How to replace engine coolant pump and thermostat

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Patrick Wong, Oct 10, 2013.

  1. Patrick Wong

    Patrick Wong DIY Enthusiast

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    My 2004 has 159K miles and I decided to replace the engine coolant pump today. The original pump actually was in pretty good condition but I purchased a replacement last year when my daughter was driving the car, had the oil changed at a Toyota dealership (AutoNation Toyota Irvine [Orange County, CA]), and was told that the coolant pump needed to be changed.

    I told her to decline the service and that I would install a replacement pump. So I ordered a new pump and was ready to go.

    However when I looked at the pump it was pretty clear that it did not require service so I left the original alone at that time.

    Today we had a relatively cool day in the Tucson area so I decided to install the replacement coolant pump, as well as an idler pulley, serpentine belt, and thermostat. I figured it was better to replace the pump at a time of my choosing rather than waiting for it to fail, probably in hot summer weather next year or who knows when.

    I refer the reader to the following two threads:

    My post #18 in the following discusses how to replace the serpentine belt:
    Service Schedule on Serpentine Belt | PriusChat

    My posts #22 and #42 as well as the surrounding discussion in the following thread discusses how to change engine coolant.
    Changing engine coolant | Page 2 | PriusChat

    To gain service access, raise up the front of the car on jackstands and remove the front tires. Remove the engine under cover on both sides and loosen the front of the left front fender liner for access to the coolant heat recovery system (CHRS) canister. Remove the flexible air duct where it attaches to the engine air filter housing inlet.

    Drain the engine coolant by loosening the valve near the CHRS canister and draining into a suitable container. When I did this today, I only got ~4 quarts, much less than my prior experience. I also loosened the engine block drain plug but only got a few drips of coolant out of that plug. I did not try the radiator drain plug.

    I used a 10 mm box wrench to remove the two nuts holding the thermostat cover in place. Tightening torque is 80 in.-lb. I needed to use a pair of pliers to pull the original thermostat out of its housing. When installing the new thermostat, note the rubber O-ring gasket fits around the edge of the thermostat body and the thermostat should be positioned so the "jiggle" valve is at the top. Also note that the new thermostat is inserted so that most of its body sits inside the hole, vs. sticking out.

    I used the 10 mm box wrench and a 10 mm 3/8" socket wrench to loosen the three bolts and two nuts holding the engine coolant pump in place. Tightening torque is 8.1 ft-lb.

    I used a screwdriver to hold the coolant pump pulley stationary when removing the three bolts holding the pulley to the pump. Tightening torque on the pulley bolts is 11 ft-lb.

    No sealant is needed anywhere, during this procedure. The coolant pump and thermostat gaskets work quite well. The coolant pump gasket is made of thin metal and is included with the coolant pump. Make sure you replace the gaskets with new parts.

    When adding new coolant, I used the Lisle coolant funnel which worked really well. That item was discussed on PC around three years ago. Here is a link to a current Lisle model on amazon.com:
    Lisle 24610 Spill-Free Funnel : Amazon.com : Automotive

    I did not run the CHRS pump manually, or use the radiator bleed valve; since I was able to add ~ 4 quarts of new Toyota SLLC coolant using the Lisle funnel.

    Here is an explanation of the photos:

    1. Original coolant pump with very minor seepage out of the weep hole. This pump actually did not need to be replaced at this time.

    2. Serpentine belt with ~89K miles of service. Lots of cracking on the ribbed side of the belt.

    3. Original coolant pump and thermostat, both are in pretty good condition. (The original idler pulley also was in good condition.)

    4 and 5. Shows part numbers of replacement parts.

    6. Shows drain cock of CHRS canister.

    7. Shows thermostat housing cover.

    8. I used a screwdriver to hold the coolant pump pulley in place while removing the three bolts holding it to the pump.

    9. What the engine looks like with the serpentine belt, thermostat, pump, and idler pulley removed.

    PA100015.JPG PA100016.JPG PA100017.JPG PA100001.JPG PA100003.JPG PA100005.JPG PA100007.JPG PA100010.JPG PA100012.JPG
     
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  2. ahmeow

    ahmeow Prius Lover

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    Thanks Patrick.
    Your 2004 is still in good shape. I bought a serpentine belt for some time but I was hesitated to change it myself.
    See when I make up my mind to do it.;)
     
  3. koolingit

    koolingit Member

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    Hello Patrick,

    Thanks for the great post. As usual, you cover things in great detail except for replacing coolant using the Lisle funnel. In the previous posts there was much talk about getting the air out of the heater core, thermos and the radiator itself!

