Running hotter with MB coolant

[koan]

When I replaced 6.9 inlet manifold gaskets a couple of years ago I bought enough M-B coolant for a 50/50 mix.

I filled it with water and rust inhibitor intending to drive it for a few weeks then check for leaks and put the coolant in. I never got round to putting the coolant in.

After the recent head work I again filled with water (only), checked for leaks after a drive then put the coolant in and topped up with water.

I was out on the freeway recently, the outside temp was about 30C, doing about 80 kmh I noticed the engine temp was almost 100C, about 10 to 15 degrees hotter than normal. When I ended up in slow traffic the temp went to about 110 and the aux fan came on.

I doubt it's a loose belt or a stuffed fan clutch, should have been plenty of airflow at 80 kmh, in fact I've heard the fan clutch cutting in and out when I've worked on the warm engine and given it some revs. I'm confident there's no trapped air and checked the thermostat in boiling water on the stove. The amount of fuel It's using suggests rich rather than lean.   

I'm puzzled as to what's going on.

koan

[Big_Richard]

whats the condition of your radiator like, has it ever been recored ? Also, its possible on any car for the impeller in the pump to be clogged so its efficiency severely drops off...

I used to use Valvoline G05 coolant, as its the OEM formula, although with a different colour additive for Mercedes coolant used in the maybach. And if its good enough for that, its good enough for a 116. On my last fill there was none left on the shelf and used some generic Australian brand compatible with aluminium. 

[13B]

Hi Koan, somethings not right.  On a 30 degree day as long as I'm moving at any speed after than walking speed the temp will sit around 90C with the A/C off and 95C with the A/C on.  Even yesterday I got stuck in the middle of that traffic jam caused by the truck diesel spil on City link and while at standstill my temp got up to 100C but came down again as soon as I was going faster than a walking pace.

My 450SE race car uses blue MB coolant, but not in the suggested concentration... only 1 bottle and the rest water.  No problems there.

Ian.

[WGB]

When I first changed to M-B Blue coolant last Xmas my 6.9 ran hotter for a couple of weeks and then needed a small top up of the header tank.

After that it returned to normal.

I think 6.9's have some sort of bleeding problem and when they finally get rid of the air trapped in the system they run fine.

My M-B blue filled car registers 80 to 85 most of the time and on the 40 degree day last week it hit 90 coming up the Kalamunda Hill.

I'd just wait but be careful - hopefully if it is an airlocjk it will sort itself out.

Bill

[koan]

About 7 or 8 years ago I had the radiator cleaned out, it's the old core but Was told it was in good shape. Also put in a new fan clutch, all hoses and new switch for the aux fan.

I thought it was OK until now, I usually get much the same temps as mentioned, needle might creep over 90 on a 25 to 30 degree day if I'm stuck in traffic, anything higher and I'm worried.

Don't think I have an air lock but I'll give it run next hot day,

If it is the water pump there might be a problem, I think I somehow have an early style pump with a round base despite the VIN indicating it should be the square base version, There doesn't seem to be changeover units for early style.

I'll see what happens.

koan

koan

[TJ 450]

The early type of pump (round base) is an alloy version of the pump on a 6.3, which is cast iron, apparently. The pump itself should be rebuildable if needs be... I seem to recall a thread on the M100 site discussing the matter.
Conversely, given my engine and chassis numbers, I should have a round base pump, but I have the square base... go figure?

Tim

[s class]

koan, when I had my W140, I found that it ran hotter with the recommended mix of coolant than with plain water.  Really I'm not sure why. 

[koan]

koan, when I had my W140, I found that it ran hotter with the recommended mix of coolant than with plain water.  Really I'm not sure why. 

My initial thought was that too considering how the car used to behave but seems odd.

If it doesn't (magically) come good looks like another job.

The 6.3 pump looks a bit different to mine in the parts picture book, I'll try and find numbers on the pump and housing.

koan

[CraigS]

The early 6.9 pump will fit the 6.3 but not the later one.

