Bought my first w116, a 6.9

[3l33ter]

I've been a Mercedes guy from the beginning, as my first car was a w123 300d. I've always liked the coupes and compact sedans, and never been much of an S-class guy. I've also had a w124 wagon, 190E 2.6 5-speed, and my daily car is a w123 300TD which we also use for road trips. Recently I realized how nice the older big sedans like the w109 and w116 are. I started looking for a 450sel and I came across a 6.9 which was too tempting to pass up.

It needs some work, but nothing I can't handle. I'm a pretty serious hobbyist and I probably spend more time wrenching than socializing. It has 160k miles, silver on blue, the body and interior are in pretty good condition, I don't see any rust except surface rust in the rear footwells, the engine and tranny feel good, suspension works, etc.

The problems (that I have noticed so far):
steam out of the exhaust until it warms up (I'm learning all I can about doing the head gaskets on an M100)
vacuum locks don't work (surprise, surprise!)
creaking from front end when turning the wheel at a stop (probably ball joints, what a fun job)
shifter is loose
no heat (but the blower works)
didn't even want to try the AC
hood star is missing, so is the small blue emblem under the star

It's really just minor stuff except the ball joints and the head gaskets. I've done ball joints before. What advice can you give me on doing the head gaskets? Where's the best place to buy the parts, where can I find a procedure, what should I do while I'm in there, etc?

I'm thinking I'll check the chain stretch before disassembling, to determine whether or not to replace the chains. I also want to rebuild the heads but the valve guides are pretty expensive from my local dealer (as are the head gaskets) and I can't find them anywhere else. I'd love to hear any advice you all may have for any of these jobs or 6.9 / w116 ownership in general!

Thanks!
Arash

[karmann_20v]

Welcome to the community!

In regards to the exhaust steam, it may not be the head gasket(s). The coolant burning has a specific smell, are you sure what you see isn't simply just condensation being eliminated from the exhaust system? Usually you'd be able to see either oil in the coolant or coolant in the oil if the head gaskets are gone.

Post some pictures when you get a chance.

[3l33ter]

Thanks!

I forgot to mention, I did notice milky condensation in the oil tank. It's a huge amount of steam, too. I read some posts about tightening the (likely loose) head bolts to buy some time, so I may try that.

I'll take some pics as soon as I can.

[TJ 450]

Once the head gasket has blown, you would probably be wasting time tightening the bolts. Corrosion or an overheat event may be the real reason for failure, too.

I would remove the heads so you know what's what, and you don't want that water in the combustion chamber for long.

Tim

[1960mog]

I too just bought my first 116 about 6 weeks ago, also a 6.9.
Unfortunately not in as good a shape as yours.

Steam on cold start and condensation under the filler cap can be normal.
Good indicators for defect head gaskets are:
loss of coolant without external leaks.
Milky oil and/or coolant.
Pressure build up in the cooling system beyond the normal pressure.
Compression loss in one or more cylinders.
Steam from the tail pipe when the engine and exhaust system are already heated up.

The best test is to check the air in the expansions tank for combustion gases.
Any good shop should be able to do this for you.

[oversize]

Welcome!  Well that's one hell of a introduction to the W116s (a 6.9)!

Yes I'd get the coolant checked for combustion gases.  Pull the plugs and pressure test the cooling system.  Leave it overnight and crank it over in the morning.  If it blows coolant out one (or more) cylinders then you have your answer!  If it checks out ok change the oil and filter a few times and make sure each time you start it to warm it up thoroughly (1/2hr) and maybe leave the oil tank dipstick out to evaporate any excess moisture in the crankcase.

Vacuum problems are either located near the firewall with damaged check-valves or hoses.  It could also be at the drivers control valve in the door.  Check to see if you have vacuum at the main reservoir above the fuel tank.

Creaking is usually bad bushes but check the ball joints for wear anyway.  If the dust boots are split the joint will be suspect

[oversize]

If I'm not mistaken the manuals should be found on this site!

[3l33ter]

Thanks for the great tips guys!

In the past, I'd always start with low trim / entry level cars and either upgrade the car or swap it for a better one, so it's nice for once to jump straight to the top. I can't fully appreciate all the 6.9 niceties yet but I'm hoping I'll learn more about w116s and the awesomeness of the 6.9 will sink in. The car already blows me away, as it's my first car with:

LSD
v8
more than 3.0L
fewer than 4 gears

Analyzing the coolant tank air for combustion gasses sounds like a good idea. I'll also look for disappearing coolant - at the rate this thing produces steam, that coolant should be depleting quickly.

Would it be sacrilege to convert a 6.9 to electric locks? I did that on my w123 and I love it. The keyless entry is nice, but mainly I like the instant lock/unlock response and IMHO it's more reliable than the vacuum system (and the vacuum system becomes more reliable without the locks).

[oversize]

I'd try to source the vacuum leak first before modifying anything.  They're usually easy to fix with a cheap vacuum gauge.  Not sacrilege, but less sophisticated with electric solenoids...

BTW it's WAY more than 3.0L!!!   

[3l33ter]

Go big or go home!

None of my friends or family have ever had a bigger engine. They mock the poor mpg, but I know they're jealous.

[oversize]

If it's just a Sunday cruiser who cares about fuel consumption?  Lots of hotties run avgas which is way more expensive than premium petrol and yet that doesn't stop them driving up and down the popular Melbourne (Lygon and Chapel) Streets!  Then there's Princess Highway.....

[navigator]

welcome and good luck!!