Kettle boiling sound with turbo boost on JB470. Help!

mobyderp

mobyderp

New Member
Just had a massive rebuild on my JB after head gasket blew/head cracked. Shop installed new head, intake manifold and gaskets, tuned up the boost (already have boost gauge), plus a million other things (waterpump, radiator, alternator), and new tubing and gaskets and studs for turbo, which was inspected. Shortly into use, far away from the shop, I started noticing a high pitched sound best described as a kettle boiling. It ramps up until I hit full boost at about 11-12psi, then goes away briefly, intermittently coming back if I'm gassing it. She holds boost just fine at steady rpms, clips along at a terrifying 60-70mph on the freeway - truly running better than ever before. But the noise....

I inspected everything with the driver's seat removed for signs of leaks, bad hoses, or weak malfunctioning clamps and can't find anything. The sound localizes to the front of the engine near the intake manifold (picture below) with a regular stethoscope. I sprayed a solid mist of brake cleaner on the intake manifold while idling and specifically the spot that's loudest and there is no change in RPMs. Does that absolutely rule out bad seal at the intake manifold gasket? And any ideas on what I should check next? And is it a bad idea to drive like this?

Appreciate any thoughts. Some pics below and these videos show the sound:

The sound:

The location?
 

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Thanks! That makes sense. I'm not the most experienced DIY'er but really trying. Any tips for accessing and determining leak on the exhaust manifold gasket? Shop recommended I double check the torque on intake and exhaust manifold which I'm doing this weekend.
 
mobyderp said:
Thanks! That makes sense. I'm not the most experienced DIY'er but really trying. Any tips for accessing and determining leak on the exhaust manifold gasket? Shop recommended I double check the torque on intake and exhaust manifold which I'm doing this weekend.
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If the torque is correct it could be a warped manifold. If it is an exhaust leak there should be evidence (soot); but you might have to pull the manifold to find it.
 
If they actually used studs for the turbo and not bolts I would check to make sure the studs were the right size. If they were to long the nuts could bottomed out on the stud, then the turbo might not be tight to the manifold and that leak could be at the turbo metal gasket.
 
Thanks so much! The exhaust manifold was replaced with a resurfaced manifold, but I guess could be warped. They used M10-1.25's for the turbo studs. Doesn't specify length other than saying 'short'. I'll dig deeper this weekend and retorque the manifolds.
 
Steven you nailed it - I believe I found the exhaust manifold leak with some soapy water. Pardon the slight out of focus video below. Is there any easy way to get past the heat shield blocking the lower bolt? My torque wrench won't fit and I want to make sure it's snugged before getting a new gasket and manifold.


Thanks again!
 
mobyderp said:
Steven you nailed it - I believe I found the exhaust manifold leak with some soapy water. Pardon the slight out of focus video below. Is there any easy way to get past the heat shield blocking the lower bolt? My torque wrench won't fit and I want to make sure it's snugged before getting a new gasket and manifold.

Thanks again!
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Nice...
I don't know about the heat shield; haven't had cause to mess with one yet. I wouldn't be keen on getting a new manifold; and it seems to me like this should be a free service by the shop in question.
 
Agreed - unfortunately the shop is far, far, away. Would or wouldn't be? And does anyone know the torque specs on the exhaust manifold? Going to make sure they are at spec today.
 
I'm at a loss. Shop took everything apart. Checked the refurbished exhaust manifold for warpage, inspected the old gasket for signs of leak - everything appeared to be seated properly (can attach pics) put a new gasket on, had the intake manifold machined as there was the slightest warp that the machinist thought was unlikely to be the culprit. Checked the turbo for play and even filmed it in action to ensure no wobble when winding up. Snugged everything up. The sound is still there! If you disconnect the turbo then the sound disappears. The only thing we noticed was the exhaust manifold gasket has a slight overlay going into the cylinder head. 1-2mm at most. Could that be causing the sound? It's still coming from the front of the engine the best I can tell. The good news is, she drives like a champ still and there is no exhaust smell or heat in the cabin. Appreciate any thoughts!
 
Check that turbo outlet > inlet manifold fitting's gaskets... it's in the same general region near the front of the engine.
 
#3? Checked that one, too. No signs of a leak. I'm really miffed. I can post a pic of the intake/exhaust manifold gasket to show the overlap going into the head if that's helpful. Seems like it seated well and there's no trace of leak from it, and sound continues after installing a new gasket. Exhaust manifold was freshly machined when they installed it. The van continues to drive great - hold boost without any issues and comfortably cruises. Sound goes away once you get to maximum boost and boost holds steady, but comes back when I hit the gas hard again.
 
running out of ideas... I suppose it could also be something like an idler pulley squealing only at high RPM or a belt slipping under high load. Try pulling the upper belt cover and hosing everything down with water to see if that makes a difference.
 
Thank you! Will give it a shot this weekend. Appreciate all of your input! Would be amazing if it's that.
 
I’m sure your to this point but pull the shroud and drive with the passenger seat up. Helps to have a buddy, best way to find odd noises.
 
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