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You have gotten a lot of advice here, but I had better success using an electric heater that connects to the lower radiator hose close to the actual radiator itself over an actual block heater that fits into a freeze plug location. Being at the low point in the system the warm coolant will circulate naturally warming more of the coolant I think since as the warmer coolant rises the colder will flow down to the heater in a circulating motion. One important point, you do need to make sure that the t'stat in the vehicle is not a completely sealed type. Many t'stats today will have a small ball check in them to let air pass by during a fill but not all. In the past where the design did not include that vent, I drilled a 3/32 hole through the t'stat plate to allow a small amount of coolant to pass through. (do not make the hole any bigger than that or the system will not function right. This will not give you "instant" heat, but my experience is the vehicle will warm up much faster than with a block heater. And as recommended by another member I would put it on a time for about three - four hours before your normal commute time. Good luck
 

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Discussion Starter · #22 ·
You have gotten a lot of advice here, but I had better success using an electric heater that connects to the lower radiator hose close to the actual radiator itself over an actual block heater that fits into a freeze plug location. Being at the low point in the system the warm coolant will circulate naturally warming more of the coolant I think since as the warmer coolant rises the colder will flow down to the heater in a circulating motion. One important point, you do need to make sure that the t'stat in the vehicle is not a completely sealed type. Many t'stats today will have a small ball check in them to let air pass by during a fill but not all. In the past where the design did not include that vent, I drilled a 3/32 hole through the t'stat plate to allow a small amount of coolant to pass through. (do not make the hole any bigger than that or the system will not function right. This will not give you "instant" heat, but my experience is the vehicle will warm up much faster than with a block heater. And as recommended by another member I would put it on a time for about three - four hours before your normal commute time. Good luck
There is a jiggler valve on the thermostat. Looks like it’s intended to flow out to the radiator, and stop flow from the radiator into the thermostat?


It wouldn’t allow much flow, but a little. So a heater in the lower radiator hose may work. I’d be a little worried for a bigger heater it may not be enough flow. And certainly not as good as a pumped heater that’s pumping into and out of the block only, as any flow going back to the radiator would be cooled off a lot. But it would probably be one of the easier coolant heater setups to try.
 

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Discussion Starter · #23 ·
I keep going back and thinking of a pumped coolant heater. If only that second bypass line was rubber, could add a check valve on the second bypass line, then run the heater in series with the first. This would pump heated coolant directly though the block with minimal heat loss to the radiator or anything else…
 

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Discussion Starter · #24 ·
This is the parts diagram for the oil cooler. I don't think a heater installed on these lines would circulate coolant through the block like it does on TDI engines on the Jetta. Both lines appear connected to the same manifold, so I suspect they are using shaped ports on the manifold to cause a pressure differential and force coolant through the oil cooler when coolant is pumping as the engine runs.


I suspect the oil cooler doesn't need a ton of coolant flow so this works fine. But I think if a heater was installed on one of the oil cooler lines, such as the line from 7 to 9 on the following diagram previously suggested, that all you'd end up doing is making a loop of hot coolant to and from the oil cooler, and it wouldn't end up flowing through the engine block. So I don't think such a heater setup would work.
 

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Many t'stats today will have a small ball check in them to let air pass by during a fill but not all. In the past where the design did not include that vent, I drilled a 3/32 hole through the t'stat
Me too, but for a different reason. Heaven forbid the head gasket leaks, any escaping fumes will vent through that small hole instead of pushing all the coolant from the engine. A new head gasket is better than a new engine, simply by having a tiny hole in the thermostat.
 

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But I think if a heater was installed on one of the oil cooler lines, such as the line from 7 to 9 on the following diagram previously suggested, that all you'd end up doing is making a loop of hot coolant to and from the oil cooler, and it wouldn't end up flowing through the engine block.
Well, that is where it is connected in the Jetta and it works really, really well. I have no basis for assuming that the Toyota is plumbed so differently that it just wouldn't work.
 

