Block Heater vs. Coolant Heater

[karrlot]

When I bought my bus I asked the guy what the silver pipe sticking out the side was. He told me it was a coolant heater. It has a timer under the steering wheel that you can turn it on. (I know it is some type of heater because hot air was blowing out the tube and when I grabbed that silver tube, it branded my fingers with the pattern from the tube.) This runs off of the batteries.

The front bumper has a male outlet to plug an extension cord into. There is a wire that leads from this back up into the engine. Is this a block heater?



This morning the temperature was in the single digits. I turned on the timer and ran the coolant heater for a while. But when I tried to start it, it wouldn't start. You could only hear the click of the starter. So I thought the batteries were dead. I pulled my car up and hooked up jumper cables. When I tried to start it after I hooked up jumper cables, it would turn over, but not start. I let it sit for a few minutes to charge, then tried it again. It would turn over, but not start. I tried that a few times.

Then I remembered the plug in the front bumper. I got an extension cord and plugged it in. After about five minutes I tried again and it turned over and started.

Do I have a block heater and a coolant heater?

When and why should I use each one?

My bus has three batteries. Can you jump start that with a car? Did I actually do anything?

Did plugging the extension cord into the front bumper help start it?
Did running the coolant heater help start it or just run the battery down?

[charles_m]

Cool bus you got. You have a block heater and a coolant heater that runs of diesel and uses an electric pump to circulate the hot coolant through the engine.

My DT466 will start down to as low as you were with no problems at all. Every engine is different, but most mechanical DT466s I know fire up easily in the cold. Sounds like you might have just had a dead or very low battery. Though that is strange because the coolant heater ususally wont work if the batteries are dead or too low--are you sure it was on? Could you hear it running?

I doubt 5 mins of a block heater was enough to make a big difference but who knows. IF you left your car connected and charging the batteries, that probably helped a lot.

You can jump a bus with a car, but it will take a while and if you work the starter too long, you could cause quite a bit of stress on your car's alternator which it may or may not be up for.

Running the block heater off an extension cord for an hour or two before you start will be good for it and is easiest and most reliable way since it doesn't depend on your batteries.

[karrlot]

Thanks for the information. That is exactly what I was looking for!
I know the coolant heater was working. I could hear the fan and felt the hot air from the little exhaust tube.

So the coolant heater burns diesel fuel to make heat then uses an electric fan powered by the batteries?

When and for how long should I run this?

It sounds like with well-charged batteries the engine should start fine, but it is better on the engine to run the block heater for two hours before starting? What temperature range should this be done in? Below 20 degrees? Below 40 degrees? All the time?

Do you use both heaters at the same time?

Thanks for your help!

[cowlitzcoach]

The coolant heater is most likely an Espar or Webasto unit. They use diesel fuel to run a heater that warms the coolant up. There is a pump that circulates the coolant to heat everything up.

It can be used to pre-heat both the engine and the interior. But it does take a lot of battery power to do so in order to run the control unit and the pump(s).

A block heater just warms the coolant and uses convection to warm things up. Most that are in diesel engines are about 500-1500 watts. It takes a long time for convection to really heat up a diesel engine and all the coolant in a bus. It will need a pretty heavy duty drop cord to keep the drop cord from getting too warm, particularly if the bus is a long way away from a plug in.

If you batteries are not up to snuff you can kill a starter trying to start a diesel in the cold. A starter will draw more amperage when the battery is low than when the battery is fully charged. In many cold climates they include a warming blanket for the battery since a battery loses almost 50% of the cold cranking amps at 32* because of the cold. If the battery is the least bit low or is old and doesn't have a lot of life in it, the cold will suck what life there is out of the battery.

At the least you need to make sure the battery(s) are fully charged before you try to start your engine. Plugging the block heater in for three or more hours before you try starting will help a lot. Most people do not rely on the fuel fired heaters to pre-heat things mostly because of the drain it puts on the battery. They were used mostly because diesel engines in school buses don't work hard enough to put out much heat on a cold winter day. I had a route that I went up to the top of the mountain and had stops all the way back down. Before I was halfway down the mountain the heaters were blowing cold air. We solved most of that problem with a weather front. But I am in western WA where a winter day is rarely below freezing. That same bus in MT or ND would have icicles hanging from the ceiling by the end of the week. Hence the need for auxiliary heat sources.

Good luck and happy trails to you.

