S320 running too hot
 

My 95 S320 has been running hot since I got it. I bought it in Nov with about 200K km on it. All winter it has been running at about 100C. By winter, I mean -20C or lower, but even on the warmer days +15C, it kept to 100C even, no fluctuations. Lately, I have been seeing the temp spiking to 105C while highway driving at 110 km/h (70 mph). And when sitting still, the Temp will almost reach 120C after it has been driven. Aux fans suck air the right way. My reading really doesn't give a good indication of what is wrong.
I hear varied opinions, from thermostats, water pumps, radiators, and fan clutches. Tomorrow, I'm going to warm the car up, and see if it's the fan clutch.
And suggestions of what and why that problem is??
Also, I have been thinking about doing a citric acid flush through the coolant system. Would I need to use distilled water, or would tap water be good enough??

I would change the thermostat.

Agreed. It's a very cheap thing to try, if you're wrong you're only out a few bucks (and you've got a new thermostat).

Does your temperature gauge accurate?

The gauge is most likely OK b/c his Aux fans are kicking in..that will not happen until temp of 105C.

Sounds like you read the 'tips' in MENU#17. . . that's a good place to start.

With 200Kmiles, it's probably due to an "old" radiator; It's not so much that it's old but it was not cared for!

Follow the step in the aqua colored table and see what happens.

Well, I drove the car to the city today to get a new tstat. As I was getting into the city, the car started to overheat. It ran in and out of the red. Made a few spirting sounds, that kind of sound like a pressure washer squirting.
There was white smoke coming out from under the car, but lucky for me, when the problem started (or at least I noticed) I was near a buddy's house. So I drove the last few hundred feet. Got there, shut the car down, but left the key on to keep the aux fans going. I turned the engine over a few times to keep it from seizing till it cooled and several times after. There was white smoke coming from the back driver's corner of the engine, and a lot of it.
So here's to hoping the tstat is the only engine problem, and I only have to fix a hose on the back. Not a head gasket, radiator, and water pump.

The "infamous" water "tee" broke. . . and that's serious. Hope that you were able to stop in time.

That tee (actually has four (4) ports) causes ALL of the coolant to be lost very quickly. Many engines have siezed when this happens b/c you don't have a lot of time to stop car and turn the engine off.

It's located on the fire wall on the drivers side.

Hope it's ok???

I don't know if it was the tee. There was still water in the system, and the car started just fine 7 hours later to drive onto a car hauler trailer. This morning, I"m going to have a look, and try to see what broke.

That is a 104 engine and if you had a stuck thermostat , you want to look at the head to block parting line at the right/rear of the engine..that is where 104 headgaskets let go when they overheat....they also leak oil there since new and are remedied with a newer style gasket.
Just something to be aware of on 104 engines.

Well, I had a look today, opened up the tstat housing. There was still coolant in it below a certain level. looks lucky for me. Most of the coolant was on my friend's driveway. The T thing did go, but it had been glued, and only a bit of the glued part had come out until I started it to get it off the trailer. Engine doesn't miss, or have problems like that. I put in a new Tstat, and I'm trying to get a new tee, which for those interested and needing the same part is called a heater hose junction.
Before I started it
I filled the engine as full as I could with water, and started it. Engine started fine. no misses or anything. Hopefully it will work without needing a new head gasket.

Yea, a heater hose junction. That sounds like what the part is!

Glued!!! Wow, are you lucky!! When that part fails, it routinely takes 'engines' with it!

Glad it's ok! Go put $2 on the Lottery . . .

Well, I got the car put back together, and a new tstat put in. I filled the car with water (no use in my mind to fill antifreeze only to have a bunch leak out) and ran the car.
There doesn't seem to be any leaks. But it was now running at about 90 C according to the guage. I"m wondering if I shouldn't do the citric acid flush and see if that helps. Any opinions??
Engine seems to run fine. Not missing that I can hear. I hope the head gasket is ok. I'll have to look soon. I dont' think it would show up overnight. If it lets go, does it bleed outwards, or into the cylinder??

If it's not leaking (either externally or internally), then I suggest that you do not leave the water in the car w/o some additive. . . . it will corrode quickly.

But I'd follow your suggestion about doing a good flush. Now is the time.

If a heat gasket blows, it's most likely internal . . a small leak into the cylinder, mixing w/ the oil to make a chocolate milk shake that you can 'drink' from the overflow resovoir. Let's hope that there's none.

Another quick question, is the S320 supposed to run at about 80 C or about 90 C (which it is running at right now, with tap water anyways)? http://www.schumanautomotive.com/forums/showthread.php?t=264

This is the flushing technique that I'm planning on using.
I will have to run my car with about a 60/40 ratio of antifreeze/water, because it frequently gets below -40C here in the winter. Mercedes dealer here actually recommends it be run at that ratio.