Installing a W126 radiator

Today’s job was installing a W126 radiator into my 1987 560SEC.   I had previously sorted out the cooling hoses as part of my monovalve eliminator install.   I was just waiting on a few extra parts I had ordered to begin this job.

Firstly I decided to replace the coolant reservoir tank.  My current one is not leaking, but the plastic was quite discoloured and looked a bit white around the hose entry.  Genuine Mercedes coolant reservoirs are still quite inexpensive, and you never know how long that will continue.   Best to change it now.   I was already planning to replace the level sender as it never alerted me to my coolant leak.  It is a pretty simple job to move all the hardware over to the new tank.  Having a proper set of circlip pliers would have made changing the sender easier, but it wasn’t so bad with the a set of needle nose after the tank was out of the car.

Coolant reservoir

The old one will be useful as a temporary spare if I ever have a problem in the other W126s.   I also replaced the coolant hose between the tank at the bottom of the radiator.  I ended up having to cut this hose removing the old radiator as it was so rusty.

Coolant reservoir tank installed

It is easier to get the bottom radiator hose in place before installing the radiator.   I used a new hose here and new hose clamps.   I don’t know the age of the current one and hoses are not expensive and worth changing at the same time as the radiator.  The radiator slides in fairly easily, but the fan shroud must be in place first.

The clips that hold the radiator in place were a bit rusty so I purchased a new set.  I generally avoid Meyle parts unless there is no other alternative.   In my opinion they are poor quality.   I figured a simple clip would be fine, but I was proven wrong.   One of the clips snapped in two with just light pressure from my thumb.   The big challenge is that Meyle seem to be the only manufacturer of W126 transmission mounts that I can find.

The Nissens radiator that I have purchased does not have a drain plug like the IMI did.   I think the Behr radiators do, but I could not get one of those.   Other than that, installing a w126 radiator is the same regardless of brand.

Installing a w126 radiatorThe top hose is easy to install once the radiator is in place.  I also used a new one here.    While I was at it, I also replaced the clip that holds the small hose to the coolant reservoir tank against the front of the car near the headlight.

When I removed the radiator, the transmission cooler hoses were very crusty and I ended up cutting them.   They looked original and it was definitely worth replacing them.   The new hoses from Mercedes have metal spring protectors as they hang down quite low.


Installing a w126 radiator - Transmission cooler hoses

It is so much nicer installing new parts that screw together easily like those hoses than all the time it took to remove the rusty hoses and hose clamps.   Once these final hoses were installed it was now time to fill the coolant.  I used Penrite coolant, which is also to Mercedes spec.

At first all was well and I could see no coolant leaks.    However, after revving the engine a bit to get the water pump going and manually actuating the heater valve by sucking on the vacuum hose I started to get a bad leak from the heater hoses.   The puddle of coolant joined the puddle of transmission fluid under the car.   For some reason if I don’t use the SEC for about a month it dumps a big puddle of transmission fluid on the ground.   Its dry and then all of a sudden lake superior appears.   A problem to solve another time.

After removing and repositioning the hose clamp the leak seems to have stopped.  I have re-filled the reservoir and will check if it has gone down at all tomorrow.

SpillageIf the car is now working properly without coolant leaks, the next step is to take it for a test drive to make sure everything working properly, and I am getting cold A/C.   As I have not yet installed the solenoid, the heater valve should remain shut and I should have no coolant flowing through the heater core.   Overall, installing a W126 radiator is pretty simple.   More simple than removing one that has been there for a while.

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