    Could you give a short outline on how things went with the Lisle funnel? How long did it take to replace the coolant from start to finish. Did you have to use any tricks to get the air out of the heater core or thermos? Did having the front of the car on jack stands contribute to the ease of replacement?

    I'm asking because your post leads me to think that what used to be a tedious and difficult task is now simple! Is that so?
     
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes, the Lisle funnel made the coolant replacement task much simpler for me. Note that I had only drained ~4 quarts during this most recent service (from the CHRS canister drain and the engine block drain.) I don't know why more fluid did not come out, I was expecting 6.5 quarts.

    I took the car down from the jackstands prior to starting the engine because I had the car backed into the garage when working on replacing the coolant pump, thermostat, idler pulley and serpentine belt. I didn't want to run the engine for a prolonged period with exhaust gases accumulating in the garage.

    So, after putting fluid into the Lisle funnel and radiator, I lowered the car, drove it out of the garage and turned it around on the driveway which is on a slight incline, which resulted in the front of the car being slightly elevated vs. the rear.

    The Lisle funnel allowed me to replace most of the drained fluid within a very short time, perhaps 20 minutes or so. I ran the engine at full throttle (which does not result in a very fast engine speed when the car is in P) and had the heater on MAX HEAT and the cabin fan at full speed to encourage fluid circulation.

    I did not hear gurgling in the cabin heater core while the engine was on; and I did not hear unusual sounds when the CHRS pump ran, after turning the engine off. That, combined with my being able to replace substantially all of the fluid that I had drained, led me to conclude that there was no need to run the CHRS pump manually or open up the radiator bleed valve.

    I checked the radiator fluid level on both Friday and Saturday mornings to top off the fluid. (It is necessary to check the level in the radiator itself, not just the translucent overflow tank.) Residual trapped air will tend to migrate to the radiator and will become apparent after the engine has cooled down. I only had to add a tiny amount of fluid on Saturday.

    Hence, I think that very little residual air remains, I'll check the level again tomorrow morning. The coolant level should be at the top of the neck when the radiator cap is removed. Then I will replace the black plastic cover over the radiator and declare victory over this project.
     
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  5. koolingit

    koolingit Member

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    Once again, great detail! Thank you very much for the reply. I'm going to order the funnel.
     
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  6. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I think you'll be happy with it. I certainly am.

    When I did this service in the past without the funnel, I spilled a reasonable amount of new SLLC on the ground. I'm not eager to waste new coolant since it costs ~$22 per gallon. Using the funnel, there is no reason to spill any coolant.

    When you are done filling the radiator, the funnel will still have some new SLLC in it. How to remove the funnel without losing that coolant?

    To remove the funnel without spills, squeeze the radiator hose to push some fluid back into the funnel. Then insert the stopper (the long yellow rod) into the top of the funnel to seal the opening. Remove the funnel and set it on the SLLC container. Remove the stopper and drain the new SLLC fluid in the funnel back into the container.

    Then remove the "radiator cap" which the Lisle funnel sits on, and top off the radiator as needed to replace the fluid that had been pushed into the funnel.

    As a side note, I would like to point out that the SLLC has done a great job keeping the engine coolant passages clean. Look at the third photo of the original coolant pump and thermostat and note the metal surfaces are totally clean. Also look at the last photo which shows the two holes that the pump and thermostat mount into, and note they are also very clean. I've just changed the SLLC twice, once at 99K miles and the second time at 159K miles.
     
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  7. koolingit

    koolingit Member

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    I came across a video this morning showing a toyota mechanic replacing a water pump:
    2006 Toyota Prius Engine Water Pump Replacement - YouTube
    What did he use to fill the coolant loop? He makes no mention of running any pumps or heater core tricks. He just said to open the radiator vent from time to time until no more air comes out. If it's good enough for him, it's good enough for me.

    I agree that the SLLC does a great job. You don't mind paying $22.00 a gallon for something that works that good; and they're not telling you have to change it every year or two.
     
