W124 operating temp

[ShivaYash]

Hello all

I hope this is in the right section of the forum. We are currently on a day out and after driving 50 miles out of London, the temp gauge still is showing the car is cold. When we get to lights, the temp increases and the needle is just below 80. When I drive again it goes down to the marker below 80, this marker has not label. The gauge definitely works but from my experience of w123s, once warm the temp does not move. This is my first MB with aircon and its been on all the time. So my question is, what is the correct operating temperature of my E200 (estate)? It's a 1994 with 119k miles.

Ps. Could it be the thermostat is not working. I've also found it to be pretty uneconomical, a fill tank with city driving yielded 260 miles with very careful driving in E mode on the box. Tyre pressure is excellent, nitrogen filled.

Many thanks.

 

[wireman]

Sounds like a dying thermostat, it should be 85-90C. Is the car taking a long time to get warm? its another indicator of a defective stat.
Cold running will adversely affect fuel consumption.
Some petrol models have a plastic thermostat housing, it may be that this will not survive the process of changing the stat, a new one might be required if the original is plastic.
Re-fill with 50% antifreeze, after a flush or two of clean water to remove all the old stuff.

 

[huey]

I agree with Wireman, definately a dud thermostat, MB have now replaced the thermo housing with an alluminium one I replaced mine they are £54.00, so be careful when you remove the plastic one and hopefully it will be OK!

 

[ShivaYash]

Thanks to both. By way of update, let me explain what I've done today, in terms of driving.

We set off this morning to Sittingbourne in Kent, about 65 miles from our house. It was a gentle drive and I enjoy obtaining maximum fuel economy, so cruising at an average speed of 60 mph. I noticed the temperature gauge was showing the car still wasn't properly warm. My W123 runs at 85 on the nose, and never moves, even in heavy traffic. The W124 is a new car for us and during the week its main task is to collect my wife from work, in Central London, a round trip of sub 10 miles, and this usually takes 1 hour with about 5 minutes waiting. During this sort of usage, I didn't expect the car to get up to temp.

So I posted this thread, seeking advice. Having just returned, the gauge was showing just below the 80 mark all the way back, again a gentle drive, no traffic, other than a bit in the Blackwell Tunnel, but it was moving. The odd thing is this, the fuel economy today has been incredible...! I had half a tank, roughly, and was able to do 275 miles on it, the yellow warning light came on about 5 miles from home. We had the a/c on throughout.

Previously, in the city use, a full tank gave me 260 miles.

I'm happy to change the thermostat - and the housing, a job I can do myself with little bother. But could this be something else? A broken gauge? The other gauges on the panel seem fine, oil pressure is good, and moves properly.

How do I 'flush' the radiator? Many thanks!

 

[huey]

That sounds good mpg, if you need a new gauge they are very expensive from MB,
Regards flushing the rad when you change the thermostat remove the bottom hose to drain the system, you will have to remove the top hose anyway, then put a hosepipe in the top of the rad and "flush it".

 

[wireman]

To flush it properly the drain plug in the block needs removal to drain it fully, the stat needs replacing with a rigged stat that is always fully open, and the thing needs filling and draining several times, once with flushing chemicals (run engine up to 80C), second with neutraliser and then at least once with clean water only. The heater should be set to hot with the blower off.

When only replacing the coolant it is of some importance that all the old stuff is washed out first.

 

[ShivaYash]

Hello

I purchased a replacement thermostat from MB Colindale. It was the wrong part, for the M102 engine! Swapped it over this morning for the correct M111. On the drive to the dealer, the temp was just above the 40 indicator. I drove 11 miles and would have expected the car to reach operating temperature. Got home, swapped the stat, the coolant was totally clear and I only lost a little of fluid, just topped up, checked for airlocks and went for a drive. The temp gauge now shows half way above 80. I think this is still not right. See the attached photo. Is this normal?

 

[huey]

Yes that look's about right shivayash, that's where mine sit''s when up to temp, I reckon your sorted

 

[ShivaYash]

Thanks - I'll monitor fuel economy in town now and report back.

I thought operating temperature was 110 - the next indicator up, the one below 120?

 

[robparker]

Nope, yours is spot on.

 

[ShivaYash]

Thanks Rob. Much appreciated.

 

[Bolide]

its main task is to collect my wife from work, in Central London, a round trip of sub 10 miles, and this usually takes 1 hour with about 5 minutes waiting

That's not a journey, that's torture

I'd work on gallons per hour, not mpg

Nick Froome

 

[ShivaYash]

Totally agree- torture. She is heavily pregnant and now off work, so the car is just used at weekends! Thanks Nick.