2004 Sounds Like Teapot

Patrick Wong · 03-22-2008, 06:10 PM

My 2004 has 47K miles. Springtime has arrived in southern CA and the weather has turned warm (high 70's to low 80's F ambient temp.)

I notice that after driving for a while and then turning the car IG-OFF, I can hear a continuous sound from the engine compartment, almost like a teapot whistle. After several minutes, the sound stops momentarily, resumes, stops, resumes, stops, resumes, then finally stops.

This is a different sound than produced by the engine coolant heat recovery pump or the brake pressure accumulator pump. The sound does not happen in colder weather.

I tried to localize the source of the sound within the engine compartment, but that is not easy. It seems to be coming from the engine.

This happened last spring as well, and continued into summer. I replaced the radiator cap. The engine coolant level in the reservoir stays at full.

The presence of the sound seems to imply that higher pressure is venting to lower pressure. Can anyone think of a cooling system location where high pressure & low pressure exist - maybe the electric coolant pump for the cabin heater? The overall system appears to remain sealed since the reservoir coolant level does not drop.

Has anyone experienced this problem before; if so what was the resolution?
Thanks!

galaxee · 03-22-2008, 08:25 PM

hmm, interesting... DH has not heard of this before.
there is nothing in the engine itself that would be pressurized like that when the car is off. it wouldn't be the coolant system, unless it's the radiator cap, which you already replaced.

a brake system pressure issue would kick off the accumulator pump.

there are vacuum lines running to the evap system, but there's not enough vacuum held in reserve to last that long while making that kind of sound.

how long until the sound stops for good?

do you know what temp the engine is reaching when this happens?

Patrick Wong · 03-22-2008, 11:31 PM

Quote:

Originally Posted by galaxee

how long until the sound stops for good?

do you know what temp the engine is reaching when this happens?

Hi Galaxee,

Thanks for your reply & for consulting with DH. The sound probably lasts a couple of minutes; I'll time it next time it happens.

I don't have instrumentation on my 2004 but there's no obvious sign of engine overheating.

I posted to one of the Yahoo Prius groups and heard from a Nevada poster w/ a 2004 who noticed a similar issue.

galaxee · 03-22-2008, 11:41 PM

while he lets that one incubate in the back of his mind, he says you can get an automotive stethoscope and it will help you localize the sound. that will help in diagnosis.

Patrick Wong · 03-23-2008, 12:13 PM

Thanks, Galaxee.

I am planning a drive to San Diego today. When I return home the engine should be nice & hot and I expect to hear the sound again. I am planning the following:

1. Use a length of rubber hose as a make-shift stethoscope to see if I can localize the sound. Maybe the sound is just coming from the radiator cap allowing pressure release into the overflow container.

2. Slightly turn the radiator cap to allow the pressure to vent into the overflow container (doing so without injuring myself). When I vent the pressure, I believe the sound will go away which would prove that the sound is coming from the hot engine coolant system.

IIRC the radiator tank opening for the cap is black plastic. When I replaced the radiator cap last year it seemed that the fit was not as tight compared to my 2001 that had an aluminum tank opening for the cap.

Have you ever been in a motel or apartment where the plumbing was cheaply constructed? When someone is taking a shower, you may have heard the high-pitched sound that the pipes make as water flows through. This is what the Prius sounds like.

Patrick Wong · 03-23-2008, 10:51 PM

The sound does not seem to be due to engine coolant system pressure. While hearing the sound this afternoon I opened the radiator cap and the sound continued.

My next move will be to disconnect the wire connector to the positive jump start terminal in the main relay fuse box, to see whether the sound is produced by a 12V-powered device.

galaxee · 03-23-2008, 11:37 PM

let us know how it goes. one step at a time.

alanh · 03-25-2008, 01:44 AM

Are you using the A/C? The pressure equalizing in the A/C system could cause this sort of sound.

03-22-2008, 06:10 PM	#1
Patrick Wong DIY Enthusiast Join Date: Mar 2008 Location: Green Valley, AZ Posts: 4,052 My Car: 2004 Prius Model: N/A Package: #9 Thanks: 21 Thanked 212 Times in 183 Posts Friends: 44	2004 Sounds Like Teapot My 2004 has 47K miles. Springtime has arrived in southern CA and the weather has turned warm (high 70's to low 80's F ambient temp.) I notice that after driving for a while and then turning the car IG-OFF, I can hear a continuous sound from the engine compartment, almost like a teapot whistle. After several minutes, the sound stops momentarily, resumes, stops, resumes, stops, resumes, then finally stops. This is a different sound than produced by the engine coolant heat recovery pump or the brake pressure accumulator pump. The sound does not happen in colder weather. I tried to localize the source of the sound within the engine compartment, but that is not easy. It seems to be coming from the engine. This happened last spring as well, and continued into summer. I replaced the radiator cap. The engine coolant level in the reservoir stays at full. The presence of the sound seems to imply that higher pressure is venting to lower pressure. Can anyone think of a cooling system location where high pressure & low pressure exist - maybe the electric coolant pump for the cabin heater? The overall system appears to remain sealed since the reservoir coolant level does not drop. Has anyone experienced this problem before; if so what was the resolution? Thanks! __________________ 2006 Highlander Hybrid 4WD-i 2004 Prius 2001 Prius (sold Feb. 2008, 75K miles) 2000 Ford Mustang GT conv.