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  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    This video makes it look really easy. However, a few comments:

    1. The mechanic apparently did not drain the engine coolant prior to removing the coolant pump. Note the gush of coolant when the pump is removed.
    2. He uses a very large wrench to grab the pump pulley. You must be very careful not to mar the surface that the serpentine belt rides on.
    3. It is not easy to get the new serpentine belt on the crankshaft pulley while working only from the top of the car. I found it much easier to have access to the bottom of the car, which I needed anyway to replace the thermostat.
    4. The video does not show the mechanic assessing the belt tension of the new serpentine belt, but that is something which must be done.
    5. Since it appears that only the engine was partially drained of coolant while the CHRS canister was left undisturbed, it is much easier to purge air out of the coolant loop.
    6. It appears the mechanic is also using a Lisle funnel, or something quite similar.
     
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  9. koolingit

    koolingit Member

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    The main reason I wanted you to see this video was to show that a toyota mechanic was using the Lisle funnel.

    When I see a video like this, I realize I'm just getting the headlines and it helps a lot just to see what he did and how he did it. I didn't care for his use of pump pliers to hold the pulley either but he did put a line of text saying he is careful not to grab the pulley where the belt rides. I think I could come up with a better way -- I'd have to since I don't own a behemoth pair of pump pliers.

    I would also install (or try very hard to install) the belt from the top. I'm a 67 year old whale and would have to think long and hard about getting under the car; for that same reason, I think a thermostat change would have to be done by others.

    If you look at the video again, you'll see the mechanic is feeling the belt with his left hand while tensioning with his right.

    All in all, I thought the video was pretty good. I just wonder how his employer lets him make these videos on the job. Like you said, "This video makes it look really easy." A customer going in for a water pump replacement after seeing this video is going to argue about the dealer's price.
     
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  10. Zedhomme

    Zedhomme Member

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    Here are a couple photos of my 2007 Prius Water Pump with the "pink crust". Dealer noted it at 104,000 miles at an oil change. I changed pump, gasket and v-belt myself at about 109,000 miles when I saw crust increasing. I always figure it's better to do that one before it fails you on the road. Pump replacement about 30 minutes including getting the mounting surface smooth. Refilling coolant and getting all air out took about another 30 minutes. No Lisle funnel. Have a little over 130,000 miles now and going strong.
     

    Attached Files:

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  11. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Thanks for posting your photos.

    I'm surprised to see your original pump apparently has two weep holes. I also noticed your car's original pump is marked "AISIN" compared to my car's original pump with "TOYOTA" markings.

    I agree that your pump needed to be replaced. Good to hear the job did not take you too long.
     
  12. Zedhomme

    Zedhomme Member

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    Patrick,
    The repair manual describes one as the water hole and one as the air hole for coolant leakage.
    The bearing and shaft still felt good, but with that amount of pink crust I decided it was best to replace it.
    V-belt wasn't in bad shape, but same deal. Good for another 110,000 miles.
    I have a friend who was a certified Ford mechanic before he joined the AF that helped me.
    I'm pretty good, but there are some distances working on cars that my bifocals just aren't great for.

    You have a lot of good ideas on tools. I was going to change the hoses and thermostat when I changed the engine coolant, but the clamp pliers with cable I got broke first time I used it on one of the Toyota clamps.
    Any recommendations for a good tool for that?
    My service manager just told me I should return the hoses. He had never seen a radiator hose go bad on a Prius.
     
  13. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I don't have a specific tool for removing radiator hose clamps.

    I would agree with your service manager: at 159K miles the top radiator hose on my 2004 (which is the hose most likely to fail since it receives hot coolant coming from the engine) was still pliable, has no cracking, and therefore I left it alone. I did not try to separate the hose from the thermostat cover when replacing the thermostat.
     
  14. Zedhomme

    Zedhomme Member

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    Sounds good to me. He told me they charge $1100 to replace the two hoses and thermostat and then advised to just return the hoses. He is a pretty honest guy, so I try to throw some business their way so I get a good deal on the next Prius.
     
  15. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Wow, sounds like they are billing more than 6 hours of labor time at $150/hour... That would really encourage DIY.
     
  16. Zedhomme

    Zedhomme Member

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    It definitely did. I did the whole coolant drain myself, just failed the hose replacement when the grommet popped off the hose clamp pliers. Hoses looked OK, so just refilled and bled air. Didn't do the thermostat, but may backtrack and do that. Probably can do it with minimal coolant loss.
     
  17. Chris Dragon

    Chris Dragon Junior Member

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    Hi Patrick,

    Thanks so much for your guides and advice. My pump is leaking liquid at 122k and needs replacement, but I've been wondering why you replaced the pully assembly? That doesn't really strike me as a part that should be likely to fail although I guess it does a lot of rotating... but there's lots of other rotating parts that never seem to fail.

