To Pre-Heat or Not?, That is the Question.

[ftm1776]

A diesel tech told me that heating the engine with a block heater could aggravate or cause or accelerate some sort of galvanic or electrolytic corrosion within the engine. He recommended not doing it unless the temperature is really cold. Just to be clear, this is the type of heater that fits into one of the plug holes on the back of the block and has an electrical coil in the coolant and uses AC current...about 400 watts.
Is it advisable to NOT heat the engine if the temps are mild?

Thoughts on this, please.

[theman53]

I cannot comment on the acceleration of corrosion, but I can say over 10f I haven't needed a heater. Between 10f and 32f if you use the block heater it helps to warm up the heater and the oil, so it is worth while.

[410]

Up here in Canada we have no problem using block heaters.  Good antifreeze and proper grounds drastically reduce the electrolysis between dissimilar metals. 

[Renax]

This heater will warm up the oil in the nearest cylinders and after a while the oil will be too thin and run down causing less lubrication in the start moment.

This is the theory my friend has after seeing multiple engines with bad compression on the 2 nearest cylinders..  (this is where the main road is closed for winter 8 months of the year because of snow)

Hot-frog or similar would be better;-)

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[TylerDurden]

I can't see the electrolytic process changing from current, as the block is not part of the circuit. The heater element is isolated to prevent shorts.

I can't see the temperature being an issue, since the heater does not raise the mixture temperature very high and convection circulates the mixture.

[ftm1776]

Renax,

Good point, I've wondered about that now and then.

Hmmmmm......

[sdubfid]

I know standby diesels that have been plugged in for decades without issue

[Renax]

I know standby diesels that have been plugged in for decades without issue

Yea, in Norway i bet at least 50% of all diesels have a heater unit, most claims it will do good.
And the engines starts better with preheat.

But its curious that many engines with this heater has measurable more wear on syl 3&4 which is where the heaters often are...

I would rather use one with a pump that's circulating the water causing even heat, and also heats the coupe...

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[Sillycaddy]

The only issue I've had with a block heater so far is, it seems to boil the coolant and cause it to overflow from the heater core valve depending on how long its plugged in for. This really baffled me for a while and I chased everything from headgasket to a plugged radiator because the rad hoses would swell from the pressure. I ended up putting it on a timer after I figured 30 min to an hour is all it really needs to kick over.
Considering the truck has had some issues frying glow plugs it was my only option last winter. Its a tired 1.6d that I boosted around january, and I am sure the compression isn't what it used to be. But the gain in milage, let alone performance was well worth it.
I would tend to agree with sdubfid that a unit with a circ pump would be preferable.
Anyway, just thought I'd share my experience hopefully this post wasn't too off topic.

[ftm1776]

The circulating pump is something to consider. I assume that it is installed in the radiator hose line.

Does it have any effect on the cooling system when it is not in operation?? i.e., does it restrict the normal flow of the coolant under running conditions???

I think that an in line temp sender might do the same?

Or does the coolant pump do its job even with these restrictions in the line??

ftm1776

[mtrans]

I put in series with cabin heater,2 kw,pump and T-stat,220 ac volt all,nothing bad till now,but not tested in deep winter.
It must have pump,believe me,I try w/o -nothing.Merc have 12 volt dc coalant pump if you see benefit in that.