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Discussion Starter #1
hey guys

with my 500sec as ive mentioned it runs at 100c no matter what....AC on or off, streets or hwy....doesnt matter

ive mentioned this issue before in matts thread and before in my own a while back when i first got the car a yr ago

ive started to get to work on this project now so i have a few questions

I did check the fan clutch, manually, its stiff and is comparable to MY sel which mostly behaves at 80c

I am planning on getting a new radiator, i believe it maybe original, its a behr and Ill buy a NIssen.

The radiator car seal, looks meh.....im gonna a new one...Question for the rad cap..is genuine the only way to go, or is a Behr or mahle cap OK.

Lastly, with the thermostat....my car has a new one when it was serviced before my purchase....the thermostat used is 1162000215 which is the 84 degree and im wondering is it because it has the 84 , is why it may also go up in temp

so question i have is can the 1162000315 which is the 80 c thermostat, can that work in a 85 gen 1 car, because when i put in the parts on the sites it says the 315 will not fit my gen 1 car

any truth to this

thanks
 

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i also did rig the aux fan to run with alligator clips and ground and it did nothing with imporving the temp
 

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Have you confirmed the temp is actually 100?

If the problem was the radiator, it would not maintain a constant temperature.

The pressure cap has no bearing on the temperature.
 

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hey guys

with my 500sec as ive mentioned it runs at 100c no matter what....AC on or off, streets or hwy....doesnt matter

I have a few questions

I am planning on getting a new radiator, rad
The radiator car seal, looks meh.....im gonna a new one...Question for the rad cap..is genuine the only way to go, or is a Behr or mahle cap OK.

Lastly, with the thermostat....my car has a new one when it was serviced before my purchase....the thermostat used is 1162000215 which is the 84 degree and im wondering is it because it has the 84 , is why it may also go up in temp

so question i have is can the 1162000315 which is the 80 c thermostat, can that work in a 85 gen 1 car, because when i put in the parts on the sites it says the 315 will not fit my gen 1 car

any truth to this

thanks
In addition to the helpful advice from fellow members, I have some T/stat ideas from my year long 100C T/gauge readings which seem to parallel your experience..

I feel, in addition to the new radiator & pressure cap, your car will benefit from the installation of an 79-80C rated thermostat. From my latest research in my car I found that with that range T/stat my temp readings finally mimic my 16 years with my 560SEC readings. In short, I am pleased.

I was sent a 1162000215 by mistake & looks rather different than the 'Gen 2' T/stats I was messing with, and research into MB cooling system designs I found differing details..

With that T/stat, I believe yours is Coolant circuit [2 phase] design as discussed in the enclosed pdf, starting on page 3.

In my photos here: 1162000215 is to the far left and differs as to the seal gasket and an inch long pin off to the side that goes into something called a 'Control Bore'. That pin's sole function is to keep the 'control Bore' free of various schmutz over time. This is Gen 1 territory. The other thermostats have a ball valve to allow the device to bleed air out. As they are similar configuration and settings, they can be used with another application with good result [in my opinion]. During my research into your issue, I looked at R107 thermostats as well... as they have a similar engine & sometimes lower T/sat ratings in catalogs.

As you can see from the center one & one to the right side, they are of differing lengths & also have different diameter bypass valves at the foot. In my experiences earlier in the Summer, I found neither the overall length or the valve diameter to have negative effects at all. The thermostat temperature rating was the factor delivering the goods. I think you and I IMed about this at the time....

That said, if you can find an 80C T/stat that looks like the one with the pin, I think you'll be right where you want to be.

Here's the PDF on the cooling system too, just in case.

I wish you luck .. I know that '100C_no_matter_what' scenario all too well.

M.
 

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Actually ... it does (IMO). The lower the opening pressure of the relief valve, the higher the temperature gets. Is not in vain that is supposed to open at a certain pressure (1 Bar = 14.5 PSI).
Water boils at 100C at atmospheric pressure. A 14 psi cap won't open until the temperature reaches roughly 125C, (absolute pressure about 2 bar) ergo, the cap will have no bearing on the operating temperature but it will affect the temperature at which the system boils over.
 

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Water boils at 100C at atmospheric pressure. A 14 psi cap won't open until the temperature reaches roughly 125C, (absolute pressure about 2 bar) ergo, the cap will have no bearing on the operating temperature but it will affect the temperature at which the system boils over.
What you are describing is the ideal case of a cap that opens at the correct pressure, but if his cap fails to maintain pressure the boiling point is lowered, the coolant is unable to remove sufficient heat from the engine and the temperature of the coolant gets above what it should have been normal with a well-functioning cap.
 

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Dumb question... if it is indeed 100C, why is that a problem?

.
It may just be a comfort level with me...my SEL has at 80ish all the time and that where i like looking at the needle

at a 100 its just too close to red for me
 

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Have you confirmed the temp is actually 100?

If the problem was the radiator, it would not maintain a constant temperature.

The pressure cap has no bearing on the temperature.
good question

today i bought a IR point and shoot temp gauge gun

i know its not very scientific but i pointed it at various areas..on the thermostat housing temp read around 87-90C while the dial on dash said 100

I swappped the cap with my SEL for the day and that made no difference to the SEC

i dont understand that with the aux fan running it had zero affect on the temp.figured to have some difference there
 

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In addition to the helpful advice from fellow members, I have some T/stat ideas from my year long 100C T/gauge readings which seem to parallel your experience..

