2001 Prius Inverter Pump

It has been a long time, 2005, since I last had to bleed the inverter loop. Mostly I remember a container of coolant that over the next week, I would use to top off the reservoir at each stop. Eventually, the level stayed constant. It has been long enough, I probably need to flush the engine and inverter coolant as well as have the brake fluid tested.

Bob Wilson

 

Hello everyone. I'm new to the forum and would like to start by saying thank you to you all. I've been pouring over many treads since recently purchasing my 2001 Prius. I bought the car for very short money since it has a transmission overheating issue. The car has just over 138k on it and it isn't in that bad of condition. Got some dings and banged up bumpers but since this will be a commuter it's fine with me.

One of the first things I did when I got the car home was pop open the hood and look for anything unusual and obvious. The only thing I noted at the time was the inverter coolant was low. What I didn't know was that the inverter and transmission had the same coolant reservoir. I immediately emptied the transmission lubricant having read so much about this on the forum. A couple interesting notes here. First, the pan was new, or newer at least. It still had the stickers from the dealership on it so I knew it wasn't that old. Draining the fluid I found it to be pitch black and smelled something awful. Getting the pan out I found a lot of sludge on the bottom. I found no large metal chips or shards but lots of metal flake. I also noticed there was no magnet in the new pan. While I had that apart I decided to pull apart the lubricant pump and take a look at it since it was so easily available. All looked very well there. I cleaned up the pan, added a magnet, re-installed, and filled the case with the Type IV lubricant. Test run.

All test runs are done on the highway which is only 10 minutes from me. After 10 minutes on the highway I got my alerts of the overheating. This was just as I was told by the PO.

OK, so lubricant must not be the issue. I'm really hoping to find the issue without having to replace the transmission all together.

Back to the forum and more research anywhere I could find info on the web. I then realized that the inverter reservoir was also related to the transmission and there was a transmission radiator as well. I went to my local Toyota dealer and got the SLLC as required. I topped off the low reservoir and went for test ride #2. Same results but I found the coolant level low again when I got off the highway after receiving the alert. At home I found the drainplug leaking, albeit only dripping. Thought maybe the system is under pressure whence driving and that drip could be a stream under load. New Al washers and an extra container of SLLC just to ensure I won't need another trip to the dealership for awhile, so I hope. Completely drain coolant, looks good and clean. New washer. New coolant. Try to bleed system as read about in the forum with little success. Test ride #3 with lots of stops and checking the system for leaks and lowering fluid level. All looks good. Hit the highway, same results. Although I don't have temperature probe I notice that the coolant level is high in the reservoir and it's not hot at all to the touch. Limp back home.

Tear into front end. Pull bumper partially off, headlight out, and checkout the pump. Pump appears to come on as it should. Doesn't have strange sounds that I know of. Can look inside and see it running when lines removed. Run compressed air through the lines checking for blockages, none that I can tell exist. Further research tells me the pump can appear to be working normally but may not have the appropriate pressure or can stop running while driving. The reservoir doesn't show any signs of turbulence, I can't feel any in there as well.

A new pump gets ordered from MetroToyota in Cleveland, best price I could find online. The pump that's ordered is the newer part number but when I receive it I'm very concerned as it looks exactly like the one in the car. Maybe the original pump has already been changed? I get the new pump in and the fluid refilled. This time I use my handheld vacuum pump to pull the air out of the bleeders. Turn the key to "ON" and I hear a bad noise coming from the new pump. Reach in and feel it vibrating and give is slight shake and it goes away and can hear the pump start moving fluid. Clearly this pump has issues right off the shelf. Metro gave me no problem and a new pump is on it's way now.

That's where I stand now. More to come. Thanks for reading if you made it this far...

 

The stator windings for either of the two MGs (usually MG2) can develop a short. When that happens, they will overheat. How does the car drive? Does it make any kind of humming sound that varies with speed and does not stop when rolling in N? Does it feel at all 'coggy' at any time?

Do you have any of the Prius-capable scan gauges able to read codes from the HV ECU?

Which of the service manuals do you have (volumes 1, 2, the wiring diagram manual, the new-car features manual), or do you have a techinfo.toyota.com subscription?

It sort of looks as if the PO had a problem, maybe had a shop take enough of a look to guess how big a problem, then unloaded the car on you.

In the manuals there is no procedure to correct a winding short (if that's what you have) other than to replace the transaxle. (It's possible to buy the two transaxle MGs individually, but Arts Automotive did it that way once and decided the shop time to properly reassemble the tranny after MG replacement cost them more than putting in a complete unit - you can find the story on their website.) Others have since developed a technique for replacing only the MG2 stator if that's what the trouble is. Jack Rosebro developed the technique and it's been written up by Carolyn Coquillette of Luscious Garage (they also made a video). You need to obtain a complete MG2 to harvest a stator from, but a lot of the labor can be avoided.

A first step would probably be to have any codes read from the HV ECU if you haven't already. You also might see if you can obtain service history, for example to find any notes made by the tech at the time the transaxle pan was, apparently, recently dropped.

