1984 300CD, installing new radiator
 

I just ordered a new Nissens radiator. I'm trying to decide if I should install it myself or take it in do have it done. Are there any secret problems when doing this job?

The radiator removal/replacement is extremely simple. Twas me, I would do a system flush before removing the current radiator. And I always replace caps when I replace radiators, even if the cap isn't actually on the radiator. And no better time to renew the hoses if they are long in the tooth.

Installing a radiator in a W123 car is not difficult. If I remember correctly the radiator has two round bumps on the bottom of the radiator which fit into two similar size holes in the bottom of the core/radiator support. Be sure that the bottom of the radiator is firmly seated at the bottom. The fan shroud fits into slots which are molded into the radiator.

This is a good beginner task. PLEASE make sure to avoid the green coolant!!! Stick to ONLY Genuine Mercedes Coolant or Zerex G-05 gold. Otherwise you can risk blowing ahead gasket, rusting out your system or replacing the water pump.

By 'flush', I assume you mean to somehow put pressurized water through the system? I've drained many a radiator/engine of coolant, but never 'flushed'. Please elaborate.

For sure, "flush" can have a wide variety of meanings. What I recommend is buying one of the available coolant system cleaners/flushes and using it per the instructions. The idea being to get the system reasonably clean so as to avoid having any residual contamination or sediment wind up in the new radiator. On the 617 engine, to finish up, I remove the block drain plug and run plenty of fresh water through the engine via the upper radiator hose.

Not wanting to start another coolant debate, I agree with the use of G05 in these engines. However, I believe when these cars were made, they only had "green" coolant (or the same formulation in possibly a different color). There is talk of Diesel engines needing the additive that prevents cavitation (found in MB (blue) and G05 coolants), but it is only needed for engines with wet liners. Our engines have dry liners. It has been my experience that MANY (I have had/worked on hundreds of these engines) of these iron block and head engines have been using green coolant for years with no ill effects whatsoever. On aluminum head Diesel engines, I imagine G05 or equivalent is a must. I personally don't believe all the hype about damaging anything by using green coolant in an iron Diesel engine. YMMV

EDIT: Also, be sure to use distilled or R/O water with your 50/50 mix.

I completely agree. G-05 is better, but conventional coolant isn't going to cause any damage when properly maintained. Just like synthetic oil might be better, but conventional oil isn't going to "damage" anything.

John Deere Cool Gard II is a superior option now that MB doesn’t offer G-05, but rather G-48, which has 2-EH, a concerning additive.

Granted, G-05 can be had in lots of places so has great availability. G-05 is great stuff but the Cool Gard II is a newer chemistry and possibly better especially for mixed metal engines.

I agree with the comments to do a flush. At minimum remove the block drain and then fill
And drain the system with distilled water. Then reinstall and use the right coolant of your choice.

New Radiator
 

If you're handy with tools do it your self .

It's CRITICAL to use two wrenches when loosening / tightening the transmission cooler hoses as the fittings in the bottom of the radiator are easy to rip loose, ruining the new or used radiator .

The oil cooler is held in by to 10MM bolts, use a 1/4" ratchet to loose then withdraw them, raise up the cooler slightly and push it 1/4" to the driver's side then raise up the entire radiator maybe 1" and stuff a rag underneath it , this holds it up so you can easily reach the two tranny cooler hoses and the lower hose clamp .

Have towels or a large, wide drain pan handy as a fair bit of ATF is going to dribble out as you remove and replace the radiator .

The flushing is critical because as mentioned there's almost guaranteed to be lots of old rust silt, scale and solder bloom that will get into your new radiator making it less effective .

Use Citric Acid powder of maybe the yellow bottle Prestone flush at your F.L.A.P. S. .

Before flushing, drain all the old coolant out and refill with clean water, distilled water is best and if you shop around some store almost always has it for $1 / gallon .

No shop will ever do the job properly (not even the Dealer) because it takes time and effort to do it just so .

Remember, when the flushing is going on you need to have the heater on FULL HOT to get the silt out of the heater core, that's the lowest part of the cooling system and is always silted up to some degree .

50/50 is really to thick, 60% distilled water and 40% coolant will give you good protection and better cooling to boot .

Nothing difficult / special here, just basic hand tools and you paying close attention, nothing needs to be tightened until it squeaks .

Mind the old coolant ! . it's DEADLY POISON to pets and small children because it tastes sweet and once they drink a tiny bit it causes liver failure, no cure :eek: .

I lost a wonderful dog to fresh coolant once, I looked away for maybe two minutes and he ran to the drain pan and slurped some, that was that :( .

Let us know how it goes, maybe post photos ? .

I’ll tell you that G-05 is as bitter as can be. Had some clear liquid on my garage floor and wasn’t sure if it was antifreeze that had leaked out of a bottle, or water that leaked from the side trunk drains of my w123. Put a little on my finger and touched it to my tongue. I could taste the bitter for the rest of the day.

Generally I’d never partake in a taste test to determine a chemical, but I wanted to see if there was bitterant in G-05. Sure was!!!

It Depends on the brand .