Yet another 450SL running HOT thread - Page 2 - Mercedes-Benz Forum
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post #11 of 49 (permalink) Old 06-16-2019, 09:47 AM Thread Starter
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The AC definitely causes the engine to run hotter. I assumed that this would be because it is the original 42 year old compressor ( which was converted from R12 to R134 at some point) and that it probably creates too much drag when the compressor is on.

AC cooling is not a huge priority at the moment so I tend to leave it off so that it does not add to the problem. I plan to address other issues such as the AC if I ever get the engine temps under control.
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post #12 of 49 (permalink) Old 06-16-2019, 09:58 AM
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Your electric fans should be turning on. you can jump the temp sensor on the engine and the fan should turn on. There is a patch to install a 1.1 ohm resistor (search for this to be sure on the resistor value) that makes the fan turn on earlier.
The is also a temp switch on the AC that will only work if your ac is properly charged.
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post #13 of 49 (permalink) Old 06-16-2019, 10:08 AM Thread Starter
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Aux Fan

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Originally Posted by rumb View Post
Your electric fans should be turning on. you can jump the temp sensor on the engine and the fan should turn on. There is a patch to install a 1.1 ohm resistor (search for this to be sure on the resistor value) that makes the fan turn on earlier.
The is also a temp switch on the AC that will only work if your ac is properly charged.

Funny thing that you mention the aux fan. I installed a new 212 self grounding switch. It works but it does not appear to help much. I even tried attaching a ground wire so that the fan would run when the car engine was running and I did not see any improvement. The auxiliary fan does work and I blew smoke in front of it to visually confirm it was sucking up air - It was.
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post #14 of 49 (permalink) Old 06-16-2019, 10:15 AM Thread Starter
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At highway speeds there should not even be requirement for a fan. 60 mph unlimited air ramming through the radiator due to the forward motion of the car should completely overpower any amount of air your fan could push. In fact, at highway speeds your fan may even be an impediment to air flow.

Did you check the A/C radiator fins for blockage? Something may be restricting airflow through the radiator.
How about oil? Are you using the correct grade of oil? Is there an oil cooler?
That new fan clutch you installed that made you car sound like a truck (fan roar) happened to me as well, I too put the original back and the fan roar was gone.
If you turn on the heat does the temperature come down?
Are you using the recommended type of coolant?
Does you car roll free or is there excessive drag?
Is the fuel mixture too lean? To be honest I don't know how to check it.
Any blockage in the exhaust?

Just thinking out loud.

Turning on the heat brings the temperature down a bit but the hot air that comes out is INTOLERABLY hot.
I have tried both the Mercedes Blue and the green stuff. I observed no difference between them.
The car appears to roll free. I can take the foot off the gas when going 30 MPH and it seems to want to coast just fine.

Muffler is new. The CAT/Resonator thing is the original. Hot air comes out the tailpipe but I honestly don't know how to tell if the flow is less than normal.
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post #15 of 49 (permalink) Old 06-16-2019, 10:44 AM
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Not sure if it applies to your year but on mine I was seeing the same thing (high temp related to high rpm).

Setting ignition timing from factory specs (canít even remember what that is) to 5 BTDC helped mine.


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post #16 of 49 (permalink) Old 06-16-2019, 11:38 AM
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The CAT/Resonator thing is the original.
Original? I would change that before doing anything else. Or perhaps if you'd prefer to be certain that the original is bad, try disconnecting the exhaust... I know it will be noisy but if you can put up with the sound, see if it cures your running hot problem.

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post #17 of 49 (permalink) Old 06-16-2019, 03:34 PM
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Original? I would change that before doing anything else. Or perhaps if you'd prefer to be certain that the original is bad, try disconnecting the exhaust... I know it will be noisy but if you can put up with the sound, see if it cures your running hot problem.
Before doing something drastic like replacing catalytic converters, I would confirm the cat's health with a back pressure test. Any good exhaust shop will do this for like $40-50 . No sense replacing good parts :P

I'd also go and replace the expansion tank cap (the small cap where you put in coolant). Those do go bad and can cause hot running conditions. Cheap $6 to do.

I would also confirm your hot running temperature with an IR gun on the water pump housing. Someone here once posted a before and after with a coolant gauge showing a drastic change in temperature between the two.

As stated, not all cooling gauges are the same. It's worth confirming with an external tool.
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post #18 of 49 (permalink) Old 06-17-2019, 12:58 AM
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Originally Posted by diplonasty View Post
Turning on the heat brings the temperature down a bit but the hot air that comes out is INTOLERABLY hot.
I have tried both the Mercedes Blue and the green stuff. I observed no difference between them.
The car appears to roll free. I can take the foot off the gas when going 30 MPH and it seems to want to coast just fine.

Muffler is new. The CAT/Resonator thing is the original. Hot air comes out the tailpipe but I honestly don't know how to tell if the flow is less than normal.
Quote:
Originally Posted by diplonasty View Post
Funny thing that you mention the aux fan. I installed a new 212 self grounding switch. It works but it does not appear to help much. I even tried attaching a ground wire so that the fan would run when the car engine was running and I did not see any improvement. The auxiliary fan does work and I blew smoke in front of it to visually confirm it was sucking up air - It was.

I'll risk repeating myself, above bold text confirms my thought on thermostat not doing its job of diverting sufficient coolant to the radiator (cabin heating runs on coolant straight from the engine, before thermostat). Thus increased airflow through the radiator will not help

see the coolant flow diagramme and it will make it easier to comprehend as to why thermostat can keep otherwise perfect engine hot - by not diverting enough coolant to the radiator making everything appear as functional but actually being faulty!

In depth:
https://www.startekinfo.com/StarTek/..._56/20-005.pdf

Thermostat change over (generic image):

Last edited by Djenka018; 06-17-2019 at 01:01 AM.
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post #19 of 49 (permalink) Old 06-17-2019, 05:24 AM
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Originally Posted by Djenka018 View Post
I'll risk repeating myself, above bold text confirms my thought on thermostat not doing its job of diverting sufficient coolant to the radiator (cabin heating runs on coolant straight from the engine, before thermostat). Thus increased airflow through the radiator will not help

see the coolant flow diagramme and it will make it easier to comprehend as to why thermostat can keep otherwise perfect engine hot - by not diverting enough coolant to the radiator making everything appear as functional but actually being faulty!
That explains everything I have observed in my own engine (116.962). Excellent information... thank you.

During colder months my temps run around 90 but now that days are warmer the temp is running a hair under 100 (and will stay there even at highway speeds). Turning on the heater brings the temp down to about 90, maybe a little higher... now I know why.

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post #20 of 49 (permalink) Old 06-17-2019, 05:26 AM Thread Starter
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Quote:
Originally Posted by Djenka018 View Post
I'll risk repeating myself, above bold text confirms my thought on thermostat not doing its job of diverting sufficient coolant to the radiator (cabin heating runs on coolant straight from the engine, before thermostat). Thus increased airflow through the radiator will not help

see the coolant flow diagramme and it will make it easier to comprehend as to why thermostat can keep otherwise perfect engine hot - by not diverting enough coolant to the radiator making everything appear as functional but actually being faulty!

In depth:
https://www.startekinfo.com/StarTek/..._56/20-005.pdf

Thermostat change over (generic image):

Thanks. I installed a BEHR thermostat. Would a WAHLER work better?
Also, I understand there may be an auxiliary water pump (https://www.autohausaz.com/pn/0008356964OE) - Where is this component located?
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