Circulating Tank Heater

[Brucey]

Instead of going the regular route with installing an OEM block heater before winter, I went with a universal circulating model:

Amazon.com: Kat's 13100 1000 Watt Alumininum Circulating Tank Heater: Automotive

Amazon.com: Kat's 13100 1000 Watt Alumininum Circulating Tank Heater: Automotive

Why?

Two reasons:

1) It's 1000 watts versus the 400 watts OEM style. This should give much faster warm up times for me in winter and make it easier for me to use it if I know I'm about to go out. I don't always leave at the same time 7 days a week, so I can use a timer for some of it, but I would like it to be a real boost if I know I'm going to leave in 30 minutes.

2) The circulating kind seem to perform much better. Most reports on this model is it's powerful enough to melt snow off the hood and windshield, and full heat is there in your driveway. And well, that'll hopefully be nice when it gets to 0 again this winter.

Anywho, I started looking at the instructions and it looks like I "Y" it into the heater hose and the lower radiator hose or the coolant block drain plug. This bypasses the thermostat and allows it to warm everything in the engine block, as it circulates the entire line.

Now onto my problem:

I'm having a hard time finding the coolant block drain plug. The only one I found on the block is the massive freeze plug where the OEM block heater would go. I thought there was a smaller one in the 14mm range based on this thread:

My latest subaru engine improvement - Ultimate Subaru Message Board

But mine aren't there. The FSM isn't much help.

So basically, where is the block drain plug?



Edit:

Here and Here are the install instructions.

[rockhopjohn]

Circulating is definitely the way to go. I had one of the OEM block heaters on my 1998, and I don't think that **** thing did anything. I have always heard that with the circulating units you pretty much have heat on startup on those cold morning.

As for the drain plug? No idea, I have only messed with the honkin' big freeze plug.

[Brucey]

I'm having a bithc of a time finding it. I might end up tapping into the lower radiator hose but I'd like to avoid that if possible, the thing is already going to be pretty tight in there and having it on the lower hose would mean it has to mount even lower than where I've got it planned.

[plain OM]

Hmm. The heater instructions seem oriented to vertical cooling system engines (6, 8, perhaps 4) with the t'stat at the top of the block, and the lower rad hose having a clear flow path into the lower block.

But in the Subie, the lower rad hose-to-block flow path is blocked by the t'stat. So unless the stat gets hot enough, using the lower hose will not provide any circulation through the block.

Never saw a reference to a readily accessible block drain on the Subie, other than the large plugs on the bottom (where the oem block heater would be installed.) I'm not sure what the USMB thread means by "head plugs" that were drilled out to provide fittings. I'm thinking the reference is to those large plugs, and basically a smaller fitting was tapped into them. In other words, the large fitting that is removed (screws out) to install the oem block heater is where the smaller fitting for the drain was installed.

From the USMB thread:

" . . subaru made the cyl head plug on the driverside useless, because if you want to drain that side, it still pours all over the crossmember, exhaust, whatever... either way I wanted to be able to drain the coolant without getting my torso covered in ethylene glycol!

"I started by drilling the head plugs (on a lathe, I know I am spoiled), and then I tapped the heads to fit standard 1/8 pipe thread, so I could fit brass hose barbs in them.

"Put on new gaskets and some #1 sealant on the plugs, but used more of a teflon based sealant on the brass threads.

"Then I ran the hoses out in front at the bottom of the radiator, and joined the two sides with a Tee, and then attached another length of hose with a petcock."

[Brucey]

I'm going to try the monster bolt then. I'll get an extra one while I'm out tomorrow so I can work on it first before busting the car open.

I think I can drill and tap it for an elbow barb fitting, put it in the car, then put in the barb. I'll probably do this on both sides to get even block heating.

[plain OM]

I wonder if there might be another approach that could be easier; namely, reversing the instructions' use of the heater "in" hose and the lower radiator "out" hose (or block drain plug).

The instructions' use of the cabin heater "in" hose and lower rad hose is, again, to provide open flow paths through the block for the coolant warmed by the block heater. In the traditional approach (note instructions reference to the "arrow" on the block heater), I believe coolant is heated and pumped up to the "Y" in the cabin heater hose. It then flows "down" in the block till it gets to the lower rad hose (or the block drain plug fitting) where it returns to the lower side of the block heater.

Because of the boxer's reversal of the t'stat position, it would seem just a matter of reversing the connections. The cabin heater outlet (drain) hose goes to the inlet of the pump (also the engine side of the t'stat), while the upper rad hose is connected to the crossover pipe, which links to both heads. (It also goes to the cabin heater "inlet".) With the block heater off the side, the flow would, presumably, be from the block heater to the upper rad hose, through the crossover pipe and down both heads (and block) back to the pump. (This is reverse of the normal coolant direction.) From there it would go to back to the block heater for reheating. This would also probably result in some flow through the cabin heater core (from the upper rad hose, through the crossover to the heater core inlet pipe, through the heater core, and then back to the "Y" in the cabin heater outlet hose).

Alternatively, the block heater could be connected straight across the cabin heater connections, which are quite accessible at the firewall, although this might be somewhat less efficient in moving warmed coolant through the engine.

[Brucey]

I get what you're saying, I think. Looking at the diagram of the coolant flow I'm not sure it will work. Could you draw a picture on the diagram I posted above? The upper radiator hose is on the top of the drawing and splicing in with the "In" on the heater core looks like it's not going to do a lot.

[plain OM]

Here's my attempt at it. The program I'm using to cut the diagram out of the FSM has only one color for marking, so I hope my text additions help separate whats-what.

(The connection according to the instructions assumes one end is at the lower rad hose, which won't work because of the t'stat. The alternative is to put this into the block somewhere low, as in the plug where the oem heater goes, which is #11 in the diag.)

I appreciate that you've already started into this, but was wondering if the need for long hoses to and from the block with this external heater doesn't negate some of the advantage of the higher Wattage. It seems to me that unless the circulation is quite fast, a lot of heat will be lost to the cold air around the connecting pipe, which could be quite long. In reading the KAT's website, I had the impression that the circulating-type heater was intended for situations where an in-block heater isn't an option. Kat's does market in-block heaters, and refers to them as the most efficient.

"•Also referred to as Freeze Plug heaters, or simply Block Heaters.
"•The most reliable and efficient way to pre-heat your engine.
"•Operates by being directly submerged into coolant and heating the block."

[Brucey]

I dont know, I've used those frost plug style before and they're not a big help really. I picked up a couple extra freeze plugs at the local sube shop so I can #1 buy a giant allen to fit it and #2 drill it out and tap it on my own time. I'm thinking I can drill it, tap it for a hose connector, and still leave the allen hole entact to put it back in.

[plain OM]

#2 drill it out and tap it on my own time. I'm thinking I can drill it, tap it for a hose connector, and still leave the allen hole entact to put it back in.

That's how I read the USMB post and it looks as if it worked out okay, although in reading it again, I note that he drilled for a 1/8 pipe thread, which seems rather small (relative to the 5/8 hose used for the circulating heater. (But then his interest was a petcock-type drain, not necessarily circulation, so the size of the hole and hoses might have been of less concern.)

Will the install be covered in another of your super DIY threads?