HVAC Rebuild on 1977 240D Manual Trans. - PeachParts Mercedes-Benz Forum

anghrist · #1 01-16-2012, 11:43 AM

Hey guys & gals.

My girlfriend's 1977 US Spec, 240D w/manual trans and manual A/C & Heat controls is having some HVAC issues. Here are symptoms and conditions:

1) It's a bit drafty. The center vent/recirc switch bleeds cold air in the winter. Just want to keep out the cold when my fingers are freezing.

2) Have a heater core steam leak. No fluid collects anywhere, but on hot summer days, I get out of the car smelling like coolant. Eyes tend to burn a bit on those days.

3) Leaves, dirt & who-knows-what-else blows out of vents when I turn on the fan some days. I have replacement firewall drain tubes for the originals which rotted off, but have yet to install them.

4) Car/engine gets uber-hot when A/C system is turned on.

5) A/C compressor is not holding pressure. High side pressures are all over the map. Still has original York compressor.

6) Lost both v-belts rather dramatically one day. Both belts were actually snapped! The idler pulley arm was yanked counter-clockwise about 120 degrees from where it had been tightened as well. Was wondering if the compressor & clutch for the A/C might have seized? Have been running without A/C belt without problems for the last 3-4 years.

7) Actually plan on keeping this car for a very, very long time.

Now the questions:

1) Would it be ideal, here in California where 70mph freeway speeds are a reality, to replace the York with an alternative compressor, since the York is non-functional anyway?

2) Since the heater core/joints might be leaking, would it be worth totally removing and cleaning out the heater/AC box?

3) If yes to #2, then I will be considering repair replacement of everything vacuum related under the dash. How many vacuum diaphragms are on these manual heat/AC systems? 2? 3?

4) I had planned on sticking with R12 in the compressor, are there any alternatives with will be cost beneficial?

Thanks for the input.

I will probably need to clean everything up under the hood as well during this go-round.

franklynb · #2 01-16-2012, 04:56 PM

Quote:

Originally Posted by anghrist

Hey guys & gals.
My girlfriend's 1977 US Spec, 240D w/manual trans and manual A/C & Heat controls is having some HVAC issues. Here are symptoms and conditions:

1) It's a bit drafty. The center vent/recirc switch bleeds cold air in the winter. Just want to keep out the cold when my fingers are freezing.

I've taken five heaters completely apart. Every one had the seal around the radiator
heat exchanger, which was originally foam tape -- corroded past use. The side
effect is that the radiator is no longer sealed inside the chamber, tending to leak cold air around the top of the radiator into the side dash vents.

On my last rebuild -- without re-sealing -- there was so much leakage after cleanout and re-assembly that I could get cold air from the right dash vent, but warm air from the driver's vent at any speed above 45mph. At lower speeds, the leakage couldn't
"overpower" the heater.

The leakage is make-up air for the center vent spilling into the heated air chamber.

Quote:

Originally Posted by anghrist

2) Have a heater core steam leak. No fluid collects anywhere, but on hot summer days, I get out of the car smelling like coolant. Eyes tend to burn a bit on those days.

Check the tubes that source coolant to the radiator. There are three. They bolt to the
radiator using gaskets. Some times the gaskets weep, and the fluid collects in the bottom of the evaporator chamber. I believe MB still sources the replacement gaskets.

Quote:

Originally Posted by anghrist

3) Leaves, dirt & who-knows-what-else blows out of vents when I turn on the fan some days. I have replacement firewall drain tubes for the originals which rotted off, but have yet to install them.

There is also a gasket made from urethane compound that seals the firewall hole around each tube. One "double hole" gasket is still available. The singles are not.
I just cut same shape from three layers of bicycle inner tube, which seems to work.
Punch a 7/16" hole using a standard gasket punch. It will stretch enough to
work around the 16mm diameter tube.

The A/C evaporator chamber collects an amazing amount of soot, leaves and dirt. Since the evap is only SLIGHTLY smaller than the chamber box, its impossible to clean without removing the chamber and disassembling it. Given enough fresh air, it will find its way into the outer vent path.

Quote:

Originally Posted by anghrist

4) Car/engine gets uber-hot when A/C system is turned on.

Consistent with a coolant leak. Low pressure, fast temp rise.

Quote:

Originally Posted by anghrist

5) A/C compressor is not holding pressure. High side pressures are all over the map. Still has original York compressor.

York rebuild kits are still available from Peterbilt dealers. OTR trucks still use this
same basic compressor.

Quote:

Originally Posted by anghrist

6) Lost both v-belts rather dramatically one day. Both belts were actually snapped! The idler pulley arm was yanked counter-clockwise about 120 degrees from where it had been tightened as well. Was wondering if the compressor & clutch for the A/C might have seized? Have been running without A/C belt without problems for the last 3-4 years.

Nothing like a thumper to break a leg on a motorcyle, or a belt on a car. Yorkie! The clutch should freewheel without signal.
...

