‘Stormcloud’s cooling system had been neglected by the PO, and required remediation before being used as a daily driver for my piece of mind.
The radiator leaked, the temperature gauge was not operating, and the water pump bearings were shot.
Green coolant was seeping from the climate control servo, the block heater, and various hoses.

Since ‘Desert Rose’ recently developed a turbo bearing failure, I had to press ‘Stormcloud’ into daily service sooner than planned.
I was not able to complete the full cooling system rehabilitation.
I still need to replace the fan shroud, coolant reservoir, reservoir cap, various hoses, and also work on the cabin heating system (which is bypassed for now).

Below is what has been done to ‘Stormcloud’ prior to the failure of ‘Desert Rose’s turbo seals:
The temperature sender, on the block between cylinder number 2 and 3, had very high resistance and a used PNP sender took its place.
This restored the temperature gauge function.
The radiator, heater core, and transmission oil cooler were bypassed to allow for a thorough flush, de-oiling, and citric acid flush of the engine.


Next, the water pump housing, and thermostat housing were removed, and treated with a weeklong Evapo-Rust soak to remove corrosion.
Scrubbing with a nylon brush removed the converted aluminum oxides.
Repeated soaks of the parts in a citric acid solution softened the heavy scale buildup, allowing it to be removed with a nylon scraper
Not all of the scale dissolved even after one month of soaking.

Attached Thumbnails

         

__________________
78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Below is what has been done to ‘Stormcloud’ to get her operational after the failure of ‘Desert Rose’s turbo seals:
There was some surface pitting at the water pump housing hose nipples and thermostat housing hose nipples that were smoothed out with some 400 grit sandpaper.

Gasgacinch was used to coat both sides of the paper gaskets used to seal the thermostat housing to the block,
the water pump housing to the block, and the new (rebuilt) MB water pump to the water pump housing.

A smaller diameter 1985 water pump pulley, shorter 1005mm alternator belts, a short 4 ply silicone hose to connect
the water pump housing and the thermostat housing, a new 9 blade plastic fan, and a new-ish PNP fan clutch were installed.

Attached Thumbnails

         

__________________
78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

A used PNP radiator re-cored by San Leandro Radiator was installed.
The system was filled with a 50/50 mix of Zerex G05 coolant and distilled water.
New flexible transmission oil cooler lines were also installed.
A pressure test was performed, and there were no fluid leaks.
The system held 15 psi for 20 minutes.

‘Stormcloud’s heater core is bypassed for now, so no cabin heat until “Desert Rose’s turbo oil leak is fixed.
Operating temperature for ‘Stormcloud’ has been about 175 degrees F on the daily commute this past week.
More updates to come…stay tuned.

Attached Thumbnails

         

__________________
78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Excellent work! I enjoy seeing seeing clean repairs like you’ve performed.

__________________
1998 E300 Turbo Diesel, 221k Miles
2018 Chevrolet Colorado Z71 4X4, V6, 19k Miles
2007 Honda CRV, 115k Miles
2011 Kawasaki Trans Mule, 212 hrs, (grandkid hauler)

Thanks for this -- interesting and helpful.

How important is the fan shroud to general driving cooling efficiency? And to efficiency at an idle?

Cheers

__________________
1980 300TD

Fan shrouds are essential on most models of vehicle, no matter the brand. They direct cooling air over the engine

__________________
Strelnik
Invest in America: Buy a Congressman!

1950 170SD
1951 Citroen 11BN
1953 Citroen 11BNF limo
1953 220a project
1959 180D
1960 190D
1960 Borgward Isabella TS 2dr
1983 240D daily driver
1983 380SL
1990 350SDL daily driver alt
3 x Citroen DS21M, down from 5
3 x Citroen 2CV, down from 6

Extremely important. The fan shroud ensures that the fan blade pulls air through the radiator and exhausts it through the engine compartment. Without the shroud, the fan blade is recirculating a large quantity of hot air within the engine compartment instead of pulling in fresh air through the radiator.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Agreed X2.
The shroud literally funnels the air on the desired path.
It is like the ductwork for an HVAC system.

__________________
78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Thanks for that -- I guess I need to get mine back on ASAP.

Does anyone have experience trying to replace it without removing the fan and the belt pulley?

Cheers

__________________
1980 300TD