[WGB]

I can't see why the water pump will suddenly stop pumping just because the coolant was changed any more than that there is an observed temperature rise with a change in coolant.

I would still think the most likely cause is an air lock somehere in the system - or else the radiator has become clogged with the dismantling or whatever was happening prior to the dismantling.

?Did you have a headgasket problem that was putting unwanted matter into the cooling system - I've done that before a few times?

If it continues I would be inclined to check the thermostat and get the radiator rodded again before i suspected the water pump.

Bill

[carl888]

Hi Koan,

All my cars have always run hotter with an anti-freeze mixture (Ethylene Glycol) greater than about 20% compared to plain water.  Apparently, the reason is that EC doesn't conduct heat as well as water.  At 50% you mind find the concentration too high, hence the increased temperatures.

I notice that Shell and Mobil recommend about 33% for a freezing point of -18 degrees, I'm sure that's fine for us!  Anything below about 20% and the corrosion inhibitors wont be active enough to stop corrosion.

Regards,

Carl.

[pez]

Carl's point is exactly correct....I like to go to a 30-70 mix for summer, then 50-50 mix for winter. The 30-70, with 70% being water, offers much greater heat transfer.  I also am fond of redline water wetter....not sure if you get that in Oz, but it's a super common high horsepower motor trick - somehow chemically allows for greater heat transfer.

All that being said, my best guess for what you've got going on Koan is that some rust developed in your radiator while you had everything apart....and now that you have put it all back together, either things are clogged or the rust/sediment has moved around and caused a clog.  I would start by pulling the thermostat and examining it...any rust or sediment in the system would certainly accumulate at the small spaces in the thermostat, and this would be a good indicator.

You could also drain the system and do a flush with the acid cleaner [I believe the good ones that M-B uses, at least here in the states, are citrus based].  What comes out would certainly give you some clues.

[koan]

The cooling system sat open to the elements for a few months so some corrosion could have occurred.

I've tested the thermostat, it's OK. Head gasket problem wasn't leaking into cooling system.

I found a good website here. An ethylene glycol / water mix does have less heat capacity than water and is harder to pump around at lower temps.

Why I went for a 50/50 mix when 20% is appropriate for anywhere in AUS I don't know.

It's going to be warm here today and tomorrow, I'll go for a run, see if things have improved.

koan

[Big_Richard]

The cooling system sat open to the elements for a few months so some corrosion could have occurred.

I've tested the thermostat, it's OK. Head gasket problem wasn't leaking into cooling system.

I found a good website here. An ethylene glycol / water mix does have less heat capacity than water and is harder to pump around at lower temps.

Why I went for a 50/50 mix when 20% is appropriate for anywhere in AUS I don't know.

It's going to be warm here today and tomorrow, I'll go for a run, see if things have improved.

koan

At least your not in my boat - my custom aluminium radiator is a $2k big piece of shit - Well, it'd be fine if a 6.9's engine bay could fit a decent sized set of thermo fans in it - but it simply cant. the 16" one I've got installed is inadequate and basically pissing in the wind when it comes to keeping the engine cool at stand still. I'm going to have to some how remount the clutch fan with another custom shroud, which means modifying the mounts so it will fit. Alternatively I'll cut my losses, throw the heap of shit into the recycling bin and just get my old radiator re-cored be done with it. That money would of been better spent on wood restoration - Why didn't i listen to you Nathan! 

luckily my best mates father inlaw owns a metal fabrication factory with a million dollar laser cnc machine so the shroud should be a walk in the park... hopefully

[WGB]

I'm fascinated to hear about a temp increase with 50:50 Glycol.

Why does M-B fill it's new cars with this mix and then have no problems?

I was also under the understanding that if you wanted to be sure that your car was safe to the red line on the temp gauge you needed a good pressure cap and the 50:50 mix as it is not only anti-freeze but also anti-boil.

I understood mixtures above 50% are not good and many of the glycol cold and hot properties begin to deteriorate at 55% but my 6.9 happily runs on a 50:50 mix on 40 degree days as does my 450  and my two ML's.

Bill