    I can also see the thermostat possibly wearing out, but was there something in the maintenance schedule or elsewhere that made you think it needed replacement?
     
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  18. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Hi Chris,

    If you don't wish to replace the idler pulley, you need not do so. Should the idler pulley bearing fail, it is easy enough to replace on its own. I replaced it because it is not particularly expensive, it had logged 159K miles, and I was working in that area.

    The reason that I replaced the thermostat was strictly due to time and miles in service. The old thermostat was still operational. Again, this part is quite inexpensive.

    The impact of a failure of the thermostat is to potentially cause costly damage to the gasoline engine. If the idler pulley bearing freezes, the serpentine belt will come off. (In practice, you would expect the bearing to make substantial noise before that happens so an alert owner will have lots of warning and time to take action.)

    Does it make sense to squeeze out the last remaining bits of service life to save a few dollars? It's up to you to determine whether your maintenance philosophy is either 1) waiting for a part to fail before you take action; or 2) deciding to replace less costly parts on a preventive basis to reduce the likelihood of unscheduled downtime and potential damage caused to other expensive components.

    The 12V battery is a good example of a consumable part where some owners (perhaps out of ignorance) appear to want to eke out the last dregs of service life, and seem to be OK with being stuck in a parking lot at an inopportune moment. We see many such stories each winter, posted here in the G2 forums. Should you need to replace the battery on an emergency basis you have the obvious inconvenience, and may be hit with markups and service fees that you would not face had you planned the battery replacement to occur at a time and place of your choosing.

    My practice is to keep the battery fully-charged and to replace at no later than 6-year intervals. (For those owners facing cold winters with snow on the ground, 4-5 year intervals would seem appropriate if they don't go to the trouble of periodic supplemental battery charges, especially if they log low miles annually which means the battery remains in a state of partial discharge.)

    I happen to live in an area with hot summer weather and do not wish to be stuck along the side of the road in 110 degree F ambient temps. My interest is in keeping all of my vehicles maintained at a very high service standard, each is ready for a cross-country trip at all times.

    Although I enjoy working on my vehicles, I like to plan ahead so that I don't need to be doing such work when the weather is adverse (whether too hot or too cold.) This is why I replaced the engine coolant pump (and the other parts) in the fall.
     
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  19. Chris Dragon

    Chris Dragon Junior Member

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    Hey, that's a sensible way of doing things. But in my experience, the early failure rate on anything new I buy these days, even when I buy the best reviewed stuff and not the cheapest crap, is at least a few percent. Maybe it's not the same with car parts, but my concern is that you're also inviting risk by replacing components that have been working with new components that may shortly fail. I just replaced my rear shocks and the KYB boot I got was built with a different design such that it would always be getting compressed and would clearly fail within a few years vs the OEM boot that was hard plastic and still sound after 10 years. So I kept the OEM (another lesson is I should have ordered the OEM in the first place). Same with the KYB rubber cushion parts. The new parts were too thick to fit things back together and the hole drilled in one of the parts was off center. One of the OEM front boots I got has what seems to be a permanent crease in it from the factory so I'm not sure it's going to hang right. Quality of things seems to just go downhill over time as manufacturers try to make things cheaper to boost sales or profits, and since we can't see what they're doing inside of parts like pullies and pumps, I think there's more risk of installing something bad.

    There's a general rule with consumer electronics that if they survive the first few months, they're likely to survive for years. It's probably not nearly that bad with car parts, at least not with ones that don't involve electronics, but I wonder. Having recently dealt with returning an Insteon thermostat twice because it didn't measure temperature accurately, I definitely worry that replacing a known-good thermostat with a new one could turn into an early failure of the new one and cause all that expensive damage you hoped to prevent by replacing the thermostat early. Of course if thermostats are expected to last only around 100k, then it definitely needs replacement around then, but what if it's expected to last 300k or longer? In that case I'd feel safer keeping the old one, especially since it's a component that's very hard to notice when it's not working right until something horrible happens. So it would be really great to have some source to look up how long these parts are expected to last.
     
  20. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I understand your concern. This is why I usually will buy only original equipment manufacturer parts and I have not been disappointed yet - over a span of 40+ years starting from being a teenager to now... I have absolutely no concern about Toyota-branded parts.
     
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