How to replace engine coolant pump and thermostat

Thanks Patrick. Based on this post, I've decided to replace the thermostat, but based on this post I'm going to leave the old idler pulley. It should be obvious if it starts to fail and very easy to replace without draining coolant or removing anything else.

 

I've now replaced the coolant and the coolant pump (and the belt and thermostat) and I can tell you that even with all the coolant drained from the drain cocks and the car on a level surface, coolant still remains in the coolant pump and thermostat. Both gushed coolant when I removed them (and both almost spattered into my eye even though I tried to be extra careful after it happened the first time, so I encourage people to wear wrap-around safety goggles) so I don't think we can know if the tech in that video drained the coolant or not before replacing that pump. I would think that if he hadn't drained coolant, it would have kept gushing coolant a lot longer since the radiator is so much higher than the pump.

Using the Lisle funnel, I could not get the air out of the system without running the CHS pump by shorting the relay as Patrick described in post #44 of this thread, so I don't know how it could have worked for the tech. Even the Toyota repair manual says you need to run that CHS pump to bleed the system. On the other hand, I had followed a guide that incorrectly instructed to disconnect the CHS temperature sensor and I forgot to reconnect it, so that may have prevented the car from doing its normal running of the CHS pump and maybe that's why it wouldn't break the air lock. As soon as I ran the CHS for a single second as a test, a ton of air suddenly started bubbling out of the Lisle funnel. I then ran CHS for 30 seconds at a time and it pulled about a quart of coolant in over the next 5 or 10 minutes.

Another thing that video fails to show is connecting a 1/4" ID tube from the radiator bleed outlet back to the radiator expansion tank. I ended up dribbling a ton of coolant from the bleed valve because of that omission.

BTW, if you get a check engine light after doing the fluid change and you use an OBD2 reader to see a P1118 error code, you likely forgot to reconnect the CHS temperature sensor plug like I did. Although, again, you're not supposed to disconnect that sensor in the first place, you're supposed to stop the pump from running by disconnecting the CHS pump power plug higher up on the CHS canister, or disconnect the 12V battery from the trunk.

 

I decided to replace the ICE water pump on my 2006 Prius with 132500 miles yesterday. Once installed and test run, I noticed the new pump is leaking around the new gasket. Any thoughts / ideas on how to fix? Should I remove the pump, add a small amount of sealant to both sides of the gasket to stop it from leaking? Any advice would be helpful!

Thanks,

Mylar

 

Thanks for the reply Patrick! I had installed a new Toyota OEM water pump and gasket. I had a service appointment at my local Toyota dealership to complete 3 recalls as well as check out the AC system. I just decided to let them take care of the leaking ICE water pump as well. They installed a new gasket and put the black rtv around the screw heads, something I did not do. It's no longer leaking but it did set me back an additional $206.44. I most likely could have done the job myself, but I have done significant work to my car over the past two weeks and at this point was ready to take a break.

 

Was the bolt torque properly in the initial installation? First I've heard of this.

 

Not sure. After spending all day working on the car and then to have an issue, I was more than happy to pay the $200 to correct the issue. Below is a picture of the old water pump which was removed at 132k miles.

 

I am about to attempt replacing a gen 2 Prius water pump. I do not have too much experience working on cars but I have read as much as I can about this water pump replacement process. The one thing I need advice on is reapplying tension to the new belt after replacement. I do not have a belt tension gauge and I have read this is an important step. How can I perform this step without a tension gauge? Thanks!

 

Do you have a common reference so I could have an idea about how hard to press? I have no idea what 22lbs of force would feel like if I was pressing on something. Thanks for the response!

 

maybe you could press on a bathroom scale to get the 'feel'.

 

I didn't move the tensioner pulley when I did my '04 pump; I took the pump pulley off first and just stretched the new belt enough to hand start the pump pulley bolts and then weaseled the pulley into place and carefully tightened the pulley bolts. of course you got to be very careful cause you don't want to cross thread your new water pump. tension of the new belt seemed fine.

 

Thanks for the response! I haven't gotten to the repair yet but I do think I will take off the pump pulley. I guess I will bring out a 25lb weight to help me guess for tension. Another question I had was with holding the water pump pulley in place when I need to remove it. Can anyone describe the best method for doing this? I read on this forum that the best way to do it was to use a wooden dowel or something similar to keep the pulley from turning. I couldn't tell whether they were wedging the dowel between a belt and pulley, or inserting the dowel betwee a spoke on the pulley and then wedging it against a solid non moving part? Thanks!

