450SL Heater Box Removal

So just how hard is it to remove the heater box from a 1975 450SL? Well, it all depends on what you consider hard.

Mercedes-Benz 1975 450SL Heater Box with ducting attached (pre auto climate control)

I would suggest it is not very hard, but it is very time consuming and requires plenty of patience and detail oriented work. If you are going to tackle this project, a considerable amount of the cabin needs to be removed and that is not necessarily fun. That said, it will save you a great deal of money to do it yourself. I will say, whatever someone charges for this job, deserves every penny. I inquired with Mercedes and was told it would be about $3,900 to remove and reinstall the box. The price would go up even more if parts were needed. 

So, if you don't have heat, or leaking / dirty evaporator that's not cooling properly, and you desperately search the online forums for how to reroute hoses to bypass the leaking heater core, consider doing the job right. There is no reason to own one of these great classics without the creature comforts. Moreover, the relatively short time it takes to do this job will give you many years of enjoyment.

Some things to know upfront however, before you get started. This blog will not go into detail on the project but give an overview of the process. Should anyone wish for more detail you may respond to this post and I will consider a more step-by-step write-up.  

If you own a 1973-76 SL/SLC, the following will or may need to be removed, depending on the model year. 

I am going to cover the heater box removal specific to a 1975 450SL. Remember, Mercedes relocated a few components here and there over the production life.

Not necessary to remove, but very helpful:

• Both seats. 

Necessary to remove:

1. Steering wheel
2. Center console 
3. Dashboard (A pillar trim must also be removed at this point)
4. Exterior air intake grills at cowl (remove No. 5 first to see if you can access the hose clamps from there. If not, proceed back to this step)
5. Heat/A/C blower unit
6. Front floor mats
7. If the car is equipped with refrigeration, that system will need to be vacuumed down.
8. Three quarts of coolant will also need to be drained from the radiator, not the overflow tank to prevent even more coolant from flowing into the car.
9. Cruise control unit 
10. ECU
11. A/C drain hoses (each side of heater box)
12. Center dashboard / console brace
13. Front heater box brace
14. Upper heater box mounting bolts
15. Main ducting from heater box to side and floor vents
16. Zip ties retaining main wire harness and vacuum lines along support brace


NOTE: Cover all remaining flooring with plastic and towels as a quart or more of coolant will drain from the heater core when it is being removed. 

Once the previous items have been removed, it is now time to remove the heater box. Again this is a brief overview of the process.

1. If equipped, disconnect the two A/C lines to the evaporator. 
2. Disconnect the two heater hoses from under the cowl area. You may have to access the hose clamp screw by depressing the fresh-air inlet flap from the outside.

NOTE: I used half-sized, labeled Ziplock bags for each nut and bolt I removed for easy re-assembly. 

Once the above items have been removed, the heater box can be removed from the passenger side of either a LHD or RHD respectively. I found bringing the wire harness up and over the top of the support brace worked easier than dropping it below to gain the necessary room to pull the heater box forward enough to free the  heater matrix (core) pipes from the firewall. Once the pipe ends have entered the cabin, gently bend the pipes downward on each side to allow the heater box an easier journey to the footwell of the passenger side floor. It will take some wiggling and gentle rocking and twisting to free it from the transmission tunnel. 

When the box is removed, be sure to check for rust from above and below! Now is the best time to deal with that.

View of dash area once heater box has been removed. It looks worse than it really is.

Heater box right after removal

Parts to renew while you are this far into the system:

1. Heater hoses
2. A/C hoses
3. Plastic rivets for air-inlet grills
4. Expansion Valve
5. Vacuum actuators (fresh-air inlet flaps)
6. Heater box drain hoses (if equipped with A/C)
7. Drain hose grommets through transmission tunnel
8. Clips (if any were lost or damaged in the process of removal)
9. Heater box / blower motor gasket (can only be replaced with heater box out of car)
10. Heater matrix (core) firewall grommets 
11. Check red throttle linkage grommet if worn or brittle. Now is the time to change that.
12. Vacuum switches (X2) at rear of flap levers (if not functioning)
13. All rubber vacuum hose connections.

All parts listed above are still available through Mercedes-Benz.

