News:

www.W116.org
The #1 resource for our W116! Established 2004

Main Menu

Removing air intake 6.9 - a big job?

Started by Jan S, 17 March 2022, 02:30 PM

Jan S

The engine is a US 1977 M100.985 (6.9) with K-jetronic.

I'm playing with the thought of removing the air intake, do some thorough cleaning and replacing the two left-right gaskets and the eight rubber pieces.

Is this a big and "risky" job?

- easy to remove?
- what is the probability that one or several of the air intake bolts will break?
- difficult to install and keep all gaskets in the right place?
- other difficulties?

I sense it's a good time to do this:
- I have a vacuum leak, hence I'm replacing all rubber boots and vacuum lines around the aux air valve/ idling house as well as the "100 090 01 82"-hose, during the next 2-3 weeks (I had 5 leaks in this area)
- I'm not sure I have a leak under the air intake, but wouldn't surprise me after 47 years
- Cooling system is currently drained
- I seriously need to clean under the air intake - it looks terrible...... potential fire hazard?
 
Any advice? I haven't done this job before.
1975-mod W116 450 SE with 6.9 engine

Jan S

Here's the pic
1975-mod W116 450 SE with 6.9 engine

rumb

If you dont have a problem I would skip doing this. Odds are you will break a bolt. You can spray carb cleaner around the gasket areas while the engine is running to see if you have any air leaks.
The 8 gaskets are $$$.

You can probably clean underneath with compressed air. There is a drain hole on the left rear, you can more easily find it from underneath the car and run a wire up to clean it out.
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550, '16 AMG GTS

daantjie

Indeed that drain hole was a mystery on the forum for a while or maybe just for me 8)
From below you will see it aft of the oil pan/sump on driver side (LHD).
Mine was full of crap and took multiple flushes to run clear.
From the top it is very much hidden beneath the oil pressure feed and vacuum connection at the firewall,really tough to see it.
Happy hunting  ;D
Daniel
1977 450 SEL 6.9 - Astralsilber

UTn_boy

The odds of one of the bolts breaking are slim, but possible.  It depends on if one of the intake manifold gaskets has leaked coolant over the years around one of the bolts.  It also doesn't help if cheap green coolant was used and not changed every two years.  It turns very acidic after two years. 

The round rubber doughnut seals are something you replace out of principle.  Would you trust a 47 year old belt or radiator hose?  Of course not.  These round seal are no different, and they DO leak with age.  The only other things I'd replace are the injector seals and heater hoses.   

The job itself is time consuming, but not terribly difficult.  Be sure the drain the coolant out of the block from the block drains underneath to get as much of the old coolant out as possible. 
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1971 280sel Black/black leather
1973 300sel 4.5, silver blue metallic/blue leather
1979 450sel 516 red/bamboo

Randys01

I am less sanguine about this particular job. 
You had better check that the 8 o rings are in fact available before you start.
Invariably the stud holding the manifold to the head at 243 and 238 will be seized rotten.
Hose 265 maybe no longer avail depending on your model variant.

I have done this job and it was in my instance a freaking big deal!!
Yes it's do-able............but

Jan S

Thanks to all of you for sharing your insights and experiences -- this is very useful!

I haven't decided yet - do it or leave it? I need to sleep on it  :)

A few comments and questions:

- I have already replaced the injector seals (and injectors) and the supply heater hose. Not the heater return hose (goes through the firewall? Do I have to go under the dash?)

- various parts are arriving the next 2-3 weeks for the "100"-hose (hose 265). NLA, hence self made. Pics will follow

- the drain hole - one of the few remaining mysteries, indeed  :) A job for tomorrow.

- Yes, I will need to check the availability for the two gaskets and the eight doughnuts. Are URO doughnuts ok?

- UTn_boy: is draining the engine block necessary to do this job? Or you recommend it in general when replacing coolant?

- UTn_boy: wouldn't you replace the two gaskets left and right?

- Randys01: what made this a big job in your case? Studs breaking? Other things? Would be interesting to know, before I decide
1975-mod W116 450 SE with 6.9 engine

goldacre

Hi Jans,

The 210 'O' rings are 'rubber' so will fail eventually, and lets face it, our cars are long in the tooth :/)

Both parts you have circled when they fail will cause a vacuum issue (lean..) so a diagnostic tool to use is a gas cylinder with the hose that would plug into the gas BBQ positioned to purge the areas of the inlet manifold in those accessible areas in and around the inlet areas (cylinders) of the 'Valley'. Not sure how safe this is but have been told its a 'diagnostic' method for old school mechanics, no sparks should be OK :/ and we did it and got the result we were looking for...

So.... Propane is around 110 octane, so if any part of the inlet system has been compromised and is letting air in post fuel inlet, adding propane addition will cause the engine to 'balance out' as in run 'smoother...', it did mine and i now know i have compromised inlet manifold gasket and/or those 210 'O' rings around cylinders 7 and 8.

