I couldn't find the main thread about grill blocking. Today I discovered I can drive 70mph in 60F weather and be fine. I assume my thermostat was opening. Was only a 20 minute drive and only 10~ of that was at 70mph. I also have oversized AT tires and a 1.5" lift, so extra drag/load. But yeah, I have the bottom grill fully blocked off. I used 1/2" ID pipe insulation. Had the half cut seam thing. Cut it all the way and then pinched it inbetween each fin space in the grill. I think it was 25" and you need 2 of them. The ends kinda point inwards and that's what secures them. It was putting off heat like never before. Been having some 30-40F mornings and it just struggles. About a 20 minute one way to work. 7 miles, lots of stop lights and such, top speed about 45-50mph. Engine struggles to put out any heat. Even started to drive in B mode because it kept turning off the engine at lights that would only get to 130F water temp. Would turn back on at 120F~ anyways. About 5 minutes into my drive, at 30-40F, it starts to put out some slightly warm air. But by the end of my drive, it still hasn't warmed up the whole car enough to be comfortable. Just wanted to share.
I’ll stick to 50% lower grill block, as long as ambient isn’t staying below freezing. That’s one (1.5” OD) tube, versus two for full block. So far this “winter” I’ve done nothing, it’s been so mild. Helps that we’ve got the block heater. Thanks for the reminder though, I should put in that 50%. one other thing: year ‘round I’ve installed short sections of aforementioned tubing, pushed onto the crimped edges at top of fenders, along the hood side seams. Keeps engine bay air and warmth contained better, but never had overheat. (I’ll post a pic in a bit.) Maybe the thread you’re thinking of: 2010 Prius Grill Blocking strategy | PriusChat
Man our gen3 had no issues making heat 21° weather 18 no problem didn't do anything nothing in front of the radiator none of it course we're not in super cold area here it gets cold for a couple of days and then it's warm for a couple of days and then it gets cold again back and forth back and forth 5 6 7 times in the season And then we're back up into 70° days but the threes never had a problem making heat I didn't even know that was a thing but we are also hot natured we're not looking for 88° in the car generally speaking 73 maybe
Gen4 & newer hybrids have active grill shutters. That may be where some wondered about improving the Gen 3. Blocking the lower grille could have the engine run less to maintain its temperature, improving winter fuel economy.
Pic of aforementioned engine bay tube, plus 50% lower grill block, attached. The latter is secured with Velcro tape: easy to install/remove, and reusable.
Sounds like your thermostat is partially or fully open; there should be minimal coolant circulation into your radiator - if that thermostat is closed; so you shouldn't have to block the radiator. Especially at those mild temperatures. The grill shutters on the gen4 is to reduce aerodynamic drag, not expedite warming of the coolant. Doesn't that gen3 have an EGHE? YMMV
Well, he ran the car for 14 years without having to block the grill at relatively high temperatures. Truckers block their radiators when they're running is subzero temperatures, he's running mostly above freezing temps. I understand the 2010 Prius is suppose to have a 180 degrees thermostat in it, and his engine is shutting off at 130 degrees - so the thermostat shouldn't have opened and blocking the radiator would/should be a moot point - If it's working correctly. If he's going down the highway @ 70 mph, that engine should be ON, unless he takes his foot off the accelerator pedal and the engine should reach 180 degrees - but it doesn't. I just think that replacing the thermostat would've been less than or same amount of work as blocking the radiator, but you wouldn't have to remove the blockage in the spring or summer months. YMMV
I don't normally go 70mph. That day, it was putting off great heat. Engine temp was around 195F maximum and seemed to be opening the thermostat. The vents were putting out H O T hot air. I've only owned the car for 7~ years. These last 4 or so years, I've been grill blocking in the colder months. When I'm doing my work commute, is when it barely gets over 170F at all. Usually towards the end of the drive. It's more around 130F for the majority of the drive. The heater is on high, fan high, feet and face vents. Fresh air, which might be where I'm screwing myself. It just dries out the air so bad even on fresh air.
You can block the entire bottom grill and engine be under 195F but other components that doesn’t have a temp monitor is suffering from higher temp while on highway driving.
And especially when coasting down long hills with engine stopped (or being spun without burning fuel) Coolant temperature drops fast in that circumstance in <40°F weather, even with grill ~50% blocked. Then on the next level or uphill stretch, the temperature might recover to normal, then the yo-yo cycle repeats on the next downhill...
I had no problem blocking the whole radiator with a sheet of cardboard. The secret is to leave a good gap, so the fan can move air when it needs to.
