How long do you keep your freeze plug block heater plugged in?

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Zack1978

Zack1978

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Hey everyone,
My 87 FJ60 is getting a 400W freeze plug block heater put in on Wednesday. Once it is in, how long should I leave my truck plugged in? Can you burn out a block heater, if you leave it plugged in too long? I assume that 400W is good for the 2F?

Thanks,
Zack
 
A loaded question. Depends mainly on ambient temperature and what temperature you want it to heat up to. Typically they shut off around 120 F. Typical around here in NW Montana is 4 hours. Lows are usually in the low teens. You want it on long enough to heat the entire block to warm as much oil as possible, not just the coolant. Put it on a timer and make yourself a "I AM PLUGGED IN" card to put on your steering wheel. Nothing like driving out still plugged!!!
 
It will not hurt the heater to leave it on all night every night.

But even at subzero temps a couple hours should be all you need. Four hours will be plenty.

You won't really warm the oil much. All of the coolant (and the iron of the block too for that matter) is above the oil pan and there is little radiant heat passed downward and little convective heat passed through the sheetmetal of the oil pan.


Mark...
 
Mark W said:
It will not hurt the heater to leave it on all night every night.

But even at subzero temps a couple hours should be all you need. Four hours will be plenty.

You won't really warm the oil much. All of the coolant (and the iron of the block too for that matter) is above the oil pan and there is little radiant heat passed downward and little convective heat passed through the sheetmetal of the oil pan.


Mark...
Click to expand...



Ok thanks! I am looking forward to having instant heat on the VERY cold NJ days!


Zack
 
Sorry to hi-jack but this is near to the subject. I wnat to install a block heater as part of my rebuild, anyone have any thoughts on which plug to install it into? I have a header.
Thanks
Jonathan
 
Second from the front is usually the easiest and there is a bit more room behind it (and the second from the rear) than there is in the end positions.


Mark...
 
Nope. A tank heater dumps most of it's heat into the air around it and the hoses that the coolant has to flow through to reach the block. Block heaters run 400-600 watts. Tank heaters go 1000-2000 watts. Not because the put more heat into the engine. Because they are that much less effective.


The only good use of a tank heater is as a preheater for an intake manifold on a header equipped Cruiser engine.


Mark...
 
If a tank heater is the same as a perculator type that fits into the hose system I have to say mine worked very well to heat the cooling system.
Well enough that I would have, lets say, warm air right away from my heater, and easy starting.
What bugged me about plug in heaters is that after a long cold night without it I forgot how to start a really cold 2F.

devo
 
Yeah, the tank heaters will warm your engine. They just burn a lot more energy to do the same job as the freeze plug style. It works fine, but the ineffeciency of it just doesn't seem right (coming from a guy who loves carbed 2Fs...) ;)

I actually run both on most of my engines. The tank heater is plumbed from the block drain port on a 2F, and to the hoses immediately under the intake manifold fluid heater. The hot water goes through there before entering the block via the top heater hose connection.

This warms the intake and carb and the fuel in the carb very very nicely. The rig will start like it is the middle of summer, even when it is -20F and colder. I can plug the rig in for less than half an hour and it will start right up.

I really like a setup like this. But unless I am using it to warm the intake specifically, I stick with a freezeplug heater.


Mark...
 
I believe a 400w frost plug heater to be adequate for most cold mornings. That's probably what's in my 2F and what I should install or have installed in the 2H. "Instant heat" is somewhat of a joke, unless you go to a high wattage preheater. Even though they are inefficient, they can be quite effective. Back when scientists were worried about anthropologic global cooling, the tank-type heater in my vehicle (not a cruiser) kept the frost off my windshield while plugged in at -40. At that time, the $7 or so flat rate per semester for a UAF parking (and plug-in) permit was well worth the money.
 
The tank heater is plumbed from the block drain port on a 2F, and to the hoses immediately under the intake manifold fluid heater. The hot water goes through there before entering the block via the top heater hose connection.
This warms the intake and carb and the fuel in the carb very very nicely. The rig will start like it is the middle of summer, even when it is -20F and colder. I can plug the rig in for less than half an hour and it will start right up.
Click to expand...
Mark, this sounds great for speeding intake manifold warmup.

Could you clarify the coolant flow path?

I'm visualizing: Block drain port, threaded barb, hose, elec. heater, hose, manifold heater plate, then out to...?
A Tee fitting in the cylinder head heater outlet hose?
 
From the drain port to the tank heater. From the tank heater to a "Y" fittining the hose that is coming from the cab heater. From the "Y" fitting into the manifold preheater chamber formed by the aftermarket blockoff plate. From the blockoff plate to the head.

Keep all the hoses as short as possible and keep the tank heater as upright as possible.

When the engine is running and the heater valve is open, the coolant flows in the same manner as if the tank heater wasn't there (there is a check valve in the tank to prevent backflow). From the head, through the manifold preheat chamber, to the heater and back to the lowerradiator hose to return to the engine.

When the engine is off and the heater is active, the coolant flows from the bottom of the block, through the heater and the preheat chamber, to the top of the head. It then travels downward through the engine and back to the drainport to start over.

The flow is probably more effective if you shut off the valve for the cab heater so that none of the heated coolant can flow that way, but it doesn't seem to hurt things enough to notice if you leave it open.

If the heaters have been plugged in I normally start and drive away without using choke (maybe a small amount just as I turn the key, purely from habit), even at -20F

No stumble and no warm up period waiting for the engine to run right.


Mark...
 
Now I am lost, is this "Y" fiting one you need to buy or is it already on the vehicle? do you have a pic, maybe? The PO installed the intake heater but never hooked it up so I have no idea how it is suposed to be plumbed.
Thanks
Jonathan
 
The "Y" fitting I mentioned usually comes with the Tank heater for any installation. You can use this or use any generic T or Y connection of the right size to connect into the existing hoses.


If you are just hooking up the block off plate for the intake, then you run the hose from the firewall to the plate and another hoise from the plate to the fiting on the head.

The setup I described above is for including an external tank heater in the circuit to warm the intake before the engine is started.


Mark...
 
Thanks
 
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