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Mercedes Block heater install


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All parts used in these pictorials are available at the diesel parts for sale page


Mercedes Block heater install

Since it is starting to get chilly in most parts of this great country, I know that I am not the only one that can benefit from a little heat in the morning.  Since Mercedes did not see fit to install block heaters in every diesel engine from 1985 and earlier, you may be wondering what it takes to get that temp up in the morning.  If you are one of the unlucky ones that either have a defective block heater or no block heater at all, this pictorial is for you.  If you are running WVO or some other veggie substance then a block heater is mandatory.  The problem with the factory set up is that it is very hard to get to, and you can run into problems that can be very bad.

Most of our cars are 20 plus years old at this point in time.  Trying to remove the original block heater that is defective or trying to remove the factory plug, can be a nightmare.  20 years of being surrounded by water and outside elements all but freeze the plug or defective heater in the block for good.  Removing said items can require a torch, 6 foot breaker bar and a lift.  Done improperly and you can crack your block.  I recently got a quote from an indy on installing a popular brand of block heater into the factory location.  Almost $250 for the labor.  Why I asked?  He said that they have to heat the plug cherry red to break the rust in the threads.  Well I was NOT going to spend that kind of change, and risk my block getting brittle from the high heat and maybe have a crack down the road.

I decided to go a different route.  Since heating the coolant is not real hard, I decided to do it in a place that I think is much easier to install and I believe is more efficient in heating the entire cooling system.  The lower radiator hose has some advantages if used to heat the coolant.  One being that the rubber hose acts as an insulator for the heat, to get into the engine.  Since the 2nd law of Thermodynamics tell use that heat moves from a warmer place to a cooler one,  and that if a temperature difference is maintained, heat will continue to flow to the cooler source.  Since heating in the lower radiator hose, little heat is transferred to the surrounding air because of the insulating qualities of the rubber hose.  Heat moves into the cooling system from convection currents and is a very efficient means of moving heat.

What does all this mean to you?  That the advantages of using the lower radiator hose as the "vehicle" to heat the cooling system is a great way to get the job done, and a whole lot easier on the wallet to.  We will be installing the DieselGiant lower radiator hose heater kit for your viewing pleasure.

In the shop again as the "pictorial" mule, is the ole '79 300d.  This is my daily driver and I might say is the slowest car I have ever driven.  Lets give the ole car some heat!  Please do this when the car is cold, NOT HOT!

Safety and security tips:

Please remember to recycle all your used fluids at an appropriate recycling center.  Be mindful to not spill or splash fluids on yourself, others or the ground.  Also as a safety tip please remember anytime you are working on, around or under your car, to wear safety glasses and secure the car with wheel stops and approved jack stands! 


First remove the radiator cap.  If you have a turbo diesel then your cap is on your expansion tank located on the passenger fender well.


This is a good cap.  Note that the rubber is NOT cracked or missing and is still very soft.  Replace your cap every time you do a coolant flush. (2 years)


Drain the radiator from the plastic plug on the bottom of the radiator.  It is on the driver side and has a slot for a large slotted screwdriver.


Yuck!  This is a good time to get rid of the green anti freeze, do a flush and put in some Mercedes coolant.


Be careful with the plastic plug, it will break if you are too aggressive with it.  Make sure the rubber seal in in good shape.  If it looks suspect, just replace the whole thing.


This the DieselGiant block heater kit and is how it is shipped.  Yes I make them myself in my shop.


Remove the old lower hose at the t-stat housing inlet.  Do the same at the lower connection to the radiator.


Remove the old hose and look at that gunk!


Old hose and new block heater hose.


If you have some buildup of gunk, please clean it at this time.  It just takes a few minutes.


I used a soft wire brush and made sure all the surface was nice and clean just like the pic.


Install the new hose as a trial fit.  You may have to loosen the middle clamps to orient the heating element so it does not rub on the radiator.  Then just take the hose back off and give the middle clamps their final tightening.



There is plenty of room for the heater and all you need to do is route the electrical cord to the front of the car, where its convenient for you.

Refill with coolant and check for leaks.

Please note**  This block heater gets very hot!  You must run your engine for at least 2 days to completely rid your engine of air, BEFORE you plug the heater in.  If there is any air in the hose where the block heater is, it will burn out!  Your cooling system must be completely full and void of any air for the heater to work properly.  Do not plug the block heater in to test it, the element will burn out if not surrounded by water.

Under normal circumstances you only need to have the heater plugged in for about 3-4 hours to heat properly.   Do not leave it plugged in overnight, it is not necessary.

Its a whole lot easier to do it this way, and will give you great results.