Yet another query over engine running temperature...

Steve_Perry

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As you may recall I had a dealership service recently (15 Aug 03). One of the maintenance tasks performed was a total flush and renewal of the engine coolant system, which for my car is meant to be performed every 2 years (I think, maybe 3).

Well after 3 to 4 weeks of car use I would swear my car is running slightly hotter than it used to. I'm pretty sure my car used to run between 80°C and 90°C depending on conditions before it was serviced, whereas now it seems to be cycling between 85°C and 95°C and I believe the cooling fan cuts in slightly more than it used to, or maybe I'm just more aware of it.

Should I be concerned and take the car back to the dealer for a check or am I worrying over something trivial? I would have thought that after a system flush and refresh the car would run at a lower temperature if anything or am I mistaken? Is it possible to get air-locks when completely draining then refilling an engine with coolant?

I feel a phone call to George is coming on.

Just wondered what the general thought here is, as I value your opinions.

Ta,

S.
 

Ian B Walker

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Steve, I know very little about the new breed of Mercs but I know from past experience on my ex 190 that after refilling the system I had to disconnect the heater pipes and remove an air lock. ( I forgot to leave the heater on hot before re filling). Just a thought, but there again here is another one. I just wonder if the antifreeze mixture is more concentrate than what was taken out , would it allow the engine to run hotter?
 

fuzzer

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My 240 sat religiously just above 80 no matter what you did to it.

Do you maybe have an airlock or something in there??? I dunno how these things work , but , could be a possibility.:crazy:
 
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Steve_Perry

Steve_Perry

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Originally posted by fuzzer
My 240 sat religiously just above 80 no matter what you did to it...
Jase,

That's exactly how mine was before the service unless it was sat in traffic for extended periods in hot weather, otherwise the needle would hover just above 80 for 95% of the time without much movement. Now it seems to cycle around the 90 range (half way between 80 and the next un-named mark which I presume is 100) and the weather isn't that hot, certainly not over the last few days.

Ian,

I have had a look in the expansion reservoir and the fluid does look alot more concentrated than I remember on the previous coolant fill, it does have a very deep blue colour to it, definitely more pronounced than before.

S.
 

Brian WH

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Air lock is a possibility, normally in the heater circuit. Put the heater on full and run it for a while as this should circulate the water round the heater circuit. Take the radiator cap off , when it has cooled, and see if the level has gone down. If it has that was your problem M8. Top up and should be OK.:cool:
 
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Steve_Perry

Steve_Perry

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Originally posted by Brian WH
Air lock is a possibility, normally in the heater circuit. Put the heater on full and run it for a while as this should circulate the water round the heater circuit. Take the radiator cap off , when it has cooled, and see if the level has gone down. If it has that was your problem M8. Top up and should be OK.:cool:
Thanks Brian :D

I shall try this out now, hehe time for a drive in just a t-shirt with the heater on full whack. I don't suppose the fan speed setting will matter or how the air is routed into the cabin? Ahh it'll remind me of the old days when my controller was up the duff :p

S.
 

Flyer

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Hi Steve

My car does the same, but I hadn't put 2 + 2 together. I had mine serviced in June (coolant replaced) and I've noticed that the temperature has been higher this summer. Hmm. When I get it back, I'll try Brian's advice.

Cheers
Andrew
 

sym

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Mine is at 82 - never moves when cruising along nicely . . . rises to about 95 max when stuck in traffic. I don't know whether this is normal or not . . . it also seems to warm up VERY quickly from a cold start . . . gets to 82 in about 30 seconds tops !

S.
 
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Steve_Perry

Steve_Perry

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Thanks Bri :D

Well guys,

I've just been out for a 45 min drive with the heater on both left & right on full heat with the fan setting at 5. For the entire journey (which included some local stop start traffic as well as open country roads and dual carriageways at *ahem* her majesty's speed limit ;) ) the car behaved as it did before I had the service. i.e. hovered at just over 80°C and never moved away from that. Also because I'm not sure how the different settings affect routing through the heater matrix core I also switched on internal air recycle and switched off A/C (Economy) for periods of time too.