Again, if there is an interest in a more detailed breakdown of the process, I will consider doing another blog with additional photos. 

The next step is giving the heater box a good overhaul and testing all the systems. My heater box was full of dirt and some stuff I was not expecting to find.

IMPORTANT NOTE: If you own a 1973-1976 SL/ SLC, the A/C evaporator is factory sealed into the case. According to the Mercedes-Benz workshop manual for the heating and cooling system, the case "can not be separated without damaging the heater box." With much study of the system, I was able to cleanly and easily remove the "factory seal" and restore the unite as original. This step is very worth the time, effort and money (if you can't do this step yourself) if the box is already out.  

I contacted many shops around the world to see if a new unsealed heater box could be obtained and  they are simply no longer manufactured. Later boxes will not work as the system was changed to an automatic climate control system from Chrysler Motor Corp. and one you don't want to retrofit. The manual system is far superior.

UP COMING BLOGS

• Heater box overhaul

• Dashboard refurbishing

• Weather seal installation 

450SL RESTORATION UPDATE - JOURNEY THROUGH TIME

It's been a while since the last post, but the Mercedes R107 450SL is ready to come home after nearly five months in the body shop. 

The body shop has done a remarkable job in both prepping and refinishing this car. Enjoy the journey in photos. Next up, interior and trim.

If you are enjoying this blog, I hope you sign up to receive notifications when new articles are posted. There is much more to come! 

Dismantled at body shop 

Stripped and Bondo work being done

Primed

MB 904 blue color coat being applied to hood

Trunk lid

Super high quality "show clear" being applied to hood

Body ready for paint

Ready for hood, trunk, trim and final buffing...

Mercedes R107 450SL Interior Video

The video in this blog was initially to serve as a record for me on the progress of the complete restoration of my 1975 450SL Mercedes-Benz. 

Upon completion however, it was suggested that this video be posted for other classic Mercedes and automotive enthusiasts to enjoy. 

The filming is not precise as it was done hand held using an iPhone 7. It was also spliced as it was a bit difficult to rotate my body 360° in one go. Enjoy.


Additional photo of interior. I will continue to post as the car progresses through the restoration process. 

Mercedes 450SL Interior Removed - Restoration

The 1975 450SL is hopefully just a week away from heading into the bodyshop. Only remaining items to be removed are the dashboard and center console. 

As you can see someone was very desperate to keep the dash cap in place and went crazy with silicone caulk! Sadly the dash was not that bad. I am going to attempt to salvage the dash by removing all the silicone with 3M silicone remove and refinish the dash. 

Trying to salvage the original sound damping mats was unfortunately impossible due to the glue doing its job very well all these years later. It is important however, to pull all of this up to inspect for any damage or rust. Thankfully there is only superficial rust on the floor pans.

Easy Removal of Mercedes R107 450SL Seats

I was shocked at how many different stories and methods of removing the driver seat of a Mercedes 107 there are online. So I decided to post on just how simple and straight forward this job really is for both seats!

The passenger seat is very straight forward. Four 13mm bolts and two countersunk Phillips screws. Getting a good photo was harder than taking the seat out so several diagrams will be used for explanation. The following shows the set up of the passenger and driver seating rail systems and function. The following diagrams and images are from a 1975 450SL. Check your model for variations.

To operate the driver seat hight adjustment: If adjustment knob handle is horizontal the seat is in the low position. To raise the seat, pull knob handle straight out and rotate as shown on both rails. This step must also be taken to gain access to the screw that retains the knob in order to remove the seat.

The passenger seat is removed as shown below.

As for the driver seat you will need a large flathead screwdriver bit to do this job correctly. Too often jobs are very difficult because the correct tools are not used.

Do not attempt to do this with a standard screwdriver. You may also benefit from heating the screw slightly with a pencil torch. 

Other than a few changes to the mechanism of the seat, the driver seat comes out just as easily as the passenger. 

I purchased a Pittsburg socket screwdriver set from Harbor Freight with a 1/2 in. driver socket. Largest driver bit however needed modifying as the flat head screwdriver was too thick and did not properly seat. I simply ground the flathead down on a bench grinder until it fit snuggly and will remain in my Mercedes specific tool kit.



