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Another turbo issue

599 views 5 replies 6 participants last post by  Tommygunner 
#1 ·
Ok. Here's my issue.

1999 C3500 dually, 6.5, 4L80, 4:11 gears. 133k. Bought it a couple years ago. Needed a Y pipe. Replaced that, but truck has always smoked under any sort of load. Plus it's a pooch.

I took an interest is fixing this thing up. Checked waste gate operation - not closing at idle. Check fire vacuum at turbo - none. Checked for vacuum at WG solinoid - no. Replaced vacuum pump. Now I have good (great) vacuum at turbo @ idle.

Here's the problem now... turbo operationis intermittent.

Picture this. Stopped, pulling a 1 place car trailer with a car on it. Take off at moderate throttle (half +/-). Truck takes off, pulls good, no smoke. Lasts for 3-5 seconds. Then (I'm assuming) waste gate opens - black k smoke, real poochy. Still holding same throttle, turbo will come back (no smoke, plenty of power). Sometimes boost will last 1 second, sometimes for blocks. No boost is just as random.

I did not change vacuum lines, BUT, testing at the solinoid, both the turbo and pump side will hold 20in of vac for a minimum of 10 min
 
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#2 ·
definitely replace the lines with rubber lines, get rid of all the old plastic and brittle lines... if you are getting random boost and it drops off, u may need a new solenoid, they can work intermittently, kicking on and off and dropping boost cause it is dropping vacuum to the wastegate randomly.
 
#3 · (Edited)
X2 ^^ Replace your stock vacuum lines with rubber line
 
#4 ·
It's nice to have a good gauge too...
I've always been a fan of eliminating as many variables as possible so I like going with the vac pump delete and a manual spring on the waste gate.
 
#6 · (Edited)
X2 on above^. your wg solenoid is flaking out. Also would not hurt to check check your vac lines.
A vac gauge is a need to have thing and a fairly simple install. It would tell you a lot about how your engine in running.
 
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