An old and defect expansion valve will decrease performance in your AC system. That can result in either the commonly too warm air, or in fact too cold air causing frost on the vents! The air can also alternate between these two modes. The more expensive consequence is that it can also wreak havoc on the AC compressor since coolant will always flow (unless the compressor has a shut-off clutch).
In the final part of this “AC 101” series we will look at changing the expansion valve. If you need to read upon how the expansion valve works in an AC system look at Air Condition Systems 101.
The Ac expansion valve is quite accessible under the passenger side dashboard, but you will need some large spanners to loosen the AC hoses.
Before you do anything, make sure the AC system is completely emptied of refrigerant at a workshop. I repeat what I have written earlier in this series; The AC refrigerant is a highly volatile greenhouse gas. And if you have an old R12 system, the system might contain old freon gas which will deplete the ozone layer as well as being a volatile greenhouse gas.
So do that and then go shopping.
New Expansion valve
New AC gaskets – You should change these to avoid leaks.
Little flat screwdriver
Large open ended spanners
Start by removing the passenger side lower dashboard cover. It is held in place with three screws at the top under some brittle plastic covers and a plastic screw on the lower right hand side. Remember when dealing with old interiors you have to take extreme care to not breaking any parts or loosing them. Replacement parts are long out of production by now and are not available except used ones (if you can find them) at often very high prices.
Use a narrow and thin flat head screwdriver to carefully pry off the three small plastic covers.
Then unscrew the three philips screws on top and the lower right plastic screw. The left side and back side of the dash cover is held up by tabs in the floor and wall construction.
With the cover off. You can immediately locate the AC expansion valve. You should detach one end of the ventilation hose so you can access it. Detaching it from the left side is much easier and you don’t end up breaking stuff.
The expansion valve is covered by some foam that is long past its lifespan. Touch it and it disintegrates. So be prepared to get some styrofoam replacement (which you have to fabricate yourself). The only practical function of this foam is to protect the other plastic from the very cold valve.
Start by unscrewing the hoses, they might site quite hard and getting to them is a bit of a grind. Start by removing those who you find easiest and remove the other ones as you go.
Note the orientation of the old valve before removing.
After the expansion valve is removed you should change the old gaskets with new ones before you install the new expansion valve.
The new expansion valve also says R134 on the side so it can in fact work fine with newer AC systems. The old one was for the obsolete R12 system.
Remember to change the gaskets and then start to screw in the hoses making really sure not to cross thread them. Take your time here. The hoses should go on quite tight to make a tight seal under the pressurized gas.
Then install the dashboard cover again and your job is done, for now at least.
I highly recommend to perform pressure testing of the AC system before filling it with new gas, since many workshops do not even do this before they fill. You basically have to demand it before they fill. An AC leak is quite nasty since you will get a dirty cleanup job, not mentioning the greenhouse gas effects…
So how do you change the fuel filter? It is in theory simple, but in practice it can be quite messy and also tricky to fully access in the rear end fuel delivery system on the w123 chassis. You also need to make sure you have as low fuel as possible or drain the fuel tank dry.
WARNING : There is a high explosion and fire risk when dealing with petrol fumes, so don’t light up your cigarette and avoid sparks!
Fuel delivery assembly rubber bushings – I highly recommend to change these
Main tank hose
High pressure hose
Low pressure hoses
Fuel hard line and fittings
You need to access the rear end fuel delivery system on the rear right end of the car. It consists of the fuel pump, fuel filter and the fuel accumulator. They are suspended from 4 rubber bushings secured in a weird metal clamp. It is partly hidden behind a plastic cover near the right rear wheel.
Start by removing the battery, trust me, you dont’ want sparks while working under the car with petrol fumes! And don’t smoke!
Then jack up the rear end of the car up on jack stands and block the front wheels from rolling. As extra safety measure I always leave the jack in raised position on the same side as I will be working.
Remove the rear right wheel and you have better access to the fuel delivery system. Locate the plastic cover which is held by a few screws, use a long thin socket extension to remove these.
Now you have to drain the fuel from the tank to avoid petrol spills and excessive fumes. This can either be done with using a vacuum pump with a hose down into the filler neck, or by disconnecting the main hose to the fuel pump. It will also leak fuel from the delivery line to the engine, and this can be blocked from continuously dripping with a hose clamp on the high pressure hose. Make sure the clamp is of high quality with no sharp edges, since a new high pressure hose is quite expensive.
