Odd noises coming from Turbo...any thoughts?

dgeist · **Posted:** Fri Jul 24, 2015 2:43 pm

So, I'm having some strange behavior with my turbo. First, just after starting up, there sounds like an "over-spin" condition if I hit the throttle a little then back off. Once warm, it continues, only the noise is more of a "grumbling chatter".

I've checked the actuation with a hand vacuum pump and it seems okay. Also the lateral play seems fine when I last pulled my hoses and checked. I replaced the little filter on the vacuum system recently, but that doesn't seem to have made a difference.

There are two active components at the turbo, right? A solenoid that opens and shuts with the ignition that's mostly to keep pressure in the line for startup, and what I'm guessing is an actuator of some kind? Any good pointers on how to identify problems with these guys?

Thanks.
Dan

diesel_guy86 · **Posted:** Fri Jul 24, 2015 4:51 pm

Do you still have the fcv installed? It could be stuck partially closed, surging the turbo. Think of it like stopping a leaf blower, it revs higher and the air has no where to go.

dgeist · **Posted:** Fri Jul 24, 2015 5:19 pm

FCV's been broken (open) and unplugged for years. Your description of the sound is accurate, though. Almost like the variable vanes are supposed to be getting actuated when the boost demand decreases, but isn't happening.

Dan

thermorex · **Posted:** Sat Jul 25, 2015 2:26 pm

Dan, check your boost. See if in full throttle you get over 20. This assuming the turbo is healthy of course...

WWDiesel · **Posted:** Sat Jul 25, 2015 2:36 pm

With the engine off, check the turbo vane linkage movement and make sure there is no sticking or binding from min to max. With the vacuum line disconnected from the turbo actuator, you can use your finger to move the linkage and feel for any sticking or binding. Some on here have reported sticking vane linkage and had to lubricate it with some good quality penetrating oil like PB blaster.... :wink:

dgeist · **Posted:** Tue Jul 28, 2015 8:26 am

If by linkage movement, y'all mean the movement of the little shaft in the center-top of the turbo body when vacuum is applied/released? If so, yes, I hooked up a hand-pump with the engine off and the actuator seemed to move smoothly and through its full range (I remember finding another thread with that approx distance, but can't remember the distance at the moment). I might have gotten that wrong. How far is it supposed to move and where does one spray the PB (since it probably couldn't hurt).

The noises do seem to be more pronounced in certain situations, also, like loaded vs unloaded engine the "throttle let-off" yields very different sounds.

If one (or both) of the components in the vacuum path were faulty, what would the result be? Perhaps I can correlate certain faults to what I'm hearing?

Dan

dgeist · **Posted:** Thu Jul 30, 2015 9:04 am

So, I bypassed the vacuum solenoid (which I noticed was doing a "death-buzz") and the lag and poor shifting/boost qualities seem to have gone away. While I'm waiting on a new one from IDParts, I have to wonder: Why does the turbo need one if it runs fine without it?

The other noise (slight grumbly whirring noise when I let off the throttle) seems to be less pronounced but still present. I did check the vanes, and they're free. There does appear to be solid vacuum on the actuator, and I don't see any signs of it sticking. For all I know, it could be something else in the exhaust path just chattering a little when the pressure backs off. Wondering if a good TDI shop (since there's no such thing as a good CRD shop around here) would be able to listen and tell me exactly what this noise is. VW uses a very similar turbo setup AFAIK.

Thermorex, how does one measure boost without a dedicate boost guage? Can I pull that off ODBII?

Dan

flash7210 · **Posted:** Thu Jul 30, 2015 9:20 am

If you turn the radio on do the noises go away? :lol:

Seriously though, if the turbo is functioning properly and there is no excessive movement in the turbo shaft and there are no boost leaks, then the turbo should be fine.
Turbos do make some noise. How much of that you hear can depend on a lot of things.

I recently removed that insulation mat from the inside of the hood. Now my turbo and engine noises are more pronounced. Drove me nuts at first trying to figure out why I was hearing things.

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

If you bypassed the EVM with the little air filter on it, then the turbo will have the vanes full closed all the time and most likely overboosting. Not good for turbo life.

dgeist · **Posted:** Fri Jul 31, 2015 1:39 pm

GreenDieselEngineering wrote:

If you bypassed the EVM with the little air filter on it, then the turbo will have the vanes full closed all the time and most likely overboosting. Not good for turbo life.

