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#1
Mechanicals / Re: Mercedes 450SEL 6.9 engine...
Last post by tcj - Today at 03:11 AM
broken rotocaps do make such noise.
A (small) crack in the exhaust manifold can add to this too. Look for gas pulsing on the downside of the exhaust.


#2
Mechanicals / Re: Mercedes 450SEL 6.9 engine...
Last post by harrycarry250 - Yesterday at 03:36 PM
I have not thought to check the rotocaps specifically. But I have spent many hours staring at the valvetrain and I did not notice any abnormalities. Exhaust manifold is solid, if that is what you're referring to.

Thank you
#3
Mechanicals / Re: Mercedes 450SEL 6.9 engine...
Last post by tcj - Yesterday at 02:59 PM
Have you already ruled out the rotocaps?
Crack in the manifold?
#4
Mechanicals / Re: Mercedes 450SEL 6.9 engine...
Last post by harrycarry250 - Yesterday at 02:01 PM
Hello all, thank you to everyone who posted their insight over the years!

The saga continues on this vehicle. I took a long (LONG) hiatus from looking at the car. I put stabil in the tank and started up the car periodically over the years to the keep the suspension happy. Shockingly the vehicle has remained in a relative state of quality as the years have gone by.

Since we last spoke:

I did the full valve shim procedure and while I did make many adjustments, the sound of the engine did not change whatsoever. I also inspected inside the cylinders and did not notice any scouring.

The motor still makes the exact same noise but it does not seem to be getting worse.

Here is the link again. Any thoughts? The only thing I have not done from the thread is to remove the hydraulic pump and run the engine without it. I feel like the next step after that is to inspect the rod bearings. Does anyone have a video of their engine with a bad pump? I would be shocked if a pump could make such a noise.

https://youtu.be/TFkaaZfeUj4?si=bRRY-xCOS7dTWmYQ

As an update to newcomers: Strange intermittent ticking noise from engine. Valves adjusted, chain and guides replaced, all hydraulic lifters replaced.
#5
Mechanicals / Re: A/C compressor confusion? ...
Last post by 79W116 - Yesterday at 11:39 AM
Anyone know any good mechanics around the Howell Michigan area that know these cars?
#6
Mechanicals / Re: A/C compressor confusion? ...
Last post by 79W116 - Yesterday at 11:31 AM
That is unfortunate.
#7
Mechanicals / Re: A/C compressor confusion? ...
Last post by daantjie - Yesterday at 09:44 AM
Unfortunately it's very hard to get to without essentially stripping out the dash.  It sits under the dash and probes the evaporator temperature with a capillary tube.
#8
Mechanicals / Re: A/C compressor confusion? ...
Last post by 79W116 - Yesterday at 07:56 AM
Well, this morning I tried jumping the pressure switch together to see if that would get the clutch to pull in, but it did not. I had the car running, full cold on the dial, A/C switch on, and Auto High.

Where is the "ETR" switch located?
#9
Mechanicals / Re: A/C compressor confusion? ...
Last post by daantjie - 14 April 2024, 08:00 PM
Before removing the switch I would take it to an AC shop and have them test the high and low side pressures to see if you're in range.  I would assume switch failure to be an outside chance but I would start with pressure testing first.  You may have a leak in the system which the shop can check for which would have to be tended to before anything else.
#10
Mechanicals / Re: A/C compressor confusion? ...
Last post by 79W116 - 14 April 2024, 07:13 PM
Quote from: daantjie on 14 April 2024, 03:53 PMIf you bridge the terminals for the pressure switch at the drier then the clutch should engage, as the pressure switch is a safety feature to not engage the clutch with a low gas charge.  There is an "ETR" switch which also locks out the compressor under a certian temp reading to privent freezing up, but I'm guessing your current ambient is higehr than the cut - out so I doubt this is your problem.
Ah OK, I'll try to bridge then and see if that works. So if the clutch does engage then I'm replacing the pressure switch then, correct? Which means having a shop remove all r134, replace switch, then recharge, right?