Is my inverter coolant pump slowly failing?

There should be movement in the coolant reservoir, not a gushing, but a definite swirl, I find the best way to check is to carefully remove the cap, and shine a flashlight in and take a peek! Good luck, and welcome to PriusChat!

Edit: When the system is in "Ready" (of course! )

 

Possible? Absolutely.

Without reading the codes stored in the various computers in your car, replacing the pump would be unwise. At the age and climate, the HV battery may also be to blame. That is why it is important to get all the clues the car has to offer before jumping to a repair.

 

IMO, inverter pump produces fluid movement equivalent to a very gentle stream. Some like to describe the fluid movement as "turbulence," which to me entails white water rapids.

You hear the inverter pump and see fluid movement, albeit it's weak by your stadards. It is working IMO. the dealer should have retrieved some stored codes, even w/ the light off.

You can always replace any wear part (ie inverter pump) premptively, to minimize unwanted breakdowns. These pumps seem to last a LONG time, 100K+ miles. For ypur peace of mind, you may want to just replace the inverter pump.

Test health of 12V batt again w/ a greater load.
1) Let car sit overnight again.
2) Foot off break, press Start twice: IG-ON mode.
3) Headlights on HIGH
4) Vent fan on high, AC off
5) Radio on, low volume.
What reading do you get?

12V in ACC mode is light. I bet you'll have a lower reading in IG-ON, with lots of things on.

4-6 years seems to be the unofficial range people get. Some get longer. Consider getting a smart AGM capable charger. You can always do a periodic maintenance recharge to ensure your 12V batt is fully charged, to get as much life as possible.

I remember one person here has a very aggressive and premptively approach to 12V batt: always replaces when the batt is 4 years old.

 

11.2 sounds a bit on the low side! At least 12V under load (head-lights and accessories), and ~13.8V (in "Ready" mode) if the TractionBattery and the Inverter are OK…

 

Found a useful SOC (State Of Charge) chart.
Remember, ambient air temp has a big impact on SOC readings. Cold Winters will have lower number readings than warm/hot Summers. Best to check batt like you have been doing: first thing in AM, which is plenty of time for any recent chargng from inverter to dissipate. Checking too soon after a recent drive will give a false high.

11.2V is LOW. Factory radio would not present much of a load; maybe 11.0-11.1 reading, if radio was part of load test.

Get battery recharged or replace.

Useful to have a charger at home.
Scumacher SSC-1500A/CA, $54.80 at Amazon.

CTEK MUS 4.3, $63.75,

Noco Genius G3500, $59.95,

 

In HawaiI, with the bright sun and moderately high temps, the 12v would not be expected to last more than 5-7 years MAX.

Was the HV battery new from Toyota? If not, don't discount it as a possible cause as rebuilt batteries are often as good a bet as the tables in Vegas.

FIY, you can jump a Prius from most motorcycles, the 12v in these cars is only slightly greater in capacity than many modern bikes.

 

Yup, when customers have no options, dealerships quickly become STEALerships.

 

Why not buy miniVCI ($20-30) from Amazon? Install onto an obsolete 32bit Windows laptop (XP, 7), as a precaution against any malware the hacked Techstream software might have. You will now have dealer leve diagnosis capabilities!

One code reading trip to the dealer is usu a minimum of $100+.

Only do this if you can live with the guilt of using pirated software. If only Toyota would price the software reasonably or do what Microsoft and Adobe do, cheap subscription pricing.

 

Ask co-workers/friends/family if they know anyone in IT (Information Technology). These people will likely have access to obsolete 32bit Window laptops just sitting around, or they will know someone who will likely have a spare collecting dust.

All the mini VCI cables on Amazon, crapBay (eBay), will likely come from the same one or two suppliers in China. It really doesn't matter who you buy from. B/C these are knock off cables, there is no quality control; some cables will work, some will work intermittently due to a bad pin. Ultimately, luck of the draw.

Techstream software is the only way to go, if you want to read ALL of the codes on the Prius. Everything else is junk b/c those universal OBD2 readers CAN NOT read ALL of the Prius ECUs, or misread, and are unable to bleed the Prius brakes. The latest software version will be required for the latest (newest 2018 model year) Toyota. Toyota = Toyota, Lexus, Scion, Daihatsu (JDM); anything made by Toyota, you can read.

 

It doesn't really sound like an inverter coolant pump problem to me. That usually shows up under sustained hard driving in hot weather. You'd be the first person that I know to report it only showing after returning to the car while it had been sitting for 15 min.

I don't think it's related to your 12V battery either.

TBH it sounds more like the traction battery overheating.

- Did the dealers check and clean the battery cooling fan when they did the battery?
- Do you ever hear the fan in the back running at moderate to high speed?
- Is there a lot of downhills on your trip from work to town, and when this has happened have you been parked with a high state of charge (green bars showing on the energy monitor)?

 

BTW. A very easy way to check if the inverter is overheating is just to take a look at the 12V battery voltage in ready mode when this issue happens (while it's still hot).

- If the inverter is not overheated then the 12V battery voltage will be about 13.8 volts or more.
- If the inverter is overheated the 12V battery voltage will be about12.5V or less (as it won't charge the battery while overheated).

This is a simple and definitive test.

 

Yeah, it's sounding more and more like the battery overheating. The battery can heat up when it gets right up to maximum charge levels like that.

When you park the car the battery fan turns off, but the heat is still building up in the pack, so it happens exactly like you said. When you return to the car 15 to 30 minutes later the battery can be overheated. This exact same thing happened to me a few years ago, and when I checked it out, the cooling fan was all clogged up with dust.

One thing seems odd though. In my case, when I returned to the Prius after about 15 minutes the first thing I noticed upon turning it on was that the rear cooling fan came on quite loud (and I know it wasn't loud like that when I had turned it off 15 minutes earlier, so the heat definitely had built up while it was off).

I'm not sure why you're not hearing the fan, but you should make sure that it is indeed working properly. Start by just listening for it after any drive of 20 minutes or more on any moderately warm day. It shouldn't be loud enough to hear from the drivers seat, but if you leave it in ready and just walk around to the right rear door and put your ear to the vent you will definitely hear it humming away. (and feel some air flow). At least make sure that is working.

You should also take a look at the fan and see if it's clogged. Here is a good thread to read on this, and I've linked to some photos I took while cleaning mine which shows the location of the blower. See how much gunk was in mine. Fur and dirt causing major battery problems | Page 2 | PriusChat