[opus]

Originally Posted by cowlitzcoach

But it does take a lot of battery power to do so in order to run the control unit and the pump(s).

An awful lot of battery power. I ran mine once on batteries and then changed it to run off a 110v power supply and its been that way for years.

Batteries dont like the cold to begin with let alone running a unit like a Webasto for more than 10 minutes then expecting to start the rig.

[family wagon]

Mostly it sounds like the batteries were low. FYI I wouldn't recommend running the car while trying to jump start the bus or much else. For jump starting a small engine hook up the cables, turn off the charged car, then start the other one. For jump starting a large engine hook up the cables and high-idle the charged car to maybe 1000-1200 rpm for a while, maybe 5 minutes. Then turn off the car and try to start the bus. If unsuccessful, re-start the car and let it high idle longer to charge the batteries more.

The reasoning behind both these recommendation is this: a starter motor takes a lot of energy.

• It's a good way to overload an alternator. Overload can stress the rectifier diodes in the alternator, and overload stress causes early or possibly immediate failure. So that's why I recommend jump starting with the source engine off -- it prevents loading the alternator.
• The starter on a big engine needs a lot of juice. More than will be easily supplied through jumper cables and alligator clips, thus the suggestion to let it sit and charge a while so that the vehicle's own batteries can do most of the work. Also, alternators generally don't produce much power when the engine is at low idle; thus the suggestion to rev it up.

Yes, the coolant heater burns diesel to make heat. It has an electric fan to push the exhaust out and it also has an electric pump to circulate coolant. It produces much more heat per minute/hour/whatever than the block heater does. If the engine just doesn't want to start cold, you could run the coolant heater to warm it quickly and run a battery charger to avoid depleting the batteries. Or run the block heater alone for several hours.

A diesel vehicle is usually designed to start reliably in moderate cold without help. I'd guess that most should start in 0-20 F using only a healthy battery and the glow plugs or grid heaters or whatever start aid is built into the engine (which may be automatic or manually operated). Colder than that, or if the start aid isn't working, or the battery is weak, supplemental heat like block or coolant heater can be required. At those temps or warmer where supplemental heat isn't required, it will still make the engine start even easier. That can be convenient and it can result in faster cabin heat. If the engine would require extended cranking to start, then the supplemental heat can also reduce engine wear by reducing raw fuel washing the oil off the cylinder walls (and oil contamination with fuel) and by getting the oil pump running sooner.

[leadsled01]

Maybe you have an intake heater similar to the ones we have on the trucks at work? I am not a diesel guy so someone else needs to chime in here.

[Tango]

Most Cummins have a few options. Not sure about other engines.

1. External plug in 110v Block Heater (warms the coolant via a heating element in the water jacket...sloowwly but will keep it from freezing in most situations)

2. Intake heater (runs off battery and only heats the intake air as it goes into the engine...pretty effective for helping cold starts)

3. Optional coolant heater (Usually a Webasto as described above)

If anyone know about other options...please...

[opus]

If going electric, a circulating tank heater beats a block heater greatly.

[Tango]

That should beat a standard block heater all to pieces since it move the water as well as heating it. Nifty!

[opus]

Some of the things you are sheltered from, living in TX. ;)

[Hank's P-O-S]

I'm confused now! I though that a block heaters function was to primarily heat the oil?
That's what I was always told at least..... When it's -56 with the windchill noting it going to keep the coolent warm.

[opus]

Originally Posted by Hank's P-O-S

I'm confused now! I though that a block heaters function was to primarily heat the oil?

Negative Goose.

[karrlot]

Thanks everyone for your help!

As I was thinking about this, I realized that since I bought the bus in October, I've only started it a few times, just to move it in or out of the driveway. It probably never ran enough to charge batteries. In addition to being in the single digits, the batteries were probably kind of low, then I ran the coolant heater for an hour or so.

It sounds like the coolant heater, when running off of the batteries, should be used to supplement the heat and not really to keep it warm for starting.

[jazty]

Originally Posted by Hank's P-O-S

I'm confused now! I though that a block heaters function was to primarily heat the oil?
That's what I was always told at least..... When it's -56 with the windchill noting it going to keep the coolent warm.

You're thinking of an oil pan heater. They can come in a mat that sticks to the underside of the oil pan and will evenly heat the oil by convection.

The block heater on my T444e made starting much easier in some -40C weather last winter, just before I ran away from the cold