay, but gas mileage was noticeably down and I could hear that whistling. I had my intake on and off 3 or 4 times in a week, of course it was a week where I was commuting 60+ miles working at a different location so I probably put 800 miles on it that week. Anyway, I called Dorman tech/customer support about it. Their response was to say they were aware of the problem, and then blamed Ford saying it was a difference in cylinder heads. Which, of course is complete bullshit since every single NPI 4.6l manufactured between 1996 and 2000 has the exact same head casting, and that is every single engine that the Dorman 615-178 intake manifold is supposed to fit. Its not Ford's casting that is the issue, its Dorman's reshaping of that gasket combined with their total inability to properly align an intake flange with the rest of the manifold. I would have less of an issue with it if they had simply added that bit of direction to their install "instructions" sheet, but it said nothing about it. I've since installed 2 more of these intakes (even though they are garbage, they do function fine and are usually the cheapest option) and with some RTV in that alignment divot, they are just fine.

[porschpow]

So, on the heads by the cylinder four area there is a divot (put there for intake/and gasket) alignment) that the new gaskets go over. Gotcha, I was afraid of this, DANG IT!

Oh well.

Thanks so much for the help. BTW, did Dorman offer any reimbursement or anything at all because of this foul up?

When I take off the intake, will the "gaskets" be ok to reinstall them? Or will they be too crushed to do anything with them.

[86VickyLX]

Leave it with me, I'll find and fix it.

[porschpow]

It wouldn't happen to have a Dorman intake manifold on it, would it? Like, one installed since mid-2013. Dorman changed their intake design around june '13. The newer design is defective and causes a vacuum leak on cylinder 4. It is a whistle while running, seems like its coming from the back of the engine. I installed one of these in 2014 on my '97, ended up taking it on and off 3 times before I figure out WTF is going on with it. Its a design flaw that will likely effect each car slightly differently since Dorman can't align a manifold flange to save their own ass. Like you, the normal methods of diagnosing a vacuum leak found nothing, likely because the leak is under the intake and only effects that one cylinder. Simple fix, but it means pulling the intake back off the car.

Does the whistling go away when you get off the gas?

Also, does it get progressively worse as the car warms up?

Let me guess, cylinder 4 is on the passenger side right?

[sly]

yup. 1-2-3-4 front to firewall passenger side... 5-6-7-8 driver side.

[porschpow]

Dang, I am beginning to hate that #4 cylinder with a passion!

[porschpow]

Yeah. They redesigned the shape of their "gasket" around all of the intake ports, which is fine, except on #4. In 4.6 heads there are 4 little divots on the intake flange surface. On a stock style intake, these were used to align the stock gaskets which have tabs that slot into those divots. They are there by cylinders 1, 4, 5, and 8. The reshaped gasket on cylinder 4 runs directly over top of one of these, which if the hole falls to the inside of the gasket its fine. However, no 2 Dorman intake are aligned the same and on mine and a few others that I'm aware of, it causes a vacuum leak that has a distinct whistle to it as air flows thru the alignment divot an right under the Dorman intake gasket. The solution is to simply fill the hole with RTV, which seals it up just fine, but this is something you need to know before installing the intake and Dorman failed to include that bit of instruction on their install sheet.

I was thoroughly PISSED when I saw what was causing my vacuum leak. The car ran okay, but gas mileage was noticeably down and I could hear that whistling. I had my intake on and off 3 or 4 times in a week, of course it was a week where I was commuting 60+ miles working at a different location so I probably put 800 miles on it that week. Anyway, I called Dorman tech/customer support about it. Their response was to say they were aware of the problem, and then blamed Ford saying it was a difference in cylinder heads. Which, of course is complete bullshit since every single NPI 4.6l manufactured between 1996 and 2000 has the exact same head casting, and that is every single engine that the Dorman 615-178 intake manifold is supposed to fit. Its not Ford's casting that is the issue, its Dorman's reshaping of that gasket combined with their total inability to properly align an intake flange with the rest of the manifold. I would have less of an issue with it if they had simply added that bit of direction to their install "instructions" sheet, but it said nothing about it. I've since installed 2 more of these intakes (even though they are garbage, they do function fine and are usually the cheapest option) and with some RTV in that alignment divot, they are just fine.

With your situation, did the whistling occur when the car is at operating temperature? Like it doesn't do it when it is a cold start?

[porschpow]

Is it possible to reuse the gaskets that are built into the dorman intake once you take it off to fix the hole (plug with RTV)

[sly]

They're supposed to be. I generally think that if no RTV was used yet, it should be reusable up to about 3 years before it starts to get too stiff.

[porschpow]

Ok cool, cause I am guessing if you would have to replace it, you would have to rip out the gaskets out of the intake and buy the gaskets separately