Water temperature uphill roads

[mauro12]

Hello guys , I don’t know if this is normal but I’ve noticed that my car during hot days like these in Sicily right now , especially during uphills roads very steep with low speed , the needle goes in the middle between 180F or 80c and 200F or 100C . Let’s say around 90 Celsius average ( never reaches 100c).
When I get regular  speed the needle stays very stable at 180 during motorway too .
I’ve replaced 4years ago the water pump with thermostat and new coolant . What can I do to improve the cooling ? Probably replacing the coolant once again with a deep radiator flush ? Are my numbers unusual ? Thank you

[Garry]

i would be replacing my coolant more often than four years. I do it each year, a cheap bit of insurance. Some say do it every two years. I regularly drive in hot temps of 38-40c or 95-105f with out any problems

[mauro12]

Yes you are right . This is the next thing I will do . Do you replace also the thermostat every 2 years ? I’ve replaced mine 4 years ago too . Does your car stay stable at 180 during uphill roads too ? Never reaches 200?

[Paul & Dolly]

Hi Mauro
My 250 behaves much the same as yours, and I don't think there is any problem.
Mine normally runs just below 180F, and if stressed runs midway between 180 and 200.

I have had the car 12 years and we have been in France,Italy and Germany in the summer without any cooling problems.

It may be worth checking the viscous coupling of the fan if you are concerned.

Keep well

Paul

[mauro12]

Thank you . The fan looks ok and spins fine . Maybe a good radiator flush will improve the problem and a shorter coolant replacement interval .
By the way , I read in the owner’s manual that is normal if the car reaches the red spot or a little bit less during uphills or stop and go traffic . This makes me some general doubts .

[mBdrvr]

My 280 SL runs fine at 60 MPH and below but if I run at 65 MPH or more it starts to overheat.

I understand that there is a kit, no sold by Bud's Benz, that is equivalent to the Mercedes kit for the 70 and 71 cars.

Has anyone used this?

Paul

[rwmastel]

Hello guys , I don’t know if this is normal but I’ve noticed that my car during hot days like these in Sicily right now , especially during uphills roads very steep with low speed , the needle goes in the middle between 180F or 80c and 200F or 100C . Let’s say around 90 Celsius average ( never reaches 100c).

You're concerned about 90c?  100c is normal boiling point for water, but your coolant system is under pressure, which raises the boiling point.  It also has coolant/antifreeze mix to also raise the boiling point.  90c is no risk of overheating. 100c should be no risk of overheating.

[WRe]

Hi,
I have tested a lot (bypass, electric fan, new water pump and thermostat, ...) to protect my engine for overheating but the most effective solution was to increase the efficiency of the fan, means the nearest distance to the radiator (you can arrange the rad) and a fan shroud after descaling the cooling system.
You can find here a lot of stuff dealing with overheating, e.g.
https://www.sl113.org/forums/index.php?topic=27735.msg199515#msg199515
...WRe

[Paul & Dolly]

I don't think 250sl usually suffer overheating, it is usually more a problem with the 280sl

Paul

[Pawel66]

What is the quick but good method to test the fan clutch? Theoretically it should spin fairly easy when engine is off and cold. But not too easy... if it just spins freely it means the clutch is bad. And much harder on hot engine.

Is it correct?

[WRe]

Hi,
The visco clutch/fan works hydraulically and temperature-dependently and is controlled via a bimetal spring.
When cold, the fan should be able to rotate without play but with noticeable resistance.
When the engine is running cold, the fan initially runs, (audible blowing) then it only runs at low speed without any power flow.
If the engine temperature rises above 90 degrees C, the bimetal reacts and opens the clutch's oil supply via a pressure pin.
The fan gets power again and runs at around 3500 rpm. The function can now clearly audible again.
https://www.kfz-tech.de/Engl/Biblio/Kuehlung/Viskoluefter.htm#google_vignette
...WRe

[Pawel66]

Thank you!

[mauro12]

do you have the same video of the fan clutch engaging in our car ? honestly i've never noticed any sound differences during hot or cold temperature . Also if the fan clutch engages when the temperTURE IS above 90celsius , chances that you will hear the fan is very limited , the car has to be very warm.

[rwmastel]

Also if the fan clutch engages when the temperTURE IS above 90celsius , chances that you will hear the fan is very limited , the car has to be very warm.

When the car is hot, park it and turn it off.
Open the hood and see if the fan turns by hand.

[WRe]

Hi,
When the viscous coupling starts, it is very clear and loud. But most couplings don't work particularly well.
I've tried a few couplings, all with poor results. One supposedly new coupling arrived with oil leaking out.
Another problem is that the area around the bimetal is often very dirty and no longer works correctly.
...WRe

[mauro12]

Just in case mine is broken , I’ve seen aftermarket parts with reasonable price . Is it good to buy an aftermarket part ?

[Pawel66]

A 000 200 04 22 is not available.

I crossed checked the numbers: FEBI BILSTEIN 18142

About EUR 100,-

[mauro12]

I've read somewhere that the fan clutch engages at 3500rpm only ? is is true or maybe is misunderstending ? That would be strange because at that speed the natural air flow is even better than the fan itself . My car tend to warm up a bit more , in the 90-95 degrees celsius range , during 1 and 2 gear in uphill roads for very prolungated time . Should the fan be on during this conditions ? My fan ,with totally cold car turned off has a very noticeble resistance to turn by hands . Is that how it should be ? Thank you

[rwmastel]

The visco clutch/fan works hydraulically and temperature-dependently and is controlled via a bimetal spring.
......
The fan gets power again and runs at around 3500 rpm.

Why does it engage at a given rpm if it is temperature dependent?

I've read somewhere that the fan clutch engages at 3500rpm only?

Somewhere?  You read it in this thread! 

[WRe]

Why does it engage at a given rpm if it is temperature dependent?

Hi,
Maybe my English was a bit misleading, because the viscous coupling is temperature controlled and runs at a maximum of 3500 revs.
...WRe

[mauro12]

Not only in this forum . I meant this .

[Cees Klumper]

My car behaves like yours Mauro, it sounds perfectly fine to me. Coolant temperatures in modern cars also fluctuate, but the car's electronics don't show any fluctuations on the gauge unless they exceed some margin, so as to not 'scare' the operator.
No need to replace the thermostat every X years if it operates properly. You can test it easily by placing in pan of water together with a thermometer and seeing when, and how far, it opens.
No need to replace coolant every year either. Make sure to bring old coolant to a hazardous waste disposal facility.
Most important is to ensure no air in the system! Many discussions on how to do this.

[mauro12]

Yes this is true ! I remember my old thermostat wasn’t working properly and was stuck totally opened .
For that reason the car wasn’t warming up at all . In winter the car never reached 65 Celsius or so .  These are old cars and when each needle is to a different position that it used to be I get alarmed . In modern cars that’s true , I’ve never had any fluctuations of temperature according to gauges .