1974 280C M110 Operating Temperature Question

[dquance]

Folks:After improving the running of my Garage Queen by re-torquing the carb and cleaning the coil connections, the operating temperature has increased.

I had also replaced the viscous clutch and removed the condenser which had most fins bent restricting airflow.

I have the OE thermostat, 189 F, 87 C installed.

When warm and driving the gauge is reading at the unmarked line between 175 and 250 F.

I have seen conflicting info that the line is either 194 F (90 C) or 212 F (100 C).

The spacing on the gauge does not place that line at the midpoint, it is closer to the 175 mark.

Two questions:

1) is that an appropriate operating temperature, or should I install a lower thermostat.

2) What is the definitive temperature of that line on the gauge.

TIA

--
SANTÉ
Doug Quance

[Sugar Bear]

I think the line you are referring to is 212F but I'm not certain. Running at that line cruising on the highway is on the warm side. Using an infrared thermometer check some underhood engine temps to confirm gauge accuracy. Check radiator temps in many locations trying to find cool spots indicating a blockage.

As for changing the thermostat, I would if the infrared shows the gauge is accurate. As to what temp, the OE spec.

If the temp increases on the highway and the thermostat is good, that is a sign of a radiator problem. Examine the lower section of the external fins of the radiator for corrosion or blockage.

Good luck!!!

[rumb]

Retorque carbs? If you have an air leak then closing it would have the engine run richer, which would also be cooler.

If you havent replace the thermostat, they are inexpensive. 87 degree is good. You may have air in the system?

Make sure the fan blade is close to the radiator and the shroud is covering the blades.

[Frank Reiner]

dq:

Is the car a USA model, and if so, is it a Federal spec car or a California spec?

Emphasis is usually placed on the removal of energy from the cooling system, however, examining the input of energy is equally important.
In the first two years of use of the M110 in the US, MB did not use catalytic converters, but relied on manipulation of ignition timing to achieve some reduction of emissions. The ignition timing is deliberately kept more retarded in some conditions than would be desired for best engine operation. If, for any reason, that retard is maintained after shifting into 4th gear and driving above ~25MPH, rejected energy flow into the cooling system will cause an increase in water temperature.
As a first step, ignition timing must be checked, and, as a test, the vacuum controls on the distributor should be defeated. In that condition timing should be set to ~35* BTDC @ 3500RPM.

[dquance]

Thanks for the feedback:
Sugar Bear, I did scan with a laser thermometer some time back and got confusing readings, I will do it again. The reading next to the temp gauge sender and switch for aux fan was reading 300 deg F?

rumb: My car has no shroud around the fan, is there suppose to be one on this model?
It would certainly help the cooling.

Frank Reiner: I am not sure if it is Fed or Cal, how can I tell?
I had disconnected the vacuum line to the distributor and set the timing at 10 deg BTDC at about 900 rpm.
I will try the 35 deg BTDC @ 3,500 rpm.
I have found when setting the timing, it jumps around somewhat, is that a problem with the distributor? Not sure I want to try and find a new one, any thoughts.
Thanks

[Frank Reiner]

Originally Posted by dquance

Frank Reiner: I am not sure if it is Fed or Cal, how can I tell?
I had disconnected the vacuum line to the distributor and set the timing at 10 deg BTDC at about 900 rpm.
I will try the 35 deg BTDC @ 3,500 rpm.
I have found when setting the timing, it jumps around somewhat, is that a problem with the distributor? Not sure I want to try and find a new one, any thoughts.
Thanks

Re: Fed vs. Cal
Does the engine have an air pump (smog pump)? Does it have it have two bulbous exhaust reactors on the right side of the engine? If yes, it is Cal.
Re: Jumping timing
If your timing light is steady on another engine, then there may be a distributor fault. There are folks on this forum with spare M110 parts, but yours most likely can be made right.

[rumb]

Yes you should have a fan shroud. 1145050755

https://www.mercedespartz.com/store/1145050755/

[Benz Dr.]

87C is probably too hot. Most run 82C and the coolest one you can get is 79C.

[dquance]

Frank: It does have an air pump, with no belt attached and I do not intend to add one.
It does not have any reactors.
How can I make my distributor right?

Benz Dr: 87C is the oem, I have purchased a 75C, but have not installed it yet.
The previous owner had drilled 2 small holes in the thermostat, and to me then it ran too cool and was not running as good as it is now.

[Frank Reiner]

Originally Posted by dquance

I have the OE thermostat, 189 F, 87 C installed.
When warm and driving the gauge is reading at the unmarked line between 175 and 250 F.
Is that an appropriate operating temperature, or should I install a lower thermostat?

dq: What was the ambient temperature when you observed the above noted reading?
And what was the ambient when it "ran too cool" as noted below?

