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How safe are engine block heaters on classic cars?


RJD2
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I have several classic cars, and in general, I try to let each car warm up before putting it in gear(I'm less diligent on a mid-80's F.I. car than I am on 60's/70's carb cars). One of these cars takes a long time for the oil gauge to move at all. I'd love to find a way to heat the  oil previous to driving the car. I see 3 types of heaters exist on the market:

 

-dipstick style heater(seems the riskiest)

-pad-style heaters that are sealed to the oil pan with silicone(car in question has a ribbed oil pan)

-magnetic oil pan heaters

 

the last of these three seems ideal. I would love to be able to plug in a heater an hour or two before I drive the car and shorten the driveway run time. Almost all of the reviews for these products seem to be centered around tractors. How safe are these to use on a 45 year old V12 car engine? Thanks for the tips!

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I think your pretty safe using the block heaters. I agree with using the magnetic one on the bottom of your list. We used block heaters all the time on the farm and the worst thing that would happen is they would just stop working internally. Never had a problem with one catching on fire. Dandy Dave!

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 I applied a magnetic heater to an oil pan after cleaning it well and it melted the plastic that it was made of and fell to the floor.

 It is a good thing that the concrete floor did not have any flammable items on it!

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3 minutes ago, Roger Walling said:

 I applied a magnetic heater to an oil pan after cleaning it well and it melted the plastic that it was made of and fell to the floor.

 It is a good thing that the concrete floor did not have any flammable items on it!

Ouch. Defective thermostat me thinks. You got a lemon. Dandy Dave!

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They use to have those oil or kerosene pots that you hung on the radiator brace rods or placed under the motor to keep things warm in cold weather..never heard a story of a car blowing up...Why would engine block heaters with no open flame be of any danger?  

 

The heating a plastic anything and it fails ,is too funny..Duh!

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When I think of a block heater something that heats the oil is the last thing that comes to mind.  If the car has a heater an inline heater that is inserted in a heater hose

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  You probably aren't doing your cars any favor by idling them to warm them up. The best way to warm them to operating temp is to drive conservatively til they reach normal temps and pressures.

 

  It would be possible to build a pre-warm and pre-oil system. It would be a lot of work for no real gain.

 

  Industrial and marine plants are configured that way. The standby emergency generator engines in a (now shutdown) New England nuclear power plant had constantly heated coolent and lube oil circulating all the time. They had to come under full load within fraction of a second of startup. They were tested on a regular basis and had crankshaft problems.

 

  You may be overthinking this.

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In the pre-antifreeze days, my father-in-law would run an extension cord from the house, and hang a light bulb between the block and radiator of his car.

Of course the idea of "Cold" here in New Orleans is very different from what Dandy Dave, and other northerners will experience.

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This coming from South Dakota cold winters.  I have never heard of a problem caused from an engine heater. The problems start when the heater quits working. The preferred type is what they call a soft plug heater. When they come on new cars from the factory that is the typed they install.

The next most common type are what we call tank heaters.  They can be installed in a hose coming from the top of the engine block to the bottom and circulate heated water through the cooling system. They can also be installed in a heater hose but cannot be used if the cars heater uses vacuum or electric controls. 

Next is one that I've used frequently with good results and that's the lower radiator hose heater. If a soft plug is not readily accessible then these are a good option. 

To be most efficient the heating element should be installed directly into the coolant. Your better off pumping cold oil through a warm engine than pumping warm oil through a cold engine. In a perfect situation both oil and coolant would be heated but I'm not aware of anyone doing that except for standby emergency equipment. 

