On a Cat 3126. Turbo. There is a vacuum chamber mounted below it. What is the purpose of it and how do you test it?. I tried to move it with a pair of pliers and it seems to be frozen. . How do you check it out. How will it affect engine performance if frozen?.
Is that hooked to a wastegate on the exhaust side of the turbo? If it is, then the shaft of the wastegate is locked up, and not letting that chamber move. The chamber operates on turbo boost pressure to limit it to a maximum, so it not functioning would only affect operation above the intended maximum boost.
Is this vacuum operated? Could it be tested with a hand vac. pump? If wastegate is frozen up, can it be taken apart and freed up? If bad would this affect power or torque at lower RPM? Truck seems to run fine once you get it above 1500 RPM but below that it has no power. Appreciate your help.
Put a boost gage on it and see what your geting.
What's the "control" line hooked up to? if it's hooked to the intake manifold then it's operated by boost pressure, not sure you have any vacuum on a 3126? maybe slight vacuum from the air filter if you want to quibble. You might get it freed up, kinda tricky though, and maybe not worth it. If it won't move with a pliers then it's frozen shut, it is supposed to be shut unless the boost pressure exceeds the designed pressure. I don't think this will affect the power at all, but the turbo could be toast also. What are you comparing this engine to, 1,500 is the bottom of the power band on a medium size diesel like that. Or did this lack of power just develop?
Those wastegate actuators have a pretty stout spring in them. It will affect boost and mileage slightly. You will get a bit more boost if stuck closed. However, if it is stuck open, you will swear you lost your turbo. Substantial reduction in boost, and your exhaust will run extremely hot.
Yep. Plus one on that. I had a C7 a few years ago with the wastegate stuck open. Low power, overheating and excess smoke. Took a while to track it down as well. I put some visegrips on the actuator lever to see if it was free and the thing suddenly snapped shut. Nearly broke my fingers.
You ask what am I comparing this to. This is a 2003 KW T300 with a 4.10 rear end, std trans. GVW 26K. I bought it this spring. I usually run it at max GVW with a tank on it. On the low end, power wise, it is sick. No torque at all. Runs great as long as you keep it wrapped up. Slightest hill and it falls off dramatically. No power at all in low gear when taking off if on a hill. I am comparing it to a 1997 GMC C6500 with a Cat 3116, 4.10 rear end, std trans, tank on it, all kinds of power in low end, and decent power in higher gears, for a 3116. 2002 FL 70 with a Cat 3126, with a 4.10 rear, std trans, seems to have decent power in low end and high end. GMC at 2000 rpm, speed is 50 mph, and I don't push it much faster than that. (seems geared low) KW 2000 rpm at 65mph. I don't understand the difference in gearing and speed with the same rear end. I cant give you a honest assessment of the FL because I don't have a tank on it yet to really compare it. On the GMC if you were on pavement and on a steep hill, I think it has enough torque that it would twist the drive shaft if you pushed it. On KW it just kills the engine . Appreciate all your help and suggestions. (just trying to drain the pond by eliminating one alligator at a time)
OK, I guess you know what low power feels like. I hadn't even considered that a wastegate could stick open because they're shut when sitting and that's when they get rusty.
Engine # CKM65522 Truck 2NKMHDs6XX3M390830 (this one does not smoke or run hot)
We used to have a KAL C7, not sure how similar it is to your 3126 but about a 2005 model year and that thing never had any power under 1500 RPM even when it ran right, which was seldom. I was going to say it is the nature of the beast but it sounds like you have another one that runs better so who knows if there is anything wrong or if it is just a difference in model year/engine arrangement. The 3116 is not really a fair comparison, it was (usually) a full mechanical engine and the injection system bears no resemblance to the 3126/C7.
If it has good power from 1500 to 2500 rpm I wouldnt worry about the turbo. ours doesn't really start pulling until about 1700 and starts loosing power at about 2200.