 

Patrick Wong I have a question for you: My water pump was replaced not to long ago. However, I just replaced the 3-way valve for the cooling system and I believe the P1116 code is telling me to replace the thermostat. Can you confirm that the thermostat is on the passenger side of the vehicle, down next to the water pump???? After replacing the 3-way valve (Heater bypass valve), I attempted to put new coolant back in, I needed 1 1/2 gals. I could only get 1gal to go back in. I have read the forums and watched the youtube videos, showing how to turn the water pump on using a multimeter or a wire on the pump relay. Non of those methods worked for me. I tried everyway possible to get the air to bleed out. It just isn't happening. If I run the car, turn it off and let it sit overnight, water still wants to come out of the radiator cap, when I try to take it off. At this point, no more fluid is going in, yet it is 1/2 gal short of what I took out. I went and talked to a Prius tech at the dealership. He said that this is no way to get the air out, that is stuck behind that new valve that I replaced, without being hooked up to the dealship's laptop. This guy seemed like he would tell me if there was another way. All I know, is that I have tried everything that has been mentioned in these forums and I have not had any success. So, before I go pay for an hour labor at the dealership to remove the remaining air, I want to change the thermostat. I would like confirmation on it's location, if you would help me. Thanks, Shane

 

100K maint - 5 shows where the thermostat is located in the second to last picture on the page. He's holding a rectangular mirror in front of a pipe and you can see the thermostat in the mirror. The thermostat is a mechanical device and the coil you see in the reflection is a spring that holds the valve shut. When the fluid around it heats enough it causes it to open. Since the car can't directly talk to the thermostat, it seems unlikely that the car would have any way of knowing if the thermostat needed to be replaced except maybe if it notices the coolant temp hits 176F and doesn't slow down increasing in temperature above that point. The car does have an electronic thermostat somewhere and I've watched the temperature hit 176 quickly and then slowly increase because the mechanical thermostat let coolant start to flow. If you have the Torque app you could perform that same experiment but maybe not if you think coolant isn't reaching part of the system.

When I did my coolant change I used a Lisle funnel and followed the steps shown in this video:

Here's a bunch of notes I took regarding the video and the process:

• Attach Lisle funnel and always keep it filled about halfway.
• Despite having no real seal between the funnel and the radiator throat attachment, the funnel only leaked a couple drops throughout the process.
• Hook a ¼” ID hose up between the bleeder and the radiator expansion tank. You can see the silver tube where the hose can be hooked on above the bleeder if you lean back and look through the hole that allows access to the bleeder.
• Open the bleeder and pour coolant into the Lisle funnel until it won’t take anymore.
• The official instructions say to add coolant to the radiator cap (where the funnel is) and squeeze inlet and outlet hoses a few times to work out air. I did see some air come out when I did that.
• Close the bleeder.
• With your foot off the brake pedal, press the start button twice then press and release the gas pedal twice.
• Press the brake, shift into neutral, release the brake.
• Press the gas twice.
• Press park button (another guide said hold brake before pressing park but I don’t think I did) and press the gas two more times.
• You should get a “Problem” message on the MFD. I didn’t actually see it say “Problem” like in his picture, but it did show a triangle with an exclamation.
• Hold the brake and press the start button to “ready on”.
• It should go into inspection mode where the motor runs continuously and I think it keeps flashing the triangle exclamation.
• When in Inspection Mode, engine speed depends on accelerator pedal position:
• Accelerator pedal not depressed: idle (approx. 1000 rpm)
• Accelerator pedal depressed <60%: approx. 1500 rpm
• Accelerator pedal depressed >60%: approx. 2250 rpm
• Patrick Wong used the above inspection mode but also set heater to MAX HEAT “so that coolant would flow into the heater core”, whatever that means. May as well do it.
• It’s important to run the CHS pump by shorting the relay. Short the relay when the car is off and the pump will run immediately as soon as you touch the terminals. I didn’t expect it to run immediately so I flinched away after the pump ran about a second and yet air and a plume of coolant immediately came out of the lisle funnel leaving faint spatters. It kept going for a couple minutes, draining at least half the funnel into the car. I added a larger black funnel pointing down into the Lisle to prevent the plumes from spattering everything.
• After running the pump for 20 seconds, waiting, and running 10 more seconds, the tone of the pump changed significantly from high fast to slower and lower pitched. A couple mins later bubbles stopped coming out and the pump sounded possibly even lower pitched when I ran it again, spurring a few more bubbles.
• I ran the car on max hot for a couple minutes. I meant to put back the relay but forgot, so I guess it didn’t matter. Coolant in funnel hadn’t changed noticeably. Turned off car and ran CHS pump for 30 seconds but no more bubbles appeared.
• Ran car again for a few mins, ran CHS, no bubbles. I noticed that the first time I’d run CHS, the coolant kept pulsing up and down in the center of the black funnel. But the last two times I ran it, fluid remained perfectly still. So I’m going to call it done. I did open bleeder valve periodically and never saw anything happen.
• Open the bleeder periodically until only coolant ever comes out.
• Coolant came out of the bleeder before I put a hose on it but after I put a hose, nothing ever came out. Wth?
• VIdeo says "Top off the coolant reservoir" (I think he means fill the expansion tank to full) and you’re done.
• Close bleeder to 13 IN-lb. I don’t have anything I can easily measure that with so I just push my thumb pretty hard on the short end of the allen wrench since 13 inlb is pretty meager.

 

P1116 is the coolant temp sensor out of range. That may be because it's in air, not water, if your engine is not bled correctly. It's probably not the water pump. Wait until you get the system bled, see what happens.

You really have to figure out a way to run the CHRS pump. (Is it plugged in? I think the instructions I followed for the valve replacement had me unplug it.) If you can't get the hack to work, buy a Mini VCI. I got that and an old computer for about $50. I wouldn't drive it until you get that 1/2 gallon in, and get the P1116 to turn off.