How I took out my 1981 W123 300D (euro) non-turbo engine - PeachParts Mercedes-Benz Forum

Stretch · #1 12-08-2010, 03:59 AM

I read somewhere on this forum that there isn't an W123 engine removal how to. Having just done the job quite recently here's a write up for you all. I admit that this is a pretty tedious thread – but I've added in many photographs that may be of use even if you are not taking out your engine.

I want to make this clear at the beginning: I've only done this job on a 1981 W123 Euro 300D => OM617 non turbo motor.

It is a bit of a marathon but it is quite simple really...

...so here is the short version:-

All you need to do is disconnect everything that is attached to the engine and lift it out.

That's it.

That's all you do.

If you want the long version – the very much longer version read on!

Stretch · #2 12-08-2010, 03:59 AM

1) Think about whether you are going to remove the bonnet / hood or not. I guess you could put the bonnet in its vertical position and get the engine out. However, as I'm working outside, one gust of wind could have really ruined my day so I opted to remove it. If you are doing this you need to make a nice safe place for your bonnet / hood before you start!
2) Get a decent engine crane. I bought a 2 ton model and used the 1 ton extension position with a load distributor. If you are going to hire or buy a 1 ton model – make sure that the point at which you connect the hook (the bit that will hold the engine's weight) is going to go far enough over the engine in your car. If you don't have this hook point more or less in the centre of gravity of the thing you are lifting the whole weight of the engine will swing to compensate! This is when you could do yourself or the car or the engine some damage.
If you don't go for something that is purpose made – make sure that the structure and the lifting gear you are using is capable of lifting the engine (and gearbox) together.
DO NOT OVERLOAD YOUR LIFTING EQUIPMENT – even if it will “only be for a few seconds”
3) Remember that when you lift the engine out of the car the front suspension will raise the front of the car. The cross member at the front of the car – the bit that holds the hood / bonnet catch – is likely to go up in the air by at least 6 inches. It is best to make sure you can lift the engine over this before you start. However, as you'll probably just end up guessing if it is going to be OK or not it is worthwhile remembering that if you don't have enough height in your lifting gear you can do the following things:-
● Let air out of the tyres
● Put the car on low axle stands and remove the front wheels
● Get different lifting gear!
It is best to consider these options before you have the engine dangling on your lift.
4) Consider whether you're going to need an engine stand or not.
5) If you're working outside consider getting a cheapo party tent that will protect you from the bright sun (if you're so lucky) or more likely the rain.
6) Although it might look a bit daft consider labelling each wire / hose / pipe that you are going to disconnect. This is advisable if you are not used to working on your car / this type of car. It is also pretty handy to take pictures of things as you go – then you'll know how to put them back. Experience has taught me that you nearly always end up putting stuff back together in a rush and the daftest most obvious label often helps when you're in a panic / tired / pissed off

Please note although I'm not going to cover the following way of doing things you could in principle remove the gear box first – dropping it from the engine under the car – and then lift the engine out. This isn't the easiest way of doing things but it could be done if for some reason you couldn't lift the engine and gearbox out together: Like when you haven't got lifting gear that is strong enough. I wouldn't recommend it as I think the chances of damaging the gearbox are greater – but I guess it could be done that way...

During my engine rebuild I've been busy weighing my engine and other related parts so I can post the weights you can expect to meet. I couldn't find this data and I still haven't found this data anywhere else – I've only come across guestimates.

Start the job by disconnecting the battery.

Stretch · #3 12-08-2010, 04:00 AM

A selection of sockets 6mm to 24mm
A selection of Allen keys – preferably Allen head sockets (check for any torx heads – these are not fitted as standard but they do find their way onto these cars!)
15mm open ended spanner for undoing propshaft flex discs
15mm socket for undoing propshaft flex discs
7mm open ended spanner for holding flat on engine shocks
41mm and 46mm open ended spanners for “collapsing” propshaft
An engine crane
A load balancer (recommended)
Cross point and flat blade screw drivers
Water pump pliers for removing engine shocks
Drip trays for emptying fluids
Rags for wiping stuff clean and protecting stuff
A digital camera (recommended – take photographs as you go!)
Masking tape (recommended – for labelling the parts you remove)

Stretch · #4 12-08-2010, 04:03 AM

Open the hood / bonnet and disconnect the windscreen washer hose at the point where it splits between the two sprayers on the upper surface of the hood / bonnet (see photo). Pull the hose out of the way.

