DIY 2nd Gen Water pump replacement

Thanks for the nice write up OP!

I am chasing an overtemp issue in my Taco and have a few questions if someone could assist me!

Doing a search for a 2015 4.0l V6 Aisin water pump I get part # WPT-136 as opposed to the

$116 WPT-802 New Engine Water Pump with Gaskets - Compatible with Select Toyota 4Runner, FJ Cruiser, Tacoma, Tundra

WPT-802 listed here. Aisin's parts catalog shows both part numbers to be compatible but I have also had this issue in the past where parts that do fit the 15' are listed as 'not compatible' and so forth.

Quick rundown on my issue - Texas heat here and I've been noticing towing my boat trans temps have been intemittently getting up to 190-200 and I've been a bit stumped by it (aftermarket cooler). Sitting in backed up traffic last Saturday my A/C stopped blowing cold, I checked my digital gauge and coolant was 210, trans was 185. My dash gauge was still pegged center. I turned a/c off, rolled down windows, threw it in idle and revved it to 1k and managed to keep the temps around 200 doing this until I got moving again. Sitting at a stop light I would hit 195-197 and then drop to 190 once I got moving again.

Flushed coolant system and installed new Aisin thermostat today - Took it for a test drive and tried to simulate sitting in traffic (suns already going down, ambient temp is 102F) and she wouldn't go above 194, trans temps settled at 181, A/C stated blowing warmer air as well. I'm wondering if the water pump might be getting weak?

I redneck tested the cooling fan with a roll of blue shop towels after coming up to temp and could not get it to stop spinning so I think the fan clutch is fine.

 

Very interesting, I'm glad I clicked on this thread. I ordered the WPT-802 from RockAuto months ago planning to do a full service but never got around to installing yet. I just re-checked RockAuto and now they are only showing the WPT-136. I'm hoping that maybe the WPT-136 supersedes the 802 but now I'm questioning this as well...

Edit: Doing further Google searching for "WPT-802" it returns a RockAuto parts search which then redirects only to a WPT-136. I'm guessing this is an updated part but visually they look identical from online image search. None of the sites officially list the parts as cross compatible which is odd.

Edit2: Correction to my previous statement. The RockAuto page for WPT-136 lists the WPT-802 as an alternate part number.

 

Used this and several utube videos as a guide to replace all my coolant system components on my Taco with 200K. It was preventive maintenance but glad I did this as the bearing in the water pump had some play and the weep hole had some coolant buildup.
Some notable notes on this write-up:
Step 4 - since I was replacing the radiator, I pushed the fan shroud back and removed the radiator first, then the shroud, then the fan clutch. Unscrew the fan clutch before removing the belt as friction from the belt will help with unscrewing the pulley nuts.
Step 7 - remove the all the pulleys except the lower one. That coolant inlet thingy with all the little hoses attached to it can be removed for easier access for water pump removal; your pump kit will include an O-ring for the pipe it slides into. That thingy has five bolts, all the same size - three attached to the water pump and two to the block/timing cover, note there is one little hose attachment in the back and but has easy access to the hose clamp. But you also need to remove the air box assembly to access the rear clamp on three of the hoses.
Step 8 - in the first pic which shows the opening in the block, I found thick pieces of FIPG gasket material hanging in the opening. I pulled off the largest chunks. Some of the bolts also had this black material in the threads.

I used blue thread locker all all bolts, but not on the fan clutch pulley nuts. Since you can't fit a socket in there to torque the nuts, I'm gonna pay close attention to those nuts in the future to make sure they don't come loose. I didn't want to use thread locker in case that made it too difficult in removal next time. I realized later I have pink thread locker I could have used.

