‘Stormcloud’ - Coolling System Remediation–Part 2 - PeachParts Mercedes-Benz Forum

Alec300SD · #1 04-22-2020, 01:36 AM

Well it has been over a year since Part 1 was posted.
With lots of free time from the shelter in place orders, the previously bypassed heater core is now operational.
Finally there is heat available in the cabin, no more shivering in the car during cold weather.

The metal pipe lines for coolant flow from the engine to the servo (lower pipe on MB part number 116 830 34 150),
servo to heater core (upper pipe on MB part number 116 830 34 15), and servo to water pump (MB part number 116 830 35 15) were severely corroded and needed to be replaced.

Unfortunately, both parts are NLA, but I figured out a workaround.
Months ago, I remediated two used pipes pulled from a car at Pick-n-Pull.
They were soaked in EvapoRust for about a month.
The interiors of the pipes were scoured with a long brass bristled bottle brush.
The exterior ends were scrubbed with a steel wire brush.
Then they were powder-coated with a shiny black finish.

Removed the leaking Servo Valve (aka Evil Servo) (000 830 03 84), removed the seized Auxiliary Pump (000 835 69 64),
removed the rusty Pipe Line from servo to water pump (116 830 35 15), and removed the rusty Pipe Line between engine and Servo (116 830 34 15).

Alec300SD · #2 04-22-2020, 01:37 AM

Removed coolant reservoir, reservoir pressure cap, and overflow tube.

Cleaned right side of engine bay. Output nozzle of windshield washer pump is broken.
Rust present on and below battery tray, PS headlamp cover, and below ACC servo unit.

Installed new MB parts: coolant reservoir (126 500 15 49) with blanking plug kit (126 500 00 84),
new over flow tube (021 997 76 82), and reservoir pressure cap (123 501 02 15).
Installed remediated (de-rusted, and powder coated) Pipe Lines (116 830 35 15 and 116 830 34 15).
Heater bypass hose (5/8 Dayco) installed between lower pipe line (from engine to servo) and pipe line from servo to water pump.

Alec300SD · #3 04-22-2020, 01:41 AM

Back-flushed heater core with garden hose, and then pressure tested heater core for leaks .

To pressurize the heater core, I made an inlet port from a tapered silicone plug.
I cut about 3 inches from an old thick-walled ALDA boost sense line and inserted it into a hole drilled in the center of the silicone plug.
The inlet port was inserted into the heater core inlet hose and secured with a hose clamp.
A solid silicone plug was inserted into the heater core outlet hose and secured with a hose clamp.
The Mighty-Vac was attached to the inlet port, the heater core was pressurized to 15 psi, and there was no pressure drop after sitting overnight.

During Part I, I was concerned that a citric acid flush of the heater core might remove too much material and cause the heater core to leak.
For Part II, I used a gentler product (Evapo-Rust THERMOCURE) over a 36 hour period to remove rust and scale from the heater core.

Alec300SD · #4 04-22-2020, 01:43 AM

Because the servo unit was very corroded and not operating, I decided to eliminate it and install a ball valve instead.
Installed a Joywayus 5/8” Hose Barb Ball Valve, 2 brass 5/8" T fittings, hoses (from old servo as well as new heater hose) using Norma type hose clamps.
Ran the engine, checked for leaks, and topped off the coolant recovery tank with 1 quart of Zerex G-05 coolant.
On a freeway test drive, obtained vent temperature readings of 110 degrees F with the ball valve open all the way.

Installed the missing lower left fan shroud clip (004-988-23-78), and then installed the fan shroud (116-505-05-55) without removing the fan (it can be done!!).
Eventually will need to replace the servo unit or go to manual interior control from a non-ACC donor vehicle.

The cooling system is pretty much up to snuff right now.
The only other task remaining is to replace the block heater due to very slight seepage.
That will be done when the ceramic coated exhaust manifold is installed.

vwnate1 · #5 08-13-2021, 08:22 PM

Looks pretty good ! .

I see you used a factory auxiliary water pump to flush the heater core .

How do you regulate the heat now ?.

Alec300SD · #6 08-13-2021, 11:58 PM

Since the leaky servo has been removed, I obtain heat by opening the ball valve (second photo in post #4) varying amounts depending on the expected ambient temperature.
The more open the ball valve, the more heat in the cabin.
To get a bit more heat, I also can turn on the blower motor by pressing the defrost switch.

Not as precise or convenient as the manual euro system, but faster heat than the old servo system, and quite adequate for now.

vwnate1 · #7 08-14-2021, 01:06 AM

O.K., sounds good .

I took the time to learn how to service the Klima I system on my '78 & '80 NA 300CDs, once it's working it's far better than any other Mercedes system but I hated it for all the hassles and how delicate it is .

I'd think maybe the cable operated hot water valve from a Dodge truck would work, I can't see opening the hood to change temperature when the out side temperature swings 40 degrees in a matter of minutes here .

As long as it woks good deal .

The manual hot water valve has the correct asymmetrical hose nipples and by passes the heater core completely when closed, this ould be nice as I can feel radiant heat in the Summer from my W123's .

BillGrissom · #8 08-14-2021, 02:40 AM

I replaced the OE mono-valve in both my 300D's (1984 & 85). In my 1984, I installed a later mono-valve for a W124 which appears to be more available. I installed it in place of the aux water pump (slipped into its bracket) and soldered wire to run forward. I had to buy the mating connector since the pins are larger.

In my 1985, I installed a vacuum-operated water valve (1 tube w/ spring return) for a newish Ford ($10 ebay) and a vacuum switch (had on hand) which the monovalve wires actuates. It is neat to see the valve open and shut by the automated temperature control, whereas with the monovalve you are blind to what it is doing. You can buy a kitted setup from Klima using M-B parts but pricey. I understand that setup is what later M-B cars used. Search for my post for photos.

The firewall routing looks like a drunk German plumber designed it, but needed due to selecting a 3-tube heater core (for frigid winters). In my 1985, I ripped out the OE tubes and fabbed silicone hoses w/ a tee to plumb to the heater core tubes. I didn't trust the old hoses and new ones are pricey and hard to source.