Quote:

Originally Posted by anghrist

1) Would it be ideal, here in California where 70mph freeway speeds are a reality, to replace the York with an alternative compressor, since the York is non-functional anyway?

The Delco a compressor is a bolt in option. Brackets are easily obtained. It has less
slap-bang load than a Yorkie.

Quote:

Originally Posted by anghrist

2) Since the heater core/joints might be leaking, would it be worth totally removing and cleaning out the heater/AC box?

Nothing you can do costs less for more benefit. Seal the radiator, wash it out, and test all the vacuum actuators ... while you're in there.

Quote:

Originally Posted by anghrist

3) If yes to #2, then I will be considering repair replacement of everything vacuum related under the dash. How many vacuum diaphragms are on these manual heat/AC systems? 2? 3?

I think three; one for the defroster leg that runs along the firewall edge; one for the
fresh air door; and one for the recirc door. I can check if required, since I have one
open on my shop floor.

Quote:

Originally Posted by anghrist

4) I had planned on sticking with R12 in the compressor, are there any alternatives with will be cost beneficial?

Alternative gases? An update will require a complete hose and condenser change
as well as cleaning. And cooling performance may suffer, especially if you have
mostly freeway driving in your cycle. OTOH, if you idle a lot, losing the Yorkie may
drive a couple of MPG....

franklynb · #3 01-16-2012, 05:05 PM

Picture of the heater core tubes:
https://picasaweb.google.com/lh/photo/fIjAO11PvyudDR1aiyUNudMTjNZETYmyPJy0liipFm0?feat=directlink

Dirt inside the evap chamber:
https://picasaweb.google.com/lh/photo/N9wjvBiAEQiw3ri2vUvNfNMTjNZETYmyPJy0liipFm0?feat=directlink

Clearance between the evaporator and chamber box:
https://picasaweb.google.com/lh/photo/3vQB7zdKP05JtzpxLUppwtMTjNZETYmyPJy0liipFm0?feat=directlink

The sealing urethane around the heater core tubes:
https://picasaweb.google.com/lh/photo/HjA5afEXhiw97qXNLK0OC9MTjNZETYmyPJy0liipFm0?feat=directlink

hth.

anghrist · #4 01-16-2012, 06:32 PM

Thank you very much for all the info.

I think this car will be getting a Sanden replacement compressor, heater box clean, scrub, reseal, and recharge with R12.

I will take it slow and replace all of the vacuum equipment under the dash as needed as well. No need for you to count, I think that I had suspected three diaphragms as well.

How right you are about the dusty desert. I believe I should have a few quarts of dust and sand in the heater.

After trying to replace the thermostat on my '99 E300, I'm very frustrated

and think that the old '77 is the keeper out of the two.

Stevo · #5 01-17-2012, 10:41 AM

As to a leaking heater core....I did a fix that involved pumping/circulating hot water and a "stop leak" product through the heater core using a small 12v submersible pump. I disconnected the two heater hoses at the firewall and circulated the solution first one way then the other for about 15 or 20 minutes then flushed it with plain water. Its been a couple years now and still holding. I read a post about this fix here of course

sixto · #6 01-17-2012, 12:16 PM

OT - how do you put manual AC in recirc?

Sixto
87 300D

anghrist · #7 01-18-2012, 12:07 AM

Quote:

Originally Posted by sixto

OT - how do you put manual AC in recirc?

Sixto
87 300D

I may not understand this correctly, but I thought that the slider for the center vents would set the flap for either outside fresh air, or close the vent flap and recirculate the cabin air.

Is that right, or am I mistaken?

franklynb · #8 01-19-2012, 06:59 PM

Quote:

Originally Posted by anghrist

I may not understand this correctly, but I thought that the slider for the center vents would set the flap for either outside fresh air, or close the vent flap and recirculate the cabin air.

Is that right, or am I mistaken?

I'm pretty sure that the RECIRC intake is at the right end of the duct above the
fan, behind the glove compartment.

If its open, the fan takes intake air from the car compartment. If closed, from the heater duct, which leads to the fresh air intake vent cowl.

The fan output goes through the evap chamber and exits up into the heated
chest. Heated air exits through the defroster vents if they're open, or if the
vac pod for defroster doors fails. Excess air goes out through the side grills,
dash vents, and lower vents; pretty much in that order
since each presents a longer path to exit .

Later cars, or Siemens heaters have doors that lead to the floor vents. I've seen these
on a pod in ACC3 cars. I think they didn't exist on early manual heaters. I'm not sure about ACC2.

The fresh air door is just a bypass to the center vents, operating a channel above the
heater chamber. So it gets a mix of cold and slightly warmed air. it doesn't affect the
heated circuit in manual cars. In AC2&3 the center vents are programmable, but
still handle the same semi-heated airflow. The programming makes a difference. For
instance, the center vent is popped by the ACC3 controller to drop the cabin temperature a bit in an overheat.

