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Old 11-06-2015, 11:46 AM   #1
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Join Date: Feb 2015
Location: South Dakota
Posts: 193
Year: 2002
Coachwork: Thomas
Chassis: Freightliner HDX
Engine: CAT 3126B250
Rated Cap: 84
2001 CAT 3126B250 mechanical wastegate

With the radiator, intercooler and shroud out of the way, I'm poking around the turbo which is a new thing to me, as are diesels and air systems. So, it looks pretty rusty and from what I can determine, it has a mechanical wastegate. It looks simple enough: something puts pressure on the bar that rotates a flap in the exhaust stream. How do I know if this part is even functional? There is a lot of rust. Everything ran "fine" as far as I know. Am I just placing concern where there shouldn't be any? I would think that I should be able to put pressure on the bar to move it to see if it moves freely but how much pressure should it take, and should I even do it? There are no boost gauges on the dash which will change in time, just not in the next few months.

Again, the rust. When I removed the rust from the intercooler tube, there were 2 holes all of the way through. Could rust similarly compromise the turbo in the same amount of time? What would be the worst that could happen if the wastegate was stuck in the closed or opened position?
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Old 11-06-2015, 01:25 PM   #2
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Join Date: Oct 2015
Location: Spring Valley AZ
Posts: 445
Year: 2000
Coachwork: Bluebird
Engine: 5.9 Cummins
Rated Cap: 2 elderly children
Wastegate stuck open, low power, closed mo' power but no safety blow off.

Sounds like an exhaust brake?
Don and Mary
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Old 11-06-2015, 03:43 PM   #3
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Join Date: Aug 2011
Location: Stony Plain Alberta Canada
Posts: 2,939
Year: 1992
Coachwork: Bluebird
Chassis: TC2000 FE
Engine: 190hp 5.9 Cummins
Rated Cap: 72
Yes holes in your intake / turbo plumbing is a big no no. After the air cleaner, but before the turbo would cause dirt and other contaminants to be sucked into the system.

After the turbo, all the plumbing is pressurized to what ever your turbo is pushing. This could be as little as 7 psi to as much as 40 psi.

Loosing boost pressure will cause the engine to loose power and burn rich, wasting fuel and fowling the engine. Basically the engine is not getting enough air to burn the fuel delivered.

Waste gate is there to dump boost pressure over a preset amount of PSI to protect the engine components.

A simple boost gauge installed after the turbo will tell you a ton. With a boost gauge, and some technical specs for your engine, you will be able to tell if your leaking boost, and if the waste gate is working.

"Don't argue with stupid people. They will just drag you down to their level, and beat you up with experience."

Patently waiting for the apocalypses to level the playing field in this physiological game of life commonly known as Civilization
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