2003 XC70 TVC test - no vacuum or pressure of any kind from red,blue,yellow hoses

[mramend]

Hi-

I'm a DIY kind of person, a bit old school - I don't have an OBD scanner (yet).. just a 2003 xc70 with very poor performance (turbo used to sound kind of noisy then it just stopped about 20k miles ago). It still gets me to work and back, has about 187,000 miles. I just don't think the turbo is working at all. If I put my foot to the floor, yes of course it accelerates and can reach high RPMs.

I started wondering maybe there was something simple I could test. Maybe something I could fix without having to climb over the engine to access the turbo itself in that limited space

I have a Harbor Freight combo vaccuum/pressure gauge. I saw a video on utube about how to test the TCV by hooking a vacuum gauge up to the boost/yellow output on the TCV. It apparently should show vacuum at idle and then that should drop off to zero when the RPMs go up. I was thinking that maybe my gauge would even show that process (vacuum switching over to pressure). The guy states that if the vacuum and drop off with increase in RPMs occurs, your TCV may be ok.

I had no vacuum on yellow. So then I thought ok the TCV must be bad. But then I saw the simple functional diagram out there on the web of the P2 turbos that made me think of this test scenario:

Connect vacuum+pressure gauge to the blue hose. Start the car. Should show some reading. I had none.
Connect same gauge to red hose. Start the car. Should also show some reading. I have none.

Therefore.. I conclude in my simple non-auto mechanic mind: the TCV might be ok. The hoses OR something else might be at play. Any suggestions on how to continue to chase this down without a scanner? Am I on the right path?

Many thanks,
Mark

[howardc64]

Might also want to take a look at the CBV besides TCV. Here is a diagram



Diagram doesn't show rest of CBV bypassed air path. It basically goes back to front of the impeller (kills off the boost, designed to protect over boost conditions)

You don't have boost 2 different ways

- TCV opening the waste gate and turbo doesn't spool up to generate boost.
- CBV open the bypass valve and bleeds off the boost pressure.

google "Volvo CBV" and you will come across some failures (not sure which model/year is more prevalent) Basically a simple diaphragm valve that can rip. Uses a spring to set the pressure to open/close. Here is an iPD upgrade that comes with multiple pressure settings

https://www.ipdusa.com/products/1180...r-bypass-valve

I tested it once, here is the link on that

http://www.volvoxc.com/forums/showth...247#post184247

I even opened it up and took a look.. quite challenging with no space. However, I did find a trick to reinstall it

http://www.volvoxc.com/forums/showth...521#post184521

[vtl]

"turbo used to sound kind of noisy then it just stopped" - sounds pretty much like it is seized.

I took a turbo out of a donor engine, it had a typical axial play in CHRA. With time the hot side wheel grinds the CHRA, you can't even rebuild it after that.