Coolant-based engine pre-heating

Horace T

New member
Hello all

I've been reading on the site for a while and finally have a specific question/created an account. Our expedition vehicle of choice is a 1991 F250 7.3l IDI. It's going to have a custom flatbed and permanently mounted home-built camper for some summer, primarily winter adventuring. Part of the allure of this truck was the ability to run veggie oil and/or biodiesel for free/cheap fuel while on-the-go. The main pitfall of this engine however is its reluctance to start in the cold without some kind of warmer in the engine block. Plugging in is the obvious and easy solution, but we're hoping to do some extending winter ski trips where we may not have access to an outlet for several days or more at a time, in potentially quite cold temperatures (zero deg. F or colder). Using a plug in + generator is another option, but is also heavy and space-consuming. I have a third idea and wanted to run it through here to see what folks thought.

Our camper will be a bit different from most commercial models as we're going to emphasize space inside rather than conveniences. No plumbing, fridge, or toilet but we will have a small woodstove for heat and optimal drying of wet snowy gear. In researching winter heating solutions for these types of engines it seemed as though an Espar heater was the ideal solution (http://www.polarmobility.com/fuel+fired+coolant+heaters.html - main Espar webpage seems to be down at the moment). These units, however, are more expensive than our budget really permits as this is a highly DIY project with a much smaller budget than many of the rigs featured on this website!

My thought was to use the woodstove to heat a coolant coil, and then have a secondary water pump that could be used to circulate the hot coolant through the engine to pre-warm it before starting on very cold days. Same principle as the Espar but using wood rather than diesel. The coolant loop through the camper could be sealed from the main coolant system for normal operation of the truck, opened with a cold engine and woodstove on to heat the engine block, opened with the engine running and woodstove cold to provide some radiant heat to the camper from the engine while driving, or closed and circulating with the woodstove on to provide radiant heat (floors?) in the camper. The last two options may not be realistic because too much heat would be lost into the camper to properly heat the engine block if it were designed to act as a radiant heat source, but was just an idea to consider.

What do folks on here think about this idea? Worth pursuing? Worthless? I would greatly appreciate any input you might have, especially information from someone who has set something like this up or considered but rejected it.

Thanks for the advice.
 

Buliwyf

Viking with a Hammer
My friend used to convert cooking oils into biodiesel. Now his aux tank is filled with regular diesel. Can't find cooking oil anymore. They don't give it away free anymore.

He would start and stop on his regular diesel tank. The Bio tank was used only on the highway, his heater hoses were routed to an element in the bio tank to warm it. A Racor fuel filter with glass bowl and drain is a good idea to add.

You can tee a Kim Hotstart heater off your lower hose and the tee it's output into your heater hose or anywhere higher. (If you don't want to use the regular freeze plug style heaters, I prefer external heaters)
 

toymaster

Explorer
The idea would work in theory. You just need a 12v pump to create enough flow and a suitable heat exchanger with all the necessary lines and valves. I would not chance a coolant leak going down the road. Valving the extra plumbing off right at the factory heater lines is best.
 

Horace T

New member
Scrubber3: It looks like the final post on that thread had someone with the same idea. I PM'd to see if the idea ever panned out, but couldn't find much relevant information beyond that.

Buliwyf: Some places still give oil away for free. You just need to know where to look. The Kim Hotstart heater is intriguing but presents the same problem as other plug-in block heaters, namely that we're looking for a non-plug in solution.

toymaster: Yep, that was the idea. Glad to have a voice saying that it makes sense and could be feasible.
 

Riptide

Explorer
Not sure just how limited your budget is, but I would pursue looking for a used Espar instead of a wood-fired coolant loop. They seem to be pretty common in Dodge Sprinters; maybe you can find a salvaged one...

The idea of connecting and disconnecting a coolant loop, and figuring out what to do with the loop filled with anti-freeze would be enough to dissuade me.

I have one on my Sprinter, and love it.

I usually find that when I try to engineer my own mousetrap, I invariably end up spending just as much money as if I had gone with the item I was trying to copy.

YMMV...
 

Horace T

New member
I usually find that when I try to engineer my own mousetrap, I invariably end up spending just as much money as if I had gone with the item I was trying to copy.

This is a good point. I think we're going to keep our eyes out for a used Espar at the moment.
 

Athabasca

Observer
I run a 99 superduty and have about 2000 watts of plug in heat which includes the factory coolant heater, an oil pan heater, Tranny oil pan heater, battery trickle chargers (2) and battery heaters (2).
Overkill? further south maybe but I wanted something that would allow me to get it started at -45C and it does.
The engine only makes heat though at high idle or driving so once its started you need to get going.

I will probably add an espar at some point but up here in Canada there is always a plugin available except out of town.

Your idea has merit if its done right but the espars are proven in the semi world. They are designed for exactly what you have in mind and will mount under the truck. The woodstove will heat a massive area and takes up alot of space but its kind of cool and an ice age will be no problem. There are plenty of sourdoughs up here with chimneys sticking out of small campers.

let us know how it works out
 

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