[cyclingtrav]

TL;DR The small engine bay on the 4runner with the V8 means there's about 0.5" of space between the rearmost bolt securing the Check Valve and the firewall, making it literally impossible to extract. We resorted to draining the coolant, disconnecting both air ducts from the pair of valves, and dislodging the bracket to which the valves were mounted (couldn't fully remove the bracket because of an electrical connector being mounted to the back of it). Now, the biggest challenges after mounting the check valves to the bracket will be to reinstall the bracket and connect the two ducts that mate to the valves (each with 2 screws that are really difficult to reach, even with several extensions on a ⅜" drive wrench)

I recently got myself a 182k mile 2008 4Runner Limited with the 4.7L V8. The seller disclosed a few items that would need attention upon sale: cracked exhaust manifold, failing fuel sending unit, and CEL due to a broken SAIS Check Valve (seller had a Hewitt Bypass Gen1 installed). I knew I would order a set of DT shortie headers and have a shop install/weld them to the cats, and the fuel sending unit is a DIY job I should be able to take care of in a few hours.

At first, the check valve replacement seemed like a feasible DIY job and a relatively less costly one (~$100) than the more frequently talked about SAIS pump replacement (~400). I found plenty of great references from people who'd done this work on larger platforms (Tundra, Sequoia, LX/GX), so I ordered the parts, called over my father in-law and we got to work.



Once we had the intake plenum removed, we could not figure out how to get to the two bolts securing the check valves. We tried many different ways of finagling wrenches through the narrow opening between an encased wiring harness and the firewall. We eventually pivoted and resorted to removing the bracket to which the valves were mounted, which entailed draining coolant from the radiator and disconnecting the line that routed through the right side of that bracket.







While I had got the intake off, I confirmed that both the SAIS Pump and the AIR Switching Valve both work.

Has anyone done this job before? If yes, do you have any tips or suggestions to make reinstalling the check valves more feasible?

IMPORTANT NOTE: OBD2 reader gave me the following error codes:
P1442: SAIS Switching Valve No.2 Bank1 Stuck Closed
P1445: SAIS Switching Valve No.2 Bank2 Stuck Closed
P2441: AIR System Switching Valve Stuck Closed Bank1
The part I ordered was "Switching Valve No2" but it seems to me that it was actually No1 that was malfunctioning. Once both were removed, I compared the plunger movement with vacuum applied. My old Check Valve No2 functioned identically to the new part. In Check Valve No1, the plunger barely moved and the diaphragm didn't hold the vacuum at higher pressures like the new part. I've ordered a new Check Valve No1 and will compare it to No2.

I will update when the new part arrives and again once we've reassembled everything (I hope).