Block Heaters 101

[Sri Ram]

What does the block heater on my 91. 5 heat, oil or coolant? Also, does the block heater pre-heat the fuel in the fuel filter?

 

[Nate]

block heater heats coolant.

 

[Sri Ram]

Any idea to what temp?

 

[JasonCzerak]

Any idea to what temp?

after a nice 25 degree day and 8 hours of bloack heating I see 90-95 if I recall correctly on the edge-attitude monitor.

 

[TRadke]

When Is It Needed? How Cold?

Only had my truck for a month now... diesel newbie.

We got down to about 32*F recently, truck fired right up that morning, w/o block heater. No white smoke or heavy rattlin'... just normal startup.



It rarely gets colder than about +15*F here, and usually not for long. Average overnite low Nov-Feb is about 40*F, but gets down around +25*F frequently.



At what outside air temp should I think about plugging in the block heater?



I get up about 2 hrs before I go to work. Would 2hrs worth do any good, or does it need to be plugged in all night?



TIA,

Ted

 

[Sri Ram]

At what outside air temp should I think about plugging in the block heater?

I don't know what the exact recommendation is for your year of engine, but for my 91. 5 the block heater is "recommended under 40* and required under 30*. " I follow this and even plug in for a short while under 50* as my commute is only 2 miles.



As for your plug in time, that depends on how cold it is…Get a timer and have it come on 2 or 3 hours before you leave. I try to heat long enough so the 'wait to start' light doesn't come on. Perhaps someone with more technical knowledge can chime in here?

 

[EKlem]

At what outside air temp should I think about plugging in the block heater?

Everyone has their own theory on it but I wouldn't worry about it until it gets below 20 or so. There are 4 of us here at school that have dodges with the cummins and none of us have a spot to plug in. We have never had a truck fail to start other than one that needed a jump because of old batteries. I have personally started mine at -25* without being plugged in. At these temps, the engine runs rough for 30seconds or so when you start it up but it will start.



I find that the biggest difference for me is made by running synthetic oil. My roomate runs dyno oil and his truck cranks noticeably slower in the winter and it takes longer to build oil pressure. It always starts but doesn't pop off quite as fast as mine.



There are 3 major reasons that I can think of to plug in. One is if you want heat in the cab more quickly. The next is to keep your oil at a temperature to do its job. The final reason is that when it is really cold, it might be necessary to be plugged in to get your truck started. Remember that it takes a lot of electricity and costs a lot of money to run a block heater. If you are willing to wear a jacket and run synthetic oil, I wouldn't bother until it gets below 20*.

 

[DieselDoghouse]

R u guys in N'Hampsha double-cycling you intake heaters? With my '98 12V I found the heater works ok with as little as 2 hours lead time - I would avoid an all-night plugin if I could. I only used below 20°F even though I cringed when starting in the twenties thinking of the jellied oil!!

 

[EKlem]

R u guys in N'Hampsha double-cycling you intake heaters?

I only do it when the temp is below 0* and even then, it will start it with only cycling them once. The viscocity of the oil at those temps is what worries me most which is the reason that I run synthetic.

 

[Cummins Pilot]

Two hours of heat is plenty with temps above 10f. I start plugging in at 30f. After about 10f I'd heat for about 4 hours if the block is cold soaked. Its only a 750watt heater and there is a lot of block to get warm. The #6 cly in the way back will still be cool-cold depending on temp and time.



I run triple 100watt oil pad heaters. One pad to 10f, two down to -30, all three after that. I'm running synthetic. With my Espar I don't run the block heater anymore. I leave the oil pan heaters on all day (I work nights).



I know mine will start at -15f completely cold soaked. I cringe at the wear damage I had to incurr that day.

 

[chuckwilson]

Mine started at -21F one morning (Breaker tripped) cold soaked. your engine will start, but the block heater will shorten the warm up time a bunch. The heater heats the coolent, & is usualy installed on the right side close to the oil cooler so warn oil goes threw the engine at startup. You should unplug it BEFORE you start the engine for long heater life!!!!

 

[WBusa]

I never use the block heater above 20 to 25* F; just double-cycle the intake heater. Even below 20*, I seldom if ever use the heater for more than about 1. 5 hours before starting. If the night is going to be real cold I plug the heater into an extension cord, leaving the other end of the cord (unplugged) in the garage. That way, when I get up in the A. M. I just go into the garage, plug in the extension cord, and get ready for work... no trudging out into the cold before my first cup of coffee.

 

[mhenon]

I've disconnected my grid heaters, for several reasons, and plug in the block heater anytime the temp gets close to freezing.

While the Cummins will start fine in cold temps. . no diesel engine likes cold weather. They want to be hot. . really hot. I generally throw a blanket over the engine and leave the block heater on all night. In the morning the whole engine bay is toasty warm even though outside temps are in the single digits. Engine starts instantly.

If you have access to an outlet, I would always recommend plugging in the block heater than relying on grid heaters or glow plugs.

Mike

 

[SHaugen]

I love my hydronics heater by Espar.

 

[GoodmanS]

does the factory block heater actually heat the block? I was thinking that it doesn't move the coolant, so might not get the whole block. ??



Also, sorta looking into an aftermarket coolant heater that's diesel powered, like webasto, any ideas?

 

[Allnew2Me]

I believe that the coolant actually does move by a thermal siphon process, where the heated coolant rises, starting a slow circulation. I know that my block gets uniformly warm when I have felt it.