OverHeating !!!

[MM]

Greetings All !

And what a fine weekend its been ? apart from my car giving me worries again...

The problem this time is that whilst i appreciate it was very hot this weekend - i only drove my 300SL a few miles - albeit at a very slow pace (not posing - stuck in TRAFFIC) and noticed the tempreture needle rise to about 105 - 110 degrees, it just so happend that everytime it did get that far - i was pulling up at my destination (i didnt have te bottle to let it run and see what happens), since then, i.e today i've noticed that having driven my car about 500 yards from cold - the temp needle is already sitting at 85 degree(ish) !!!

Tell me...................Should i be worried ?

I have the fan, thermostat and coolant replaced only 8 months ago...

Your input would be most appreciated.

MM

 

[nicky]

Could be the thermostat sticking closed.....Do you drive the car every day????

 

[fwb44]

Does your car have electric fans in front of the radiator in addition to the belt-driven one? Are they cutting in as required?

When having my air-con regassed yesterday I learnt that the belt between the same two fans is broken, meaning that only one of the fans has been working, which has resulted in engine temperature rising above the 'normal' mark towards the '10 o'clock' mark when driving in traffic or at tickover, whatever temp. that signifies.

If you've already had thermostat and coolant replaced, you might also check that all hoses are OK & not blocked, kinked, disconnected &c. It might pay you to do a radiator flush at some point.

Good luck!

 

[Myros]

500yds to running temperature!!!!!!!

be afraid, very afraid. Even in this sub-tropical heat, it should take you a mile and about 5mins to reach operating temp, driven normally.
Either your pump is not pumping, your rad or one of the hoses is blocked, or the fan belt isn't belting.
There is of course the possibility of your gauge being a bit iffy as well, but that isn't going to damage your engine as much as any of the above.
Squeeze all the water hoses you can reach (engine off, cool) and watch the expansion tank. You should see the level bouncing around with your squeezing. If you get no action there, that's a big clue as to what the trouble is.
Run the engine for as long as it takes your gauge to warm up. Engine off, gingerly feel all the hoses to see if they are all warming up as well.If your level didn't move before, does it move now when you squeeze.
Is your coolant clean and happy, or mucky, dirty and grumpy.You could check the coolant concentration with one of those testers which you can buy at decent motor stores.
Eliminate as many possibilities as you can before you start stripping bits off the engine. Try to be logical.
Good luck

 

[190D]

Sonds to me like a faulty temp gauge sender unit or no water in your car.

 

[andy_k]

good advice has been offered so far but don't forget that there comes a point where the fans aren't actually doing much good.

Take a quick look at the "science" and you'll find out that a fan doesn't actually provide any cooling properties (actually the reverse is true as it heats the air very very slightly) so if the air outside has a temperature of 85 or above then that's the lowest temperature you can hope to achieve (speaking very roughly)

Most MB thermostats and fan couplings open and close at approximately 105 degrees (as you know pressurised water with the correct coolant in it will boil at a much higher temperature than an open comtainer) so it is likely you just reached the point where it was about to open and switch on the fans.

Check the water level and test the efficiency of the thermo/viscous coupling (whichever is fitted) on the fans drive but I wouldn't stress too much

HTH

Andy

 

[Mark663]

probably just the thermostat. You could bleed the rad system to make sure there isnt any air in it. this could cause less water to flow round the system and therefore make it over heat. Taking thermostat out is prob easiest and testing it in a cup of boiling water.

good advice has been offered so far but don't forget that there comes a point where the fans aren't actually doing much good.

Take a quick look at the "science" and you'll find out that a fan doesn't actually provide any cooling properties (actually the reverse is true as it heats the air very very slightly) so if the air outside has a temperature of 85 or above then that's the lowest temperature you can hope to achieve (speaking very roughly)

Most MB thermostats and fan couplings open and close at approximately 105 degrees (as you know pressurised water with the correct coolant in it will boil at a much higher temperature than an open comtainer) so it is likely you just reached the point where it was about to open and switch on the fans.

Check the water level and test the efficiency of the thermo/viscous coupling (whichever is fitted) on the fans drive but I wouldn't stress too much

HTH

Andy

 

[MM]

Many thanks to all that replied - your prompt response was much appreciated.

The answers to some of the questions are as follows:

I donot drive the car everyday - probably twice a week,

I have had the thermostat changed along with the fan, tried the "carrot" test - and it passed with flying colours,

There are no turbid deposits on the inside of the oil cap, and thak god - n oil in the rad..

However i got the bonnet open (major achievement for me - i only know how to drive cars and not work on them) and pumped every hose i could find, some made the water in the reservior bounce around alot - whilst others just caused minor ripples. I drained the whole system out and replaced it with 60% coolant and 40 % water (or there abouts) - i then let the engine idle for 20 minutes - and watched the tempreture needle rise to the 8.45pm/am postion (if this maes any sense) i'm assuming this is about the 100 degrees mark - or just below, it didnt move from there so i took it for a quick drive and noticed the needle drop as i cruz'd along - but go back to the 8.45 postion on stopping or slowing down. Upon my return i let the engine idle again for another 15 - 20 minutes and the needle stayed at 8.45, not passing the 100 degree mark and not causing the fan to come on, neither of the two smaller fans came on !