 

 

 

 

 

 

 

 

Edited by Fossil (see edit history)
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I’ve used two types of heaters with success and no worries of fire. I believe Fossil has described them above but using different terminology on one. We called them block freeze plug heaters. You put it in place of any freeze plug on the side of the block. The hot water it generated circulates thru the whole cooling system. We used a timer on the plug an hour before we would leave for work it automatically turned on. My wife even got the principal at the school she taught to rig up an extension cord out a window to her reserved (closest too the school) parking space. She drove a Fiat 850 Spyder that would not start of cold. This was in the Chicago suburbs. 
The other was on the radiator hose and again circulated the water. Good luck. 
dave s 

Edited by SC38dls (see edit history)
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I would agree with using a coolant heater if it makes you feel better, and very much agree with Fossil's comments about cold oil thru a warm engine rather than the other way around. I think about the only way you could damage your engine would be if the heating device ever caused a leak so bad you overheat and have no idea you'd lost enough coolant to do so- which seems unlikely to me.  

 

Coolant warms up fairly rapidly with an idling engine, but generally speaking, oil circulating in a cold engine on idle takes a very long time to heat up- it will heat up much quicker if you're driving down the road under load, probably why you're finding your oil temp doesn't move much during your warmups, the engine isn't under much load at all sitting there idling. 

 

People write articles that claim that allowing your engine to idle on cold days to warm up can be quite detrimental to the engine, and some have written that modern engines need as little as 30 seconds to warm up before heading out. Their theory is that a cold, rich running engine at startup is dousing the rings with gasoline, washing away oil, and damaging cylinder bores. Better, goes their thinking, to just start it up and drive, and let it warm up quickly to reduce this issue. In modern cars I find this notion to be absolute hysteria, and I think these writers have other axes to grind. What do car companies think people in the midwest in January are doing every day with their factory-installed remote starters? Modern FI systems are just too efficient. I know cold engines run a little richer, but I don't believe for a second my wife's 2012 Pathfinder is flooding itself so badly with gasoline at cold start that it's going to ruin her engine.  I could maybe see a carbureted engine running way too rich at startup, as carbs are not particularly efficient at vaporizing fuel in a cold engine. Even still, I'm dubious you're going to grenade your classic car engine with a few minutes of quiet idling before taking off on a cold day, unless your carb is way out of tune (ok carbs, or maybe FI??? You said you have a 45-year-old V12. Do I smell a Jaguar here?)      

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8 hours ago, JimKB1MCV said:

You probably aren't doing your cars any favor by idling them to warm them up. The best way to warm them to operating temp is to drive conservatively til they reach normal temps and pressures.

Yes!!!!!👍

 

Here in central Virginia I never even used the factory installed block heater (freeze plug type) on my 350 diesels. Both went almost 300 K miles before the bodies became rusty....🤗

Edited by Frank DuVal (see edit history)
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Roger, was there oil in the just cleaned oil pan?

Fossil, I thought I agreed with you about cold oil thru a warm block being preferable to warm oil thru a cold block, but upon reflection, I have to ask why ?

JCH, RJD didn’t state wether it was his oil temp or pressure gauge that was slow. Having an oil temp gauge lends credence to the idea we’re talking Jaguar, no ?

 I can attest that a light bulb hung in the engine compartment of a Model A with a packing quilt thrown over the hood and radiator keeps everything toasty

My only real experience with a direct heater was our 3 phase “Scotch Watchman” Locomotive type that thermostatically warmed and constantly circulated lube oil and plain cooling water in a 2000 HP ALCO. It was in a hut with quick disconnects and a 5 line telephone notification chain if the juice went out. 
A Fiat 850 that wouldn’t start when cold ?  Who’da thunk………..

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2 hours ago, Jim Mead said:

Fossil, I thought I agreed with you about cold oil thru a warm block being preferable to warm oil thru a cold block, but upon reflection, I have to ask why ?

Bear with me here, The oil passages in an engine block are pretty small and the mass of that same block is large. The oil will only have to travel a short distance through those cold passages before it is chilled again. On the other hand cold oil will have to only travel the same short distance before it is warming up in a preheated engine. The BTU's generated from the combustion of the running engine is more than enough to overcome the chilling of the cold oil. Hopefully that makes sense. 

