Author Topic: 6.9 engine removal  (Read 146 times)

raueda1

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6.9 engine removal
« on: 10 August 2019, 10:59 AM »
This is where I now find myself.  Pulling the engine seems like it will make everything easier, including renewing various things that I wouldn't otherwise be doing - maybe new timing chain, chain rails, fixing small leaks, motor mounts, clean up radiator, etc.

I've got the German 6.9 microfiche CD manual with the lousy pix.  It actually makes the procedure look pretty straightforward.  Some steps are pretty general and funny though, like "remove all the cables and hoses."   Just a couple questions:

     1.  Any major caveats or hints that I'll wish I knew beforehand?

     2. Any chance of doing this without removing the AC compressor and associated lines?  System is running great
         with the old Freon R12.  If I have to purge it then I'm looking at full Freon R134a conversion,
         which I'd greatly prefer to avoid. 

     3. Any reason not to mount a 6.9 engine on a regular engine stand?   
         I assume it's less than 1000 lbs without transmission.

     4. Suggestions for small, non-obvious things to replace/clean/renew/fix while the engine is out? 
         The oil hoses seem to be in excellent condition and power steering hoses are new. 
         Flex plates and driveshaft center assembly are new too. 

The adventure continues.  Thanks for any input.  Cheers,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

rumb

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Re: 6.9 engine removal
« Reply #1 on: 10 August 2019, 11:43 AM »
If you have never removed the 3 large oil hoses going to the sump you are in for some work. I bought a set of larger crows feet wrenches and an additional breaker bar to get them all loose. The AC compressor is a bear to remove and very heavy put I suspect with work you could get it out with all the lines attached, not entirely sure though.

Yeah in general "just" remove everything that is connection the engine to the chassis. wires go to trans, ground straps. With your engine hoist use a leveling bar and attach to the 3 provided lift hooks on the engine. get the front chain as tight as you can to achieve the steep angle needed. remove the grill and you will also have to remove hood hinges and prop hood open even further. The round chassis cross member will probably catch the front of the bell housing, you can remove a few bolts and lower it some. Drain all fluids and expect the trans to bleed like a stuck pig on everything. If you have to remove the intake manifold be aware the bolts can easily break and you cant get it off until you somehow drill out the remaining part of the bolts. the rubber donuts underneath are wicked expensive.

I talked this morning to a very knowledgeable shop owner about hydrolock if that is what happened then you have very likely bent a rod. fortunately it was at low speed as it can crack blocks or break heads.  A 1000 lb stand should work but invest in one with a crank to turn the block if you can. https://www.jegs.com/i/JEGS/555/80059/10002/-1  I did all my engine work on the floor but I did not remove the heads, crank or pistons ever. I think engine weighs 800 then plus trans so at least 1500 for hoist.
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

raueda1

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Re: 6.9 engine removal
« Reply #2 on: 10 August 2019, 02:31 PM »
Thanks for the comments Robert, just what I was hoping for.  The tip on the oil lines is great.  I'll check my crowfoot wrench sizes.  The starter will be out so that may make it easier to deal with the AC compressor.

As for hydrolock, at this point I'm pretty convinced that's what happened.  It's really the only thing consistent with the whole history and symptoms.  Let's hope it's only a rod and nothing else got trashed.  Perversely I'm looking forward to this.  The last engine I pulled was decades ago out of a 1966 230S - a much, MUCH simpler car though still similar in many ways.

My engine stand doesn't have a crank, guess I'll just have to live with it.  Hoist is plenty big.  Cheers,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

UTn_boy

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Re: 6.9 engine removal
« Reply #3 on: 11 August 2019, 09:46 AM »
The a/c compressor would be in the way of lifting the engine out if you left it in.  What you do, after discharging the system, is disconnect the low side line (somewhere on the left lower side of the engine bay) and the high side line from the drier. You'd then remover the engine with the compressor and the manifold still attached to the engine. 

Don't worry about having to convert to from R-12 to R-134A.  You can still buy R-12 all day long on ebay and craiglslist.  (don't pay over $20-$25 per can)  Anyone that possess a 609 certification can legally buy old stock R-12 and service automotive a/c systems.  (in the U.S.)  Since you're in Utah you haven't anything to worry about.  Just be certain to renew the drier and add back in enough mineral oil to compensate for what was in the old drier.  (2-3 ounces).

Unless you have R-12 recovery equipment you'll not be able to save it.  And remember that a field full of cows with flatulence is more harmful to the ozone than what little R-12 is escaping in 2019. 

The manuals are, and have always been, very vague in many regards.  Mercedes wrote the manuals assuming (surprise) that they'd never fall into the hands of the inexperienced, and that the technician reading the text would already have a thorough knowledge of the car and its systems.  So when it says "remove all hoses, lines, and electrical connections", they means to disconnect the radiator hoses, fuel lines, heater hoses, exhaust, hydraulic lines for suspension system, hydraulic lines for transmission oil cooler, power steering lines and hoses, a/c lines, ignition system, any wires for the 212 switch, a/c compressor, and oil pressure switches, and vacuum connections (brake booster and climate control).  Obviously, don't forget to disconnect the drivehaft, shift linkage, kickdown solenoid wire, speedometer cable, etc.  You'll need to also  remove the radiator and the fan mounted to the water pump in order to allow for room to tilt the engine and transmission assembly as it comes out.  Make sure that the front of the car is up high enough to allow for the rear of the transmission to tilt downward as everything comes out.  You'll likely have to remove the hood, too. 
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1973 300sel 4.5, silver blue metallic/blue leather
1976 280s astral silver/blue MB Tex
1978 450sel 6.9 Euro, Anthr/velour

raueda1

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Re: 6.9 engine removal
« Reply #4 on: 11 August 2019, 12:25 PM »
The a/c compressor would be in the way of lifting the engine out if you left it in.  What you do, after discharging the system, is disconnect the low side line (somewhere on the left lower side of the engine bay) and the high side line from the drier. You'd then remover the engine with the compressor and the manifold still attached to the engine. 