Good luck!
-Chap

 

Thanks for all the good info Chap.

How does the car drive? Around town it's absolutely perfect. Seems as though I could go all day without incident, it's only on the highway. No humming sounds that I can distinguish or coggy feeling either.

Do not have the scan tool to read codes but think I'll bring it to Autozone to have the codes verified. Mr. Wilson let me know of a few scan tools that are good options to pick up so that may happen if I can find a deal on any of them.

Due to my serious frugal-ness I have yet to pick up any service manual other than a Hayes manual which is relatively useless, but I did learn a few things from it. I'm keeping my eye on a pair of manuals on eBay for about $115. No subscription either...

The PO had the problem, she brought the car to a local dealer and they told she needs a tranny swap. I knew this going into it but couldn't say no to the car for a mere $1K.

Before taking the tranny out I'll be sure to have the lubricant tested in Tampa as has been suggested by Mr. Wilson. Actually I need to get going on that...

She gave me all the service records she had, and her Dad before her. I've scanned through them quickly but need to comb through them carefully.

Hopefully the new pump is in tomorrow.,

 

When the pump is working correctly, there is a level difference and evidence of turbulence in the resevoir. Do you see any?

FYI, great photos of the pump swap out.

Bob Wilson

 

Not only do I not see any level difference, I can't feel any flow in there when I stick my finger in there. Also, I evacuated out the pink SLLC in the reservoir and put in yellow/green coolant in there with the thought that flow would be easily observed and the coolant in the reservoir would immediately turn pink. No color change at all with the old pump...

Thanks for the kudos

 

Heck no. At that rate, if it's in otherwise sound condition, you can afford to put a tranny in and not look back.

I do think, though, that trying to make do without the Toyota service manuals is a false economy.

It sounds as if you don't have symptoms of a coil short, but from your description your coolant flow seems blocked even with a functioning pump. A contributor, hobbit, has described a gelatinous substance that can be found between the fins in the coolant passages. I read that an early step in aluminum corrosion is the formation of an aluminum hydroxide gel (and I'm pretty sure I've seen and felt the stuff, when I changed the anode rod in my water heater at home recently). It dries into the white crystalline form familiar on dry corroded aluminum.

I guess if your coolant passages were very heavily gelled you could see the things you're seeing. I can't really think of much else. (Kinked hose somewhere?) Badly bled system, maybe, but I'd think it would have to be so badly bled the pump was actually airlocked, before you would see no flow at all as you seem to be describing.

-Chap

 

Chap-
Excellent assessment! Yes the books are a must. I just received the second pump today but the boy's baseball got in the way of installation, that always comes first . So tomorrow night I'll get the pump installed. If I find no obvious flow in the reservoir then I'm taking out that radiator and testing that in the sink to see if I can get water flowing though it. There's one on eBay now for $80. I have noticed some chatter in inverter cooler relay...

 

Good news I think. I installed the new(er) pump tonight. Bled the system with the Smityvac. Pump sounds very quiet. I see flow through the reservoir. Test drive will need to wait until tomorrow though.

In the meantime I still have a low coolant light and a check engine light to think about. Both ICE and the inverter now how have full coolant levels. That coolant light (blue not red) didn't pop up until I fooled with the fan switch on the radiator. Hoping I didn't kill that switch, all I did was disconnect and reconnect the electrical connection, I didn't remove it. Maybe it'll clear up with the test drive... I think I'll take the test drive to Autozone tomorrow and get the codes read there.

 

it's normal for that blue coolant light to be on until the coolant has warmed up to about 50 C, no worries there. (It's not a low coolant light, just a low coolant temperature light.)

If you're sure you never saw it before fooling with an electrical connection, then your fooling must have actually fixed it.

-Chap

 

Thanks for the good news Chap! Still haven't got the test ride done! The boy's baseball and a visit by the in-laws tied me up. Tomorrow for sure! On the flip side, my bro-in-law hooked me up with a softcopy of the Prius manuals. I have to dig through them a bit...

 

Hi -- I am totally new to this forum and would like to ask question. I have a 2003 Prius, runs excellent, 206,000 miles on her. 206,000 -- not a typo. I backed her up a long drive way, steep hill and the "Dont' Drive" icon came on. Immediately turned off the car. Turned it on again a few minutes later, light still on, left it off. Waited a few hours and started engine again, light still on, turned engine off. Had it towed on flatbed to Toyota dealer. Was told it is possibly the inverter cooler pump. Was told it needed to be replaced and the inverter itself could be damaged, which would be approx. $3800.00 to repair. The pump will be approx. $468.00 (labor included I believe.) I would like to know, do you know the possibility or probability of the inverter system itself from actually being damaged from what I described. If it is damaged, I don't think I want to put close to $4200.00 in repairs in a car with 206,000 miles on it and ten years old. But if the probability of it being damaged is low, I would consider spending the $468.00 as I don't have a ton of $$ to spend on a new car or newer model at this time and really need the gas mileage.

