What is this black and white check valve for

dcmike · Post by **dcmike** » 11 Aug 2018, 07:52

I have a 98 v70r. This little black and white check valve keeps coming off and my mileage drops. What does this valve do and why?

Mike

jsloden · Post by **jsloden** » 11 Aug 2018, 08:41

If I remember correctly that's actually part of the EVAP system. So I would assume that it could definitely effect mileage. You can buy those little rubber pieces at ipd fairly cheaply. I replaced all of mine when I did the PCV system. There are actually several of them throughout the system.

Post by **misha** » 11 Aug 2018, 10:58

It is one way valve for SAS solenoid on fan shroud.

dcmike · Post by **dcmike** » 11 Aug 2018, 11:08

Why does the valve keep coming off the line from the SAS? Is their to much pressure?

Post by **misha** » 11 Aug 2018, 11:50

Could be that SAS valve is stuck open and recirculating exhaust gases via vacuum line....i had this problem.
Check the air filter for water from exhaust condensation and carbon from exhaust gases.
If so....it will kill your MAF.
It killed two of mine...brand new from Volvo a long time ago.

EDIT***

I mixed this line with purple vacuum line from SAS valve....there is no danger of exhaust gases here nor for the MAF sensor.
This line goes from vacuum tree to sas solenoid at fan shroud.
Purple one goes directly from SAS valve to a vacuum tree.

Post by **scot850** » 11 Aug 2018, 11:53

Could just be vibration and a really worn out rubber elbow. Not sure if that part of the system is under pressure or vacuum. Remove one en of the pipe with the engine running and stick your finger over the end of the valve and the end of the pipe and see if it is sucking or blowing form one or other to determine if the system is vacuum or pressure.

If it is vacuum then I can only believe it is the vibration that is causing it to work loose. If it is under pressure then the worn out rubber is probably to blame. If a new rubber elbow does not fix it the valve may be partially blocked or there is too much pressure in the system. When was the PCV system last serviced?

Neil.