Help, nearly no heat!

Agreed! It sounds like the OP already has a means of monitoring temperature anyway.

I would seriously not be concerned about overheating w/grille blocking if OAT is <40 F.

Sigh.... the answers have already been given to you several times in this thread. There have been many others (including at least 1 of the moderators) who have been blocking their grille during cold weather for many years. Go buy some pipe insulation and just do it.

I've been blocking my grille in cold weather ever since I moved to WA state. It doesn't get to <37 F that much nor for that much of my driving though. My drives are generally short now (definitely <20 miles) and I don't have any real problem w/lack of cabin heat other than me intentionally setting HVAC fan to OFF when stopped and coolant temp is <=145F (FWT on Scanguage), to prevent the ICE from running.

I haven't seen FWT in cold weather w/grille blocked get to anything I consider worrisome. (I've looked seen FWTs when living in the SF Bay Area in the hot summer weather, w/o grille blocking.)

 

Dave,

I understand your reluctance to grill block. I didn't do it at first either.

Who knows where any individual car will go when it leaves the factory?
Our little car was designed to operate across a broad range of temps,
from the -40s degF in upstate Minnesota to the 110s degF in Arizona.
But when the car is being operated consistently at one end of the scale,
for you and me that's the colder end, there are things that can be done
to help try to move the operating conditions towards the middle of the
scale. Grill blocking and/or a block heater are two that are typically
done.

The incident that changed my mind on grill blocking wasn't directly
related to the car. I was barbecuing with my Weber kettle on a 20 degF
day. I was using twice the charcoal I used in the summer to keep
temps at 350 degF. I was surprised, so I was idly thinking about
insulating the kettle. Then my eye fell on the Prius in the driveway.

Doh! I realized that in those temps, it too would be loosing massive
amounts of heat, especially when moving due the "apparent wind"
being pushed through the radiator, and around the ICE, "tranny," etc.
I went right out and got some pipe insulation. I block the upper grill
year 'round. I block the lower grill below 50 degF, starting at the top
and adding another strip for each 10degF drop in temps.

I also got a ScanGauge to monitor coolant temps. Now, two years later,
I know that it is rare to see coolant temps above ~190 degF in temps
below 50. So the SG is nice to have, but not essential.

Folks here have tried to put your mind at rest about grill blocking. You
can either take their word for it -- Hint: look at the poster's join date,
number of posts, and number of Thanked posts for a quick reliability
estimate. -- or forget about it. This just something that is part of the
Prius' high efficiency package. The 1.5L engine wastes little gas making
waste heat. If house-like cabin temps are important, then you can't
afford to loose any of the heat in the engine block, tranny, etc. If you
don't grill block though, there is little room to continue to complain about
the inverse relationship of cabin heat and MPGs.
Make your decision, move on.

FWIW, I try to retain ICE heat beyond grill blocking with a radiant heat
shield loosely draped over the ICE:

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

Life goes on, and we're all counting the days to the last day of frost in
our area. For me that's around the middle of March...

 

It occurs to me that if we have a bit of difficulty getting enough heat from our efficient little engines, how the hell are they going to supply heat in the Leaf? From the battery? The range is going to drop to 3 blocks in our current weather.

 

Isn't that why the Nissan Leaf is only being offered for sale in a few western and southwestern states? Maybe Nissan figures that those owners will never need to turn on a cabin heater.

 

Dave,
The Prius engine is much more efficient than engines in conventional cars. This translates to less waste heat, which is what is used to heat the cabin. You may be more comfortable driving a land barge getting 12 MPG that has an easier time providing a cozy cabin.

I drove to work Saturday in 15 degree temps, 27 miles down the freeway at 70 MPH, and while it kept the cabin comfy, the coolant temp never reached 195, which is the temp I see during the summer while driving distances on the freeway.

This is another example of give and take. Part of the cost of the high MPG car is less waste heat and the effects of it.