Arrange some protection on the windscreen so that when you undo the bonnet bolts (that attach to the hinges) the chances of scratching or damaging the scuttle or the windscreen is slim. I used some garden furniture cushions and some rags.

Wedge a broom to hold up the bonnet / hood (see photo).

If you can, release the spring tension of the hinge mechanism by flipping the vertical position catches as though you are putting the hood / bonnet into vertical mode! Mine were really stiff so I couldn't do that...

...Anyway undo the bolts that attach to the hinges (photo) and lift the bonnet / hood away from the car. Don't worry about dropping the broom! I managed to do this fairly easily by myself. Being over 6 foot tall with long arms helps. It is probably easier if you can find someone to help you with this though. I admit that this is quite an awkward piece of steel to lift with outstretched arms.

Stretch · #5 12-08-2010, 04:06 AM

You're going to need to drain the coolant out of the cooling system at the very least. There is a screw underneath the left hand side of the radiator (see photo) and a screw on the right hand side of the engine block to drain the rest of the system (see photo).

If you've got an automatic gearbox then you'll also have to disconnect the oil cooler lines – under the radiator. If you can find a way of stopping these lines from leaking then I guess there is no real need to drain the whole gearbox. I did do this though as it was time for another fluid change anyway... I used tie wraps and plastic bags to stop dirt from getting into the pipes (see photo).

For the engine oil cooler lines that run from the filter housing to an oil cooler next to the radiator you could also just disconnect these lines and try and stop the engine oil from pouring out. Again I drained the whole system and lifted the filter out of the housing – then wrapped the ends of the pipes in plastic bags.

The power steering pump also needs to be disconnected from the engine. I guess you could just unbolt the pump and try to tuck it away next to the windscreen washer bottle if you don't want to disturb this system... but again I drained the system and disconnected the hoses at the steering box. To drain the power steering system either jack up the car so you can turn the wheel almost all the way to the left – or if you are strong and you don't really care just turn the wheel to the left – or roll the car onto a slip plate and turn the wheel to the left (this is what I did – see photo). Next undo a 12mm nut on the underside of the steering box (see photo). The fluid will drain through the steering box nicely – so you don't need to waste time trying to siphon or suck the oil out of the steering pump with a turkey baster etc. (see photo).

Stretch · #6 12-08-2010, 04:10 AM

Here are the other photos

Stretch · #7 12-08-2010, 04:18 AM

To gain access I removed the air filter and the air filter housing (see photo). This works really well for a non-turbo OM617 – I guess it wouldn't help much if you had a turbo sitting underneath.

Disconnect the exhaust pipe:- Here I undid the bolts at the flange of the manifold (see photo). I then removed the exhaust and inlet manifolds. I did this because it makes it easier to reach the starter motor and the automatic gearbox inhibitor switch wiring. Along with the manifolds I removed the coolant pipes from the cabin heater system that run underneath. Again you only really need to disconnect the exhaust manifold from the exhaust pipe... but you do need to disconnect the cabin coolant pipes at either the bulkhead or the engine (see photo).

Remove the shroud around the cooling fan. Sorry I don't have pictures of this as I junked my cooling fan some time ago and installed an electric one instead. Anyway the shroud is held on with clips much like the radiator. I've made a photo of these radiator clips... so remove the radiator! (see photo).

You then need to unplug the alternator wiring (see photo).

You now have a choice. You could also opt to remove the alternator, cooling fan (mine was already gone), and the crankshaft pulley to gain some extra space at the front. I opted to do this as I was working by myself – I was working on the principle that the more space you have around your engine the less chance there is of something being scratched. Don't worry if you can't get your crankshaft pulley off though – it is positioned at the front of the engine and consequently can be stubborn to get off because of crud and rust. In my opinion it is worth giving it a go and if it doesn't come off, don't worry too much, and don't waste any more time on it. It will probably be easier to drill out Allen head bolts when the engine is out anyway (if you need to do it – see photo).

If you have air conditioning then – according to my Haynes manual – you need to disconnect pipes from the pump. If you have cruise control then you need to free that too. The same can be said of the self levelling suspension pump that is attached to the front of the cylinder head. According to my Haynes manual “all you need to do is” to remove the pump housing from the engine, BUT do not split the housing! Sorry I don't have these extras so I can't show you photos of those bits...

