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Date: 13 Dec 2002 10:42:22 -0800
From: walt.woytowichnopsamatico.ca (walt woytowich)
Subject: Re: in-line block heater for 92 900T


"g c" <nbtrownopsamet.on.ca> wrote in message news:<uvhoeui4a8ba1fnopsam.supernews.com>... > *e: SaabCatalogue.com: search on Engine Block Heaters* > After realising that the web site needs cookies enabled..... > I finally got to see two heaters.... one that is the standard type of > engine block heater, which replaces a frost plug; and another which is a > lower(?) rad hose heater that would heat up the rad, but I'm not sure about > how effective it would be in heating the block (wouldn't the thermostat stay > closed, and block off any circulation through the block?) > I agree with the concerns about uneven heating, and also have a concern > about the heater coming loose/out (happened to someone in this group, and > was written up recently; might be rare, but prefer not to join an exclusive > group who've experienced >that< failure!!) > Next thought - can a tank heater be connected so that it takes from the > block low down, and returns into the block through the heater core bypass? > the heater core won't get hot, but the flow through the block should be > improved without the resistance of flowing through the core. (might need a > check valve somewhere, or the heater system always shut off when the block > heater is on) > Whatcha all think? > anybody got a diagram of the heater hoses? > > and > *re: Walt Woytowich who wrote: > what is described is just a plain old tank heater but installed in a > manner for which it wasn't designed. The tank heater circulates > coolant by convection which means the hoses must be short and > vertical. The original installation method was to connect the intake > of the tank to a drain plug hole in the engine block and the outlet to a "T" > in one of the > heater hoses. Even with such a direct routing the flow wasn't always > reliable, this sometimes led to hardening of the upper hose. The efficiency > of > the tank heater is about half that of a block heater, this is reflected in > the the wattage recommendations published by heater manufacturers. > About the block heater: the cost is certainly low but what is the > cost of installation? A block heater may ( will?) heat the engine > unevenly,- engine temperature will vary from near boiling next to the heater > to > almost ambient at the extremities, according to a heater manufacturer. > I found that even an engine with aluminum heads and block had a > temperature difference of 26F between the left and right sides of the > engine when heated by a 600 watt block heater in a -40 degree chamber. > I would be most interested in learning the average temperature of > a crankshaft in such a situation i.e. steel crank aluminum block. > > Walt* GC; Your comment re the lower rad hose heater is right on. How can it possibly work? Just like the Canadian gun registry,- The time , money and effort that goes into the installation is all wasted but uninformed people feel they're accomplishing something. As H.L. Mencken once said "No one ever went broke by underestimating the intelligence of the (north) American public". If the upper hose on a tank heater goes to a "T" in the heater hose connected to the thermostat housing the movement of coolant is as direct as it can get. Even so, I've had reports of charred hoses due to overheating tsnk heaters. Tank heaters are usually fitted with a basic (flap) check valve which might keep the heated coolant from going backwards. The original in-line heater (BTW my name is on the patent) uses two check valves, one at each end of the container and permitting flow in only one direction. This arrangement allowed installation in a heater hose. The resistance presented by the cab heater was easilly overcome by the steam pressure developed. As withe tank heater, the necessity of bringing the coolant to a boil made it only `50% efficient at -25C. That means that about 400 watts ( 1360 btu)was lost. The in-line heater became popular mainly because of easy instsllation in a variety of applicatiions. It faded from the market because of its'bulk and the lack of under-hood space. Walt

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