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Mysterious Coolant Overflow

3K views 17 replies 8 participants last post by  sbaert 
#1 ·
Hi all,

First post - just got a '95 E320 wagon with 165k . . . love it.

It's in great shape, but needs a couple things here and there.

So today I was running errands and returned home - backed into my driveway - and then sat for 10/12 minutes while the car was running.

I heard some odd sounds and stepped out and noticed a ton of coolant on the ground - didn't get a chance to see how high the temp gauge went, but it was above normal - don't know if it came down. Dumped at least a quart on the ground.

1. The leak came from the overflow hose just below the cap - totally brittle - the entire thing. Easy enough to fix that and will get to it tomorrow. I've read that the only time that extra overflow tank is used is on a wicked hot day - not 60 degrees and shady.

2. Why would it overheat? Took it out again tonight and let it idle a ton, not problem - rock steady. Drove it around some more - no problems. I'm thinking a stuck thermostat or maybe a fan relay?

What do you guys think? First thing is to replace the thermostat - can't really go wrong with that.

thanks,
dave
 

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#3 ·
thanks - will do.

I replaced the overflow hose and when I pulled the fender the overflow tank, was totally full. Emptied that out.

Will get a thermostat and a new cap - the cap looks great and the rubber seals look good. will replace anyways.

i was told only use mercedes brand coolant - is the zerex the same? the mercedes brand stuff is supposed to somehow help avoid head gasket damage - don't ask me how.

thanks,
dave
 
#4 ·
G5 spec is the same as the MB coolant until a couple of years ago when it was updated to the blue stuff.

If your current coolant is yellow then you already have G5 in there and just need to top up. If it is anything else, drain, flush and refill with G5 or G48 (the current spec MB fluid which looks like airline toilet water
 
#6 ·
I'm almost certain it's the viscous clutch.

Just like last time I let the car idle a bunch and watched the gauge go up to the line above the mid-point - about 3/4's - what is that, like 90?

I took a celery stalk to the fan (no carrots) and made a huge mess, but managed to stop the fan. And then stopped the engine and could easily turn the fan.

I'm guessing the clutch should have been engaged with the engine idling that hot.

I have a new cap and thermostat and will replace on thurs when i get garage time - the system is definitely pressurized as when i undo the cap it hisses.

anyways - i've got lift time on thursday, the clutch won't make it in time, but i'll fashion myself the rod with the bent tip so i can unscrew the fan.

In line on thurs is the neutral switch (car doesn't start in park sometimes), the second fuel pump and fuel filter, and then take the wheels off and figure out what the thunking is.

it's not so much big bumps, but when it's going over smaller bumpy parts of the road - i hear thunking - hoping it's sway bushings. going to take a crowbar to the bushings and see which ones need to be replaced.

will report back - i'm hoping after the thermostat, the cap, and the fan clutch, i can let the car idle forever.

thanks,
dave
 
#7 ·
Got in there today.

changed out the clutch, and only broke off one shard of the fan while doing it . . . . I don't know why they give torque specs on the 8mm allen. not like you can get a wrench in there or anything.

fashioned my own tool to hold the pulley.

one thing i noticed off the bat is that the new viscous clutch has a lot more resistance when it's cold - didn't allow the fan to spin so freely.

I changed the coolant cap - but am saving the thermostat for another day.

I have a local garage that charges $20/hour or $100/day to use the lift and tools.

I did the fuel pump/filter (the second one), viscous clutch, neutral switch (car occasionally didn't want to start in Park), adjusted the parking brake, and balanced the tires.

looking forward to idling in the driveway when it gets warmer to see if starts to overheat. The broken shard didn't seem to make the fan imbalanced.

I did notice the sway bushings seemed worn and the front two wheel bearings were a bit loose - thinking i'm just going to tighten them up a bit instead of replacing. hopefully those two things will stop the clunking over uneven roads.

-dd
 
#9 ·
Yes Jim. If by "shard" the OP is talking about one of the vanes on the viscous clutch - not such a big deal. But if its a fan blade as it seems to be, that is a big issue that will show up as noise as well as marginally reduced airflow and an imbalance that will cause damage over the long term.
 
#11 ·
Before doing the clutch do the thermostat and cap. The thermostat can break and cause really wierd temp fluctuations. If the cap is bad that can also screw with things. Age and condition of the radiator can be an issue too. If it's clogged and not dissipating enough heat the fan clutch won't necessarily work right. Also when you start the car cold a dead give away of fan clutch failure is that it won't roar. A few sec after a cold start raise the rpm to 2500 or so and the fan should roar. If it doesn't it's no bueno. But if it does I'd be hesitant to replace it just yet before making everything else right in the system
 
#12 ·
Radiator is brand new - cap was changed, but the old one was fine I'm pretty sure.

Did the change yesterday. The old clutch failed the carrot (celery test). After I put the new one in I could feel a big difference in its firmness.

Will know once the weather gets a bit warmed - above 50 degree ambient if it idled too long it would get warm.

will keep ya'll posted

-dave
 
#15 ·
So I made the change to the new clutch.

I left it idling forever yesterday and it didn't creep above the line that's just above the 50% - it would get close and then go down a smudge. It was only 40 something degrees in Denver yesterday - will try this when it's warmer and see what happens.

A big thing I've noticed is that as soon as I start the car up I hear the whoosh of the fan for a bit.

As of now it appears fixed.
 
#17 ·
Don't forget to bleed or burp the cooling system when you open it up anywhere other than the reservoir cap. If air gets trapped in the engine block the coolant will not circulate properly.

After filling up the system and making sure all is tightened, just open the coolant reservoir and let the engine warm up at idle. Once it gets around 60C just loosen up your bleed screw on the thermostat housing and let the bubbles out until only coolant comes out. Then you can close the reservoir with the cap. You can also loosen the coolant temp sender if yours doesn't have a bleed screw.


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#18 ·
Running a damaged fan is the same as having a tire imbalance. The imbalanced fan will cause excessive strain on the drivebelt system and motor mounted items.

Replace. Damaged items need to be replaced, there is no way to justify not to.

With the factory shortie hex socket and pulley holder tool, R&R is a snap. Only a few bucks at the dealer.
 
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