Engine Pre-Heat

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Kevin Means

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A couple questions for you diesel engine RVrs (Mine have been gas). How cold does it have to be before you need to pre-heat your engine, and how long do you pre-heat it before you start it?

Kev
 
Hi Kevin,

The only time I've worried about preheating was when we were in the midwest for a week in sub-freezing temperatures. Many diesels have a block heater that plugs into 110V, so I merely plugged it in a few hours before we planned to leave.

The big CATs on our boat don't have block heaters, but they fire up on the first or second revolution here in northern California, where it rarely gets much below freezing. The generator on the boat has a pre-heat switch (glow plugs?) and I usually hold that on for approx 10 seconds prior to pressing the start switch.

Others will no doubt chime in with their practice.
 
My Cummins ISL 450hp seems a lot less sensitive to the cold than my old C-7 Cat was. If it's going to be freezing or below for the night, we turn the block heater on at bedtime if we are leaving in the AM. Right at freezing does not seem to be near the problem as when it gets in the low 20's or below for an extended period of time.

It's just easier on everything to spin a warmer engine. Frankly, we try to avoid traveling or even being in those kinds of temperatures.  8)
 
Kevin Means said:
A couple questions for you diesel engine RVrs (Mine have been gas). How cold does it have to be before you need to pre-heat your engine, and how long do you pre-heat it before you start it?

Kev

Below 30* is an average. How long depends on the type of heater. Obviously an electric block heater will take much longer than an AquaHot. I'd leave the electric block heater on overnight if leaving in the early AM with sub freezing temps. Aquahot with an already warm boiler will only take a few minutes.
 
Aquahot with an already warm boiler will only take a few minutes.

It will take more than a few minutes to heat up all the iron and oil in a big diesel engine block.  If it's not below freezing, we usually run the block heater for a couple hours in the morning as we pack up for travel.  If it's colder than that (we try to avoid those nights) we'll turn in on the night before and let it run overnight.  Using the block heater this way the engine always starts just as if it were a warm summer day :)
 
Generally CAT and I believe Cummins recommend the preheat if the temperatures have been below 40? F.  Some where I have time information for a CAT 3126/C7 if someone wants that information, send me an email and I will dig it out.  It is also available on the Newmar owners list on Yahoo and possibly on the Freightliner Chassis Owners Club on Yahoo also.

Generally if the temps  are in  the 20s, I would expect  a couple of hours, at least, of the preheat.  On the other hand, using the CAT recommended procedure of turning on the key till the wait to start light goes out at least 3 times, I have been able to start the CAT 3126 at temperatures as low as 10? F.  If cold temperatures are predicted, I generally turn the preheat on the night before.
 
I have just received the Cummins newsletter that addresses just that issue.  The Cummins uses a grid heater in the intake manifold to preheat the air charge before it goes into the cylinders. The grid heater is automatic depending on how cold the engine is at start up, and may remain on for about 30 seconds if it is really cold outside.  The block heater function is necessary at -20 degree temps.  Here is the link that addresses the topic. 

http://turbodiesel.cumminsnewsletters.com/2013/02/grid-heaters-and-glow-plugs/
 
Our Cat has an air inlet heater grid as well but we still use the block heater when cold to get the oil flowing sooner.  I sure wouldn't wait for -20F to use it :(  Then again, I shouldn't be anywhere it could get to -20.  I would think the fuel would be jelling at those temps.
 
We flip on our engine preheat (Hydro Hot) any time it is 35 degrees or less. Only happens a few times a year, as we try to stay where it is warm.
 
I have a diesel Dodge pickup, now I know not exactly the same thing but close.  My block heater stopped working a few years back.  Even with not having it I can get her to start in subzero temps.  It is rough and she sounds like a rock crusher for a few minutes but it starts on the second or third try.  The air intake heater will cycle on and off as long as the engine remains at idle.  The real thing to be concerned about is fuel gelling.  Some engines have a fuel heater or have a high pressure lift pump that recycles back to the tank.  The action of the pump actually warms the fuel a bit.  If you are going to be in the extreme cold make sure you have anti gel additives in the fuel.  Fuel that is totally gelled up will shut a diesel down.
 
I don't know if I have one.  Ours is a 20 year old Cummins and even at 20 degrees no issue starting, turns over the 1st time..  Now our diesel generator does have a preheat switch that you leave on for 30 seconds before you start it.  Need to get the manual out again and read if we have any kind of preheating.
 
My plan is to stay away from places that require the use of block heaters I have been out trying to start a car at ?10 and some times you can get them started but just so you know
The block heater only warms the water in the block it does not warm the oil in the pan. You can get oil heaters for really cold temps. I have seen a couple of different kinds. Some use heat blankets that attach to the bottom and sides of the pan. The cheap ones for a truck or cars replace the dipstick. Colder weather is one more good reason to run full synthetic oil like Mobil-1 5-40 as it flows better when cold.
Bill
 
My Caterpillar manual has a table for ambient temperature vs. engine Pre heat time. When we would test run emergency back Diesel engines in the refinery we would always Pre heat them.  When they kicked on automatically they were never Pre heated.  After a run we always plugged the fire engines into a battery charger and a block heater.  When I turn the key there is a wait to start light while the air heater warms up.  The length of time this remains on depends on ambient temperature (if I am not using the manual Pre heat).  I have just gotten in the practice of using the manual pre heat switch whenever the ambient temperature is below 50 degrees (okay maybe not always).  The first thing I do after start up is call up the engine computer display to check oil pressure etc.  The engine temperature is usually in the neighborhood of 87 degrees.  It works for me.
 
Ned said:
It will take more than a few minutes to heat up all the iron and oil in a big diesel engine block.  If it's not below freezing, we usually run the block heater for a couple hours in the morning as we pack up for travel.  If it's colder than that (we try to avoid those nights) we'll turn in on the night before and let it run overnight.  Using the block heater this way the engine always starts just as if it were a warm summer day :)
I can assure you that an AquaHot with a fully heated boiler will only take a few minutes to warm a Detroit Series 60 from below freezing to an easy start temperature. Remember that you are not warming it to operating temperature, just warm enough to start. Been there, done that on many occasions.
 
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