 

rvndave,

What dealership in Ohio had the right mechanic and solution to your heating issue? Thanks Mike

 

Hi rvndave,

Very interesting. Just goes to show WHY we should all have temp gauges in these cars!!! Its a shame Toyota does not provide them as standard equipment.

 

Great news.

1. Did your mechanic think that the original thermostat was actually bad or did he replace it just to be sure?

2. It sounds like the new engine thermostat is not opening to allow coolant flow to the radiator, if engine coolant temp doesn't get higher than 173 degrees F.

 

Very interesting... I wonder if some of the reports of people w/2nd gens w/poor fuel economy also have this problem.

Too bad, it doesn't seem like any warning lights or codes will be triggered and since there's nor coolant temperature gauge/display. One might only find out via tools like ScanGauge and by stumbling across this problem in cold conditions or having little or no heat.

 

I was wondering about that too. I hope the Prius computer takes inputs from more than one thermistors to determine if the engine is overheated so it won't be fooled by a thermistor stuck in an air pocket.

 

I believe that there is only one engine coolant temp sensor, located in the cylinder head.

 

etf vs. FWT?

Any idea where the engine temperature sensor is? I'm talking about etf and etc at http://priuschat.com/forums/gen-ii-...ist-gen-ii-xgauges-scangauge.html#post950412? It seems that they are reading from two different sensors as the etf sometimes diverges a bit from FWT when I have them both up on my SG.

 

Re: etf vs. FWT?

Yes there are two different temperatures reported by passive CAN IDs and the engine coolant temperature reported by standard OBD message requests can be different from both of them - it may be some intelligent combination of the two "raw" measurements.

See graph below for a short record of the two temperature readings:

The graph shows in the beginning of the drive the coolant T (wT) rose quickly due to the hot fluid from the thermos but also fell back down soon after the ICE starts and mixing cold fluid from other part of the system. On the other hand the temperature of the ICE (iceT) just rose up slowly. So we can be quite certain that one sensor (wT) is in good thermal contact with the coolant while the other (iceT) with the engine block. But I don't know where exactly they sit.

In the beginning of the drive the standard OBD reported coolant T reads close to wT, but after things all warmed up, wT would shoot up higher than iceT, and the standard OBD reported coolant T now reads closer to iceT. I haven't figured out what algorithm the Prius computer uses to combine wT and iceT to generate the OBD reported coolant T.

Now I think of it, since the iceT presumably won't be affected by air bubbles due to its intimate contact with the engine block and Prius "thinks" the coolant T being iceT once things all warmed up, there is less a chance of missing the event of air bubbles causing engine overheat as we were considering earlier. That thought gave me some piece of mind.

 

Thanks for the thread Dave. I bought an '06 recently and even with a 85% grill block it still takes a very, very long amount of time for the car to warm up. I'll have to take it in as well. The other day it was 3 degrees in the am and it took about 30 minutes to get the car slightly warm. Once that happened the temp did rise in the cabin quickly. For as long as I can remember I've never had a car where I could see my breath for at least half my 35 mile commute when the temps are below 25 or so.

 

Consulting the SFI System system diagram on pp. 05-9 - 05-10 of the 2005 repair manual, I see an engine coolant temperature sensor (which is located on the side of the cylinder head facing the inverter), the OAT sensor (located within the MAF sensor mounted to the air cleaner housing) and the CHS tank outlet temperature sensor (located near the CHS canister.)

I am wondering whether the data labeled wT in post #37 actually reflects the CHS tank outlet temp sensor while the data labeled iceT is the output from the engine coolant temp sensor mounted on the cyl head? I doubt that the cyl head itself would show such a rapid rise and fall in temperature as the wT line indicates.

 

The Leaf uses a electrically driven A/C compressor just like the Prius, and adds a reversing valve (Like the PHV Prius does) so the A/C compressor can operate in cool as well as heat mode (heat pump). Like most heat pumps, They probably also have a resistance heater. This will be less efficient, but might be needed for really cold days.