05 VOLVO truck VED D12 engine lacks power and makes 4mpg.. what is wrong?

i Have same problem from last month on my 06 volvo d12 465,lack of power, no jake brake, poor fuel milage,i couldn't finds the problem..yesterday i found the big crack under the turbo boost sensor(may be its was small before) i changed the intake manifold($ 147.48from volvo) now its run great..

 

I found a large leak the hose between intake manifold and CAC. I took the coupler off the turbo and connected a home made pressure tester and charged up the intake with air. Air came rushing out of hose that wasn't on the hole way. Fix that then found CAC leaking. Replaced that and now last 30 day Mpg's 6.78. The month of Nov 5.75 average. Never even hit 6. 2007 Volvo 630 D12D

 

is that aluminum can located behind turbo ????

 

Yes, has an air line going into the bottom if it

 

What is the CAC?

 

Air to air cooler in front of youre radiator and behind the ac condenser in youre cooling pack

 

Hi bravoo67 !
Have you had this problem solved? I've got 06 volvo670 d12 with mostly same symptoms.
The truck has been done head, injectors and one of egr that I heard of the seller.
pls let me know what is the solution if you have fixed your truck. I'm a newbie in this trucking job.

 

Have you checked your overflow valve? I've had the same problem you are talking about. The dealer checked my motor and nothing, no air leaks, no fuel leaks, 5.5 mpg with 39000 or better. I just changed the Overflow valve, there seems to be several 1 for the lower rated motors, one for the 465 hp motor and one for the 800 hp motor, when I pulled mine off it was barley tight, the ball on the end of the valve, was loose and to push it in took no where near the 50 lps required to move it. the valve is intended to keep 50 lps of fuel pressure on the fuel rail. if it leaks the fuel injectors won't get the required pressure to operate properly. low power, poor milage.

 

Where is this "overflow valve" you speak of??