While I had to do a few things to the climate control system, the A/C worked pretty well after being charged up.   The main issue was a leak from the compressor.   For a while, I was able to get away with charging it up annually, but recently it was degrading pretty quickly only a couple of months after a charge.    It was obvious that the leak was coming from there by using a blacklight.

Since I was already having the compressor changed out, I also thought this was an opportunity to try and upgrade I had been considering for a while.   Klima Design Works offer an uprated W126 A/C condenser that is designed for R134A.   R134A is not as efficient as R12, and this uprated W126 A/C condenser is billed as 30% more efficient than the stock unit.    That help restore the A/C performance lost through R134A.

I did some research on the various US forums and found good feedback from W126 owners in climates like Texas and Florida.   Basically the consensus seemed to be to either use R12, or this upgrade.   The upgraded W126 A/C condenser comes with the requisite brackets and hoses to interface with the W126 A/C system.   They offer two types depending on year and model.

Obviously, since I was having the compressor changed as well, I supplied a new receiver drier and TX valve to be installed alongside the compressor.   Like with my 300SE, I went with a brand new Denso compressor.   I’ve not had a lot of luck with rebuilt A/C compressors in the past, and given the high labour cost to have it installed, its much better to go with new.

While the car was in the shop, the front brakes were attended to.   On a recent brake pad change, I noticed that one piston on the front drivers side was not moving at all.   I ordered the rebuild kits, plus pads and a new set of front rotors.   My rotors were pretty crusty and within 2mm of the wear limit.   A good time to change them.   The rebuild kits were advertised as Bendix, but my mechanic later told me they were actually ATE units.   This was really annoying as I paid quite a bit more for these kits.

In doing the install, my mechanic told me that the fit of the uprated W126 A/C condenser was really tight.   This probably added a bit to the cost, but in my mind is a good thing as its using all available space for cooling performance.     There was also a little bit of interference between the secondary air snorkel on the 560.

The other issue he ran into during the install was the missing aux fan guard caused a rag to get sucked into the fan and damage it.   This was a problem with the Meyle auxiliary fan I installed a couple of years ago.   Since then, they moved to an improved design that does fit the fan guard.  I have that one on my 560SEL.   I’ve ordered one of these fans to fit to the car.

So far the weather has not been hot enough to really test out this upgrade.   We’ve had one day where it was about 25c and fairly humid and the A/C worked very well.   Better than before.   However, It was previously able to handle days like that.   The real test is when the temperature gets up into the high 30s and humid.

I’ll use this summer to see how I go.  If I’m really happy, I’ll also fit this uprated W126 A/C condenser to my 560SEL.   On really hot days the A/C performance is sub par.  A new TX valve would improve things I am sure.  However if this upgrade works really well, I may do it too.

The post Uprated W126 A/C condenser appeared first on Classic Jalopy.

Looking further my design wasn’t going to quite line up.   Once I put the elbow piece on the end, it was too long and the hoses were bent too much.     I didn’t have the clearance to have another join between the heater valve and the engine block.

My solution was to use some hose offcuts to try and find a single hose that would join from the engine to the heater valve and replace the factory hose.    I created this, tested it and based on it working, I went to Supercheap Auto to find a hose that matched as closely as I could.

In the end a hose from a Toyota Hilux LN106R 2.8 I4 Diesel fit well.    I just had to trim off the ends to use the bend that I needed.  The fit is not perfect, but it is close enough that it is not putting too much pressure on the hose.

I didn’t want to use the joined up bends because the place where the join needed to go was where the hose went through the firewall.   The clamps may have chafed against the firewall.    The single piece should work much better.   Once I get a few more parts I will be able to re-install the radiator.   From there I can make sure I don’t have any coolant leaks.

From there, I was able to install the heater valve  and join it to the engine block.    Next step will be install the solenoid and vacuum connections.      The hoses will be eventually hidden by one of the control boxes.  I think it is for either the ABS or the CIS-E system.

The post W126 Monovalve eliminator – part 3 appeared first on Classic Jalopy.

In the first part I removed the W126 monovalve, auxiliary water pump and other hoses.   This gave me the room to give the area underneath the heater hoses a good clean.   There were some leaves and other detritus.   Its important to remove this stuff it can cause rust.  The mud stays wet far longer than if the area was clean.

