Just got a rebuilt IP put on 2 days ago. Also a HD (non-EGR) intake manifold. The EGR line was plugged by me long ago. I also have a sizable gap between the downpipe and cat flanges, along with a hollowed cat (poor man's exhaust system). Truck runs well, a little temporary rough idling after a warm restart (with more smoke than before). Don't have a boost gauge yet, hope to remedy that soon.


After picking up the truck, I was surprised by how much more I could hear the turbo whistle, it started in around 2000 RPM. After about 15 miles of driving, I got on it a little harder and heard the turbo sing pretty good, then it just stopped. I figured I just overpowered the vac on the wastegate. Since then, I haven't heard the turbo whistle once.


Is this some kind of "learning" that the Computer does after a new IP?


Thanks,


Doug


'94 K2500 L56

No, I would say it's time to check for vacuum at the turbo~15", and egr "T" to Baro~25".


If you have vacuum It's most likely a solenoid causing the problem.

QM, thanks for the reply. I checked the vac at the WG and it showed 14". Unplugging the solenoid dropped it to zero. Vacuum from the pump was good.

When the vac to the WG is unplugged, the WG moves freely, but the doesn't look to have broken free of the shaft. I tried manually closing the WG while the wife revved it to about 2K, couldn't hear it whistle, but maybe free revving (not burning much fuel, so gases are cooler) doesn't spin the turbo that fast.

Guess I'll be getting a boost gauge soon.

Thanks,
Doug

Everything checks out so far.


Also, check the actuator on the turbo for leaks by plugging the line in and trying to move the arm back and forth. It shouldn't move, with no air leaking past. And just to be sure, remove the vac lines and individually test them for leaks.

QM,


The WG vac line checked out ok. Should the WG actuator hold a vacuum when suction is applied straight to it? Mine doesn't. I'm not sure if this is normally vented, or I have a bad diaphragm. It did pull as long as I was steadily applied vacuum.


Thx,


DougEdited by: HamhockTX

The vacuum actuator is vented on the other side from the vacuum port but there must be a good seal on the diaphram to keep the WG pulled closed(although it cycles and opens and closes). The actuator is ~$300 but can possibly be rebuilt with a section of innertube.

Boost at idle is not a requirement for a Diesel engine at most altitudes below K5.


PCM would limit Boost if sensed under no-load condition.


Turbo song is muffled by air inlet ducting, air box, air filter, etc.


You were probably hearing it thru loose or unseated air filter in the air box - sound became muffled as filter seated.


15" vacuum on wastegate actuator should require very hard pull on the rod to open the 'gate.


It is not important to hold the gate closed when vacuum source is off, as in engine not running.


15" vacuum from wg solenoid into closed line should not drop when line is connected to 'gate actuator - otherwise, the actuator leaks excessively or the line leaks when connected.


A Boost gage and EGT gage are a must have accessory to get a real sense of what the engine is doing at any time.


jcwhitney.com sells a 2.125" 20psi Boost\30" Vacuum gage for less than 20 bucks - very handy to also have the vacuum function.Edited by: gmctd