turbo question

[vault]

So I believe my turbo is bad GMTD scan read 0 boost. Did the Boost check according to factory shop manual and there was no boost just vacuum. The waste gate was forced closed b/c my vacuum pump is also shot. So the during this learning experience I found the previous owner had added a spring to hold the waste gate closed. I don't know if this had anything to do with it.

So is my next step replacing the turbo:(

[vault]

I took the air in take off and the turbo fans look fine and turn fine by hand no rubbing, grinding or signs of damage. With the truck running you can see the turbo spinning but no boost being generated. I wonder if the waste gate is broken and stuck open.

[DmaxMaverick]

Unless the engine is under a significant load (accelerating or hauling a load uphill), you may not see much, if any boost. You should never see any boost at idle, or even revving in neutral.

[vault]

Ok, I was kind of confused on the factory manual inst. It says the block the truck up before preforming the test then it talks about driving the truck then shifting to neutral and quickly depressing the accelerator to the floor:confused:. So I just blocked the truck and punched it while it was parked and I saw vacuum no boost. I'll try taking the truck for a drive.

What returns the wastegate actuator rod when no vacuum is applied. The manual said it should return on its own. My rod moves freely but just stay in what ever position you leave it in.

[DmaxMaverick]

Ok, I was kind of confused on the factory manual inst. It says the block the truck up before preforming the test then it talks about driving the truck then shifting to neutral and quickly depressing the accelerator to the floor:confused:. So I just blocked the truck and punched it while it was parked and I saw vacuum no boost. I'll try taking the truck for a drive.

What returns the wastegate actuator rod when no vacuum is applied. The manual said it should return on its own. My rod moves freely but just stay in what ever position you leave it in.


It will generally just stay where you put it, absent of vacuum (engine off or vacuum line disconnected). If they're supposed to return on their own, all of the hundreds I've seen must have been broken.

No load = No boost. That simple.

[JohnC]

Are you talking about engine intake vacuum (and boost) or vacuum on the wastegate control? If the PO installed a spring, the vacuum boost control system probably has problems.

The vacuum or the spring closes the wastegate (and allows the turbo to build pressure). Exhaust pressure pushes it open to reduce boost. If the vacuum control system is working, there should be some vacuum trying to hold it shut under all conditions other than severe over boost, in which case the PCM will dump all the vacuum.

Like DmM said, you will not see any boost unless there is a load on the engine. No load means no significant energy in the exhaust stream to power the turbo.

[suburbanK-2500HD]

You can produce some boost if you hold it on the brakes in gear, and use the trottle to load the engine. I am not sure if its wise for the tranny, so be carefull.

[vault]

I took it for a drive and it did produce boost with the wastegate forced shut with the spring b/c my vacuum pump is shot. No matter I got boost and it is just the vacuum pump. Now to figure out why the manual tranny won't shift and was low on fluid:confused:

thanks for your help