300SEL 3,5 overheating

[werminghausen]

I find that my engine is overheating a lot if I get stuck in traffic.
I easily can reach 220 and over close to the red mark. What do you think this is? Aux fan is running.
Also starting the engine becomes problematic if the engine is overly hot..
What is this? Are hot starting problems and over heating related?

I don't feel well at these high temps. Any idea to solve this?
I have on my list the change the Thermostat. Is this a common problem with these engines?
I didn't test the clutch fan... needs to stop right away after engine is turned off?
Does the hot start problem go away if engine stays cooler?

Martin

[Tomguy]

Def hotter than you should be, and I'd be concerned about roasting cams and warping heads at or near those temps. A few common causes:

* Bad mechanical fan clutch
* Low on coolant
* Calcium buildup in cooling system (esp radiator)
* Bad water pump

Hot starting & overheating aren't directly related but if you're already a bit lean on normal operating temp startups, hot startups will be very hard. May need to go a click or 2 richer on the ECU screw, or a quarter turn on the idle air screw. If your thermostat were bad, it'd not get to operating temp (esp in the winter) since the "Failsafe" on these causes water to flow directly through the engine to the radiator.

[Palolo]

I have an M130, but share your thoughts. In traffic, the needle climbs. I have found that my Aux fan doesn't push crap through the condenser+radiator (I had my engine fan taken off, and decided to do an experiment to see if there was any air flow behind the radiator with aux fan (only) running: nada.) The stock aux fan is pretty useless for me here in Hawaii, and I'm not yet even running aircon.

I have also found that at idle (say, when in traffic) the waterpump doesn't push much water. Flow is barely perceptible while at idle. Step on the gas a little, and flow is visible and temps drop noticeably.

My solution to this feeble cooling setup is going to consist of an electric puller fan behind the radiator, a Davies Craig water pump and EWP Controller (to control both). See ya later thermostat, adios water pump. Maybe convert to a cross flow radiator too. Why not, it might be an improvement. Just don't tell the originality freaks... Ahem, 113 owners.

For Oman, I would consider the same too.

[werminghausen]

Originally Posted by Tomguy

Def hotter than you should be, and I'd be concerned about roasting cams and warping heads at or near those temps. A few common causes:

* Bad mechanical fan clutch
* Low on coolant
* Calcium buildup in cooling system (esp radiator)
* Bad water pump

Hot starting & overheating aren't directly related but if you're already a bit lean on normal operating temp startups, hot startups will be very hard. May need to go a click or 2 richer on the ECU screw, or a quarter turn on the idle air screw. If your thermostat were bad, it'd not get to operating temp (esp in the winter) since the "Failsafe" on these causes water to flow directly through the engine to the radiator.

Hi Tomguy,
any good way to improve conductivity of the radiator?
Any flush chemical that can clean the carbon out?
(I have chanced the radiator on my 126 and it was like day and night... but I have no chance to get a new radiator for the 109 here in Oman.
So any cure is good.

What is the test for the fan clutch...same as for a 126? stop engine and the clutch should stop right away?

So you say the new Thermostat won't help...correct?

Water pump ...yes might be bad but no chance to change at this point.

What about Waterwetter?

[Tony H]

I was reading about the Davies Craig but their website never explained how to interface to the existing water pump in a retrofit situation. Seems like a neat concept.

Originally Posted by Palolo

I have an M130, but share your thoughts. In traffic, the needle climbs. I have found that my Aux fan doesn't push crap through the condenser+radiator (I had my engine fan taken off, and decided to do an experiment to see if there was any air flow behind the radiator with aux fan (only) running: nada.) The stock aux fan is pretty useless for me here in Hawaii, and I'm not yet even running aircon.

I have also found that at idle (say, when in traffic) the waterpump doesn't push much water. Flow is barely perceptible while at idle. Step on the gas a little, and flow is visible and temps drop noticeably.

My solution to this feeble cooling setup is going to consist of an electric puller fan behind the radiator, a Davies Craig water pump and EWP Controller (to control both). See ya later thermostat, adios water pump. Maybe convert to a cross flow radiator too. Why not, it might be an improvement. Just don't tell the originality freaks... Ahem, 113 owners.

