Water pump question

none, if the old one is working, okay, one. the old one won't break

 

I'm changing out the water pump and thermostat with the engine coolant drain and fill at 125k miles. I figure it'll be a lot easier to change them now, since I'm draining the coolant anyway.

I'll be keeping the old pump and thermostat as spares.

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I changed the water pump in our old 2010 around 175k miles .

Did this as preventative maintenance. Toyota says since the pump is magnetically driven that it'll last the life of the car. But there definition of that term differed from mine .

When pulled off, there was noticeable resistance when compared to the Aisin pump that replaced it.

Since the impeller is thin plastic, too much resistance would cause the impeller to fail and the coolant to not flow.

I've done several water pump change outs on the Gen3 and all north of 140k miles. Each one had this resistance, so I'd say what you are doing is a good idea .

Pair a thermostat swap with what you are doing and don't forget the FIPG (Form In Place Gasket) material for two of the water pump bolts.

 

You mean glue so the nuts won't loosen?
The ones with a torque of 26 Nm (letter "A" in the service manual)?
Can the pump be changed by accessing only from the top or does it need a lift? Thanks

 

I changed mine - had a cross threaded bottom bolt to add fun into the mix. easy access from the top or bottom (remove undertrays and put on axle stands / ramps. I also took off the wheel and removed the plastic wheel liner to i could tap the bolt hole and resolve the issue i had with mine. other than that would have been a very easy job.

 

Nope.

Something like this:



I'm not sure which exact ones they are (I don't have the manual available), but in the service manual they are labeled.

I did the replacements without a lift. A lift would make it easier though.

 

The 2010 Repair Manual I am looking in (I am not on TIS at the moment, so it there could have been updates I'm not seeing) does not specify any FIPG when installing the water pump or the water pump bolts.

I also checked the timing chain cover installation section, as it looks like one two of the water pump bolts might do double duty as chain cover mounting (the one that is closest to the top of the crank pulley as pictured below). That's the kind of situation where sometimes you see an unexpected instruction to goop a bolt.

But the chain cover installation also does not call for any FIPG on any of the bolts. It does specify a threadlocker ("adhesive 1324") on two of the bolts, the topmost on the chain cover, nowhere near the water pump.

To be sure, it specifies beads of FIPG all along the chain cover edges, inward of most of the bolt holes, and it's easy for some of that to squish when the cover is installed, so maybe you find some in the threads when you remove a bolt.

The manual specifies two different kinds of FIPG when installing the chain cover. Most of the chain cover edges are to be done in "seal packing black, Three Bond 1207B or equivalent". But the one small loop around the water pump outlet is to be done in "seal packing 1282B, Three Bond 1282B or equivalent".

They are both black, moisture-cured silicones with a three-minute tack-free time that offgas acetone while curing. Puzzlingly, according to this ThreeBond product guide, the 1207B by itself is considered "suitable" for engine oil and for coolant. The 1282B is considered "suitable" for coolant, not very suitable for oil. I am not sure why Toyota doesn't just use the 1207B in both places, but maybe they figured out the 1282B works better with SLLC coolant specifically.

That one bolt I was talking about would end up with a bead of 1282B right above it and a bead of 1207B to its left, so one might find a little of both squished into its threads on removing it.

Also strangely, there seems to be a discrepancy about the bolt lengths between the water pump section and the chain cover section of the manual:



In both pictures, two water pump bolts are special: the As in the water pump picture, which are the Es in the chain cover picture. Those have to be longer, because they go through the water pump and the chain cover to thread into the block. The others don't: the Bs in the water pump picture just go through the pump and thread into the cover, and the As in the cover picture just go through the cover and into the block.

But the water pump instructions say the As are 35 mm, while the chain cover instructions say the Es (the same bolts) are 55 mm.

Moral: pay attention when taking the pump off, notice which two bolts are longer, even if we're not sure how much longer.

 

With an early Gen3 Prius you're better off not wasting your time replacing water pump as preventative maintenance. The issue with EGR valve turning into a blown head gasket and need for regular cleaning and an oil catch can is a much higher priority. Also engine burning oil is something to prepare for... As in you'd be better off buying a Gen4 engine to put it in it first if you want preventative maintenance of replacing the water pump to pay off.