No, the modulator is still in the flow. I bypassed the solenoid. Does it do anything other than maintain a slight vacuum when the engine is off? I can't tell any difference with it bypassed other than that the engine no longer has the lag...

As for the modulator, is there a good way to test it? It sounds like I may have an overboost (based on what I'm hearing) just after letting off the throttle after a loaded condition.

Dan

WWDiesel · **Posted:** Sun Aug 02, 2015 10:26 am

The only benefit that the vacuum reservoir provides is storage of vacuum in the plastic reservoir so the turbo has some vacuum in reserve at startup and at other times. The vacuum solenoid controls the storage of the vacuum in the reservoir... :wink:

Good information from an earlier post by PAP on vacuum reservoir solenoid bypass check instructions:
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=70602&p=757348&hilit=boost+solenoid#p757348

thermorex · **Posted:** Mon Aug 03, 2015 3:27 pm

Hey Dan, map sensor registers the boost, so I'd guess you can measure boost with an obd2 scanner.

dgeist · **Posted:** Sun Aug 30, 2015 4:29 pm

So, my solenoid has been replaced, but the problem persists. I'm getting a p0108 and a p0234 whenever I get on the skinny pedal even a little (like at 2500 RPM). I immediately get the two codes and, although it's not exactly limp mode, power goes way down in the "more than 2k RPM" range.

There does still seem to be the "vanes don't match the needed boost" chugging sound even before the CEL gets thrown whenever I let off the accelerator.

How much boost should i be able to register (min/max/healty range) and how much should the vacuum actuator be moving on the turbo? I'm figuring I either have an issue with the vanes sticking or the modulator not working right, but not sure which is more likely. I have cleaned the MAP religiously throughout the life of the engine, so unless it suddenly croaked, I'm not suspicious of it as the culprit. ODB2 should tell that, maybe...

Any other hints of wisdom for causality of certain symptoms indication specific problems? I don't want to gut it and do everything as I just don't have the chunks of time in my day to dedicate to a full tear-down of the turbo currently.

Dan

flash7210 · **Posted:** Sun Aug 30, 2015 6:10 pm

Do you have a boost gauge?
I would start by replacing the MAP sensor.
If that doesnt fix it then your turbo vanes might be stuck.

The only way I know to test the turbo vanes is to watch the actuator lever on the turbo.
While idling, pull the vacuum line and watch the lever move.
Kinda hard to see but not impossible.

thermorex · **Posted:** Mon Aug 31, 2015 9:50 am

At pedal to the metal boost goes towards 25psi, then drops to 20ish, my guess is that computer regulates the vanes to prevent boost going over 20. This is based on my observation and not anthing from a documentation manual.

dgeist · **Posted:** Mon Aug 31, 2015 1:35 pm

thermorex wrote:

At pedal to the metal boost goes towards 25psi, then drops to 20ish, my guess is that computer regulates the vanes to prevent boost going over 20. This is based on my observation and not anthing from a documentation manual.

I ordered a new MAP sensor and modulator unit from IDParts. Hopefully you're right about my sensor readings, but if they don't fix it (and I know I don't have a leak), I know where the problem is...

Dan

thermorex · **Posted:** Mon Aug 31, 2015 9:52 pm

dgeist wrote:

thermorex wrote:

At pedal to the metal boost goes towards 25psi, then drops to 20ish, my guess is that computer regulates the vanes to prevent boost going over 20. This is based on my observation and not anthing from a documentation manual.

I ordered a new MAP sensor and modulator unit from IDParts. Hopefully you're right about my sensor readings, but if they don't fix it (and I know I don't have a leak), I know where the problem is...

Dan

Lol. I am reporting readings from the boost gauge, not map reading. But when I checked the accuracy of the gauge vs map, they were the same.

dgeist · **Posted:** Wed Sep 09, 2015 9:06 am

Well, a new MAP sensor seems to have gotten rid of SOME of the problems. I'm no longer throwing codes and my responsiveness is back. I'm still getting a little of the "taking too long to spin down" grumble, especially within the first few minutes of start-up (it seems to be better once I'm down the road a bit).

The MAP was not really much worse visibly than I'd seen it before with regular cleanings, but I suppose 9 years of spraying MAF cleaner at every oil change may have taken its toll.

Dan

Odd noises coming from Turbo...any thoughts?

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