Grill Blocking Caution

I have mine arranged in a 90% blocked 10% gap on the right side of the lower grill.

Very important warning! Thanks, Efusco, for keeping track of this.

We aren't getting above freezing for a few days, so I'm not much concerned, but this is a critical warning to remember when Spring rolls around.

Would you be able to add this to the Grill Blocking Summary article? I thing we should include a link there to this posting so people can keep track of the ongoing discussion.

Thanks for the heads-up, Evan! I use the individual slat technique & have a daily commute of ~50 miles. I'll make darn sure I keep at least one lower one clear.

Thanks for the details and warning, I just blocked one upper and one lower a couple of hours ago! The temp here is 15f, but maybe I'll unblock one anyway on my highway road trip coming up soon. I don't think it helps as much for a 400 mile highway drive anyway, does it?

I'm afraid to block the grill 100% when on the highway without the scanguage.

i just blocked the whole grill this evening, went to home d**** and got it for $2. getting worst weather here in CT. so i think i can say its safe to blocked all the grill till february i guess.

will get SGII the next payday

well gee... now that i dont have CANVIEW , cant monitor MG temps. but did have it and never saw temps all that high, and what should be the upper temp levels??

i do have Scangauge and like you, i noticed it hard to keep temps in the 190's where i want them if i did not block all slats which i do and have always done it with individual pieces.

as far as water temps go, i see it at as high as 206-207 frequently, but i dont consider that too high since it never gets beyond that and its not hot enough for the fan to come on and it never stays there very long anyway. to be honest with ya, i often wondered how accurate Scangauge was because the temps always seem to fluctuate quite a bit...

i will say that i rarely drive 70 mph, usually keep it at 60... that is the limit around here anyway so that extra speed might be the culprit

The highest I have ever seen mine with grille blocking (upper 100%, lower 70%) is 195. Most of the time, the thermostat opens around 191.

Apparently, that last 30% makes a huge difference for temp. What does that equate to for MPG?

well to be honest with ya, i did monitor water temps for summer driving with AC etc., and can not find the data but pretty sure that it hovered around 202-207... so apparently the car is programmed to not go over that range under normal circumstances.

keep in mind, we have very mild winters here. after a cold snap that lasted a week, we are currently in south pacific monsoon conditions... since Sunday morning when it was snowing and 33F...the temps have constantly risen so for two days in a row, the high temperature for the day was at midnight. its currently about 60F now. granted 60 is not normal nor is snow... we usually have daytimes running around 45F generally comfortable enough that i wear shorts about 11 months of the year. (yes a lot of people think im crazy)

as far as mileage goes, i am currently in a driving pattern shift. since i got the Zenn, it has become my main car while Linds is using the Prius. three days a week, her commute is over 50 miles with half being freeway because her mother babysits Ry. On tues and thurs, i watch Ry and her commute is just 6 miles one way all city/suburban. The mileage has gone down. last tank needs to be extrapolated since she committed a major sin and did a partial fillup messing up the tank data but it was in the 49 mpg range and this is the first full tank she has driven. ( i drove 45 miles of it)

Following Evan's suggestion, I removed the insulation from the left (NA driver's side) half of the upper row of the lower grill. The rest is blocked. With OAT at 25F, at 60mph and moderate uphill grades my coolant temp. is now regulated at 190+/-5F. Under the same conditions (speed, grade, load, OAT) coolant temp. was previously hitting 204F.

i guess my question is... is 204 too high??? i run it at that a lot...but only when driving more than say 20 miles... most of the time, it struggles to make the 170's and i block everything

Without the technical expertise or experience to back me up, I'd say yes that's too high... I don't think it's designed to operate for extended periods at those temps. A little hotter and your coolant system will pressurize. That could be bad-ish, no?

To quote Ken from another thread:

"Based on the specification of the Prius thermostat, it starts to open at 82C(180F) and it fully opens at 95C(203F).
We saw the normal coolant temperature is around 88C(190F).
Anyway, the radiator is fully working above 203F and is going to a overheating range."

wish i knew... regular ICE's run pressurized most of the time in summer so dont know. regular water boils at 212...with scangauge i can check max water temps for any trip and have never seen it above 208 i believe.

also, it does not stay at that level consistently. it bounces from the low 190's to the mid 200's. to change would require me to remove blocks constantly, since most driving is at suburban conditions and since i am not the primary driver anymore that would not be possible.


*edit* ok so prev post says 203 is the danger point... ok now have to wonder how much stock should i take in instantaneous temp readings because when looking at the temp readings it does bounce around the 203 figure give or take a few degrees

I don't have Toyota data to back it up, but the Prius does use glycol coolant, and normally if it doesn't freeze at -40C it doesn't boil until it gets well above 230F.

-I- think it's safe even at or just above 100C or 212F. It -is - a pressurized system, after all. It's the inverter coolant that could be a problem. I wouldn't want to see that running at 60C or above too often. The higher the temp the less power it can handle before disaster. But I'm sure the Toyota engineers have put in some form of protection for it, such as reduction in use if the temp is too high. I'll bet it gets pretty hot in Texas summer weather.

Shortly after I installed my grill blocking the ambient went up to 20C one day. I saw 105C coolant temps under heavy load. Didn't cause any problems that I could see or feel. But yes, I was worried and was watching closely. The first time is always the worrier.