Your thoughts and input would be greatly appreciated. P. S. I am woman with no mechanical experience, but would appreciate some solid advice.

Thanks in advance -- Emasfalcon

 

P. S. I am posting this here as I did not know where to post this request and you sounded like you have way more experience then I do in this area. Again, thanks in advance for your help.

 

Put that aside, there is no male 'mechanical' gene. One of the best independent Prius shops is Lucious Garage.

The Prius does not have a reverse gear but uses the large MG2 motor. Going up the hill would have heated MG2, the power electronics, and put a heavy load on the traction battery.

I wished you let the engine continue to run and then tried to move the car. Some things to share:

• An error code will show up and light warning lights but after three starts, the car will suppress the error lights (assuming the original fault went away) yet keep them in memory. The magic number is three starts.
• You've done this, backing up a hill with this car, before?
• Did you try to put the car in "D" and move it? This lets us know if the fault was temporary or permanent.

The pump is reasonable. We know it is a weak part that needs to be replaced along with the coolant. If you haven't had it done, ask about the engine coolant and transaxle oil.

I would ask the shop . . . 'Does the car move on its own from one parking place to another?' before doing the inverter. But if the inverter is bad, I would also wonder about MG2. If the car does move from one parking place to another, the inverter and systems are still working.

If the car moves about their lot, after replacing the inverter pump, there are somethings we need to know:

• Does MG2 run cooler than MG1 after driving around the city for 10 minutes? - this means MG2 is OK and the inverter OK too.
• What are the 19 module voltages? - this is looking for any weakness in the traction battery.
• What is the 12V voltage when the car is on? - looking for 13.8-13.9V which means the inverter 12V charging circuit is working.

The problem is you may have difficulty negotiating this with the service staff. But if they can replace the inverter pump and you can drive the car off the lot, we can address these specific questions later.

BTW, if you'll update your profile location, we may be able to recommend some independent, Prius shops.

Bob Wilson

 

Well test drive number 4 was completed today. There are multiple good news items to report.
1. Prior to test drive the car was warmed up and the blue coolant light is now off.
2. Prior to test drive the check engine light is now off.
3. The car was on the highway for 15 minutes before any warnings came up, a new record.
4. After the warning lights came up I pulled over in a rest area and popped the hood while the car was still running. I saw the coolant flowing through the reservoir with high flow as it should be. Never saw this before.
5. New pump still nice and quiet.

So next step is to go to Autozone and have a code reading done to verify what codes are coming up.

 

Get a Prius-aware scanner. There are half a dozen control computers holding the detailed error codes that tell is what is broken. The over-the-counter, Autozone scanner will only show some but not the detail needed to fully diagnose the problem(s.) A Prius scanner will pretty much show exactly what is wrong.

Bob Wilson

 

Shopping around for one now. Any suggestions where to find one?

 

The ones I know work:

• ScanGauge II ($150) - requires adding XGAUGE definitions which are as difficult as sending a text message with a cell phone.
• AutoEnginuity ($500+windows PC) - a supported package, works, I bought and used it for years until a Windows virus wiped out Windows XP.
• miniVCI ($35+windows PC) - a Chinese hack, it took about 10 days to arrive.

There are reports of others but I have not personally tested them. Search this forum for reviews.

Bob Wilson

 

OK guys I received the miniVCI and have loaded the sw on the computer. Hoping to get this up and running this weekend and see what codes are coming through.

 

Good morning all, newly joined PriusChat after lurking it seems forever (bought 1st NHW11 new in 2002, now on 2nd copy since 1st written off). Have (tried to) read all threads on this topic, and this seems the best one to add to - certainly the most obvious title!

My HV pump failed suddenly a few days ago causing a turtle/triangle. No DTC info cos my Graham miniscanner is still at v0.41 - must update that soon. Since I was away from home in the middle of the night I just turned the car on and off 5 times then noticed a red thermometer which only lasted one second. Checked with the miniscanner and found MG1 and MG2 inverters over 100C. Waited for them to cool and proceeded, watching temps on miniscanner.

Here are my contributions to science. After resetting 5 times, you get one flash of the red thermometer but it doesn't stay on. When driving with a failed pump the MG1 and MG2 inverter temps rise much faster than the MG1 and MG2 motor temps. You can drive indefinitely if you minimise use of the elec motors - gentle accel and as much braking on "B" as possible. That's watching the miniscanner and keeping the inverter temps below 81C (outside temp is 25C). Note that regen braking heats them up just as much as heavy pulling.

The turtle/triangle comes on when MG1 inverter reaches 110C. I only did this once, accidently, before I realised that regen braking was to be avoided, so cannot say whether it's a repeatable absolute limit or based on some temp difference. Sure feels strange trying to use the ICE and avoid MG1/2.

I don't have a new pump yet, so cannot remove the old one. The failed pump measures 1281 ohms from IG2 pin 3 to ground. I unplugged the pump and checked each wire for continuity and they are good. I've jiggled the connection and tapped the pump but no change. The coolant was bled properly some while before the incident and is still full, but of course no turbulence (and no pump vibration).