How to replace engine coolant pump and thermostat

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.

 

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.

 

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.

 

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.

 

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.

 

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.

 

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

 

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.

 

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.