Background:
Pulling a 12row planter home on our 30ft gooseneck trailer; gettin' going from a stoplight something "popped", sounded like an intercooler boot but never lost boost. It popped, I let off immediately but got back into it because of traffic and everything seems to run fine, but now it's got a weird noise when it builds boost beyond 10psi. We pressure tested the whole system up to 20psi just after the turbo and found no leaks or anything. Have tried to check the intake side and don't see anything wrong. Pulled the turbo to check impellors and everything looks fine. Have had two different shop techs run codes and nothing shows up. It creates a whine (reed sounding noise) when it builds boost and I just can't figure it out.
The sudden pop when it happened also confused me as to what it could be.
Wondering if anybody has experienced this or can offer any ideas and things too look at.
Thanks!

 

Hmm, usually that means you blew an intercooler pipe out of one end of the boots. But since you didn't lose pressure, and since you didn't blow a boot and still have boost pressure, i dont know what it can be. I was thinking a blown seal in the intercooler, maybe a ruptured end tank, but you have an aluminum one probably, and you were only at 10 pounds of boost you said. Hmm i am lost if the turbo still works fine. Are you sure it wasn't the implement?

 

Check all theboots around the clamps. Might have torn/ripped one and it only leaks when added pressure, just a thought.

 

Yes.
Find a shop that has one of those smoke machines for finding vacuum leaks and hire them to introduce smoke to the intake. The leak will be easy to find.

 

Thanks for the input guys.
I have taken out all the intercooler pipes and cleaned and looked over all the boots, have completely removed turbo, even pedestal to check all that and saw nothing. The noise starts to become audible around 10psi when driving the truck and increases from there. I used compressed air with a psi regulator, some PVC pipe and cap and pressurized everything right after the turbo(intercooler and all boots) to 20psi and never heard anything except the air movement. That's what's got me baffled? I still hear the noise when driving, but everything seems to work fine. The only thing is the higher boost(more weird noise) I get I notice the boost gauge will start to flutter, which it hasn't done before.

Could it be something with the wastegate?? That it is doing something when running and so I hear the noise then, but when we pressure checked everything the engine was off and so it was inactive?? Couldn't really see anything wrong regarding it when the inspecting the turbo, but you can't see much of it anyway.

Kwik- how do you go about using a smoke machine to find a leak? Is the smoke introduced into the system to see it leaking out or around the outside to see if it gets drawn in?

Thanks for the help!

 

I saw that you checked your bearing, but does this sound familiar, it's from a previous post of mine? "Eventually, the bearing got loose enough for the turbine to hit the case and chip some blades. After that my truck sounded like a police siren, and I knew it was time for a new turbo."

The onset of this was a pop and a whine while towing up grade at 24+ boost. I was sure hose had come part way loose as I've blown one before. After checking under hood and finding nothing obvious, I continued on. Truck ran ok except for whine above 10 psi. Made it to Browns Valley Truck shop and even did a dyno run before pulling turbo because I was going to do upgrade and wanted to measure improvements. Point is truck still made full power, just had whine! The two chips were very hard to see at the very tips of two turbine blades, but enough to make the whine.

 

I didn't think of this until it was too late to edit previous. This is a test I tried several times (while towing to the truck shop) to help determine if my problem was a pin hole leak or a bad turbo. It's easy to do when towing, but might be difficult to perform empty.

Produce a condition where speed and boost are constant at about 15 psi (where you're hearing the mystery whine), and then quickly modulate the fuel to vary turbine rpm without changing boost. Due to turbo lag this can be done. In my case, I found that whine varied with turbine rpm at near constant boost, which convinced me that I had a bad turbo.

I digress, but only to explain how well my truck ran, even with this condition. After first dyno, guy see's my SES light due to over boost, and without asking cuts my MAP hose and installs a boost relief valve. Insists we do a second dyno at no charge so he can demo improvement. Got 12 more rw hp, up to 297 if memory serves. Of course, I didn't want the valve, I had tried and removed years ago, SES was good reminder to take it easy and causes no harm by letting PCM de-fuel. I even installed a counter spring on replacement turbo to further limit boost.

 

Thanks ernesteugene- the "sounds like a police siren" is quite accurate. When it happened, first reaction was let off from the pop, second was to check mirrors because it sounded just like a siren whining like I was getting pulled over.
These turbos don't have bearings(the way I understand it), but run on a film of oil, but the same could still have happened. I did look close at the tips to see if it scratched the housing anywhere, didn't notice anything. May try to replace the impellor wheel and see if that helps. It would be the cheapest fix anyway.

 

Well, they are actually brass bushings, that do not touch the shaft when its under oil pressure and spinning. Do not run the truck as much as possible, as the siren noise is most likely two pieces of metal touching, that shouldn't be. Could get into the engine. Pull the intake and see if you can move the compressor wheel/shaft in and out, and side to side.

 

In my case, the siren was do to small chips in the TURBINE blades, not the impeller. Here is another report of the same symptom (siren) and same damage, turbine blades.

So, here is the problem: I was running in 80Hp mode, climbing onto the freeway on ramp, and as usual, nailed the throttle. The truck took off like a Raped Ape, EGT's just under 1200 (as usual), Boost right around 26-28 PSI (as usual). After about 5 seconds of this, I start hearing a high-pitched whine sound, coming from the intake. I'm running an AFE Stage II intake, which lets me hear EVERYTHING about the turbo.

We found a sloppy feeling in the bearing, much more than usual. So, the turbo came off the truck, and after removing the housings, found a very damaged turbine wheel on the exhaust side. The housing is pitted, and the vanes are destroyed.
Click here if you want to see some pictures: I posted them on a special page on my website.
http://forums.itpdiesel.com/showthread.php?t=521

 

That is one sad looking turbo!

 

dude, how many miles were on that thing?

 

Ouch, that is the worst i ever seen. Looks like a complete thrust bearing failure. Was the turbo (particularly the thrust bearing) ever apart before this happened?

 

Hope everyone realizes that these pics are not from my blown turbo, but from a thread on another site! I'm just trying to convince farmboy that I think he's barking up the wrong wheel so to speak, and shouldn't waste his time & $$ replacing the compressor wheel in an attempt to fix his siren noise.

BTW I don't think the siren noise is from metal-to-metal (it only occurred >10 psi), but rather the chips out of the turbine blades make it just like an actual siren where air passing over blades makes the noise. However, after seeing these pictures I'm glad my turbo didn't come apart during dyno runs (which were done against my better judgment) and completely ruin my engine.

 

Thanks for the continued help. I'll have to remove the turbo again and disassemble it to inspect both wheels and housings.

Seems like I should be looking for a new turbo. They've got some used ones on ebay, but I'm skeptical for obvious reasons. I just wish they'd make an easy upgrade to a BB turbo for the early '99s, but everything I've seen is for 99.5 and later.
Anyone have any good leads to upgrade kits for early '99s??
Thanks again!