Radiator Temperature

temp fluctuations are very normal. i block ALL the grill and at 28º F you should be too. in fact i block the entire grill all the way up to 50.

but the engine temp is going to jump around based on how cold it is outside and what kind of driving you are doing. normal temps for me first thing in the morning in winter usually just above freezing. i can take off, driving at street speeds bet 35-40 mph, heat up to 175º turn on heat, and temps will drop down to 165. stop at a light, i will drop another 10º. leave the heat on and i have seen it drop down as low as 135-140.

so, i pulse the heat for the first part of the trip to help heat up the Pri and keep it warm, but unless jumping on the freeway (even here, your car can cool off, just not as much) it will always be a struggle maintaining any real warmth.

Saturday, did a trip of around 30 miles one way, mostly freeway...with heat running most of the time, water temps were ranging bet 180-192 or so. turn it off and temps would peak around 200-201º

today, temps were in low 50's so never turned on the heat at all and did same trip. water temps ran from 200-204... so you can see what a difference running the heat can make.

had a PCD participant who brought some higher rated thermostats and i hope to get mine installed sometime this week, hopefully the will see some progress towards keeping the car warmer longer

 

I have one of them "hot" thermostats. I was driving with the standard thermostat in 48 degrees Celsius ambient and coolant temperature went only to 90 degrees but it was flat terrain. Theory is that once the thermostat opens it shouldn't put any additional heat load on the system, with the scangauge I can keep an eye on it.

 

well i got one because 80% of the driving on the Pri is done at suburban speeds bet 35 or 40 mph. makes it tough to pulse/glide AND keep engine warm especially when temps are in the 30's and 40's F.

if the thermostat opens at a higher temp, its jus that much farther it has to go before i have to turn off heat to allow engine to warm back up (this creates CONSTANT "discussions" with SO who prefers to have it very warm...heck she wears hoodies (long sleeved hooded sweatshirts or zip-ups year round)

which leads to biggest reason why my mileage sucks during winter so much... she is normally the primary driver since i take Zenn....now mileage on most recent tank is good but only because we were on vacation for a large part where I WAS DOING THE DRIVING, otherwise the numbers would be 2-3 mpg lower

 

I just received and installed my Scangauge yesterday for one reason in particular..Water Temp,and my question is..At what temperature would it be deemed critical,that the thermostat had failed and the engine was overheating?

 

oh, i wouldnt worry about it at the very least until you get to 212ºF. i can say for certain, i block 100% of my radiator up until the OAT is 50+F and i have never seen anything above 208

 

Cheers Dave!!

 

A fan should activate to provide cooling. In over a year of having the grill blocked to some percentage my fan has yet to turn on. The highest temp I've seen on the Scangauge is ~190.

 

It's good to know from these post what temps can be regarded as normal operating temps,recently a fellow Taxi driver with 220,000mls+ on his 04[without a ScanGauge] had a head gasket blown,thermostat failed.......Expensive!!

 

From personal playing.... I found that on cold mornings with temps in the any where from -10F to 20F you can have the prius warm up to 175F with the heater in the car of except for a brief period to keep the windows clear. Driving 55mph you can easily bring the water temp down to 130F once the car warms up and stops pulling heat out fo the car you can bring it bake up to 190's while still going in the 55 to 60 mph range. This is with all but bottom most grill openings blocked. going slower you start to get less heat and it can go down.

 

Could you outline what it took to put in the thermostat?

In particular, I'm curious about how to bleed out any air in the heater.

Thanks,
Bob Wilson

 

Mainer,

I've run grill blocking with a ScanGauge for a year now.

What you've experienced sounds typical. Blocking only the upper grill
achieves little in the way of ICE heat retention/warm up. Below 40 degF full
blocking of both upper and lower grills is the way to go.

Road speed would be a surrogate measure. Coolant temps vary depending on
how often and how hard the ICE is actually running. Above 42 MPH, the ICE
is always running and can be relative heavily laded, so the temps stay
above say 160 deg. Around town, below 42 MPH, ICE can run less than 50%
of the time, and is usually lightly loaded. Coolant temp falls and if it reaches
135 deg, the ICE comes on just to warm itself, even if you happen to have 6
or more bars on the HV battery gauge on the Energy Monitor.

