Hello,

I would try a good heat gun on the valves before you give up. One other long shot; cooling system chemical flush will often free up these valves. Try the heat first.

Hmmm, five hours quite impressive. I have the MB factory time guide for this model. The book time is 9.1 hours for blower replacement by factory trained technicians, with access to any special MB tools, under best working conditions, and when these cars were fresh and new!

These days, add thirty years of dirt, stuck valves, stubborn bolts, rust, less than perfect working conditions, and lack of experience and you are looking at two long days of tedius work by most week end warriors.

The V-8 engine models with AC are the most difficult and time consuming.

Joe Alexander
Blacklick, Ohio

If a 108 is like a 109, the guy at the MB dealership (old guy) told me it was 28 hours of labor.

__________________
MB-less

..and in a 6.3 the cluster will come out at connect with the steering wheel as you leave the traffic lights

The valves in the heaters need careful soaking with good penetrating oil and as has been suggested,a little heat from a hairdryer. The white deposits from bad coolant seem to a accumulate in the hole in the valve body and make it stick . I have often resorted to connecting the heater to a hose on the engine side and running mercedes own citric acid flush through the heater to release stuck valves plus the hair dryer.

When I get the heater core out, I will try your suggestions-the MB citric acid sounds intriging. Following Twinoakchef's lead I tried using my hand to reach up behind the instrument cluster but had no luck-I did not relish suffering the same discomfort. So, by going in thru the radio opening and disconnecting the speedo cable first, I was able to gain clearance to use a threaded rod with a 45 degree bevel on one end and long enough to gently tap the knurls on the nut in a way to loosen it. This procedure worked Ok but I still will have to figure out how to put it back on.
Thanks,
MBG

Undo the handbrake bracket,the lever will drop out of the way far enough to get even my big hands up there. The knob is to the right of the cluster and is easy to reach once you understand where it lives.

So far I have taken everyone's advice and today managed to wrestle the heater core assembly from the firewall into the great outdoors. One little tip which might help another forum member who is tackling this job: the (4) clips which hold the housing together at the blower motor (left side) were removed. This faciliatated just enough downward movement of the housing so that the assembly came out without additional muscle. Before this little trick I was contemplating a come-along hooked to the heater core assembly because it was really tough to move.

Take time to ensure the fan is operating properly too. And replace ther sponge pads on the doors so it will work as it did when new.

That was an area I noticed needs restoration. When I cleaned-up the housing with my air gun, the foam or sponges as you call them were blowing away. Are these parts something I should fabricate from, say, an AC unit filter or have you found another solution?
Thanks,
MBG

It's just regular sponge or foam rubber. I spoke with someone last week who used dish washing sponge cloths . because they have a closed cell surface on one side which is ideal was face and doesn't collect dust like the factory stuff does.

Would there be any problem with heat affecting a washcloth?
The PO was not concerned with service in so far as the climate control system is concerned. If you have followed the replies above, I have had a time just dealing with the heater core as well as the housing. At this juncture I am replacing the core and the blower. Do you know if the rubber mounting gaskets which insulate the core from the heater box are available? Also, I will need some clips for the heater lever assembly-assume these will be a dealer item.
Thanks,
MBG

ha ha no,it doesn't get that hot Just remember to use new ones,not some you have liberated from the kitchen sink.

I'm not too sure if new gaskets are available,try the mercedes Classic center in Irvine California ,Tom Hanson will be able to tell you straight away if they are still sold. I would say that making some new ones from sealing strip will work just as well. I have never tried to buy new parts,such as the clips, for the heaters because i have a pile of used heaters here 4 feet high...

The left side gasket has imbedded itself into the housing-rather appears to have melted in. If the OM gasket set is available and not outrageous I'll try a set; otherwise, your idea for some strips to hold the core in place sounds good-what type of rubber strips did you use?
On another note the wire harness for the blower has a spring (fusible link?) in between the blower feed and the motor. Is this something I should worry about? My intention is to leave the connections the way they are. Before I put the blower motor in I am going to test it by connecting directly to a 12volt source the way I would test a starter motor prior to installation. In your opinion is this an acceptable procedure.
Again,
Thanks,
MBG

Thats the resistor for the motor it has 3 different speeds so be careful you don't break it. For the seals,I just use sponge strip thats made for sealing around windows or screens on houses.

be careful on testing the blower straight off 12volts. I did it with the first blower I put in and later on some of the plastic parts melted. I believe that this happened because of the excess voltage that was applied to the unit.
Isn't there a resister inside the housing to reduce the voltage? Or is it just a fusible link.
I used thin foam rubber, with an adhesive back, for all of the vents and around the core. It formed a very nice tight seal.
So was your original core beyond repair? Mine was completely clogged(stop leak) but the radiator shop was able take it apart, clean it out and seal it.

__________________
Britton McIntyre

68 280 SE coupe 'Hairball'
70 280 SL
71 280 SEL - RIP May 2010

I was careful to purge the core before I pulled the assembly out so Anti-freeze wouldn't go all over the floor board.
The two valves presented a problem. Even after soaking with penetrating oil for a suitable time and applying heat, I was unable to budge them. I tried using the fitting for the cable to move the valves and then used the spark plug trick-to no avail. As I tried rotating the square raised faces of the brass valves each one broke off. My deduction was quite simple: if the brass is in this kind of shape and I have just spent untold hours and used words which I dare not repeat any place else trying to get to the heater core and blower, I said: replace the core and blower motor and (hopefully) be done with it for awhile-end of subject.
Am waiting on parts and will keep you posted.
Thanks,
MBG