I contacted Classic Center and now have all those parts in hand... just have to get off my arse to do it...

G
12/1979 450 SEL 148K on clock (museum piece)
12/1986 Lotus Esprit Turbo 87K on clock 'Darling, look what Q has brought for us, isn't it nice' :)

Jan S

Thanks for the advice! I'm hesitant to use propane or other gases in that area ... safety first.

Good to know the parts are still available.

If I'm doing the job, I will also replace the rubber sealing 450 and maybe the gasket 438, and give everything a thorough clean.
1975-mod W116 450 SE with 6.9 engine

UTn_boy

Of course you replace the intake manifold gaskets.  I assumed you were replacing those if the intake manifold was coming off. 

Regarding the coolant, yes.  Would you only drain half of your oil when doing an oil change?  Probably not.  Draining the block isn't necessary to remove the intake, but when changing coolant you have to get as much of the old out as possible. 

And no, stay away from anything URO.  That's just asking for trouble down the line. 

Regarding the heater hoses.....you don't have to go under the dash.  You only need to remove the windshield wipers and the aluminum cowl vent panel under the windshield wipers to gain access to the heater hose connections. 
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1971 280sel Black/black leather
1973 300sel 4.5, silver blue metallic/blue leather
1979 450sel 516 red/bamboo

Jan S

Quote from: UTn_boy on 19 March 2022, 11:42 AMOf course you replace the intake manifold gaskets.  I assumed you were replacing those if the intake manifold was coming off. 

Regarding the coolant, yes.  Would you only drain half of your oil when doing an oil change?  Probably not.  Draining the block isn't necessary to remove the intake, but when changing coolant you have to get as much of the old out as possible. 

And no, stay away from anything URO.  That's just asking for trouble down the line. 

Regarding the heater hoses.....you don't have to go under the dash.  You only need to remove the windshield wipers and the aluminum cowl vent panel under the windshield wipers to gain access to the heater hose connections. 

Thanks!

Yes, gaskets were on my list. I might leave the two coolant drain bolts for now. I know it's wise to do, but I'm a bit hesitant to get involved with those threads. A winter job.

I have decided the air-intake will be a October-December job, when the "driving season" has come to an end. First driving 2022 is planned for mid April, hence I won't start maintenance work that could potentially put that at risk. Collecting all the required parts will also take 3-4 weeks. Shipping is so slow these days.

I'm glad the heater return hose can be replaced without going under the dash!
1975-mod W116 450 SE with 6.9 engine

Jan S

Quote from: Randys01 on 18 March 2022, 01:21 AMI am less sanguine about this particular job. 
You had better check that the 8 o rings are in fact available before you start.
Invariably the stud holding the manifold to the head at 243 and 238 will be seized rotten.
Hose 265 maybe no longer avail depending on your model variant.

I have done this job and it was in my instance a freaking big deal!!
Yes it's do-able............but


What exactly made this a big job in your case? Studs breaking? Other things? Would be interesting to know, before I do this job late fall.
1975-mod W116 450 SE with 6.9 engine

UTn_boy

Quote from: Jan S on 20 March 2022, 06:41 AM
Quote from: UTn_boy on 19 March 2022, 11:42 AMOf course you replace the intake manifold gaskets.  I assumed you were replacing those if the intake manifold was coming off. 

Regarding the coolant, yes.  Would you only drain half of your oil when doing an oil change?  Probably not.  Draining the block isn't necessary to remove the intake, but when changing coolant you have to get as much of the old out as possible. 

And no, stay away from anything URO.  That's just asking for trouble down the line. 

Regarding the heater hoses.....you don't have to go under the dash.  You only need to remove the windshield wipers and the aluminum cowl vent panel under the windshield wipers to gain access to the heater hose connections. 

Thanks!

Yes, gaskets were on my list. I might leave the two coolant drain bolts for now. I know it's wise to do, but I'm a bit hesitant to get involved with those threads. A winter job.

I have decided the air-intake will be a October-December job, when the "driving season" has come to an end. First driving 2022 is planned for mid April, hence I won't start maintenance work that could potentially put that at risk. Collecting all the required parts will also take 3-4 weeks. Shipping is so slow these days.

I'm glad the heater return hose can be replaced without going under the dash!

You're overthinking draining the block.  The threads don't mess up.  The plugs are a 19mm hex head, and the worst thing that can happen is the drain hold is so plugged up with sediment that you have to punch it out after the plug is removed before coolant will starts draining out. '
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1971 280sel Black/black leather
1973 300sel 4.5, silver blue metallic/blue leather
1979 450sel 516 red/bamboo

Jan S

Thanks for your encouragement! I might do it after all  :)
1975-mod W116 450 SE with 6.9 engine

Jan S

Any idea where I can buy the two air intake manifold gaskets?

- A 100 141 16 80
- A 100 141 17 80

Seems to be NLA?
1975-mod W116 450 SE with 6.9 engine