Originally Posted by dquance

Frank: It does have an air pump, with no belt attached and I do not intend to add one.
It does not have any reactors.
How can I make my distributor right?

Benz Dr: 87C is the oem, I have purchased a 75C, but have not installed it yet.
The previous owner had drilled 2 small holes in the thermostat, and to me then it "ran too cool" and was not running as good as it is now.

See this thread for useful comments on the effects of thermostat rated temperature:
1983 240d thermostat testing

Re: Distributor
It may be assumed that the exhaust manifolds have been changed; are they now a pair of smoothly sweeping 3-into-1 manifolds?
The air pump now has no function, and could be removed.
Does the ignition timing advance smoothly from about 10-12* at idle to 35-37* at 3500 RPM without vacuum? If so, plug the vacuum line at the switchover valve, and operate the distributor w/o vacuum. The vacuum provided a timing retard in certain conditions, and operated in conjunction with the air pump and reactors for emission "control".

[dquance]

Frank: Sorry for the delay, real life keeps getting in the way. :-)
"When warm and driving the gauge is reading at the unmarked line between 175 & 250 F."
Ambient temperature about 70 F.

ambient when it "ran too cool"
That was quite a while ago, I would guess 45F, and there was insufficient heat in the car.
Since then I had set the valves, changed plugs, tightened carb and cleaned coil contacts. I had previously bypassed the dropping resistor for the coil as the
Flame Thrower coil was able to handle the extra current and the resistance of the coil
was within spec, over 3 ohms?
I have yet to check the timing at 3,500 rpm, and check the rad with a laser thermometer.
You are correct about the manifolds.
It has also been suggested to reverse blow the rad with compressed air to insure it is not blocked.
Hopefully next week will provide time to do these and report back.
DougQ

[Idle]

One quick way to tell if a Mercedes of that era is Federal or California is to look at the emission sticker. If it is still there.

Federal sticker is a black background. California is a green background. Or maybe it's the other way around. Someone will correct me on this.

I think only the 1975 had the thermal reactor. But these were $1600 each to replace and a Federal exhaust manifold from a wrecking yard was $25 so not a lot of worn out thermal reactors are still out there. Or were replaced with another reactor.

Taking the belt off the energy sucking air pump was a common thing but if they are not turning they tend to rust and freeze up. Then you have to fix them if they are needed to pass your state smog test (if your state has one). But after you have passed the test you can always remove the belt again.

And to make it even more fun the California emission package is California in name only. For Mercedes this meant Western Zone which took in a lot of western states. I bought a car in New Mexico from the original owner and it had the western zone package. I think Mercedes just made a bunch of cars and if they didn't sell in California they just shipped them to dealers that needed them in the 'western zone'.

[Mike D]

I'd advise against using compressed air to blow out the radiator. The /8 radiators are rapidly becoming "unobtaniums".

If you decide to use compressed air, limit it to a maximum of 10-15 p.s.i.

[dquance]

Re: Distributor and advance, it does advance smoothly from 10deg BTDC at idle through to 30deg btdc at 3500 rpm, with the vacuum pluged. I will assume that is ok,
as it runs very well.
I noted with a laser thermometer that the temperature beside the temp sensors was between 190 - 200F, which seems ok to me.
The instrument gauge was reading at the undefined mark between 175 and 250.
I am thinking I have a poor connection on the temp gauge sensor, or that mark is really about 200F. I will give the connections a clean.
THe other reading on the radiator were: top of rad above hose connection was 172 and 164 at the other end. The bottom of the rad was reading 93 - 98 at the front and 166 at the back of the hose end.
If nothing changes after I clean the connections I am not going to bother doing anything more, as the laser temps do not concern me. :-)
Thanks everyone for your input.
DougQ

[cleeves]

Originally Posted by Mike D

I'd advise against using compressed air to blow out the radiator. The /8 radiators are rapidly becoming "unobtaniums".

If you decide to use compressed air, limit it to a maximum of 10-15 p.s.i.

How do you get them then? That's troubling. I've noticed in the last couple summers that when sitting in traffic with the A/C on mine creeps up close to the 212F mark - so I then turn it off. Going 85 MPH with the AC on it's around 200-205F. I don't remember it getting that hot in summer 2018, and this summer seems a bit worse than 2019. Around town though, 35 MPH, it's a comfy 185F. 65 MPH is 190-195. I'm thinking I should start looking for a spare radiator in case mine goes....


Henry