If new cars sold in northern climates came with engine oil heaters instead of freeze plug heaters this theory would go out the window. 

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22 hours ago, JimKB1MCV said:

They were tested on a regular basis and had crankshaft problems.

I have an accumulator on my race car.

Throw a valve just before shut off and holds oil  at pressure in a reservoir, I can pre oil the engine with the saved pressure before start up. Might have been an idea at the power plant.

 

Moroso Accumulator, Mounting Brackets and Fitting, 3 Quart (speedwaymotors.com)

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I am more familiar with the in-line heater which heats the water than I am a oil sump heater which heats the oil. Regardless, I consider either of them a overkill if antifreeze is maintained at the proper levels in the coolant and the engine is shielded from the effects of wind chill. I lived a major part of my early life in Flagstaff, Arizona, and the temperatures there, along with 8’ snow drifts, reaches a wind chill factor of -30 degrees. However, while I can recall cracked blocks, radiators and batteries from freezing, I can’t recall a single engine which failed to start because it was too cold. And I can’t recall anyone owning a engine heater either. One bad thing I can see about using…..interpret that to mean “depending on” a engine heater is the fact that it is another thing to fail when it’s most needed. I have used Harbor Freight, quilted, moving blankets to cover the radiator and engine compartment vents of my old cars for years, and, precluding other non cold related problems, usually start right up. And the 1927 Willys Knight has a sleeve valve engine which is finicky about starting in warm weather.

Regardless of what you may choose to do in relation to buying a engine heater, I would suggest that more attention be paid to protecting the battery from freezing. A fully charged battery will not freeze, and may make the difference between having enough kick to spin a cold starter. A weak or drained battery will freeze, and becomes a dangerous explosive device if a person unwittingly tries to jump it with a well charged battery in a running vehicle. In extreme cold weather it may be a good idea to remove the battery and store it inside on a charge maintainer. 
Just saying🤓

Jack

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I once had a VW bug convertible, the engine was so bad it would burn a quart of oil every 100 miles. I was back in school, no money and I bought it for $150. Body, top and interior were ok. To save $$ I started putting STP in it instead of oil. With that it only burned a quart or so every 200 miles. If one can of STP was good straight STP would be better!  It stopped burning oil!  Now it burned STP a can or so every 4-500 miles. The problem came once it got cold in the central Illinois plaines. Straight STP definitely thickens up. I tried to drain it and it wouldn’t come out. The solution was a spotlight and extension cord. Took it everywhere I went and it always heated it up enough to get it started then it was good. I sold it to another college kid for $150 and gave him a great deal as I thru in a can of STP, the extension cord and flood light. Had a lot of fun in that car. 
dave s 

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9 minutes ago, Jack Bennett said:

coolant and the engine is shielded from the effects of wind chill.

I don't think wind chill applies here.

I think you could blow 33 degree air at water all day and it wont freeze.

Wind chill is something that weather forecasters use as a hype.  (feels like)

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57 minutes ago, Bryan G said:

My grandfather's solution, in his day, was to drain the oil into a big pot, bring it in the kitchen and heat it on the stove. Maybe women were different then!

We used to do that with the old 2cyl John Deere tractors. It wasn't to help with starting though, it was to melt the frost off the oil pump pickup screen so the engine would develop oil pressure. At -30 F. it takes a long time to drain the oil when there were no synthetics available. Best to do it after shutting it down for the day. 

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10 hours ago, JACK M said:

I don't think wind chill applies here.

I think you could blow 33 degree air at water all day and it wont freeze.

Wind chill is something that weather forecasters use as a hype.  (feels like)

Not quite. If you keep the wind away from the radiator, then there will be less BTUs leaving the radiator for the air, since the stagnant air will warm up. If you blow wind on the radiator, the air will not have time to warm up and the radiator gets colder quicker. Not hype, thermodynamics.

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21 hours ago, JACK M said:

 

I don't think wind chill applies here.

