P1121 - Coolant Control Valve Replacement (with pics)

I replaced this valve with minimal coolant loss. All seems well with that fix.

The problem was that I then had all the brake/ASC/ABS warning lights come on, and the brakes behaved badly too. For whatever reason the braking system had got into an odd state, although I do not believe I disturbed anything in that system...
One other forum user reported that he had the same constellation of lights after towing his vehicle with its front wheels on a dolly, and when I did the valve I had the front wheels up on ramps. Perhaps a connection.
Anyway, I had to learn about, buy, and use the Mini VCI cable to perform a reset on the Linear Valve. the cable was not expensive, all seems well, and I now have a new set of Prius debug capabilities!
Doug

 

I know this thread started a long time ago, but I simply had to logon to thank Stomper88 for the helpful information.

There is a lot of great info in the original post as well as the subsequent comments, but I thought I would go ahead and add my two cents on some things that might help others.

First of all, it was a total pain to remove the plastic covers from underneath the car. Most of the touch points are held on with 10mm screws, which were not the issue, but there are plastic clips on the wheel well side. The lower one works just like the ones on the top radiator cover and was no problem. The upper one, however, was a complete pain. It's basically a square shaped cylinder and I had to find a way to squeeze it on the one side in order to allow it to be pulled out of the hole on the other. Super easy to snap it back in once I was all finished, but removing it was a nightmare. I swear it probably took me 30 minutes just to deal with that one fastener. I was tempted to just cut the plastic away or use brute force to just pull it off no matter what, but eventually I managed to get it out (split my thumbnail though - ouch!). If you're planning ahead to do the repair yourself, I would suggest looking into buying a new plastic piece and just cutting off the old one as part of the removal process.

I also think that you either need some sort of lift or should use ramps to raise the front end of the car. I don't think there is any way I could have completed this job without using the ramps I bought (forty bucks at Harbor Freight), but I actually could have probably used a few more inches of clearance.

Regarding the coolant, I tested mine and it was still good, so I didn't feel the need to drain it and replace it. Instead, I tried to use hose pinchers to prevent leakage. It mostly worked, but even with the hose clamps, there was a good deal of coolant that leaked out and constant drips after the hoses were removed. I was worried about this based on reading other posts and made sure I had a drain pan for it in case it leaked and, sure enough, it did. I collected it in the drain pan, then filtered it and set it aside for later.

Another thing is that, even with the special tool to deal with the hose clamps, it was still difficult to remove and re-fit the hoses. There is just not a lot of room down there and the cable needs the right angle in order to work and also be in position to unspring the clamps. Putting the hoses back on was surprisingly difficult, but I eventually got them. I think it helps if you just wait a while. With the tool attached and the clamps not pressuring the hose, it seemed like they opened up just a bit and eventually, they just popped back on.

Lastly, even though I used the hose pinchers, a significant amount of coolant leaked out into my drain pan. I filled the reservoir and the radiator and still had nearly a gallon left. Driving the car seemed fine at first, but I started to get the big red triangle of death due to high operating temperature, so I realized that I needed to get the air out of the system. This turned out to be not too difficult, just use the valve on the top of the radiator and a 6mm hex key to turn it. After I started doing that, I was able to get the rest of the coolant back in. I found this video helpful as part of this process:

since it does a nice job of showing where the bleeder valve is as well as how to put the car into the mode where the gas engine will run continuously. The guy who posted it also said that you can unhook the little hose next to the oil dipstick to bleed the engine block, but I didn't feel like dealing with another hose clamp, so I just used the bleed valve on the top of the radiator and, eventually, it worked fine.

So, anyway, to sum things up, after replacing the part and bleeding the radiator, I once again have a working heater in the car, the check engine light reset itself and I saved myself at least $300. It would have been more, but I needed to buy some tools that I didn't already have to do the work. A local shop quoted me a fee of about $50o and I spent $80 on the part and probably another $100 on tools. From start to finish, it was probably 4.5 to 5 hours of pure working on the car, but it took me from about noon until about 7pm if you add in the time it took to run back to the auto parts store to get the 6mm hex key to bleed the radiator.

Thanks again to Stomper and to everyone who commented and helped me understand what would be involved with doing this work myself.

 

Thanks to all for the accurate and helpful advice, tips, and encouragement to proceed with this project. Just finished my swap this afternoon in about four hours. The water clamp pliers costs $30, three way valve $75, one gallon of SLLC about $25. I did put a zip tie loop through the pipe clamp with the prospect of keeping the end of the hose high enough to prevent unnecessary coolant loss. Not sure if I came out ahead but total loss was around 3/4 of a gallon. Also put just a dab of liquid detergent around the pipe clamps to make them slide a little easier on the rubber hose. Replacement of coolant was straight forward; got about 80% in with the first effort using the inspection mode (plus the bleeder valve) and just a short drive to make a final check after getting in about another 10%. One more cool check and should be good to go. All this started with the typical symptoms at 105,000 miles.

 

Hello, thanks everyone for providing all the information about the problem listed above. I have a question though. What does the valve do and will having it malfunction cause any immediate danger to the engine? Thank you.

 

The valve routes engine coolant between the cabin heater core and the coolant heat recovery system canister. If it fails it will not cause any danger to the engine.

 

Alright, thank you so much for explaining. Now I'm not as worried. Will the heat stop working if it fails? Thanks.