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I keep going back and thinking of a pumped coolant heater. If only that second bypass line was rubber, could add a check valve on the second bypass line, then run the heater in series with the first. This would pump heated coolant directly though the block with minimal heat loss to the radiator or anything else…
Keep in mind that as soon as you start up the vehicle with the engine side already a warmer the T'stat will open faster, and the colder coolant from the radiator will flow in perhaps giving you a warm then cold effect rather than a steady rising warm. This is also way I think the lower rad hose heater solution could be better as it is warming more of the coolant.
 

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Discussion Starter · #29 ·
Keep in mind that as soon as you start up the vehicle with the engine side already a warmer the T'stat will open faster, and the colder coolant from the radiator will flow in perhaps giving you a warm then cold effect rather than a steady rising warm. This is also way I think the lower rad hose heater solution could be better as it is warming more of the coolant.
How would that be different than normal operation? If I don't pre-heat anything, the coolant will warm up, and the T-stat will be closed until the coolant reaches ~180 °F, where it starts opening. During this time, no coolant has been circulating through the radiator, and the radiator has been in full blast of the cool air, so the coolant inside it will be cold. But we don't see a sudden plummet in coolant temps when the thermostat opens, because it does so gradually, and as cold coolant flows in around the T-stat it will begin to close again if it opened too much initially.
 

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Discussion Starter · #30 ·
Well, that is where it is connected in the Jetta and it works really, really well. I have no basis for assuming that the Toyota is plumbed so differently that it just wouldn't work.
So I found this thread, and from the thread the following diagrams and illustrations:



Is your coolant heater installed in the line running from 18 to 9 in the first image, or 11 to 4 in the second? If so, that's entirely different from the Sienna, as that would flow hot coolant to the top of the engine block, while colder coolant in the block would sink out the port on the bottom of the engine, right into the oil cooler hose. This would create a wonderful heated coolant circulation path that I cannot picture on a convective heater on the 2GR-FE engine.

I did poke at my engine bay more, and it's really difficult to see, but it looks like the return for the oil cooler/passenger cabin heat coil/throttle body is not the same manifold where the coolant is leaving the engine, but rather re-entering the top of the engine block. Looking back at the cooling diagram I posted of the 2GR-FE engine, there's these arrows above the cylinders pointing the opposite way. I wonder if this is the return coolant from the oil cooler/passenger heater core/etc. Where does this go if so? I wish I could find a better diagram!

If this is the case, then yeah the oil cooler line may work well, but maybe it would only circulate through the upper engine block and not the entire block? May be worth a go, borrowing the thermal camera from work and see what happens. Installing a heater may be difficult though, as those lines run under the front exhaust manifold and you need enough vertical run off the heater to get a convective loop flowing.
 

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Discussion Starter · #31 ·
You're probably getting sick of graphs, but here's one more. Probably last one until I get some sort of heater, and then I'll do heater/no-heater comparisons.

Today, there was frost on the windshield, so I started it a bit early. Probably could have scraped it but often around these temps and lower breath starts freezing on the inside of the window, so I decided to just do defrost, especially as I wanted another graph...

Van was idled until I needed to back out to let me girlfriend leave to work, and I parked on the street for a few more minutes. I left the HVAC off completely to speed up warm-up, and turned it on when I backed out into the street. I idled until the windshield bottom half was melted, and drove by ducking my head for a bit, in true midwest fashion. At 06:39, the windshield, which wasn't melting hardly at all despite warmer defrost due to the wind cooling it, was cleared completely by windshield fluid, and the window was warm enough that the residual amount didn't freeze like it does if you use it when the windshield is cold.


It also seems obvious when the transmission is locked up while driving steady at ~64 MPH, as the transmission temp is just flat the entire time, and it heats up when my speed drops, presumably because it unlocked and then heated on acceleration.