For Oman, I would consider the same too.

[sjefke]

Something is definitely wrong with your system. I have NEVER had my car overheat in Atlanta summer traffic in 90+ degree weather. It always stays right around normal and I don't even use the aux fan. But it did have a new radiator when I bought it. Plus waterpump is also new(er). Make sure you have plenty of coolant. Also check radiator cap. If it does not seal, your cooling system is not pressurized and won't cool as well.

Although unlikely, also check that the aux fan is not running the wrong way around. You'd be surprised how many electric fan systems in older DIY cars are turining air the wrong way...

Good luck,

Bert

[werminghausen]

Originally Posted by sjefke

Something is definitely wrong with your system. I have NEVER had my car overheat in Atlanta summer traffic in 90+ degree weather. It always stays right around normal and I don't even use the aux fan. But it did have a new radiator when I bought it. Plus waterpump is also new(er). Make sure you have plenty of coolant. Also check radiator cap. If it does not seal, your cooling system is not pressurized and won't cool as well.

Although unlikely, also check that the aux fan is not running the wrong way around. You'd be surprised how many electric fan systems in older DIY cars are turining air the wrong way...

Good luck,

Bert

Hi Bert,

i had the same overheating problem with my 300SDL (W126) here. I changed the radiator and it was a difference between day and night! Now the coolant stays at 85-90 degrees no matter what (here in Oman!....Atlanta is a piece of cake compared)
My radiator cap is tight. plenty of coolant too.
So I believe the radiator is clogged in my SEL or covered which changes connectivity to a point where it gets thermally dangerous. Not sure what I can do with my means and methods. Are there any chemicals which clean out this old radiator? Whatever his solid whitish stuff is that occurs around
coolant (for instance at the aluminum housing where the rubber hose is attached).
I'll check fan direction but I doubt that something is wrong here.
Martin

[Tomguy]

With the original radiator, my 4.5 overheated easily. "cth350" sold me a great used one to replace my original leaky unit. It had been boiled out by a professional shop. Prior to installation I did a flush with Prestone coolant flush, then I did a flush with water, then I flushed with water again. I put the new radiator in, and NEVER had overheating (or even close to it) after. It never went above 175° on the temp gauge more than twice, and the aux fan NEVER kicked in at all (it maybe peaked at 185°).

I know finding a good used 108/109 radiator in Oman will be tough for you, so see if you have a local shop that can boil yours out and assure leak-free operation afterwards.

[socalbenz]

Start by replacing the radiator cap. It is cheap and frequently solves overheating problems.

[werminghausen]

Originally Posted by Tomguy

With the original radiator, my 4.5 overheated easily. "cth350" sold me a great used one to replace my original leaky unit. It had been boiled out by a professional shop. Prior to installation I did a flush with Prestone coolant flush, then I did a flush with water, then I flushed with water again. I put the new radiator in, and NEVER had overheating (or even close to it) after. It never went above 175° on the temp gauge more than twice, and the aux fan NEVER kicked in at all (it maybe peaked at 185°).

I know finding a good used 108/109 radiator in Oman will be tough for you, so see if you have a local shop that can boil yours out and assure leak-free operation afterwards.

Thanks Tomguy.
This is my bet too. I assume it is the radiator core being clogged.
Problem is that I can't get a new radiator. So I will try and flush the hell out this existing one. Maybe not the entire system but the radiator it self: vinegar, muriatic acid, dishwasher soap....?

[werminghausen]

Originally Posted by socalbenz

Start by replacing the radiator cap. It is cheap and frequently solves overheating problems.

Thanks, I'll look into the cap. But I believe it is in good condition keeping pressure.

[Tomguy]

Citric acid is MB's recommended flush on these systems.

[suginami]

If your car is running too lean it can cause it to run hot.

[Tomguy]

Good point! Another cause, timing too late, including mechanical advance not working. When my rotor was cracked it messed up my timing and my headers actually glew red at night (which was how I noticed the issue)

[werminghausen]

Originally Posted by Tomguy

Citric acid is MB's recommended flush on these systems.

MB's recommendation:
What is the recommended ratio of citric acid powder and water? And for how long do I run the citric solution after draining the coolant?
Martin