The picture above shows the cleaned area.   It also shows the space I am going to fit the new components.   The two outputs from the heater core are seen on the right, and the hose back to the engine in the middle.    The bracket where the W126 monovalve used to go is on the left.

My plan is to use a T-piece to join the two outputs, run the coolant through the heater valve, and then place the vacuum solenoid where the W126 Monovalve used to go.

The picture above shows the setup I plan.   I have a few more hose clamps on order before I can fit this.   The clamps that went on the W126 monovalve side were too large.

A vacuum line will go from the end of the valve back to the solenoid and the whole thing will be covered up my the control box that was there before.   I used new heater hose except for the bend, which was in good shape.

Once the new hose clamps arrive, I will finalize this assembly and then move on to changing the radiator.   The new assembly is slightly too long but the flexibility of the hoses should hopefully allow it to work.

The post W126 Monovalve eliminator – part 2 appeared first on Classic Jalopy.

It used to be possible to purchase a monovalve repair kit from Mercedes or Bosch.  The supply of these has now dried up.   There is a kit from a company called MTC but all the Mercedes Forums and facebook groups are litted with stories about how this part never works properly.   A friend of mine put me onto a company called Klima Design Works that offer cooling system upgrades for W123 and W126 cars.    They have a monovalve elimination kit for sale.   Their kit is focused more at the W123, but can be adapted to the W126 as well.

The kit uses a vacuum solenoid to turn off the coolant flow instead of the electromagnetic monovalve.   I especially like that the valve is closed if something goes wrong.  Here in Australia it gets very hot, and A/C is used far more than heat.

The W126 system is a bit more complex than on a W123.   For starters, the heating components are behind the first firewall and the heater core has two outputs that go into the monovalve instead of one.   Klima Design Works suggest leaving the W123 monovalve in place and putting their heater valve upstream of the monovalve.    They do suggest removing some of the components to increase flow.

The picture above shows the coolant flow for the heater.  Its not 100% correct as this picture shows the duo valve for the manual climate control, but other than that, its the same.  The coolant enters the heater core via hose 68, and exits through hoses 50 and 53 where it enters the monovalve.   The monovalve controls the flow of coolant.   There is an auxiliary water pump (26) that helps flow coolant at idle to generate more heat.

The hoses are exposed when one of the control boxes (that sits in the metal frame) is removed.   The monovalve is on the left, hoses in the centre and the auxiliary water pump underneath.

The simplest way to install the kit would be to cut the hose on the engine side of the auxiliary firewall (hose 68) and install the heater valve there.   That seems like a bit of a hack job to me.   I want to keep the components on the other side of the firewall as the factory did.

The advantage of leaving the monovalve in place is that the car will look more original.   Having said that, removing it can easily be reversed, and I am planning to remove it and the auxiliary water pump.   The auxiliary water pump is only necessary in very cold climates, and it is one more thing to leak and cause problems.   On the Series 1 cars it can cause major problems as it is unfused.   Best case it takes out the climate control unit.  Worst case it causes a small fire.   The Series 2 cars don’t suffer from that problem and disable it if too much current is drawn.

I am thinking of combining hoses 50 and 53 with a T-piece.    I would then mount the heater valve on this combined hose and join it to hose 59.   This would be the simplest solution.   The heater valve would sit where the auxiliary water pump used to be and the solenoid would sit where the monovalve used to be.   Other than cutting hoses (which are consumables) I won’t be permanently modifying the car in any way.

The picture above shows the removed monovalve, auxiliary water pump and various bracketry.  It is a very fiddly job removing all this stuff is there is very little room to work between the two firewalls.   Still, with these components removed there is now plenty of room for the new heater valve and solenoid.    The picture below shows an elbow piece as an example of how the hoses will flow.

Removing all these hoses is a good opportunity to clean out the leaves that have accumulated underneath the hoses.   I’ve also removed the cowl coverings to give things a good clean in there.   It was necessary to remove the control box bracketry.

The post W126 Monovalve eliminator – part 1 appeared first on Classic Jalopy.