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Prepping a Mercedes 450SL for a timing chain

Now we are ready for step two of the timing chain replacement on our 1975 Mercedes-Benz 450SL. The first step is to decide how you will go about moving the engine and there are two options. Option 1: Remove the subframe and hold the engine in place with a hoist. Option 2: Remove the engine from the car. Yes, those are your only two options.


Mercedes engine or subframe removal 

I chose to remove the engine for various reasons. First and foremost, my friend and seasoned mechanic suggested the engine removal was much easier and faster, and it would provide an

opportunity for me to get a good 360° look at the engine. Have to admit I was a bit uncomfortable with going this rout, but realized in the end it was the best way to go. Second reason the mechanic suggested to remove the engine was to have easy access to replace the rear crankshaft oil seal. Leaking or not, a seal at 41 years old should be replaced if you are going through this much work. The third reason we decided to pick the engine, was to get a good look at all the wiring hosing etc., that is well hidden along the fenders. Not only that, it gave me an opportunity to very easily to clean the engine bay. And fourthly, it is just much easier to have the engine sitting out in the open to do this less than pleasant job. I will not cover the “hows” of either lowering the subframe or picking the engine. Please talk to a mechanic or proceed to your workshop manual for the specifics.

Perhaps if you are asking the question as to why the engine or subframe has to be removed, it is quite simple to ponder but obviously quite a big job to accomplish. In order to remove the timing cover (entire front of engine) the oil pan has to be removed and in order to remove the oil pan the subframe has to be out of the way. The timing cover is also held in place by the oil pump which is attached to the back side of the timing cover. If you just jumped ahead in this process, yes, you are right, should you need to replace an oil pan gasket you will either need to drop the subframe or pick the engine. (NOTE: if you do not have the correct hoist (hanger) for the engine you can severely damage your fenders. This would come into play should you be removing the subframe only. Again, call a mechanic or read the manual.


The cost of doing business when you own a Mercedes 

Be prepared to do some research if you are going to have this procedure done for you. Inquire as to whether or not you can supply the parts and get a good estimate up front on labor hours. I paid my friend and his shop a slightly reduced rate. The job total, including parts and a few other necessary items, we will cover as we go, came to $4,200. If you just gulped down some air, let it go slowly. While note cheap, it is less expensive then one of my local Mercedes-Benz dealers

that quoted me $5,800-$6,800 and I couldn’t have been a part of the process or purchased my own parts! Consider also that unless you have your 450SL as a daily driver and drive cross country regularly, this only needs to be done every 100,000 miles. I dare say, should I keep this car until I die, it will not see another chain or oil pan gasket.

PART NEEDED: Be sure to order an oil pan gasket with your other parts!

Now back to business...


Prep stage in detail

It’s now time to get under the hood and start removing parts and accessories. NOTE: Take plenty of before and after pictures from all angles to help you remember what you once had! Now you must remove the alternator, water pump, power steering pump, air pump, A/C compressor, belt tensioner and it would be highly recommended to remove the radiator for a much easier go at the job. The crankshaft pulley will also need to be removed along with the vibration damper (harmonic balancer).

Before you do this however, you must start by removing all necessary fluids. Drain all coolant from the radiator and engine block. There are two cylinder block drains on the 450SL V8, one on each side of the engine. When the radiator drains the overflow tank should also drain as well.

Check however to make sure that it does. Drain the engine oil. Drain the power steering fluid. You may either syphon off the power steering fluid reservoir with a baster from the kitchen before your wife can say “No!” or you can simply disconnect one of the power steering lines and be prepared to catch the fluid that way. My system took about 5 minutes to completely drain. Remember also that when you remove the water pump residual coolant will be trapped in the pump and will want to spill out. Make sure you refrigerant has also been properly captured prior to removing compressor.

Once all systems are free of fluid, disconnect the two lines on each bottom corner of the radiator. These two lines are for the transmission oil cooler. The lower portion of the radiator houses the transmission oil cooler unit (built in). NOTE: You will need to check your transmission fluid level when you are ready to put the car back into service).

It is now time to remove the fan shroud, hanging it on the fan and proceed to remove the radiator. If your radiator is original, it will be rather stubborn to get out. The manual states it will slide straight up and out...Not quite that easy, but that is what ended up happening. TIP: Have a can of, my preference, PB Blaster and liberally spray down the right and left side top of the radiator after removing the two clips that secure the radiator from moving about. While you are at it, it won’t hurt to spray any and all other bolts you will be attempting to remove. Let the PB Blaster sit for about 15 minutes and the radiator should slide straight up and out with relative ease.

PARTS NEEDED: Order two replacement rubber radiator mounts.

NOTE: Keep all screws and bolts labeled and with each component, you will have a lot of them in short order.

Now that the radiator is out, remove the fan and clutch as a single unit. Make sure your fan clutch is working properly. You may leave the condenser but be very careful not to touch it when working. You will crush the fins very easily. Next, begin the removal of the belts. If your belts are

as old and dry as what was on my car, you can simply snip them with heavy duty cutters.

