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FCP Euro Service Kits

FCP Euro Kits

If your heater hoses have not been replaced in recent memory or if you acquired a classic Mercedes-Benz and have no idea when the hoses were replaced, it is a good thing to do. In the case of our 1975 450SL, the hoses are more than likely original and need attention.

Most of the hoses are very easy to change out, such as the radiator, overflow tank etc., but a bit more complicated, are the hoses that feed the heater box from the engine. Three hoses in all serve the system and this article will show you just how to get the job done.

It is also worth mentioning that while it might appear complicated it is not, but is a bit time consuming on the first go. You will however save yourself a fair bit of cash doing it yourself. I was quoted $750 by an MB dealer for this job.

The first step is to remove the lower polished aluminum trim from the windshield as shown below, beginning with the two corner retainers. Work slowly and gently so you do not bend or mark your trim.

NOTE: plastic trim removal tools such as the ones being used on this job are the best tools to use.

This photo shows the left side (passenger) lower corner trim.


This photo shows the removal technique and tools recommended for this job.

Continue to follow across the trim with your tool to the opposite side, until all the trim is completely loose.

Once the trim pieces have been removed, find a very safe, out of the way location to store them to avoid any bending or damage which will render the trim useless. Now it will be time to vacuum the 40 plus years worth of dirt from the channel to avoid additional dirt from entering the air intake.


This photo shows the lower trim removed.

With the windshield trim removed, you will now punch, using a nail punch, the plastic “rivets” or retainer clips, through as shown. After the three “rivets” have been removed, you are now able to lift up the metal air intake grill. Under the grill is a metal debris screen which must also be removed if it is not still attached to the grill. This exact process will be repeated for both sides of the car.

Close up of plastic “rivet”

Three plastic “rivets” for each grill must be removed.
Center punch on “rivet” and strike with hammer. Rivet should crack and fall out.

Now that the air intake grill assemblies have been removed, it is time to replace the three hoses. I will be showing the left side for this article.


Grill and screen removed along with 41 years of dirt.


Photo shows hose clamp looking through grill opening toward blower motor. Standard Phillips screwdriver to remove hose clamp.

You will also see a metal flap on each side below the grill. The door (flap) can not be moved further out of the way, but the heater hose clamp is easily reached with a standard Phillips screwdriver and flap in place. A flash light will also serve you very well.

It will also make your job much easier to remove the blower motor seen in photo below while you are at it. This will not only make the job easier, but will allow you to change the weather strip between the blower motor and the body. While water is less likely to work it’s way in to this area, it is very possible when washing the car or in a heavy rain. If the seal is no good, water will enter the cabin from this point. The gaskets are still available.


Photos shows resistor along with one of four bolts holding down the blower assembly.

NOTE: The bolts holding down the blower assembly are more than likely a bit rusty, especially if the car has spent most if it’s life in a wet climate. One day prior, spray all four bolts/nuts with PB- Blaster (my preference) before attempting to remove. The nuts will be removed with a 10mm socket and extension. It will also be necessary to remove the two screws holding the blower resistor to create the necessary wiggle room to insert the socket and extension between the resistor and blower motor casing. No need to unplug the unit. Be sure your 10mm nuts turn easily. If you snap the bolt, you will be doing more work from under your dash with the dash out!


Blower removed showing weather strip, condenser and heater box hook up for left side.

IMPORTANT: When removing the bolts and the blower unit, it is critical that you lift straight up and over the stationary bolts. If you twist or tug the likelihood of braking the bolt hole ears on the blower case is quite likely! Three of my bolt hole ears splintered on the first gentle wiggle to loosen it from the old weather stripping.

In the event you do damage the housing, there is no turning back. Do not attempt a quick fix like glueing the unit down. It will be a nightmare should you or the next owner ever need to replace it. According to Mercedes-Benz the blower assembly, housing and blower, can still be obtained for a price of $1,200. The two pieces are not sold individually. The blower unit is however available as an after market part should you need that and for a much more reasonable price. You may also wish to look at several used Mercedes parts resellers should you need a case or you can always check Ebay, but they are still not cheap.

Once the blower assembly has been removed, you will now disconnect and remove the two hoses from the engine and heater box respectively. Check your hose clamps for reuse or replace with new ones if necessary. If the hose clamps have not corroded, and are in good working order. I like to keep as many of the factory products on the car as possible. By simply taking your old hose clamps to a bench grinder fitted with a polishing wire wheel, you can get a nearly new finish on many sooty and tarnished parts.

NOTE: Always make sure used parts are in good working order before reinstalling.

Having removed all three hoses (one on the left and two on the right), it is time to revers the process for installation. While in the system however, it is a good idea to check for rust, clean out any and all debris.

When everything is clean and put back together, start the car and make sure you do not have any leaks before reinstalling the air intake grills and trim. Also, check to make sure you replace any coolant that was lost should the system require it when testing. If all is good to go, button the system back up and you have completed the heater box hose change for your 450SL.


New hose on left side installed and waiting for blower assembly gasket from Germany.


This photo shows hose from valve to heater box on right side and blower cover weather striping that is also in need of replacement.

As you can see in several of the photos, my 450SL is in need of a new paint job. The previous owner painted white over the original 904 blue and had a lousy job done at that, but hopefully this too shall be a thing of the past by 2017.

Again, the heater hoses are a job worth doing on your own. While it tools a bit daunting, it is quite straight forward.

Parts needed:

*Part numbers are specific to the 1975 450SL. While many part numbers cross various chassis series, always check to make sure you are ordering the correct part for your chassis and year.

 

Helpful tools:

  • Plastic trim removal tools
  • Phillips screwdriver
  • Nail punch
  • Hammer
  • Vacuum Flashlight
  • 10mm socket
  • Socket extension
  • PB-Blaster

Shop All Mercedes Heater Hoses

 

Shop Mercedes Benz Parts Online Catalog Lifetime Warranty

 


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Written by :
Alex Fiehl


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