On a very rough initial glance through the spreadsheet, fuel flow started around 1 gal/hr and ended about 0.55 gal/hr by the time I started driving. Assuming this is fairly linear and we average 0.675 gal/hr for the 11 minute idle, that's 0.12 gal of gas. At $3.80/gal, that's $0.47 in gas for the 11 minute idle. I can calculate the total fuel used later, or have Torque log that for me on future logs.

For rough comparison purposes, using electricity to pre-heat, electric is $0.13/kWh here, so for the same gas used to idle and warm-up and half clear the windshield, I could have used 3.6 kWh of electricity. So that's like a 1000 watt coolant heater for 3.6 hours, which seems completely longer than needed from what I've read here and elsewhere, if it gets good flow through the engine. Or I could run a 1000 W coolant heater for 2 hours, plus run a 900 W interior cabin heater for 20 minutes to clear the windshield and start heating the cabin, and I'd still be at only 2.3 kWh of electricity, with a warm(er) engine and clear windshield right from the start, and the chill taken off the interior. I'd need a 20 amp outlet though...
 

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My eyes have gone crosseyed from all the graphs, so I haven't read every post. I'll quickly say:

1. I installed the little cartridge heater in the engine block slot. 400 or 500W, not very powerful. I usually run it for 5-12 hours before I leave, using an electrical timer.

In the summer, the engine temp will be a couple ticks above the lowest C temp line. In winter when it's in the 20F's I don't know that it makes much difference at all. Our climate in western Oregon is pretty mild, so I think the block heater is helpful in spring, summer, fall. Given how cheap and easy it was to install, and the lack of risk of coolant leaks, I think it balances the low heat output.

2. I also have a 2000 Jetta TDI with a Frostheater coolant heater. It's super freakin' awesome. One hour of heating will get a nice smooth start. Two hours will get a good temp at first. And 3-4 hours of heating will put the car at full operating temp right off the bat.

Without the heater, in winter, the TDI engine sounds like an angry gnome with a hammer banging on the hood....so I love using the Frostheater. :)
 

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Discussion Starter · #33 ·
My eyes have gone crosseyed from all the graphs, so I haven't read every post. I'll quickly say:
Sorry. I do love graphs. They are the best way to quickly convey lots of information. I should simplify them in the future to just engine temp and throttle position or vehicle speed. I do have a lot on those graphs.

1. I installed the little cartridge heater in the engine block slot. 400 or 500W, not very powerful. I usually run it for 5-12 hours before I leave, using an electrical timer.

In the summer, the engine temp will be a couple ticks above the lowest C temp line. In winter when it's in the 20F's I don't know that it makes much difference at all. Our climate in western Oregon is pretty mild, so I think the block heater is helpful in spring, summer, fall. Given how cheap and easy it was to install, and the lack of risk of coolant leaks, I think it balances the low heat output.
Thanks for the info. I suspect it does make a difference if you watched the OBD coolant temp. I don't think the gauge even moves until the coolant is over 100 °F. I'll try to see when it starts moving and passes the lowest cold line the next time I drive. But if it's a couple ticks above the lowest temp line, that's probably 130-140 °F. What's the ambient temps in the summer when this happens? If you're talking like 70 °F lows, that's still roughly 60-70 °F above ambient. If it's 20 °F, that would imply you could heat to 80-90 °F. Wouldn't be enough for instant heat, but if you refer to my latest graph (I know 🤣) it took 4 minutes of idling to bring the coolant from 30 to 90 °F, roughly half the time I idled the van. So just a block heater, if not providing instant heat, should still cut the time you need to idle to heat enough to clear windshield by a large percentage.
 

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That's interesting about the temp at which the needle moves. I think I'm spoiled from my Jetta coolant heater since it can easily get the car to full operating temp, so I went into the Sienna block heater with overly-high expectations.

Ambient summer temps around here at night would be around 40-55F. Also, I don't drive the van every day. It's more of a camping/projects/adventure vehicle, so it doesn't get driven super often, which is another reason I like to use the block heater when it hasn't been driven in a while, to reduce the wear and tear.