PARTS NEEDED: Order 5 belts being sure that they are variant and chassis specific.

Now begin removing all the accessories: Alternator, Air Pump, Power Steering Pump, Water Pump, Belt Tensioner, A/C Compressor, crank shaft pulley and engine vibration damper. as indicated in the photo. NOTE: In order to remove the crankshaft pulley hub, you will need a puller. This will be necessary to change the oil seal. It should also be noted to Save the power steering pump for last, as it will make detaching the TDC sensor much easier. You will notice the vintage computer port attached to the left side of the power steering pump assembly. There is a small nut holding the sensor just above the vibration damper and it will slip backward out of a small bracket.

With all the accessories removed, it is now time to disconnect the fuel lines, vacuum lines, heater hoses, fuel vapor recovery hoses, power brake booster line, cruise control cable, throttle linkage, transmission linkage, wiring harness for fuel injection, starter motor wiring, wire to oil temp probe, both engine torque dampers (shocks), upper torque damper mounting brackets (attached at right and left of engine), wires from coil to distributor and finally remove both exhaust manifolds and disconnect the transmission. (NOTE: The transmission does not need to be disconnected if you are removing the subframe. The engine hoist will hold both the engine and transmission in place) Now would also be a good time to replace the Transmission fluid filter and pan gasket. I also removed both the plastic over flow tank and washer fluid tank to avoid any damage as the engine comes out and goes back along with the charcoal canister.I also highly recommend marking all your wires if you have any doubt on where they all reconnect. In addition, this would be a good time to thoroughly review all hosing etc., for dry rot and cracks.

PARTS NEEDED: Order new heater hosing (from engine to firewall and from firewall to heater box). Again if the hoses are old and dry, it will be much easier to just cut them rather than attempting to get twisted over the engine trying to remove hose clamps. You will also want to order new engine torque dampers (shocks) and associated mounting kits. Also order new vacuum line that will most likely be cracked or cracking as you remove it and order all new rubber vacuum line connectors.

If you are going the rout of removing the engine, now would be the time to consider purchasing two new. 

PARTS NEEDED: exhaust manifolds from a pre or post 1975-76 that do not have the “built in” catalytic converters. two new exhaust manifolds will run you about $800 on Ebay. Make sure are not cracked. You will also need to order a MagnaFlow catalytic converter if you are changing your system over and 8 new exhaust manifold gaskets will also be in order. You may also elect to have the manifolds cleaned and powder coated with a ceramic heat coating, which will take off a significant amount of heat from the engine bay. It will also make them look like new.


Check it twice

At this time, double check everything to make sure all wires, hoses, etc., have been removed and will clear the engine as it is pulled from the bay. If you have not already done so, you will now remove the hood. I placed it on top of the hard top roof with a heavy blanket underneath.

Once you are certain you are ready to pull the engine, get a suitable crane and attach engine at specific built-in lifting points and remove. This engine is big and it is heavy, work carefully and don’t work alone.

With the engine now out, place it where it will be perfectly stable, even under having to forcefully loosen bolts. Be sure the engine can’t rock around. In my particular case, the engine was placed on it’s “back” allowing the front of the engine to be face up. This made the work on the timing chain a snap.

PARTS NEEDED: Check your motor mounts and front subframe mounts, along with your sway bar mounts and brackets. This is the time to get that job done as well, it’s very easy at this point. If they are in any way old, replace them! Check all metal parts for fatigue or cracks.

On the subject of cracks, a few years worth of 450SL’s were subject to a recall for the front subframe cracking and collapsing. Your car should have had one of two things happen during the recall period in 1980. Either you will have had a new subframe or a subframe brace kit in stalled by Mercedes-Benz. Be sure you know that it was done on your car. If the recall was not fulfilled, contact your local Mercedes-Benz dealer and they will take care of it for you under the recall program FREE of charge. If your car did not have the recall work performed as mine hasn’t, you run the risk of the subframe failing and your car going down the road on it’s front bumper from the front end collapsing!

This takes us up to the actual work to be performed on the engine. The third and final article will be forthcoming and will cover the chain replacement and the necessary steps for that job, along with preparing the engine to be started once again. In the mean time thoroughly clean all your lose parts in preparation of having them put back. Get any replacement bolts you might need and any other odds and ends that rear their heads in the process. Do these simple steps before reinstallation and you will have a sparkling engine and bay to be proud of.

NOTE: many parts are cast aluminum and will be ruined if the wrong cleaner/degreasers are used. As mentioned in previous articles, I use the original formula Simple Green diluted 1:1. You can soak non-electric parts for up to 15 minutes. Always rinse parts very well to remove all residue from the Simple Green and wipe dry.


Helpful tools

Example of mandatory tools. Screwdrivers, adjustable wrench etc., must be a part of your toolbox as well for this job.


Shop Mercedes Benz Parts Online Catalog Lifetime Warranty


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Written by :
Alex Fiehl

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