I think you could blow 33 degree air at water all day and it wont freeze.

Wind chill is something that weather forecasters use as a hype.  (feels like)

Absolutely true. Well……..sort of anyway. Temperatures are measured in two ways, ambient air (stationary-around us), and what we called the “wet bulb” (moving-as wind chill), used in the Army as a guide to determine extent of the winds wicking effect as it passes over exposed skin. Nature doesn’t “blow” 33 degree air constantly. Rather, if the temperature of the ambient air…..as in a radiator or engine protected from moving air…..is 33 degrees, the radiator or engine won’t freeze. But,  “wet bulb” or “wind chill” isn’t ambient air, or it wouldn’t be “blowing”, and when air moves it absorbs and removes, or adds to, and increases, warmth from every surface it encounters. To test this theory wet your finger, sense it’s temperature just standing there, and then blow across it, and measure again. Or, the next hot cup of coffee you drink, forego that cursory blow to cool it down before your lips are singed. The question was in regards to using a engine warmer, which speaks of concerns of the air not being ambient at a constant 33 degrees, and, since nature can’t leave its air alone, that brings moving air to mind….in regards to freezing radiators or engines. Whether or not to buy a in-line or sump style heater is a matter of preference, anticipated weather conditions, availability of a power source, accessibility of the equipment to be warmed, economic abilities of the user to afford any sort of gizmo…….well, this could go on forever. Regardless, keep your battery charged, if the vehicle can’t be stored inside at least park it’s front toward some sort of wind block, and go to Harbor Freight and buy a few $4.00 furniture moving blankets……even when frozen and wet, they still provide some protection from…….yep…….wind chill 😳.

Jack

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22 hours ago, JACK M said:

I have an accumulator on my race car.

Throw a valve just before shut off and holds oil  at pressure in a reservoir, I can pre oil the engine with the saved pressure before start up. Might have been an idea at the power plant.

 

Moroso Accumulator, Mounting Brackets and Fitting, 3 Quart (speedwaymotors.com)

You mean, sort of like Jay Leno, the other night on Leno’s Garage, using the provided oil can to oil the rocker arms of his antique car?

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I like the idea of those magnetic heaters. I don't start my old cars until the ambient temp is 40 deg. fahrenheit or higher, but last year we had a severe cold snap of 27 below 0 and my coolant only went down to 30 below. I went out and bought a bunch of light bulbs and a rubber mat to insulate. Worked fine, but a magnetic heater would be better and easier, I think. The heaters I hated were those in-line coolant heaters when I was a kid. Sometimes they blocked the coolant flow for whatever reason.

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Thanks for all this valuable info, folks! I appreciate it. For the record, the car in question is a 1976 Lamborghini Espada. It's not a huge displacement engine-4L-but maybe due to the layout, the oil temp takes probably 6-8 minutes of idling to even move from it's resting position. Common knowledge with this car is to let it idle til the oil temp gauge moves. I'm looking for an alternative to doing that, cause it's a drag and stinks up the whole area. The oil pan is ribbed aluminum, so I may need to fashion a spring system or something for the magnetic oil pan heater thing to work. The radiator coolant heaters are interesting as well. Thanks!

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Instead of internet gossip, have you contacted Lamborghini on how to start and drive your car? Maybe an owner's manual?

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My 1980 Chrysler LeBaron wagon came from the prairies where a block heater is necessary if you want to start your car in winter.

It also has a Chrysler authorized dealer installed "Allpar" interior heater. Very nice for those -30 mornings sitting on leather seats.

deccars 017.jpg

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  • 2 weeks later...

In the 1960's I used a tank heater on 2 cars and with no garage, in Des Moines, IA winters. It was installed in the heater hose and both heated and circulated the anti-freeze.  The built-in thermostat heated to 55 degrees and the car blew hot air in less than a block.  If you had the defroster set on, your windows were clean when you came out.  Stopped using the heater when we moved & had a garage.

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