Possible exhaust manifold issue?

[oibaf]

Hey folks,

Bertie Bongo has developed a new noise as of tonight. Best way to describe it is that it sounds like a rush if air under acceleration. The sound is only there under acceleration, it disappears the moment my foot comes off the accelerator or if you're going quite slowly.

I suspected a turbo pipe was loose but from searches here it seems like it might be an exhaust manifold stud after snapping. I think I heard a "ding" sound, followed by the "air rushing" sound so I wonder did I actually hear the bolt snap.

Question - is it safe enough to drive without immediate repair? We had been planning on doing a weekend away this weekend, covering maybe 200 miles, at most. Do we need to cancel it?

[oibaf]

Update:

Went out with the tools and removed the manifold/turbo heat shield and took a look at the manifold studs. They're all present and correct so I don't think it's the exhaust manifold.

I had a quick look under the driver's seat, I'm not sure why I did, but was glad I did because the air intake pipe going from the air filter to the turbo had split. I taped it up as a temporary measure and hoped that was the cause of the wind/air rushing sound (even though it seems to be coming from the front left of the van so wrong side for this particular issue).

Took it out for a quick spin and, under load, the same wind/air rushing noise occurs. No loss of power or anything, no black or white smoke, everything else seems perfectly fine. My mechanic couldn't do the aircon belt last week when doing my timing belt so we removed the belt and tensioner - that's hardly anything to do with this? It ran fine for 100 miles before this noise thing.

Struggling to think of what it might be...

[TravellingEnt]

You don't have your window open do you? If it's that I wish my Bongo went fast enough to make a rushing noise!

Hopefully now someone with genuine mechanical knowledge will help you......

[oibaf]

You don't have your window open do you? If it's that I wish my Bongo went fast enough to make a rushing noise!

Hopefully now someone with genuine mechanical knowledge will help you......

Believe me, when I heard it, I actually went between checking the windows were up and the radio was off!

Took it for a spin into town earlier on, about a 30 mile round trip. Apart from the air-rushing/hiss sound, it didn't lack any power or have any other symptoms of something wrong. Nothing leaking underneath, nothing amiss when I lifted the seats either.

A good description of the sound is that it's like the sound made when you have the fan on full blast in the cabin of your car. It's that kinda sound. It kicks in at 1800rpm (ish) under load, and continues to build until you let off the accelerator. It correlates with the revs basically.

[phil 1]

Check the big rubber pipe that connects to the front of the inlet manifold.
The pipe needs to be removed for access when removing the cam cover.
It is quite easy to do forget to refit the pipe on reassembly

[oibaf]

I'll go and check that at lunchtime, thanks Phil. I didn't notice anything amiss yesterday when I had a look but then I wasn't looking for this one thing either...

[oibaf]

I took a look after work and all of the pipes and hoses I can see,including to the intercooler,look fine.

However, the green and white one way valve (vacuum valve?) which connects to the EGR equipment was broken. I'd missed it the first time around because it looked fine but when I touched it it just fell apart. Quite possibly repaired with glue before.

I wonder would that be the cause of the noise? I'll be getting a new one way valve (think I saw a video which said a window washer one way valve would work) tomorrow and fitting it.

[haydn callow]

Worth checking the manifold bolts again, particularly No 1 stud at the front, it’s not unknown for them to snap but stay rusted in the manifold so it’s still looks o.k. Also look for black sooty streaks.

[oibaf]

Worth checking the manifold bolts again, particularly No 1 stud at the front, it’s not unknown for them to snap but stay rusted in the manifold so it’s still looks o.k. Also look for black sooty streaks.

Another update:

I sprayed some soapy water on each exhaust port coming from the engine and it looks like the exhaust pipe coming from cylinder one isn't sealing 100% because the soapy water showed bubbles, much like a puncture in a tyre. I took a good look at the studs and they seemed fine though. After removing the manifold cover, I gave them a good tug (oh errr etc etc) with the spanner and they seemed OK.

Despite the studs being OK it seems the manifold, or at least the gasket, must be the source of the air-rushing/hissing noise.

So now I've to decide on what to do about a manifold...given the studs seems alright how the heck is the manifold blowing?!

[haydn callow]

Remove it, skim it, replace with new gasket

[oibaf]

Remove it, skim it, replace with new gasket

Yep, sounds like the best way to do it. I can't do it all myself so will be ringing my mechanic on Monday morning. He either loves me or hates me at this stage haha!

[Northern Bongolow]

Best to replace the studs while it's off, they maybe stretched and ready to give up soon.
Exhaust studs ( hot side) are different to inlet side ( cold side).

[oibaf]

Best to replace the studs while it's off, they maybe stretched and ready to give up soon.
Exhaust studs ( hot side) are different to inlet side ( cold side).

Yep, that's a good point. I'll make sure new bolts are used as well.

Actually, on that note, does anyone have the torque spec for the studs handy?

[teenmal]

Two white knuckles

19-25 NM

[oibaf]

Two white knuckles

19-25 NM

Great stuff, not too bad, many thanks!

Here's a pic of the little bubbles being blown from the number 1 exhaust port. As you can see, studs are present etc (and didn't seems snapped inside either but impossible to tell for certain). Id say it's a very slight leak, so far, but has to be sorted.