I appreciate that today was no where near as hot as the weekend - and a good 5- 6 degrees cooler - i dont know if this has made a difference or the fact that changing the coolant and cleaning the hose pipes has fixed the problem !

Also another thing that has crossed my mind - my car was imported from Singapore last year - could this have something to do with it ???

Once again - thank you for reading this - and a bigger thank you for those that choose to respond !

 

[paulcallender]

MM, your temperature gauge readings sound about right. For info, its a little known phenomenon that more antifreeze increases cooling ability. Antifreeze mixture lowers the melting point and raises the boiling point, but has a lower thermal capacity. So, the way to eeek the most out of it in summer is to run at 40/60 antifreeze/water.

 

[fwb44]

I agree, it sounds about right. Maybe improving the coolant/water ratio for European conditions did the trick? Maybe you had an air lock in the system which was resolved by draining & refilling? What happens when you run the aircon at idle - does the temp stay the same (i.e. 8.45) ?

Take it for a good run now and let us know what happens?

 

[paulcallender]

I just re-read my post, I meant to say more antifreeze decreases cooling ability. The more antifreeze in the ratio, the worse it is.

 

[MM]

I'm at work at the moment - but will change the water to antifreeze ratio when i get home to meet the 40/60 antifreeze / water ratio, yesterday i did it the other way round !

running the aircon will be a problem for me - as my fan motor is not working !!!

could this have anything to do with it ???

Regards

MM

Oh what a nice day it is today !!!

 

[pascal]

Yes Paul, I thought that was what you meant.

The recomended ratio in the UK is 25% antifreeze, 75% water (1:3)

The recomended ratio for severe UK conditions is 33% antifreeze, 67% water (1:2)

The maximium ratio anywhere (siberia?) is 50% of each (1:1), as anymore may cause severe over heating.

Any of the above ratios will guard you engine against corosion. (BS6580)
Replace coolant every 2 years.

 

[fwb44]

running the aircon will be a problem for me - as my fan motor is not working !!! could this have anything to do with it ???

I would have thought almost certainly this will contribute to it. In this heat I reckon you need to have those fans working. Check all electrics involved?

 

[blassberg]

I just re-read my post, I meant to say more antifreeze decreases cooling ability. The more antifreeze in the ratio, the worse it is.

the Boiling Point gets elevated by the addition of the ionic anti-freeze. Therefore the liquid stays liquid until a higher temperature.

I would say that Liquid at 100+x degrees was more efficient at cooling than a gas at the same temperature??? Assuming 100+x is less than the temperature of the engine it is trying to cool.

 

[paulcallender]

Yes, there are disadvantages and advantages. The thermal capacity (amount of energy is takes to raise a fixed quantity of the liquid, by a fixed temperature) of antifreeze is lower (3855) than water (4180?), but it raises B.P. and lowers M.P., as does anything soluble mixed with any liquid. (eg salt does the same).

The reason we don't all use 100% water in the summer, is that antifreeze has corrosion-inhibiting properties.

 

[pascal]

I didn't know all that technical stuff, but was always told that too much AF can cause over heating.

But I see from what you wrote that it takes less energy to raise AF than water.

That means that at a given energy figuire from your car, the temp of the liquid would be actually higher with AF. But the AF does have the advantage of not boiling till a few degrees over the 100c.

But it is usually the actual heat that counts (head gaskets etc)

Thankyou Paul and Blassberg for the techy stuff.

 

[MM]

Right I'm Taking a Hammer to the CAR !!!

Update:

I got home and changed the water / antifreeze ration to 60/40.

I then let the car run for about ten 15 minutes and saw the tempreture needle rise to the 8.45 position (slow & steady) then all of a sudden it shot up to 110 degrees and stayed their for about 2 seconds before shooting down again (as quick as it went up !) to 80 degrees - dead on, a few seconds later it returned to the 8.45 postion and stayed their for a further 15 minutes (total 30 min idling)......

Any ideas what this means ?

Like i said the air con / heater does not work as the heater fan motor is not working - i noticed that when the temp needle shot up to 110 - the two smaller fans in fron of the RAD did NOT turn on - i would have thought that these would be used to lower the temp ????

I didthis test at 9pm - so it was fairly cool out there and nothing like day time tempretures - now then - before i go into the street and smash up my car with a hammer - any other suggestions ???

I think my car is haunted...........................From the GUTTED MM..............................Missing out on this great whether.....

 

[paulcallender]

Here is a rational explanation: there was a pocket of air in the system, this flowed past the temperature sender and this air is much hotter than the liquid (for various reasons). I wouldn't worry too much. I know some cars are notoriously awkward to bleed the cooling system, but my Mercs seem not to have this afflication. Small pockets of air tend to resolve themselves.

 

[fwb44]

Sounds good. You can 'bleed' the cooling system after a fashion by simply leaving the engine running with the expansion chamber cap off. The coolant won't boil over (or shouldn't) and any air locked in the system will rise to the surface pretty quickly.

Those pre-rad elec. fans definitely ought to be working - and you must want your heater/blower fan in the passenger cabin to be working? I repeat - check out the electrics, all connectors, relays &c. Look out for dirty contacts. There are also probably at least three separate fuse boxes in your car, your handbook will tell you which one covers which functions.

I can lend you a rubber hammer if it would help ...