Coolant flow control valve replacement

I want to thank PriusChat and the members here once again for being such a sharing community. I wouldn't have/couldn't have done this without the great support here. I tackled this repair last weekend after getting P1116 and P1121 codes on my daughter's 2008. The stealership again tried to rip me off by determining that I required a new coolant canister ($850+ repair) rather than the Coolant Control Valve. Not trusting them to do ANY work on my car, I decided to do it myself.

Cost was ~$75 for the valve and ~$50 for 2 gals. of SLLC coolant. And about a day and a half of frequently distracted attention to the car. Codes are gone now and I'll be taking it in to get the emissions inspection today.

I'm not going to go through the entire recipe as there are very good posts here and YouTube videos that cover it in good detail. But here are the lessons I have to add to the experience if any are interested. If you are new to this repair, you should read the other posts otherwise mine will lack context and detail. This one was particularly useful.

1) If you are new to repairs on the Prius coolant system, understand that there are two distinct coolant circuits - the Engine circuit and the Inverter circuit. You will be working on the Engine circuit for this repair. The Inverter circuit (which includes the coolant reservoir on the driver's side of the engine should be left alone.

2) After considering doing the "pinch" method to preserve coolant, I realized that the coolant would need to be replaced in the next 10K miles anyway, so I just did a drain/replace instead. As noted in several posts/videos, it's a good idea to measure the amount of coolant drained so you know approximately how much needs to be replaced. It helps you keep your sanity after incrementally adding coolant and wondering "am I friggin' done yet?"

3) The Lisle funnel provides a lot of convenience and order to the repair by minimizing spillage and hassle. Invest in one. And the tubing to use is 3/16" internal diameter (ID), not 1/4' ID. I had to add a zip tie to my 1/4" tubing to keep it attached to the vent port.

4) Ditto for the Cable Hose Clamp Pliers!!! I'd still be working on it now (3 days later) if not for those pliers. Well worth the ~$30 I paid for them. And I'll use them again and again, I suspect.

5) Another key convenience was having the front end up on ramps (and the rear wheels chocked) so I had full access underneath. I recommend this if possible.

6) When draining the coolant, I used the Coolant Canister drain - rather convenient once exposed. I opened the radiator cap once the bulk of fluid had drained from the canister and this vent allowed more to drain out. I never opened the Overflow tank cap to avoid having that fill up. Others have noted this.

7) Before you start, you may want to go online and buy a dozen or so extra plastic fasteners used to attach the underside and under-hood cowlings. Guaranteed you will break some off extracting them and will need them later. They are a PITA. I bought a bunch of different sizes and just keep them in a plastic tackle box for regular use.

8) When disconnecting the Coolant Control Valve, unclamp the top two hoses from the valve first, then unclamp the bottom hose AT THE COOLANT TANK PORT. And then remove the valve from the engine compartment. This will save you from trying to unclamp the hose from the bottom of the valve while it's still in the engine compartment. Simply remove the valve, detach the dangling hose from the old valve and attach to the new valve, then shove the valve back into the engine compartment and reattach the hose to the tank port.

9) If/when you open the top vent port on the radiator - usually when refilling the fluid - be VERY careful when loosening/tightening. This thing is made of plastic and I broke the top of mine off by mistakenly loosening past the limit (it was open when I thought it was closed, dammit). Anyway, I was able to tighten down what was left of it by going up to a 1/4" allen wrench and it doesn't appear to leak now. I've since learned that I can replace this plastic port and O-ring (parts ~$9) so I'll be doing part of this exercise again soon to replace the port. In the meantime, it looks like it's holding for now. I didn't see any reference to these parts on PriusChat, so here they are if anyone out there has a Yakoma moment and has to replace them.



10) The relay jumper trick was key to getting the air out of the system on refill. As all have cautioned, run this pump for less than 30 seconds at a time before rest to avoid overheating the pump. Make sure you have the connector connected at the Coolant Canister. Ask how I know this. Here are a couple of videos that were helpful to me on the refill. They could be edited for length, but are still good - better than I've produced...which is nothing.

11) Be patient on the refill. I filled as much as I could without any tricks first. Then I opened the top vent with the 6mm allen wrench and added more. Then I did the relay-jump trick and added more. Then, when that stalled, I jiggled the radiator hose near the vent and added more. Then I put the car in Inspection mode and ran it for 30 min at a time and added a little more. I would turn the engine off and let it cool for 30-45 minutes and then add more. I probably did that 4 times. Each of these things resulted in additional (but marginally less and less) fluid entering and additional bubbles leaving the system. And then, when you think you're done, you can probably add a little more before each subsequent drive after cooldown. Even this morning, I added a couple of tablespoons of coolant to top it off after about 100 miles of driving this week.

12) Finally, the biggest pain I found was replacing the underside cowlings. This took me the better part of 2 hours upside down on the roller cart. Just figuring out the puzzle of how these clips and screws attach was challenging. Take your time and maybe even take pictures before you start to disassemble. It all went back together solidly finally but there was some copious cursing before victory was ultimately achieved.

Best of luck to anyone who decides to do this repair. It's time-consuming and a bit complicated, but I'm glad I did it. The actual part replacement is the dead simple part (assuming you have the cable hose clamp pliers) - it's all the preparation, refill and restoration that complicates things. Ping me if I can be of service.

Cheers,
Randy