Some people think the factory manual is the defacto standard and that it can never be challenged and that M/B knows every single possible outcome of their engineering decisions.

Such people never worked in the engineering profession and have no idea of the multitude of variables that can never be fully addressed with the time and cost constraints presented.

Furthermore, such people believe that the engineers wrote the manuals..........which is miles away from reality.

I drill one tiny hole in my stats to bleed air.

__________________
1999 w140, quit voting to old, and to old to fight, a god damned veteran

Brian is absolutely correct.
I have to add that I have found many errors in the factory service manual .
These are errors that are fairly significant , primarily electrical, and could cause a person to spend much wasted time determining what is correct.
For purely mechanical systems, the FSM is pretty good ,yet there are errors or the method described to accomplish a task is too complex and can be done in a simpler and more efficient method such as my hard learned lesson regarding coolant re-fill procedure.
Engineers do not spend the majority of available development time creating R&R regimens or protocols for a system designed for production but do concentrate on revisions, new designs, system analysis and various other design function validation.

__________________
1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
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Temperature still higher than in summer.
I replaced the thermostat, filled the head with coolant, filled the expansion tank with coolant, started the engine, turned on the heater.
Did not need to add more coolant at idle operating temperature.
Drove some miles (5-6 at 2000-3500 rpm's) and the temperature returned to 95* +/-, probably closer to 100*.

Checked coolant again , coolant is down in the expansion tank perhaps 3/8" at 82*. Car does cool down promptly at idle back to about 82*.
I have no idea.
Sending unit on the head is new and at 80* reads 61.7 ohms.
At 90* the value is supposed to be 51.2 ohms +/- 4.3, so that may be close to correct for 80*.

My friend says - bad fan clutch or blown head gasket or cracked head.

Can't imagine how hot the car would be if this were July.

__________________
1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
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Let it sit overnight after a drive. In the morning, pinch the upper radiator hose to check if there's air pressure (there shouldn't be). Remove the reservoir cap and listen for a rush of air (there shouldn't be). Residual pressure in the cooling system is an indication of a head gasket breach or as is not rare in these engines, head cracks.

Can an IR thermometer be used to compare upper and lower radiator hose temperature to determine if the radiator is doing its job?

Does IP timing have any impact on engine temperature? I think gsxr said it doesn't.

If the usual suspects have alibis, pull the water pump to be sure the impeller is properly attached and in good shape.

Sixto
87 300D

Thanks, I'll check it in the morning to see if I have pressure in the upper hose or the expansion tank.
I seem to recall though yesterday evening when I started working on it after the engine cooled down enough to remove the thermostat (perhaps 3-4 hours) that I had no pressure in the coolant system.
I will try again tomorrow morning.

I don't know what the temperature difference should be between the upper and lower coolant hoses.?
The crazy thing is that last summer and fall the car cooled fine.
So , I pull the head because the front of the head gasket that seals the timing case is ripped / broken and leaking oil .
Replace the head gasket, have the head milled, seals etc... done. Car runs hot. Driving me crazy ... A short drive I suppose.

__________________
1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
------------------------------

I wonder if thats a quirk of the 603- mine runs up a little high after a hard or extended acceleration- I did not fill from the upper hose last time, but rather darined it all ad pulled vacuum on the entire system and let it suck the coolant in, which is supposed to prevent any air pockets. I wonder if that does not apply to this engine or if it has a spot which resists this.

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1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350

Personally, I believe it depends on the condition of the radiator. The '86 runs up in temperature so quickly, it's almost like a boost gauge. It'll run up to 100C. when the ambient is 50F. However, even in 95F. ambients, it won't go over 105F. even on a heavy upgrade.

The '87 runs cooler and won't ever climb to 100C., but it does exhibit increased temperatures under load.

It's dependent on load and radiator condition. The more clogged the radiator, the further the thermostat has to open to supply sufficient coolant. The only way that happens is if the temperature rises a bit.

Checked the upper radiator hose this morning and it is not pressurized.
Removed the expansion tank cap and heard a faint sound that to me sounded
like vacuum, not a rush of air, sort of a "huh" or an inhale - a plain inhale - not a woodstock.
My coolant is clean and oil looks fine.
So perhaps the 18 month old fan clutch is going or the water pump - don't know what else it could be.

__________________
1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
------------------------------

A fan clutch is supposed to stay in the installed position. I don't know what laying it on its flange does but you're not supposed to keep it that way for long periods. If you suspect the clutch is the problem, temporarily fix; i.e., so the fan always spins at water pump rpm, the fan and clutch and see if that brings temps back to the way they were.

Sixto
87 300D

I have read that as well about keeping the fan clutch vertical.
Personally I don't see how that will occur while they sit on the shelf at the warehouse .
Now you've got my curiosity up, how would I lock the clutch so that it spins at the same speed as the water pump.?
A friend and I talked about that some time back but I don't recall what the scenario was. I think it was to something like drilling and tapping , bolts and such. I don't remember.
Is there a simple method. ?

__________________
1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
------------------------------

Do you have an old clutch you can jam?

Sixto
87 300D

I have the old clutch that I took off but the new clutch had the new bolt pattern for the updated fan and so I had to install a new fan.

Don't have the old fan, think I trashed it. I might be able to find one though.
So are you saying just to wedge something into the gap between the 2 parts of the clutch?

__________________
1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
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Last entry in mysterious temperature increase thread.
Drove the SDL yesterday afternoon - - 65-70 mph. for about 15 miles, drove some stop and go a few miles , temperature stayed at about 82* while driving,
about 85* at idle when stopped finally.
So , the normal operating temperature is back , perhaps lower.
Did nothing to the car to change the operating temperature after filling through the upper hose.

The answer is - I don't know.
Possible answers - (ready to accept all sorts of remarks).
1. After filling radiator through upper radiator hose an air pocket remained and was dislodged overnight prior to yesterdays drive.
2. Fan clutch began working correctly after 5 months of being idle.
3. Thermal conductivity of head mating surface(s) section increased due to much finer RA or RMS finish on reworked cylinder head and new gasket material requiring a period of time to complete sealing / seating creating temporary adiabatic regions with respect to the crank case mating surface. (This one was a real stretch)
4. Rapid thermal cycling caused by multiple concurrent episodes of driving at 3500 rpm and then 2000 rpm created an abnormal temperature gradient /excursions, thus causing the normal operating temperature average to rise.
5. Who cares, I don't care , it's fine now.

Thanks everyone for your input.

__________________
1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
------------------------------

The air in the head dissipates gradually via normal engine operation. The thermal cycling of the engine probably helps with this process. In theory, the issue would have eventually resolved itself without filling the head.........you just accelerated the process.