03-22-2008, 08:25 PM	#2
galaxee resident lab rat Join Date: Mar 2005 Location: boilermaker territory Posts: 9,675 My Car: 2005 Prius Model: N/A Package: #5 Thanks: 0 Thanked 94 Times in 37 Posts Friends: 26	Re: 2004 Sounds Like Teapot hmm, interesting... DH has not heard of this before. there is nothing in the engine itself that would be pressurized like that when the car is off. it wouldn't be the coolant system, unless it's the radiator cap, which you already replaced. a brake system pressure issue would kick off the accumulator pump. there are vacuum lines running to the evap system, but there's not enough vacuum held in reserve to last that long while making that kind of sound. how long until the sound stops for good? do you know what temp the engine is reaching when this happens? __________________ black 2005 prius, a few mods that make me happy g: class of '09 in intense science DH: class of '09 in medical equipment hoping to discover the 'reward' part of the sacrifice-reward cycle soon!

03-22-2008, 11:41 PM	#4
galaxee resident lab rat Join Date: Mar 2005 Location: boilermaker territory Posts: 9,675 My Car: 2005 Prius Model: N/A Package: #5 Thanks: 0 Thanked 94 Times in 37 Posts Friends: 26	Re: 2004 Sounds Like Teapot while he lets that one incubate in the back of his mind, he says you can get an automotive stethoscope and it will help you localize the sound. that will help in diagnosis.

03-23-2008, 12:13 PM	#5
Patrick Wong DIY Enthusiast Join Date: Mar 2008 Location: Green Valley, AZ Posts: 4,052 My Car: 2004 Prius Model: N/A Package: #9 Thanks: 21 Thanked 212 Times in 183 Posts Friends: 44	Re: 2004 Sounds Like Teapot Thanks, Galaxee. I am planning a drive to San Diego today. When I return home the engine should be nice & hot and I expect to hear the sound again. I am planning the following: 1. Use a length of rubber hose as a make-shift stethoscope to see if I can localize the sound. Maybe the sound is just coming from the radiator cap allowing pressure release into the overflow container. 2. Slightly turn the radiator cap to allow the pressure to vent into the overflow container (doing so without injuring myself). When I vent the pressure, I believe the sound will go away which would prove that the sound is coming from the hot engine coolant system. IIRC the radiator tank opening for the cap is black plastic. When I replaced the radiator cap last year it seemed that the fit was not as tight compared to my 2001 that had an aluminum tank opening for the cap. Have you ever been in a motel or apartment where the plumbing was cheaply constructed? When someone is taking a shower, you may have heard the high-pitched sound that the pipes make as water flows through. This is what the Prius sounds like.

03-23-2008, 10:51 PM	#6
Patrick Wong DIY Enthusiast Join Date: Mar 2008 Location: Green Valley, AZ Posts: 4,052 My Car: 2004 Prius Model: N/A Package: #9 Thanks: 21 Thanked 212 Times in 183 Posts Friends: 44	Re: 2004 Sounds Like Teapot The sound does not seem to be due to engine coolant system pressure. While hearing the sound this afternoon I opened the radiator cap and the sound continued. My next move will be to disconnect the wire connector to the positive jump start terminal in the main relay fuse box, to see whether the sound is produced by a 12V-powered device.

03-23-2008, 11:37 PM	#7
galaxee resident lab rat Join Date: Mar 2005 Location: boilermaker territory Posts: 9,675 My Car: 2005 Prius Model: N/A Package: #5 Thanks: 0 Thanked 94 Times in 37 Posts Friends: 26	Re: 2004 Sounds Like Teapot let us know how it goes. one step at a time.

03-25-2008, 01:44 AM	#8
alanh Senior Member Join Date: May 2007 Location: Phoenix, AZ Posts: 1,043 My Car: 2007 Prius Model: Package: #5 Thanks: 49 Thanked 49 Times in 34 Posts Friends: 0	Re: 2004 Sounds Like Teapot Are you using the A/C? The pressure equalizing in the A/C system could cause this sort of sound.