The last “big bits” to think about are under the car.

Whilst you have disconnected the exhaust pipe at the manifold, and possibly removed the manifolds too, you need to disconnect the front exhaust pipe support next to the gear box. I'm guessing there is a similar set up for a manual gear box – but it is where I say it is for an automatic! Support the front end of the exhaust pipe on some blocks or bricks (see photo). Depending on how the exhaust pipe is slung at the rear of the car it may even rest on the cross member under the engine (close to the engine shocks) but I think at this stage you should try and support it in as safe a position possible so it won't get busted whilst you are taking out the engine.

The final big bit is the flexible drive disc that mates the propeller shaft to the gearbox. You'll need 15mm spanners and a socket plus ratchet to undo the bolts. The nuts are 17mm. You'll also need a 46mm and a 41mm spanner to slacken off the monster nuts on the propshaft (see photo) so that you can get enough 'wiggle' on the flexible drive disc so you can pull it rearwards and away from the gearbox.

Stretch · #8 12-08-2010, 04:20 AM

Here are the last 2 photos for the post above (I can only upload 5 at a time)

Stretch · #9 12-08-2010, 04:24 AM

In a way removing the big bits is easier than doing all of the small bits as they are more obvious.

Whilst you are under the car doing the last of the big bits you may as well hunt about for the speedometer cable that is connected to the gearbox (see photo). On my 722.1 transmission this is on the left hand side of the car. Then there's the inhibitor switch connector – this can also be reached from above if you've removed the manifolds and the air filter (probably won't help you if you have a turbo though – see photo). On my car this is on the right hand side as shown in the photo. On the right hand side of the 722.1 at the back there is a vacuum switch that you may as well disconnect in case the pipe gets snagged when you lift the motor – just pull off the vacuum tube (see photo). Then back on the left hand side you need to undo another electrical connector for the reversing light and the gear shifting mechanism (see photo).

Back up top you've got the glow plug wiring – just disconnect at the glow plugs disentangle from the injector lines (possibly more mounting clips) and pull out of the way towards the control box on the left hand side of the engine compartment (see photo).

Disconnect the vacuum pipe at the vacuum pump and the vacuum lines running from the engine into the bulkhead. Whilst you are on this side of the engine there is also the coolant temperature sensor that is fitted to the head.

Close to the engine oil filter you'll also find the oil pressure sender tube - it is a similar diameter to vacuum lines. Don't forget to disconnect this! (Thanks franklynb for pointing this out)

You've then got the accelerator linkage (see photos) and if not done already – naughty! – the battery connections. There is also an earth connection on the underside of the body close to the accelerator pedal (on a left hand drive car) that goes to the gearbox - disconnect this too. (Thanks to franklynb for this one too)

There is also wiring for the starter motor (see photo) and if not already done the coolant pipes that run into the cabin for heating (see photo). Oh yeah there are also the fuel lines...

Engine mount shock absorbers also need to be disconnected. I think it is best to remove them – but in principle you could just undo the top nut if you really didn't want to take them out. I find it is best to grip the upper body of these shock absorbers with water pump pliers wrapped in a rag (or soft jawed pliers) to stop the body from spinning when undoing the top nut. The shiny shaft at the bottom of the absorber has a flat bit machined in it that can be held with a 7mm open ended spanner whilst undoing the bottom nut (see photo).

Now I apologise for glossing over this bit, but it seems to me that there are lots of subtle variations between certain models, and on cars of a certain age the chance of getting some non standard additions is likely. I've added the photographs of my car so you can get an idea but it may not be exactly the same as yours...

For example - some cars are fitted with engine block heaters that are positioned just under the inlet and exhaust manifolds.

Stretch · #10 12-08-2010, 04:31 AM

Disconnecting fuel lines, glow plug wiring etc

Stretch · #11 12-08-2010, 04:34 AM

Ideally when you have reached this stage the only things left to undo are the engine and gearbox mounts.

Take your time – walk around the engine bay – and look for anything that should be disconnected to allow the engine and gearbox to be lifted. Crawl underneath and check there too – especially where the engine bay gets narrow towards the cabin. Now is the time to find that wire or pipe – not when you hear it twang or snap when you lift the engine free from the car.