 

Yes, it is possible that cabin heat would be impaired if the valve gets stuck in the wrong position.

 

Thanks again for replying. Do you think it could hurt the pump that moves the coolant to the thermos and back?

 

Probably not. That pump only runs for a few seconds at a time.

 

Alright, thank you so much for your replies.

 

Have the P1121 code. Checked the reservoir it is full, but when I took radiator cap off I could not see a fluid level. All I saw was a piece of black (plastic) shroud partially blocking the fins. Should I fill the (cold) radiator slowly until I see a level?

 

Yes fill the radiator. Then turn on the heater and see if you can burp all the air out of the system. Keep filling the radiator as the level drops.

 

1. You need to determine why the radiator level is so low. The most likely reason is that the engine coolant pump bearing is weeping fluid, look for a pinkish deposit on the inside of the pump pulley.
2. If the pump is at fault, plan to replace it soon along with the serpentine drive belt.
3. In the meantime, fill the radiator, make the Prius READY, turn on the cabin heater to MAX HEAT and the fastest fan speed, and repeatedly rev up the engine for several minutes. You should have excellent heat output from the cabin heater and you should not hear any air bubbling in the heater core. Check the radiator level after the engine has cooled down.
4. Use Toyota Super Long Life Coolant to fill the engine coolant system after the engine coolant pump is found to be good, or has been replaced.

 

eluo, I had to take the kudos offer, after a good laugh! My wife gets so mad that I don't throw anything away, you just never know when it's going to be the perfect tool... even toilet seat screws! Brilliant way to plug those hoses!

 

Mine failed too! I drove around for about 6 months with the check engine light coming on and off at various intervals. The 1st tip off was the nosie the Prius makes when shutting down stopped. No harm to the engine. I finally had to get this repaired in December to pass inspection.

 

Hello, I finally took the plunge and performed the replacement detailed in this thread. I got all the coolant I lost replaced (plus a little more. I hope this isn't a problem :-S) I drove the car around quite a bit and monitored the coolant temperature with my Innova 3040 and I couldn't get the temperature to climb above 170 degrees. I guess that means the engine isn't anxious to overheat (but it is only 36 degrees outside.)

My main concern is with the pump moving the coolant in and out of the thermos. It sounds very different now. I felt all the hoses going in and out of the coolant valve and they were warm. Should I be concerned about the change in sound? If anyone thinks it would help I could try posting an audio recording of the pump.

Thank you everyone!
I really appreciate all the posts that everyone has made to this thread.

 

1. How much coolant was drained and replaced?
2. Did you drain the coolant recovery system canister?
3. If yes, when refilling the coolant did you run the CHRS pump so that the canister will be filled up?
4. Does the CHRS pump sound louder or softer?
5. Does it seem like there is any air in the system?

 

Hey Patrick.

1. About 7/8th's of a gallon was drained and replaced.

2. No, I don't think I drained the canister. I only took the three hoses off the valve and allowed what was eager to to come out drain.

3. I didn't run the pump manually but I have seen where you use the wire jumping method to get the pump to run.

4. The pump sounds louder. It seems like it is running longer than it did before but I am not completely certain of that. It used to run and then finish with a sort of clicking sound. Now it just runs and stops without the clicking at the end.

5. I did hear some sloshing around in the system early on but now I don't. If I listen closely under the hood I hear coolant sloshing through the lines when I start and turn off the car. (When I was adding coolant back in I opened the bleeder valve.)

Thank you so much for help.

 

The engine thermostat is rated to open at 82 degrees C (180 degrees F) so if the cylinder head temperature sensor never reaches that level, the thermostat may not open during the course of your winter driving and you may still have air in the system.

Does the cabin heater work well? If it doesn't, that is more evidence of air trapped in the system.

I think you should try repeatedly running the CHRS pump manually, no more than 30 seconds at a time, to see whether the quality of the pump motor sound changes after running it several times. If it does change, then you were able to get some air out of the system in that locale.

Check the engine coolant level at the radiator cap, in the morning after the engine has cooled down. Do this daily, until the coolant level remains stable at the very top of the radiator filler neck.

By the way, have you inspected the engine coolant pump bearing for signs of leakage? Pinkish antifreeze deposits on the inside of the pump pulley or deposited on the AC compressor housing are signs of a failing bearing. In more severe cases you'll see pinkish spray on the hood insulator pad.

 

I took the car out for an hour drive up one of our area mountains. I managed to get the coolant temperature up to 186 degrees max. I held it above 180 for at least 25 minutes.

During the drive the cabin heater seemed to work fine. It never gets really hot but the cabin eventually does heat up. (I'm not sure whether this gen of prius usually pumps out a lot of heat or not.)

The outside temperature was about 25 degrees this morning.

When I put the car back in the garage after the drive I left it in ready, popped the hood and got out to listen. It seemed like there was a faint motor sound coming from the area where the coolant valve is and there was a much louder higher pitched sound coming from the left side of the engine. This of course was in addition to the always present whine from the inverter.

After noting all this I turned the car off but it didn't make its customary coolant motor related sound. (Is this normal?) I restarted the car waited until it had finished its warm up cycle and turned it off again. This time it made the pump sound and stopped.

I'll see if I can try the manual operating of the pump. Any suggestions for the type of wire to use?

I know it's silly but I'm not sure where the engine coolant pump is; let alone how to get to it. Is there a diagram or something that shows the layout?

Thanks again Patrick for your help.