Given how cheap and easy the cartridge heaters are, I'd say go for that first and see how it works for you. If it isn't enough heat you're not out a big investment.

This year I mixed up a 50/50 bottle of 91% rubbing alcohol and water, and keep it inside near the house front door. It melts the window ice instantly when I'm too lazy to scrape. Works great!
 

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Discussion Starter · #35 ·
That's interesting about the temp at which the needle moves. I think I'm spoiled from my Jetta coolant heater since it can easily get the car to full operating temp, so I went into the Sienna block heater with overly-high expectations.
That makes sense.

Also double checked the temp gauge while keeping on eye on live OBD temps. The needle doesn't budge until over 100 °F, and crosses the lowest mark on the temp gauge at 115 °F.

Given how cheap and easy the cartridge heaters are, I'd say go for that first and see how it works for you. If it isn't enough heat you're not out a big investment.
I think that's my current plan.

Well, that is where it is connected in the Jetta and it works really, really well. I have no basis for assuming that the Toyota is plumbed so differently that it just wouldn't work.
Quoting this for a second time... 🤣

While the above diagrams I found for the Jetta certain show it plumbed a bit differently, I think ultimately you are correct. Looking at the oil cooler return line, and the heater core return line, I'm almost certain they do not go into the manifold they came out of, which didn't make a lot of sense anyway, but rather re-enter the engine block. If so, I think they are used to cool the upper portion of the engine block and enter the water pump on the far side of the block.

If this is indeed the case, a heater on the left oil cooler line would cause coolant to rise into the upper part of the engine block, and exit through the water pump manifold. Likely here it would not enter the two main cooling paths lower down the water pump uses to push coolant around the cylinders, but rather rise since it's heated and loop around through the bypass lines across the top of the engine. So it wouldn't heat the lower part of the block directly, but certainly would go through a portion of the block.

I'm hoping to change my spark plugs this weekend, I'll get a really good look at the cooling lines when I have the windshield cowl and intake manifold/throttle removed for the spark plug change, and I'll update then.
 

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Discussion Starter · #37 · (Edited)
Or you know, I could just review the FSM that I've downloaded. While browsing to find the sections I need to change my spark plugs, I happened to open the 2GR-FE Cooling System Diagram.


While the coolant heater on the oil cooler lines may work, I feel like you're apt to get circulation loops through the bypass pipe and/or throttle body. If so, I believe those could be fixed by adding two check valves. One on the No. 1 Water Bypass Pipe, and one on the Throttle Body water return pipe. Then install the heater on the line running up to the Heater Return Pipe.


The hot coolant would rise via convection, enter the Heater Return Pipe, could not bypass via the throttle body, so it would flow along to the thermostat manifold, where the No. 1 Water Bypass Pipe is blocked via the check valve, so it must circulate through the engine to return to the oil cooler line, and the heater. If needed, could add one more check valve on the return line from the heater radiator return line, but I doubt natural convection would be enough to force much, if anything, through that loop, given the long lines and looping route they take. A check valve can be added to the No. 1 Water Bypass Pipe easily, as it has the short piece of rubber hose right before it reaches the thermostat manifold.

In fact, if a natural convection heater setup isn't practical, due to the tight quarters because of the front exhaust manifold, one could add a third check valve on the heater radiator return line. Now, you could add extra hose on the oil cooler return line and use a pumped coolant heater on the oil cooler return line, allowing the heater to be located in a location that may not work for a convection heater. The pump would pump coolant into the Heater Return Pipe, through the engine block, and return via the oil cooler return line. The three check valves would prevent any flow through the bypass pipe, throttle body, or heater core, making 100% of the pumped coolant flow through the engine block, for maximum engine heating efficiency. Such a setup would look like this:


For cases with check valves, check valves with very low opening pressure would be required, and I'd need to verify that they do not restrict cooling flow. But this would allow a pumped coolant heater setup, which I figure would be the best option for fastest engine heating and most flexible installation.

