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I have a 2004 Prius 26,000 miles For the past month the pump that puts hot coolant to the engine block & takes the coolant out to store in the hot storage tank. The pump would make a squealing noise when running. I took it to Toyota and they confirmed that the pump has failed. it was replaced and in fine now. anybody else with this failure?

Robin Prius Hoods

I imagine you mean it was noisy prior to failing. No coolant in the ICE could be catastrophic but then again I expect the ECM would keep the engine from starting without the coolant. (I guess it would have to as there would be no indication from the non-existant temp guage.)
I expect anything that runs is subject to failure.

I know of logic error codes with the CHS Tank, but I haven't heard of a squealing pump before. There's always the possibility of a one-off problem...

http://autos.groups.yahoo.com/group/toy ... 022-05.zip
US TSB EG022-05
May 17, 2005. M.I.L. "ON" DTC P1151. 2004-2005 Prius. Coolant Heat Storage Tank error code. check for SSC 40D Engine Control Module (ECM) reprogramming, then apply this reprogramming to fix a logic problem.

I'm glad you posted this. I've recently noticed my pump seems a bit noisier than it used to be. I have about 33.5K miles on my '04. The noise probably occured a few thousand miles ago.

I'll have to have this looked into. Glad I got an extended warranty! If the dealer thinks there's nothing wrong, and it decided to fail at 40K, I'd end up having to pay!

As for engine not having coolant, that's not how it works. The engine always has coolant in it. The engine coolant is exchanged with the heat storage tank. So if the pump failed, but wasn't leaking, you simply wouldn't have a pre-heated engine. Now this probably would flag a DTC, but shouldn't prevent engine run.

The pump was still pumping but was about to fail It was so noisy you could hear it in the cabin with the radio on. now that it is replaced it sounds Great.

The last couple of days I have noticed that the pump sounds "off" from waht I'm used to hearing. Louder than usual. I'm concerned, but I have the extended and don't have that many miles on the car right now, 6,700.

It is noisiest in the morning when I start up to go to work. But when I start up at lunch or after the work day to go home it seems normal. Usually sounds normal at shut down.

Questions for those with tech manuals. How long should the pump run at startup, and how long should it run at shutdown? Assuming, of course, that the temperature point for pump run have been met.

Well, one good news about that pump. It is part of the emissions system, therefore should be covered under the 8yr/100K mile emissions warranty.

A TSB relating to the heat storage (but not for replacing the pump) stated it was covered under the emissions warranty. I think it was the HV ECU giving a false reading, therefore needing replacement. Normally the HV ECU is under the HV warranty, but the TSB had it under emissions.

So did the pump make the car sound a bit like a jet starting up? Mine seems to be getting louder. After work, I open the drivers door, put my foot on the brake, and hit the power button (as I walk around the car opening the hatch and doors to let out the majority of the interior heat).

I hear a pump go, the A/C kick on, then a few seconds later, the gas engine starts. It really reminds me of the batmobile!

I had a leaking water pump about a month ago. Dealer caught it at the oil change. Small leak, but was spritzing coolant into the engine bay. I filled up a couple days before, and I check the oil level at each fill-up, and didn't notice any coolant smell, or see anything. This was the week before I did 900mile round trip (Chicago to BowlingGreen, KY). eek!

The pump had a loud squeal like the sound of a bad belt in a reagular car. The pump is located on the driverside near the fender well. when you first start a cold Prius you will only hear the pump for about 8 seconds. when I took my car to Toyota the first time they replaced the inverter pump by mistake. I think I new more then they did. I havedone a lot of reading in the tech manual

Mine is starting to sound as if there were sand in the bearings. Not too bad, but definitely different than when I bought it.

redbrest,

I'm glad you clarified the sound. That is pretty nasty, definitly something the dealer couldn't ignore or blow off. That is why I'm wondering if I should go in. Right now my pump start up noise is like what Danman describes, like sand in the bearings. Like a grinding noise. The pump only runs about 5 or possibly 10 seconds. I haven't been able to start up the car and time the length of time the pump runs. This is a cold start, meaning the car has been off for a number of hours or overnight. When I park the car after getting to work the sound is more normal, and less disburbing, however the sound is definitly lounder than I remember.

Dan, do you have the tech books? If so, could you look this up and let us know if they say anything about noise and acceptable noise levels. Also what about run times for the pump at startup and shutdown? I'd also be interested in knowing if there are two pumps on the thermos (one for incoming coolant and one for outgoing coolant) or just one pump.

Thanks.

On the whole cooling system (not including the inverter), there are 2 electrical pumps and one mechanical. One electrical pump is to transfer coolant to/from the storage tank. The other electrical pump is to circulate coolant for cabin heat when the ICE is off. The mechanical pump is the traditional one for ICE coolant circulation.

There is a temperature sensor in the tank outlet, so the pump runs until the outlet temperature changes (the coolant that was in the engine and displaced has filled the tank and is now exiting the tank) or a timeout period has elapsed (in case of pump or temperature sensor failure, causing the motor to otherwise run continuously).

From the service manual:
This system uses an electric pump to supply hot coolant stored in the coolant heat storage tank into the cylinder head of the engine, in order to optimize engine starting combustion and reduce the amount of unburned
gas that is discharged while the engine is started. Before the engine starts, the ECM operates the electric water pump to direct the hot coolant in the heat storage tank into the engine, in order to heat the cylinder
head (this process is called ”preheat mode” ). The duration of the operation of the electric water pump is variable, depending on the temperature of the cylinder head. During the normal operation of the engine, the water valve opens the passage between the cylinder head and the heater and closes the passage between the cylinder head and the tank. During preheat mode in which the cylinder head is heated, the water valve opens the passage between the tank and the cylinder head, in order to allow the coolant to flow from the tank to the cylinder head. At this time, in order to warm up the intake port quickly before the engine is started, the coolant flows in the reverse direction.
The sensor for the system, which is provided at the tank outlet, is constructed similarly to the engine coolant temperature sensor and is connected to the ECM. The CHS tank outlet temperature sensor has a built in thermistor, whose resistance varies with the coolant temperature.

I thought I was the only person who noticed this. Mine is a lot louder than when I first bought it too. I was thinking about taking it in to the dealer to have them inspect it but haven't done this yet. I also notice it is louder more than others, and sometimes is starts out loud and gets softer.

Dan, did you end up getting yours replaced?

Regards,
Bit

No, not yet. I doubt my dealer will do it, but I do want them to note it. When I asked them to check the alignment, I think they only took it on a road test and never put it on the rack. I never got a printout. I was relieved to see that it seems to fall under the emissions warranty rather than the comprehensive bumper-bumper warranty, even if I do have the extended warranty. I am fast approaching 36K.

Good idea to have them note it. At least that way if it fails you can prove that the pump was failing before your warranty ran out. Of course this is if for some reason it's not covered under emissions warranty.

I have also noticed it's harder pull on the door handles to open the door. Anyeone else notice this?