The field service manual summarizes this in a chart, so its not crystal clear for me.
IOW, I might be wrong. I run my wagon without a dash to observe the programming
and verify these actions. YMMV.

--f

anghrist · #9 03-09-2012, 12:15 PM

Woo Hoo. Sanden compressor kit should be delivered today.

Car is going into shop for fluid/filter changes and general tune-up issues.

Just put new tires on (old ones were 6+ yrs old) and replaced battery (6+ yes old).

Have been driving the 240D more lateley, but have been as busy as a bee trying to make honey for the whole hive. I'm actually having to shop out general maintenence and auto detailing to keep things running.

anghrist · #10 04-28-2012, 07:00 PM

Not exactly part of the HVAC rebuild, but I did have a new windshield installed today. Going through a lot of the issues on this car to keep it, not only roadworthy, but also comfortable.

Having fun trying to get the old York compressor off now. There doesn't appear to be enough room to get to the compressor mounting bolts unless the bracket is removed from the engine block first.

anghrist · #11 05-19-2012, 07:38 PM

Continued work on the car today. After getting all of the equipment back together under the hood, I've moved to the interior.

Had to pull the driver's and passengers seats to get the center console trim out. That was a bear of a job. in the uncooled garage. Found two things that had been broken by earlier owners/mechanics.

1) The bulb holder on the back of the A?C Compressor Control Knob Panel had one of its 'legs' broken. The previous mechanic/tinkerer had put the bulb socket in place and tied it on with some hemp twine. Worked great until someone (me) had to remove the panel for interior work.

2) The plastic cap bushing (Top Hat Bushing) is totally rotten on the manual shift mechanism. It was held in place by the center console trim. With the console off, I've had to wrap some friction tape around it and the housing to keep it in place. Not easy when there is still 35 years of gunk/grit and dust on the interior.

Unlike the DIY (I know that it's just a guide) this older W123 did not have release clips for the trans tunnel carpet panels. The plastic panels that the carpet are glued to are actually stapled onto the center console. I can tell this was done at the factory because there are no other clip nor attachment marks on the trim panels. I will need to pull all of the staples to clean and re-carpet these panels. Then reattach the panels before reinstalling in the car.

The other carpet pieces in the car are equally dingy and smelly. I will vacuum out the interior, pull all old carpet, clean the floor surfaces with acetone to remove old adhesive and then reglue/attach new carpet and possibly insulation.

After all of this the old car should smell new on the inside.

anghrist · #12 05-30-2012, 11:09 PM

Holy dashboard removal Batman.

After two weeks of business travel, I was finally able to resume work on the 240D. This evening, I removed floor vents, glove box, instrument cluster, then finally the dashboard. I was able to remove most of the ancient plastic pieces without breakage, except for the passenger's side vent. The tabs on the trim ring snapped off, so I will be replacing that.

I dropped one of the glove latch screws under the passenger seat, so I will have to hunt for that as well.

Next, I will be removing the heater/AC box and then swapping out the cores. I will also be testing all of the vacuum parts. Will also need to take some pictures of this AC system connections. Most everything is labeled at this point to make reinstalling easier.

charmalu · #13 05-31-2012, 11:37 AM

Once you get the Heater/AC Box out and start digging deeper into it. you will discover the foam on the various doors has deteriorated, and will need to be replaced.

I have one apart from an 82/83. I thought maybe the liners for a tool box drawer would work well. thinking maybe the 3M 8090 spray adhesive might work best. recommended for Hood Pads.

Be nice if there was some way to add a filter on the air intake to keep out the debris from packing in the Evaporator..

Be sure to take pictures as you dissasemble the heater box.

If you discover you need any parts, a Heater/AC box from PNP is around $60.

Charlie

anghrist · #14 05-31-2012, 04:59 PM

Quote:

Originally Posted by charmalu

Once you get the Heater/AC Box out and start digging deeper into it. you will discover the foam on the various doors has deteriorated, and will need to be replaced.

I have one apart from an 82/83. I thought maybe the liners for a tool box drawer would work well. thinking maybe the 3M 8090 spray adhesive might work best. recommended for Hood Pads.

Be nice if there was some way to add a filter on the air intake to keep out the debris from packing in the Evaporator..

Be sure to take pictures as you dissasemble the heater box.

If you discover you need any parts, a Heater/AC box from PNP is around $60.

Charlie

Thanks for the tips.

I will definitely look at the flaps and the insulation. If they need to be refoamed, I've got some 1/16th" self-stick foam that I picked up at an art supply shop. I think WalMart carries it as well.

Logging all of the little broken pieces as I go and getting ready to clean all of the floorboards and try to kill all mold and crud that makes the car stink.

This will be a decent car to drive around after I have finished with it.

anghrist · #15 05-31-2012, 05:01 PM

Also, the slastic shift bushings, inside the shifter, are really rotted and are falling apart. Lucky that I had pre-purchased these in anticipation.