If anyone thinks this post should come down - just say so. I will delete it.

Few cars run as long as ours. Long life , high miles.
Few people get to perform certain kinds of maintenance like we do.

It has been 5 years and 100,000 miles since I last removed the radiator and
cleaned out the fins on the 300SD.

It was running warm on my daily mountain climb and when I removed the radiator and held it up to the light - none came through.
All the fins were clogged.

This is basic radiator cleaning, I start with air, then water pressure, then shop vac.

Still a lot of debris left in the cooling fins. I would have used a pressure washer if I had one.

Read a few years back here about a radiator cleaning solution and decided
to use readily available drain cleaning gel.
Some of my stuff is hair like, and my prior experiments with drain cleaner proved that it dissolves hair.

So I cut a board to fit the radiator (16 7/8 inches by 22 inches I think).
Covered it with a 13 gallon trash bag to resist getting eaten by drain cleaner.

Clamped the bag covered board to the radiator so now one side is blocked
and the solution will settle in the fins and go to work.

I placed this in my wheel barrow (only thing big enough to hold my radiator).
Poured a 64 ounce bottle of drain cleaner on and sort of brushed it in.

After a few hours drained off the wheel barrow in to a bucket and poured the stuff over the radiator again.

Waited overnight and next day went back to a high pressure water rinse
(brass nozzle for driveway washing). Then air pressure.

I wrote this post because this cleaning is the best I have ever gotten.
Short of taking it to a radiator shop for a boil and cleaning this is the best
I can ever imagine getting at home.

All the fins are clean and free of debris.
And my temperatures are now stable even under load.

With rising summer heat here I notice temp changes (was 90 F this last weekend). Now I am ready for summer.

Anyone else used drain cleaner to clean out the fins ?
You folks thinking their radiator is clogged inside - have you checked the
airflow and the fins ?

__________________
80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250