When the fuel is drained. You can start by loosening the 2 lines that connects to the fuel filter. The left side (from rear) is the high pressure line and the right is the hard line. Notice the position of the two copper washers on the hard line fitting. A lot more fuel will now drain out from the filter so take care. It is possible to remove the filter from the cage without removing the whole assembly.
If you need to also change the rubber bushings, then change them one by one and you don’t have to take the whole assembly down. Alternatively to get better access you can secure the assembly with zip ties while changing them.
Installation is pretty much reverse of removal, but you have to remember to use the new copper washers that followed with the new filter. Also I found that you need to torque down the screw between the hard line and the filter for it to not leak.
After everything is put together and you have put some fuel in the tank, try to start the car, it should not take long for the engine to fire up after you crank it. The fuel pump is pretty quick pushing fuel through. When the car is running, go back and inspect carefully if fuel is leaking and check for any wetness.
If it’s dripping or you can see wetness, shut off the car. Tighten the bolts, wipe off the fuel so it’s completely dry and try again. I had to redo this step twice before it was properly sealed, and the leak was indeed between the new copper washers and the hard line. The copper washers will actually start to seal better when exposed to moisture and some small corrosion will start forming in the gaps.
Be sure to check for any wetness under the rear end of your car after you parked it the first times, since leaking fuel is bad for your wallet and is a potential fire hazard.
Too hot or too cold engine will result in power loss and inefficiency in the combustion process. In the worst case total engine failure. The thermostat is actually a wear item that should be changed every 5-8 years. In some cases even between every season if you are living very far north where the winter temperatures varies extremely much between the summer season. I think this applies even for Norway especially in a Diesel where it’s difficult to get the engine warm in the winter.
Is your engine experiencing climate change?
So how do you change it? Is it difficult? I will tell you all if you hang on with the article.
Parts you will need
New thermostat. Thermostats have different temperature ranges where it is fully open, check with the manufacturer/ owners manual what is recommended for different ambient temperatures. For cold weather thermostats that open later are common, i.e. it will open at a higher engine temperature.
New upper radiator hose and clamps? Evaluate the condition of the upper radiator hose, change if it’s worn. Since a broken radiator hose might cause catastrophic engine failure. Also the hose clamps might break if they are old and rusted.
Start with emptying the radiator coolant. There is a plug on the underside which can simply be open by a screwdriver. When it is fully drained don’t forget to put the drain plug back in. Then go to the next step.
Now you have to remove the upper radiator hose. Each end is attached with hose clamps. Hopefully the hose clamps tightener are easily reachable. They usually can be loosened with a small socket or a screwdriver. Choose the socket if you can since you might just destroy the screw notches if it’s stuck. Be aware that more coolant might come out when you loosen it so be ready to catch it.
After removing the upper radiator hose you have access to the thermostat housing. It is attached with 3 bolts. These on the M110 engine is usually ok to get out, but on some other engines like the OM617 they are terribly constructed. Now you have to take extreme care not to ruin the bolts otherwise your quick fix will turn into a long and unpleasant affair. The aluminium housing of the water pump housing will stick to the steel bolts after some time.
After the housing is removed, you have access to the thermostat. Just pull it out with your hands. Also note the placement of the rubber gasket. This have to be replaced by the new gasket which comes with the new thermostat.
If you really want you can test the old thermostat by boiling it in a kettle with an accurate thermometer. When the spring opens is when the thermostat is heat rated. Probably your old one has deviated slightly from it’s original heat rating. If you are totally paranoid you can the test the new one as well!
Clean up the housing before putting the new thermostat in the water pump housing. Put the gasket on top of the thermostat as seen below.
Before putting it all together you have to clean off the oxidized aluminium from the thermostat housing. It is important to avoid coolant leaks in the future. This is easily done with a simple wire brush.
The bolt on the thermostat housing should be tightened down until both the surface of the metal meets. Do not over tighten the bolts since you will end up stripping the soft threads in the water pump. Then you will be in big trouble. Use only a small ratchet to avoid the large torque. Get your new upper radiator and clamps ready.
After fitting the new upper radiator hose. You have to refill engine coolant. This is not as simple as just pouring in new coolant and closing the lid. You have to let coolant circulate and get out the air out from inside the engine.
Start by turning the heater on MAX inside the car. This will allow for coolant to circulate the entire system. Ideally you should have a large funnel which can be screwed down into the radiator, but this is a specialized tool which most of us don’t have. So start pouring coolant until you see it forming though the opening, but don’t make it full. Now you have to turn on the engine with the radiator cap open so air can escape from the engine. CHECK for coolant leaks!!! Did you remember to tighten the radiator drain plug? While the engine is running you will probably see the level decrease slightly while the engine burps, but bear in mind that coolant also expands as it heats so a level change might not be visible. When the engine starts to get warm and has burped some, try filling until the minimum mark and close the radiator cap.