The following shows the removal of the driver seat. Again, very straight forward. As you will see in the digram below only two of the three screws are removed. The lower screw is secured at the back by a nut and does not attach to the body of the car.

Once the seat is free to be removed, lift up on the side closest to the door opening, while tilting seat toward center console. When free of door sill, withdraw seat. It is best to do this with the hard top off or convertible top in the down position.

The seat is not exceptionally heavy but awkward, so be careful to have good control when removing to avoid damaging interior or paint work. Unplug seat belt warning light from under seat.

It is recommended that when you have the seat out you throughly clean the rails, guides and re-grease with the proper lubricant. Your seat should slide like new again. You will also find amazing things under the seat as I did from the previous owner!

42 years in the desert will do strange things to products like the three petrified cigarettes
(can you find them) and paper that was turning to powder.


I was however able to subsidize a portion of my lunch with the .62¢ I found.

Trim Removal - Part 2

The trim removal continues on the 1975 Mercedes 450SL. While it is not a glamorous job, it is extremely educational to do this exercise personally. I am finding all sorts of things in the door that I am sure go some where but have since rattled lose, broken off etc., over time and now is the time to get all that right. 

So far the following items have been removed:

• Rear taillights x2
• Trunk fueltank division panel
• Rear bumper assembly and bumper trim
• Emblems (450SL and Star)
• Chrome trunk trim
• License plate bumpers / plugs x4
• Trunk gasket
• Trunk locking / latch mechanism
• Soft top lid trim (chrome and MB-Tex)
• Convertible top
• Convertible top cover locking / unlocking mechanism
• Antenna
• Gas flap (door)
• Door molding (guards) and chrome trim at window
• Interior door skins, armrest, pocket
• Side mirror and mirror bracket
• All rubber gaskets on door and body at entry
• Door handles and locking / latch mechanism
• Seat belts
• Door sills (chrome and rubber)

And while this list seems short, I have carefully collected dozens of ziplock bags with parts so far. Labeling everything is key to remember how it all goes back in the end. Losing parts will get expensive if you are able to even find them. It is my recommendation that other then rotting rubber parts you should keep and photo graph everything until you have the new parts in your hand and know it works.

The following photos show the progress in limited detail as of today.

Convertible top and locking mechanism removed

Door latch assembly

Power window hook up. Everything looks very good in here.

Door after paneling removed

Interior paneling being removed

Side mirror bracket

Side mirror bracket removal. Two screws and two bolts must be removed to remove bracket

Mirror bracket removed

Interior of door. You can see three of the exterior molding clips along with the old insulation.

Passenger side door actuator

Latch assembly removed.

Restoration 107 - Trim Removal - Part 1

With the color scheme decided for the interior and exterior, it is now time to get the 450SL ready for the body shop.

Several weeks ago I finalized the shop that will be doing my work. I also received my final estimate and with it came two options. The first, deliver the car as is, and let the body shop strip the trim, and interior or, option two, do the interior and trim removal personally. 

The latter is what I am choosing to do as it will save $3,000+ thousand dollars. I have also chosen this option so I can personally go through every piece of the car myself and see exactly what needs to be replaced, fixed, restored, etc. as the parts come off. This option will also give me time to redo the many interior parts, such as recovering the seats, restoring the center console, dash and other interior trim pieces that will be taking on the new interior color.

Over the next several weeks, photos of parts being removed will be uploaded of each section. In addition parts that will need replacing, such as all the rubber seals and gaskets, will be included in each article and update complete with part numbers and whether or not they are still available from either Mercedes-Benz or as an aftermarket item. I am hoping not to have to get too many aftermarket parts, as I wish to keep this car as close to 100% factory as possible.


Trim Removal Begins
Complete Taillight Removal

Remove cover/bulb holder

Unplug cover/bulb holder from electrical system

Trim screws, frame and lens screws (bolts) are different as seen by a screw driver slot is fitted for the chrome trim screws the rest do not. You do not however remove the screw to remove the chrome trim, just the retaining nut.

Taillight frame still in place. This needs to be removed for painting. This piece also holds the tail lens gasket.

Frame and taillight lens removed

Entire taillight assembly removed. Chrome trim directly above opening still in place.

Chrome trim removed above taillight opening. Remaining trim to be removed in a separate post