FWIW, I left the upper grill blocking in through the summer and only
occasionally and briefly saw temps above 200 degF, never more than 204 deg.

 

Sorry Bob, I haven't put it in yet, I'm going to do it when life is just a tiny bit less hectic.

 

good question. i hope to put mine in today, but having not had a chance to look at the car (remember i went on our family vacation 4 days after Detroit so my at home time has been limited. heck i still have only half unpacked from that and most of the Detroit stuff is still in the pack we were given sitting in den untouched)

but anything we should know?? before i get started. have to have it done in a day (really only have a few hours to do it)

but then again, i guess Ken is the one to ask

 

Searching for prius thermostat spec's--Quote
Japanese Prius Tech Manual says the thermostat specification is starting to open at 82C (180F) and fully open at 95C (203F).
We see the typical coolant temperature is about 88C (190F).
Ken@Japan End quote

Also this one web page shows many Toyota models all having a
82 C thermostat.
http://www.carpartsdiscount.com/auto/partnotes?3593=95918
Search for a 'hotter' thermostat , well I couldn't find any advertised for the prius 04.
Edit I did find a prius chat page that had a link for one, 88 C / 190 F, but it's in Japanese.
http://priuschat.com/forums/knowled...f-you-can-do-improve-your-winter-mileage.html
I looked up the sites Ken suggested in following page, but found nothing at those sites. He also pointed out to a now expired ebay link, I will probably add a search for one on ebay and wait.

Driving today, temps in the 50 F 's , I've noticed by scangauge my engine temperature stays around 184 F / 84 C . I would like it warmer in the car during the cold months, I don't like cold weather. Some cars have 195 F as the open position, and am considering
changing mine, which at 160k + could be due for a change.
As long as the thermostat opens before the engine cooling fan kicks in (at around 200 F ) , good idea? I do grill block, just looking for a little more heat out the fan . I drive the prius delivering mail with the window down, so I'm probably at the extreme, I do realize.


Good or bad idea? I could probably find something with 10 degrees more heat, unsure about doing this.

Edit I did more web searching, looking for hotter thermostats and found this interesting quote
I too had an issue with a 2000 Sienna. I am a mechanic and also ASE certified, so I got less than the runaround that most had. After speaking in detail to the Toyota Tech, the conclusion is that the wrong temperature thermostat was installed. They installed a lower temp version in order to lower the emissions for the engine to pass US EPA for this year. It had to do with the NOX's. Lowering the engine temp caused the oil to stay cool enough and not allow the moisture to burn off the oil. Toyota rebuilt the engine and also installed a hotter thermostat and I have been watching the engine.

Toyota was known to have problems with sludge in their engines, it would seem like an obvious fix would include raising the thermostat temperature. My Buick V6 has a 195 F.
Pushing for the best emissions may be the reason for the slightly lower temperature of the thermostat in a real small engine, U.S. standards of course.

 

If you would like to get the 88C thermostat, I believe Bob Wilson (bwilson4web) has some of them.

Ken@Japan

 

Thanks Ken , I didn't do the right search, source was right here at priuschat
http://priuschat.com/forums/gen-ii-prius-modifications/58207-88c-thermostats.html

 

Like others have posted, I run my '08 with full upper and lower grill
blocks below 50 degF. To help retain heat in the block, I've added a
radiant heat reflector over the front, top, and back of the ICE. It's just
loosely draped front and back, and held in place by contact with the
various hoses, cables, mounting brackets, etc, in the areas.

With the barrier, I've been seeing coolant temps 5-8 degF higher in
urban/suburban driving. I also get faster ICE initial warm-up and
slower heat loss when stopped with the ICE off.

Seems to be helping FE to the tune of 3-5 MPGs too. Haven't done
much freeway speed driving with the barrier yet, so can't say what
effect it would have there.

More on the barrier here, with pictures:

http://priuschat.com/forums/gen-ii-prius-modifications/70513-ice-radiant-heat-reflector-gen-ii.html

 

Driving 55 mph. Outside temp 34 degrees. Input air temp 40 degrees. My coolant temp is about 185 to 191 degrees.

By the way, does anyone know the oil temperature when the coolant is at the operating temperature of 180-204?