Then go for a short spin. Observe the temperature gauge closely. Mine increased suddenly until over 100°C then did a sudden jump back down to 80°C when the radiator popped open. I might have had some air still in the engine and the thermostat might have been slow on the first opening since it was new. It never run above 80°C after that one time. To be on the safe side, stop the car if you see such sudden peaks in the temperature gauge.
When you are back. Let the engine cool down at least one hour, before tempting to open the radiator cap, since most likely coolant will pour out and scolding your hands. After one hour open the radiator cap and refill coolant until it reaches the maximum mark.
Is your compressor crappy? Dried out for the 15 last years and making squeaky sounds and for sure not giving any refrigerations at all? Well in this second part of the AC system we will embark on the journey to change the broken compressor. A critical part and the one to often fail due to the mechanical nature of operation and lack of maintenance.
This guide will only cover the York type compressor in an M110 engine.
The AC compressor pressurizes the refrigerant from a vapor state into a liquid state and at the same time increasing the temperature of the liquid by drawing mechanical energy from the engine via a drive belt from the crank shaft.
Some compressors are lubricated by the refrigerant itself, but the York R4 compressor has it’s own lubrication by oil inside the crank. Lack of lubricating in the compressor crank in combination of little or old refrigerant is the most common reason for these to fail.
To change the compressor you need to make a lot of preparation even though changing the compressor is not such a big job in itself. This will include emptying the AC system of refrigerant at a professional workshop. You cannot do this at home because the refrigerant can actually deplete the ozone layer (if it’s an old type of refrigerant, this is common in old cars) and they are all extremely potent green house gases that should be disposed of properly. Also a big preparation is getting hold of new spare parts, not only the compressor, but also a new receiver/drier, new gaskets for hoses/connections and compressor oil. You probably need a new pulley for the drive belt as well. You will also need some special tools to finish the job.
Parts and Preparation:
Empty refrigerant at a workshop!
Get a refurbished or new compressor, can be quite expensive
Get new gaskets, they are like 2$ only…
Compressor mineral oil compatible
New Reciver/drier (must always be changed when changing the compressor)
New pulley bearing for drive belt
New AC compressor serpentine drive belt
Big selection of long and short spanners, also ones with ratcheting mechanism to reduce time
Socket tool set
3/8 inches spanner
Clutch/bearing remover (to remove the clutch from the compressor shaft)
Brain: Some ingenuity to loosen the clutch (not easy since the compressor shaft and the clutch will rotate together)
Getting access to the various bolts and nuts around the compressor is not easy. They are awkwardly placed and there is not much space to get leverage for the spanners. Be prepared test your patience! This job is not super difficult, but will save you tons of money compared taking it to a workshops, since they will use a few hours just to remove and assemble the compressor, unless they know the car really well. And lets face it, no one knows the car like you do yourself.
WARNING: Do not proceed unless the AC is emptied of refrigerant!
Now that is out of the way, let’s proceed to the fun stuff. Disconnect your battery to avoid shorts! Locate your compressor, it’s the big thing hanging off the passenger side of your engine. The compressor probably has a serpentine drive belt if the AC has been in use before. This must be loosened first by using the adjusting screw on the AC pulley, which located on the upper part at the front of the engine. If you are not using it after, then just cut it off with a knife to save time, the compressor should have a good belt otherwise it might just slip. There is very little room between the pulley and the fan housing, but you do not need to disassemble anything when replacing the pulley.
Start by checking the pressure in the AC system, it should be empty, but just to be sure use a pin and press on the Schrader valves sticking out on top of the AC hoses. There might be a slight fizz due to a small pressure building up in the empty system.
Then you can start unbolting the compressor mounts, there should be 5 bolts holding the compressor in place. On the right side there is a supporting rod holding it on the corner, start by unbolting this. You must also disconnect the wires to the clutch actuator.
Two are located on the front left side, one above and one below the compressor. Until now these were the easy bolts, now the hard part starts. There are two more bolts located on the back left side of the compressor, and these are pretty hard to gain access to. Also you will have little room for the spanners, so if you have spanners with a ratcheting mechanism you will save tons of time here.
The bolt that is lowest actually is a long long with a cylinder, that comes off going all the way through the exhaust manifold. Don’t loose this cylinder part, and be prepared to save all shims and remember the bolts’ locations, since they are not all the same, use pictures and notes if necessary.