I feel, in addition to the new radiator & pressure cap, your car will benefit from the installation of an 79-80C rated thermostat. From my latest research in my car I found that with that range T/stat my temp readings finally mimic my 16 years with my 560SEC readings. In short, I am pleased.

I was sent a 1162000215 by mistake & looks rather different than the 'Gen 2' T/stats I was messing with, and research into MB cooling system designs I found differing details..

With that T/stat, I believe yours is Coolant circuit [2 phase] design as discussed in the enclosed pdf, starting on page 3.

In my photos here: 1162000215 is to the far left and differs as to the seal gasket and an inch long pin off to the side that goes into something called a 'Control Bore'. The other thermostats have a ball valve to allow the device to bleed air out.

As you can see from the center one & one to the right side, they are of differing lengths & also have different diameter bypass valves at the foot. In my experiences earlier in the Summer, I found neither the overall length or the valve diameter to to have negative effects at all. The temperature rating was the factor delivering the goods. I think you and I IMed about this at the time....

That said, if you can find an 80C T/stat that looks like the one with the pin, I think you'll be right where you want to be.

Here's the PDF on the cooling system too, just in case.

I wish you luck .. I know that '100C_no_matter_what' scenario all too well.

M.

thanks...yes appreciate your IMs

so i read through that pdf a few times and tried to understand the way it works...

and as u said finding the lower temp stat would be ideal...but thats the issue...i was at my mecahincs today and asked him if 1162000315 could be retrofitted to the 1162000215 spot

cant do it

gen 1's came with hotter stats and thats just it....so with mine...even though its new, maybe its broke...ill buy another and see i guess
 

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thanks...yes appreciate your IMs

so i read through that pdf a few times and tried to understand the way it works...

and as u said finding the lower temp stat would be ideal...but thats the issue...i was at my mecahincs today and asked him if 1162000315 could be retrofitted to the 1162000215 spot

cant do it

gen 1's came with hotter stats and thats just it....so with mine...even though its new, maybe its broke...ill buy another and see i guess
My intuition tells me there is likely nothing wrong with your 84C T/stat... That said, its always a possibility of a failure there.

When in my T/stat fervor earlier this year, I amassed a collection of them here.. Some came with both the Gen 1 gasket and the o-ring for the later style Gen 2 applications. I noticed that both the Gen 1 & Gen 2 thermostats are the same outer diameter and the same general length as the 'short' version in my photo above.. The fact that some thermostats came with both types of seals seems to suggest a 'backwards compatibility' for a Gen 2 T/stat into a Gen 1 engine.
What I have observed is the fact that physically speaking this IS doable.. using the Gen 1 gasket.

That said, I do not know what effect having a thermostat without that pin partially blocking the Control Bore might be over a long term..

When you install your new radiator I bet that will be a game changer.

M.
 

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i dont understand that with the aux fan running it had zero affect on the temp.figured to have some difference there
That's because the temperature is being regulated by the thermostat. If you increase the amount of heat shed by the radiator by forcing the aux fan to run the thermostat just closes a little more to reduce the flow rate and maintain the design temperature.

on the thermostat housing temp read around 87-90C while the dial on dash said 100
There you have it...
 

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if his cap fails to maintain pressure the boiling point is lowered, the coolant is unable to remove sufficient heat from the engine and the temperature of the coolant gets above what it should have been normal with a well-functioning cap.
There is no connection between the heat capacity of the coolant and the pressure of the system, as long as the coolant is not boiling. To say "the coolant is unable to remove heat" and "the temperature of the coolant gets above what it should have been" is a contradiction. It gets hot because it is removing heat.

If the coolant boils then things change. The heat capacity of a cup of steam is less than that of a cup of water. However, OP's coolant is not boiling, so the pressure is sufficient and changing the cap will not affect the reading on the temperature gauge.

TMSAISTI...
 

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There you have it...
I've been looking at a gauge that reads very consistently between about 97 and 101C.

I measured the temperature on a blob of black paint, right by the sensor and it reads consistently 87 to 91C; exactly where I wish it to be.

So I changed the sensor for a new VDO one and now the gauge reads about 95 to 99C, never over 100.

So I think the gauge is out of calibration.

Not sure what I can do about it.

And do I really care?

Maybe life's too short.

RayH
 

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It may just be a comfort level with me...my SEL has at 80ish all the time and that where i like looking at the needle

at a 100 its just too close to red for me

You may be worrying too much, imo. 100C is well within operating range.

Unless there's a catastrophic loss of coolant or the fans quit running, driving around at that temperature will not harm the engine or its performance.

Having said that, have you 'burped' the system? You may have air in the lines...
 

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To say "the coolant is unable to remove heat" and "the temperature of the coolant gets above what it should have been" is a contradiction.
I believe that I used the word sufficient somewhere in that phrase...

TMSAISTI...
Great! Thank you for your story, John. There are various stories on the Internet in connection with the dependency I mentioned, but I am fine with yours too.:smile
 

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I believe that I used the word sufficient somewhere in that phrase...
You did. Typo. Sorry. Still, increasing the pressure in no way significantly changes the thermal capacity of liquid water. Only if there is a phase change does the thermal capacity change appreciably.

But we're getting really far afield here. My point is simply that changing the pressure cap on a system that isn't boiling over isn't going to take a system that runs consistently at 100C and change it to run at 90 C.
 
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