I'm just waiting for the engine to cool down before checking the coolant level, trouble is this engine seems to take forever to cool so I may check it tomorrow. I'm certainly alot less worried about it than I was when I first posted.

Brian, have a bunch of 'narners, if we ever meet I owe you a pint :D
:bannana: :bannana: :bannana: :bannana: :bannana:

Flyer, you might wanna try the same when you get your car back? Heh any excuse to drive your car ;) :devil:

Sym, mine is the same mate... very quick to warm up from a cold start and very slow to cool down from engine switch off.

S.
 

GRAV888

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Mine started to run a bit hotter after the Germany trip.
Turned out to be the viscous fan coupling.:crazy:
The fan was spinning, but not at the correct speed when the bi-metal strip was meant to kick in.
There is a way to test this at home with a piece of paper, but unless you know what you are doing, I'd get it checked by George (otherwise you might lose a finger or two:crazy: ) if Brians advice didn't work.
Don't mean to alarm you.;)
 

Flyer

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Re: Thanks Bri :D

Originally posted by Steve_Perry
Flyer, you might wanna try the same when you get your car back? Heh any excuse to drive your car ;) :devil:

Good news then Steve. Yep, I'll try it tomorrow hopefully ... Autoglass didn't turn up at the dealers until about 5pm (despite my car being dropped off at 8:30 :rolleyes: ) so it was too late for the dealer to do my MOT :crazy: . So it sits there ...
 
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Steve_Perry

Steve_Perry

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I checked the coolant level first thing this morning and the level was tip-top, however during the commute in this morning the car was back to normal. :D Engine temp just hovered over the 80°C mark and climbed to a max of 85°C when stuck in traffic for a little while. Case closed I reckon but I'll keep my beady eye on this for a while longer. Thanks to all who responed. :)

Much better :) Bri, you're a star.

Did you get your car back today Flyer? Time to turn your a/c on full heat and full fan ;) and see if your engine returns to previous form.

S.
 
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Flyer

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Yep, got it back this afternoon. Took it for a drive, with full heat, fan on 2 (that was hot enough!). No difference :( . I don't see it as a big problem, but it is definitely running hotter. In traffic, it gets to about 90-95. Maybe when I'm feeling brave, I'll put the fan on full ;)
 

Brian WH

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Glad to see an improvement Steve.

The theory is that when they drained and refilled the system they did not have the heater on, so the water in the heater system did not get completely changed and may have caused an air lock.

If ever you change the water again, my suggestion is to do the following.

When the engine is cold, take off radiator cap, or expansion tank cap, start engine then put heater on to hot fan position on !/2.
Drain water, as water stops running stop engine. Fill in reverse, part fill, start engine with heater still on, complete filling, leave radiator cap off till water is warm and circulating, top up and replace cap. Run for 5 minutes and job done, no air locks, no overheating.

Obviously the dealer doesn't bother with this routine, just drains and refills.
 

Dave K

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Hmmm. Most post '85 cars don't regulate the cabin heat by restricting flow through the heater matrix. Instead, hot water from the engine ALWAYS passes through the heater matrix and the heat into the cabin is regulated by air flaps. This was done to avoid water sitting in the heater matrix throughout the summer months and corroding it. Turning the heater controls up or down doesn't affect the flow of water into the heater matrix at all. Therefore, the old "trick" of taking it for a run with the heater on full in order to remove airlocks just ins't relevant. I can't be 100% sure MB works like this but just about every other manufacturer does.
 

Dieselman

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I think you are wrong here. cars do still regulate water flow to stop heat otherwise your car would be like an oven in the summer due to the heater matrix being hot and radiating.

MB use solenoid valves in the water pipes. Air vents are used as well for fine control.

Wasting heat from the heater will still cool an overheated engine because the water will return cooler, even if it circulates all the time.
 

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