My other thought was potentially using the engine coolant drain plugs as connection points for a pumped coolant heater. The downside of this is reaching the plugs. The upside is you aren't cutting any coolant lines, so there are fewer fittings. I figure for this route you'd use the two cylinder drain plugs (both marked with a "3" in the following image). Connect the inlet of the coolant heater pump to one, and the return line with the heater to the other. Add a solenoid valve that opens when the heater is powered and closes when it's shut off to avoid coolant flowing through the heater when the engine is running. I think I'm leaning towards this potential setup, fewer line connections, no worries about coolant short circuiting through anything as the coolant enters and exits the engine block directly, can put the coolant heater anywhere in any orientation (at least any orientation that allows it to be purged of air). Only problem is I'm not sure where these drain valves are located, or if there's room to remove the valves and put hose fittings instead and route a hose out. I did just see a thread where someone posted pictures of these and how to find them, so I'll look for that thread again.
 

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Discussion Starter · #38 ·
So then, of course, after I figured the coolant drain plugs may be the simplest way to install a pumped coolant heater for maximum engine heating, I wondered “how can I seriously overcomplicate this install?” :ROFLMAO:

So not being able to sleep, I sketched this on my phone…


Background: Another thing I’ve wanted to do is tap into the HVAC blower, and with a solar panel on the roof, run the HVAC blower when the car is parked from the solar panel. I’ll have a solar panel on the roof for my camper van build, but that’s not the point, the point was if I did that I’d need to add an external control to the blower.

So now if you have a 2 kW coolant heater, what if you could just run the van’s blower and heat the coolant going to the heater core in the passenger cabin? I found Thermotion makes a 4 way coolant control valve, that would either loop coolant between each of the two fittings or straight through. It was intended to be used as a heater core coolant valve for OEMs to regulate heat by regulating coolant flow to the heater core, instead of using blend air doors. But it’s rated for engine coolant and is about $90. With two of those, and some hose cutting, a pumped coolant heater could either pump coolant through the engine block to pre-heat it or pump coolant through the passenger heater core, where you could program the HVAC blower to run with the vents on defrost, allowing your coolant heater to also be a cabin warmer or more importantly, melt that windshield ice. Could program a controller to pre-heat engine, switch to melting windshield ice, then back to top up the engine temp before you start your drive to work.

I know, this is crazy overkill. A better solution is to heat the engine block with the coolant heater and wire in an electric cabin heater for defrosting/cabin heat. But, you know, I love considering multiple solutions to help figure out what’s “best”.

Alternatively I could plumb the heater in-line with the heater core return line, with the check valve’s previously mentioned but on the bypass line, and a couple valves on the throttle body and oil cooler lines, like so:


Now the hot coolant flows through the engine block, out through the heater core, and back to the heater before going to the engine block again. Now when running you can both heat the engine and run the HVAC blower to melt windshield ice, or leave the HVAC blower off if you don't have ice but just want to heat the engine. If you don't run the HVAC blower you'd have some heat loss through the cabin heater cores, but hopefully not too much, and the heater core coolant loop would be warmed so you don't above cold coolant through the engine block once you start the engine and the main water pump runs.

Either of these two very overcomplicated setups would be controlled by a Raspberry Pi, which I could use to start the heater, operate the valve, and control if just a pre-heat or pre-heat plus windshield de-ice, probably on a program that adjusts warm-up time with ambient temps plus I could use my phone to remotely tell it to de-ice based in the weather forecast...

Way way way overkill...but I like it still. Or add a windshield sensor to automatically add de-icing...

Or the more practical route with automation is of course the original idea of pumped heater through coolant drain valves, plus an electric cabin heater mounted between the frost seats and blowing at the windshield area, and use the Pi to switch (via relays) between engine heater and cabin heater based on ambient conditions and available heater currents.

Save me from my over-active brain...
 
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