Components replaced:
Aisin - water pump, fan, fan clutch, and thermostat
Radiator - CSF (not the all alum expensive one)
Motorad - radiator cap
Bando - serpentine belt
Gates - 4 small coolant hoses; I got a fifth but couldn't reach the clamp going in the intake, will replace it when I replace valve cover gaskets
unknown hose brand - Replaced the three longest ATF lines, one from the ATF cooler and two on the trany metal lines. It is 3/8" ID generic oil/ATF line I got some time ago; the hose is unmarked but for the manufacture date (some time in 2017).

This pic provided by @mavfox came in handy for the torque specs.

 

If I read this correctly, you're having trans temp problems and suspect a possible water pump issue. If your water temps are good (Toyota accepts a wide range as "good" and by the time your water temp needle starts moving you are way on the high side and fast approaching NOT GOOD), it's probably not a water pump issue.

How big is your trans cooler? Is your trans cooler installed in-line with your rad? Where is your trans cooler mounted?

If your trans cooler is NOT running in-line with the rad (most are, and it is the recommended routing for most applications), the water pump is not applicable at all to trans temps.

Even if your trans cooler IS running in line with your rad, the heat exchange between the trans fluid and coolant via the rad is not the primary method of cooling the trans - that's what the trans cooler is for. In fact, one of the primary reasons for running the trans cooler in-line with the rad is to help bring trans fluid up to temp faster and avoid overcooling via the trans cooler (trans fluid is designed to work best in a certain temp range).

If your trans cooler is mounted "first" behind the grille (frontmost in the vehicle, in front of the A/C condenser and radiator), it is in the optimum place for trans cooler operation. If you have it behind the radiator or somewhere else with lower air flow, you're losing 15-35% efficiency, depending on what numbers you believe. IIRC Hayden for example says that you get 65% efficiency mounting behind the condenser/radiator.

The only other issues could be 1) you don't have a big enough trans cooler to dissipate the amount of heat you want at the ambient temps you're operating in, or 2) you have a problem with trans fluid flow somewhere in your plumbing, whether it's kinked/clogged lines, undersized openings in hardware like the trans case fittings, incorrect routing of your plumbing (I've seen trans coolers mounted in a closed loop with the radiator before, no actual connection to the trans lol), or (and I am ignorant of the possibilities here) your trans isn't pushing the fluid correctly through the cooling loop.

 

It's a Derale Atomic Cool 13705 - Install thread is here

Cooler is ran correctly, mounted behind grill. I am not saying that the water pump is applicable to trans temps persay. The stock configuration is trans to rad, rad to cooler, cooler to trans; therefore higher coolant temps will cause higher trans temps. If my coolant temps are spiking it will cause the trans temps to spike as well unless I have a large enough cooler to overcome the higher rad temps. My concern, more or less, is that something doesn't seem right that I am reaching peak temps idling. Furthermore I have experimented and watched things closely the last few trips to the lake, In the windy road areas where my truck is shifting a lot I will have the fan running and it helps keep the trans temps down therefore helping stabilize rad temps. I also noticed at long idle periods with fan on trans temps will drop below 170, yet rad temps are still approaching 190-200. I did find that my trailer brakes were hanging occasionally and that was causing increased drag therefore spiking my trans temps. Hopefully I will have my Cummins back up and running by next season and it will be my tow rig over the Tacoma.

For the time being, since we are coming into winter, I am going to leave things be but I would like to address and fix this eventually. If the water pump is indeed failing then I'll replace it but I don't want to throw money at it and get nowhere.

 

10 years from the original post and still going strong! I used it as a guide to replace my water pump and thermostat. Original pump at 292K miles was starting to make high pitched whining noises which probably means the pump bearings were starting to wear out. Took me about 5 hours since I had a hard time getting all the holes in the gasket to line up and had to retrace my steps several times. Now it runs like a clock!

 

I’m confused here. The Felpro 35654 is the o-ring that seals the pipe where the water inlet housing goes. The “gasket” that seals between the water pump and water inlet housing is also an o-ring that sits in the recess of the WP. Both should have come with the kit. I just ordered the Aisin WP from Rockauto and their pic shows both o-rings.