Stretch · #12 12-08-2010, 04:35 AM

Although I've not had any trouble with them – I understand from the vast numbers of threads on the subject that disconnecting engine mounts on a W123 can be a real pain in the backside. In principle, on the two front mounts, you have a large Allen head screw (one on each side) that you undo from under the car. It is as simple as that! Alternatively if this one bit is stuck, well then you need to consider some of the remedies that have been recommended before. I would attempt to drill the head off – but do a search to see if you fancy an alternative approach.

With the practical difficulties discussed above I recommend loosening the two Allen head bolts on the front engine mounts before tackling the gearbox mount. Once you've got the bolts on the front mounts loosened – BUT NOT DISCONNECTED – it is time to crawl under the car and loosen and remove the M8 adjusting bolt (sorry I don't have a photo – if I remember I'll take one when I put the engine back in). This runs horizontally through the rear mount into the rear of the gearbox casing. This bolt only stiffens the engine mount – it doesn't hold any weight.

Next you need to get a jack and take up the weight of the transmission. You can then remove the gearbox mount (sorry this photo has gotten lost - I'll try and find it). Don't let the gearbox drop as you could end up damaging the engine on the bulkhead and you'll not do your front engine mounts any favours either.

You can now remove the large Allen bolts from the front engine mounts. Keep an eye on the engine but it shouldn't move. It should sit quite nicely on the mounts so long as the gearbox is properly supported.

Stretch · #13 12-08-2010, 04:37 AM

ell after all that you're ready to lift the engine. I have seen in many threads on this forum of people using the lifting eyes that are attached to the head of an OM617 engine to lift it in and out of the engine bay. This is also shown in a photograph of my Haynes manual (page 79). Having done this myself I think I will be adding another strap – a ratchet strap rated to 1500kg that I happen to have – to give a little extra support. The FSM suggests that these lifting eyes are for lifting the head. Mine bent a bit under the weight of the engine, giving me the impression that perhaps some extra support is needed. Also if you look at it these eyes are only held on with four M8 bolts... I am now of the opinion that to use only these lifting eyes to pull out the whole engine is bordering on the unsafe. I guess this opinion will promote comment!

Another thing regarding these lifting eyes that is a bit irritating is that the back ones are so close to the valve cover that the lifting chains are likely to make big scratches in said valve cover. Stuff some rags between the chains and your valve cover (photo).

Attach the lifting gear to the points where you have chosen to lift the engine and position the end of your engine crane at about cylinder number 3 – perhaps a bit towards number 4. The idea is to get the lifting point more or less at the centre of gravity of the engine and the gearbox. If you have a load distributor you'll have a chance to correct for this if you need to. If you don't you may find it necessary to lower the engine back on to the engine mounts and reposition the crane during the lift. I wouldn't take out an engine by myself without a load distributor – I'm guessing you'll need help to push and shove the engine back into position if you judge the centre of gravity incorrectly.

Slowly lift the engine out of the car until the suspension no longer rises – you'll know when this is as the engine will shift its position within the engine bay. It will slide one way or another depending on how you've judged the position of the centre of gravity. If you have a load distributor you can now adjust the tilt on the engine so that the gearbox drops down and the front of the engine tilts up. Continue lifting and adjusting the load distributor until the front of the engine clears the engine bay and you can lift the whole assembly out of the car.

Doing this without a load distributor requires nerves of steel and good team work with at least another person. You'll have to shove pull and push the engine and gearbox into the required positions to get it out of the engine bay. Even with help I recommend using a load balancer. I'm not saying it can't be done without one – I think it is worth the extra money. It enabled me to do the job alone.

Stretch · #14 12-08-2010, 04:41 AM

Well there you have it - I hope you haven't nodded off!

If I've missed some bits please let me know - I'll remedy whatever is needed.

I forgot to mention:-

If you are looking for engine bay pictures with out an engine in it you can find them here:

http://www.peachparts.com/shopforum/showthread.php?t=286358

And spring pocket refurbishment here:

http://www.peachparts.com/shopforum/showthread.php?t=286079

(Jobs you may want to consider doing whilst your engine is out)

I've just had a good tip from layback40 - see below in post 24:-

"You could have added, replacement is the reverse, or just whistle at the motor & tell it to get back in there!!"

vstech · #15 12-08-2010, 10:41 AM

Nice.
only complaint I have is wondering why you removed the hood?