Yet another 450SL running HOT thread - Page 3 - Mercedes-Benz Forum
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post #21 of 49 (permalink) Old 06-17-2019, 06:57 AM
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The auxiliary water pump is used in the ACCII and ACCIII climate control system which the '77 should not have. It has nothing to do with engine cooling.
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post #22 of 49 (permalink) Old 06-17-2019, 08:24 AM
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Originally Posted by diplonasty View Post
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?
I think the auxiliary water pump just feeds the monovalve to help the heater work better. Nothing to do with cooling the engine.

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post #23 of 49 (permalink) Old 06-17-2019, 08:47 AM
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Quote:
Originally Posted by diplonasty View Post
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?
It could be as simple as tstat not quite being fitted as per service manual?

Can it be that a thermostat fitted is similar to original but still the wrong pn?
Perhaps try another make.

I believe that the poor radiator flow (as per above) would be indicated by cold bottom tank hose and extremely hot top hose.

Here's the link to the 107 Servic eManual.
It stopped working for some years manufacture but it works for similar years (e.g. 1980)
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post #24 of 49 (permalink) Old 06-17-2019, 03:47 PM Thread Starter
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Aux Water Pump

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Originally Posted by rowdie View Post
The auxiliary water pump is used in the ACCII and ACCIII climate control system which the '77 should not have. It has nothing to do with engine cooling.
Thank you for clarifying this for me. It certainly explains why I never found it.
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post #25 of 49 (permalink) Old 06-17-2019, 03:57 PM Thread Starter
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Thermostat

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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!

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

Thermostat change over (generic image):
Dlenka;

Thank you for these images. I will check the bottom radiator hose the next time I take the car for a spin.
I do know that the top hose gets hot as hell and becomes pressurized. Would this still be the case if the thermostat is only partially open? Just curious.

I do want to thank everyone for posting here. From everything you guys have contributed, I suspect my problem is either a thermostat that does not open all the way of a 42 year old CAT that has restricted airflow.

I am curious about one thing: Has anyone here taken IR Laser Gun temp readings of their exhaust manifolds when the car is at operating temperature or hotter? Mine are in the mid 400's F and I just wondered what NORMAL should be.
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post #26 of 49 (permalink) Old 06-17-2019, 07:51 PM Thread Starter
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Originally Posted by masand68 View Post
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.


Sent from my iPhone using Tapatalk

How high were the temps?
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post #27 of 49 (permalink) Old 06-18-2019, 06:19 AM
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Originally Posted by diplonasty View Post
Dlenka;

Thank you for these images. I will check the bottom radiator hose the next time I take the car for a spin.
I do know that the top hose gets hot as hell and becomes pressurized.
Check the bottom radiator hose... make sure it isn't collapsing under the vacuum created by the water pump. Lower radiator hoses generally have a coil or some type of internal reinforcement to prevent collapse under the vacuum created by the water pump. The lower radiator hose should be cooler (not cool, just cooler) than the upper radiator hose.

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post #28 of 49 (permalink) Old 06-18-2019, 03:09 PM
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Originally Posted by diplonasty View Post
How high were the temps?


About the same as your describing at high speed, high revs. Then at 55 mph, temp was just above 175. Here is my thread on it-look at MBGrahams comments about ignition timing.

How hot does yours run?
https://r.tapatalk.com/shareLink?sha...6&share_type=t


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post #29 of 49 (permalink) Old 06-18-2019, 03:47 PM Thread Starter
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Originally Posted by Jyuma View Post
Check the bottom radiator hose... make sure it isn't collapsing under the vacuum created by the water pump. Lower radiator hoses generally have a coil or some type of internal reinforcement to prevent collapse under the vacuum created by the water pump. The lower radiator hose should be cooler (not cool, just cooler) than the upper radiator hose.
The old bottom hose did not have a coil - neither doesthe new one I put in a few months ago. I never saw this in the parts list on AUTIHAUSAZ, FCPEURO, or anywhere else. Did these cars come with one?
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post #30 of 49 (permalink) Old 06-18-2019, 04:18 PM
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The only thing I did not hear you say was...did you compare the engine temp with your laser thermometer AT the engine temp sensor and compare to cluster temp gauge reading?
It is a single pin sensor at the drivers rear of the drivers cyl head. Almost the hottest part of the engine.
If that is good...I can make a suggestion but I hate that you have already replaced your radiator.
If your new radiator is a copper radiator A good radiator shop can re-core the radiator with a core that has larger cooling tubes.
It provides an additional 200 to 300 btu's of heat removal.
It is a good fix.
If this is a consideration you probably can get most of your new radiator money back on Ebay if it is a copper/OE radiator.
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