Don't worry about having to convert to from R-12 to R-134A.  You can still buy R-12 all day long on ebay and craiglslist.  (don't pay over $20-$25 per can)  Anyone that possess a 609 certification can legally buy old stock R-12 and service automotive a/c systems.  (in the U.S.)  Since you're in Utah you haven't anything to worry about.  Just be certain to renew the drier and add back in enough mineral oil to compensate for what was in the old drier.  (2-3 ounces).

Unless you have R-12 recovery equipment you'll not be able to save it.  And remember that a field full of cows with flatulence is more harmful to the ozone than what little R-12 is escaping in 2019. 

The manuals are, and have always been, very vague in many regards.  Mercedes wrote the manuals assuming (surprise) that they'd never fall into the hands of the inexperienced, and that the technician reading the text would already have a thorough knowledge of the car and its systems.  So when it says "remove all hoses, lines, and electrical connections", they means to disconnect the radiator hoses, fuel lines, heater hoses, exhaust, hydraulic lines for suspension system, hydraulic lines for transmission oil cooler, power steering lines and hoses, a/c lines, ignition system, any wires for the 212 switch, a/c compressor, and oil pressure switches, and vacuum connections (brake booster and climate control).  Obviously, don't forget to disconnect the drivehaft, shift linkage, kickdown solenoid wire, speedometer cable, etc.  You'll need to also  remove the radiator and the fan mounted to the water pump in order to allow for room to tilt the engine and transmission assembly as it comes out.  Make sure that the front of the car is up high enough to allow for the rear of the transmission to tilt downward as everything comes out.  You'll likely have to remove the hood, too.
Comments on the a/c are very helpful indeed.  I've already got a couple cans of R12 so I guess recharging it isn't the worst thing.

As for the manuals, yeah, I wasn't expecting an itemized list of what to disconnect.  It's just kind of funny how little they say and how much there is.  I'll likely have the car on a lift for this surgery cause it gives more flexibility in moving things as needed.  Thanks and cheers,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

raueda1

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Re: 6.9 engine removal
« Reply #5 on: 13 August 2019, 04:31 PM »
>>>snip<<<
The manuals are, and have always been, very vague in many regards.  Mercedes wrote the manuals assuming (surprise) that they'd never fall into the hands of the inexperienced, and that the technician reading the text would already have a thorough knowledge of the car and its systems.  So when it says "remove all hoses, lines, and electrical connections", they means to disconnect the radiator hoses, fuel lines, heater hoses, exhaust, hydraulic lines for suspension system, hydraulic lines for transmission oil cooler, power steering lines and hoses, a/c lines, ignition system, any wires for the 212 switch, a/c compressor, and oil pressure switches, and vacuum connections (brake booster and climate control).  Obviously, don't forget to disconnect the drivehaft, shift linkage, kickdown solenoid wire, speedometer cable, etc.  You'll need to also  remove the radiator and the fan mounted to the water pump in order to allow for room to tilt the engine and transmission assembly as it comes out.  Make sure that the front of the car is up high enough to allow for the rear of the transmission to tilt downward as everything comes out.  You'll likely have to remove the hood, too.
Got a lazy question for you.  I'd go to the car and look, but my garage is elsewhere.  Anyway, do any of the electrical connections on the engine terminate in a larger connector on the chassis wiring loom for ease of removal?  I'm thinking of the temp sensor, fuel pump relay, the cable to the WUR, etc.  Or do they all need to be unplugged and disentangled from all the other surrounding stuff?  Thanks,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

rumb

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Re: 6.9 engine removal
« Reply #6 on: 13 August 2019, 05:53 PM »
There is one harness that goes on the top of the engine from the back.  Just unplug everything it connects to and pull it up and out of the way. On the right front is the alternator and starter wires. On the left are distributor wires, be careful with the green wire especially where it connects to the distributor.

You probably know this, but photograph everything before you take it apart and then each component you take off lay all the hardware next to it and take another picture.
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

UTn_boy

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Re: 6.9 engine removal
« Reply #7 on: 16 August 2019, 06:21 PM »
^^What Daniel said.  The wire harness atop the engine simply unplugs and you lay it back out of the way.  The wire harness for the alternator and starter do have a brown phenolic junction junction block on or somewhere close to the right front frame rail.  It'll have three or four screws on it of different sizes.  So you don't have to disconnect the starter and alternator at the starter and alternator.  Though, I believe there is one wire on the alternator that you will have to disconnect because it is part of the vechicl wire harness.  Thankfully, It's nearly impossible to cross wires or get anything mixed up due to how/where they lay and the sizes of the eyelets. 
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1973 300sel 4.5, silver blue metallic/blue leather
1976 280s astral silver/blue MB Tex
1978 450sel 6.9 Euro, Anthr/velour