Notice the long compressor bolt and its’ cylinder.Just before the last bolt gets loosened completely you can detach the compressor and stop if from falling, it’s quite heavy so don’t crush your hand when it might fall unexpectedly.
Now that the compressor is off the engine, you can begin to remove the bracket that is attached on the right side of the compressor. This is pretty straight forward and requires little explanation, it is just attached by a few bolts. There is also a bracket still on the engine block, it is not necessary to remove this, but you can if you want to clean the area around it etc.
PROTIP: Since the compressor is removed, now you have the perfect opportunity to replace the lower radiator cooling hose, which is nearly impossible to replace when the compressor is mounted.
Since your new or rebuilt AC compressor does not come with a clutch and the clutch magnetic actuator, we have to transfer the old components over to the new compressor. Removing the clutch is the most difficult part of this job, since the compressor crank shaft will rotate when you try to loosen the clutch center bolt. You need a way to keep the compressor shaft from rotating while loosening the clutch bold. Easier said than done.
I ended up placing the compressor housing in a large wise, then using some large welding pliers (adjustable) to grab onto the inner clutch plate and while holding it still then also unbolting the clutch bolt. It was not the most elegant solution and I recommend you to find a better one, since in my case the outer plate got slightly scuffed by the pliers.
When the center bolt is loosened, the clutch is still pressed on the crank shaft. You need to find your clutch/bearing removal tool, it looks like some spider joint out of a horror movie. Unfortunately it’s a tool that seldom gets used, so don’t put too much money into a tool like this, borrow from a friend if you can. I think I only used it once earlier when I removed the center drive shaft bearing. Place the outer spiders around the clutch wheel and start tightening the center screw. This time you can use a long rod between the spider legs to act as a lever while you tighten the spline, you will hear a loud pop when it comes off. It has probably rusted in place after so many years.
The last part to disassembly is the magnetic clutch actuator. It is held by 4 bolts on a bracket, but be warned, they are Imperial sized! This is the first time I have come along imperial sized bolts on my Mercedes, but the York compressor is not made by Mercedes and this is just how it came from the original manufacturer in the United States. You actually need a 3/8 inches spanner, if you don’t have imperial sized tools, go out to get only this one spanner. I almost rounded out one bolt at first since I was dumb enough to try a metric spanner which didn’t perfectly fit.
After the clutch assembly is off, you can start by assembling the new compressor.
WARNING: Do not forget to refill the York Compressor with mineral compressor oil before assembly, otherwise it will break!
Forgetting the above step is pretty serious. So before anything else, let’s go through how we refill and measure the right quantity of oil. Also keep the protective dust caps on the compressor fitted at all time until the very end.
Make your own dipstick from a piece of steel wire, make a marking at 57mm and 41mm from the end.
On each sides of the compressor is one small bolt in the middle, these bolts are the filler holes for the oil. They are quite small so a small funnel needs to be used. You need at least 355ml of fluid (12 oz) which s corresponds to around 57mm on the dipstick and it should never be below 177ml (6 oz), 41mm on the dipstick. Use normal mineral compressor oil, some even use engine oil, but do not use ATF.
The compressor comes with a small quantity of oil in it already, pour this out before pouring in the new oil, it is not important to get all out. Put the dipstick in over the crank case at 45deg as shown in the image to proper measure the fluid level, the crank key should be facing up, there is a small nob on the shaft. It should not be hard to crank it by hand.
When filled up to the right level, start assembling the compressor. Now in opposite order of the disassembly. Remember to keep the protective intake and outtake protective caps on until you are ready to connect the AC hoses back on.
There is no need to over tighten the clutch center bolt since it will also tighten itself over time when the clutch is actuated.
When the compressor is mounted on the car, remove the protective dust caps and make sure there are fresh plastic gaskets on the inlet and outlet holes on the top of the compressor. Tighten the hoses firmly, but do not over-tighten them, the workshop will make sure the gaskets are not leaking when filling your AC system with refrigerant. Over-tightened gaskets will need to be replaced.
You cannot change the compressor without also changing to a new receiver/drier, otherwise your new compressor might fail too early and all the job you just have done might be in vain. This is the next part of the AC series, so stay tuned for part 3.
Back ground story
To be honest my AC system has not been operational in the last 8 years or so due to a broken compressor. I just didn’t get to the job of fixing the AC system until now, because you know… (Norway is cold most of the time and you really only need AC like 3 months of the year, but then it’s really nice to have on those few really hot days)