'95 E320 operating temperature
 

I have what I feel is an issue with my car running to hot. For a while now the gauge always seems to go high and run around the 3rd tick. I never hear the fans turn on, and if god forbid I turn the A/C on then forget about it, the temp will run above the 3rd bar and I get freaked and turn it off. This is all in seattle weather around 60F. Lately we've had some 85-95F days and I can't even drive it. Even while I'm driving 45mph on a local road without stops, the gauge has gone near the 120 tick with the A/C off and I pull over and the fans are never running, ever.

I took the car to a local shop when it was 80F and they ran it all day and plugged their snap on machine with the latest module and the said the car ran perfect for them and the fans turned on at 107C per spec, so they couldn't get it to overheat. They even blocked the radiator in the front. They even replaced the thermostat again (i had it replaced a year ago), and flushed the coolant. I know they do basic tune-ups on benzes, but as far as they are concerned the car works per specs and they aren't familiar enough with what the temp needle should be at during normal operating temperatures. AGain, when this is all happening I am not driving hard like I usually do, so for test's sake I drive it normally.

I called Barrier, Phil smart, and other benz shops. They all say the same, normal operating temperature should be around 90C except for real hot weather of 85F+ days.

I'd love to hear from some here who either have the same car as me, or work on them and know exactly what I should be experiencing. Ask me any more questions you need so we can narrow this down before I take it to Barrier and get raped blindly.

The pix below was taken this morning when it was 60F. I started the car, let it run for about 4 min, then went for a normal 10 min drive stop and go at stop lights occasionally flooring it. When I went fast and the cool air hit the front, the temp gauge was between the 80 and the 3rd tick which to me is normal. I then let the car idle in Park for about 15 min, which by then was 61F. You can see the temp below. Any possibility the temp gauge itself is wrong? I open the hood and the hood itself is burning and the engine is just super hot, again with only 60F. Imagine when it's 85-90F outside :(

Perhaps have them check the fan clutch. Mine wen out on a 300e and the temp went nuts!

When was the last time the coolant was changed? I can't say I have ever had one run like that but as a matter of course (especially at that milege) I just go ahead and replace the radiator, fan clutch, water pump and coolant. Kind of like preventive maintenance. Pretty straight forward job with the pump being the biggest PIA job of the ones listed.

It would bother me if mine ran as hot as yours is showing.

Why don't you first rule this out as a problem. We have to make sure these are working properly first. Also look at JIMF's Cool Harness. It will kick in the fans earlier... of course, wait until you know they are working properly. More info on them here (a bit down the page):

http://pages.prodigy.net/jforgione/MB_S500.html

tkamiya - I totally agree with the behavior of your car. But remember what you see in the picture is only after 10 min of driving and 10 min of idle in 60F weather! With regards to your comment: "What's the highest temp you've seen? Did you actually see it go beyond 107C?", yes, it does that every single time I drive it in the cooler weather and what you see in the picture is beyond 107C.

Mingson - fan clutch works like a charm from start of car to when it's running hot, it's just the 2 fans in the front that never turn on.

engatwork - Coolant was flushed maybe 9 months ago with mercedes coolant from the dealer, then it was flushed last week when it went to the shop and had the thermostat replaced as well. It's not the exact same stuff that comes in the white "mercedes benz coolant" bottle, but it's spec'd for german cars they say(it's a pink color). Any mechanics know if not running the factory coolant will make the car run hotter? Are they that finicky? Yes, it bothers me as well that it runs so hot as I KNOW that is not normal.

wjm - cool, that sounds good, but I don't want that solution as I'm selling the car right now and I want the "running hot" problem solved before I hand the car off to someone else. I take pride in things I sell, so this needs to get fixed. I already bought another car, or else I would use the kick in the fans alternative.

thx for all your answers, hopefully I get some more info from some mechanics if they might know what would cause the fans to not turn on.

As you have just had the coolant and thermo changed , I suspect you have an air bound system..
[ or a faulty therm]
The air bubble usually winds up in the thermo housing, explaining both temp readings and no coolant temp fan cut-in..
Another possible to higher temps is incorrect coolant mix %...
but that has no affect on fan operation..just something to check before hand.
A/c fan is pressure activated and has nothing to do w/coolant temps..
That can be checked by simply jumping the high side pressure sw at the reciever/drier to verify the electrical integrity of the a/c aux fan circuit.... if no fan, check fuses on top of relay..
If you get fan w/jumper, then suspect is low freon capacity [ not getting to cut=-n spec ]

NikoE320

I read your post with great interest as the 95 E320 wagon has similar temp issues. I posted the following: Hot Wagon

The thread ran towards the thermostat being most likely. I have yet to change it but will soon. It is my understanding that the 104 motors do run hotter than the 103 engines.

I would be sure the temp gauge is correct and verify the coolant temperature as a starting point. Temperature sending units do go bad, although my experience is they error to the cool side.

The other area I need to explore of course is the viscous fan clutch, although I do hear the roar of the fan when hot which is supposedly a quick way to tell if it is working.

I will bleed for a potential air pocket tomorrow and see if it makes any difference.

Haasman

Yes, after tkamiya recommended I search the site on his id for other related topics, I stumbled across the "hot wagon" post as well. I am going to go buy the mercedes coolant from the dealership today and at least start off there with a flush of the pink stuff the shop put in.

Main question, for our weather patterns here where there's maybe 3 months of warm weather (70-90F) and the rest of the year it's 35-55F, what coolant/water ratio should I use? I read some stuff on it, but then people started talking about using distilled water as well and I'm confused as to the correct approach. Is 50/50 just the safe way to go?

Also, I assume the Aux Fan fuse is along side the regular fuses in the engine bay, right?

Where is temp sensor for the Aux Fan? How do I test it?

The load fuses for aux fans are under a panel, behind the fuse box. This is the relay box and has 6 screws to be removed for access..
Once there , the fuses are on top of each relay.. one for high fan [ engine coolant] and one for low fan [ a/c ]
These will be slots B and C.
The high fan has been upgraded by Benz to a 25 [ from 15]
The low fan is a 30 [ low fan requires more amps b/c of the dropping resistor in that circuit]
There is also a fuse in the fuse box for the primary side of the relays , but that is usually not the culprit , as low relay current is nil...
Do the test TK recomends and that will verify if fuses need checking...

crap, sorry for not being able to do this, but I'm not that savvy with regards to finding the thermostat housing, or the A/C dryer.

Is the thermostat housing accesible from the engine bay? I'd rather do that test than the "shorting out" one.

Arthur, I checked all the fuses and they all were good (tested with fluke meter).

tkamiya, If I attach a pix of that area can you tell me which of the connectors there is the one I need to disconnect?

thx.

<Arthur, I checked all the fuses and they all were good (tested with fluke meter).>
So , I assume you checked the ones on top of the relays behind the fuse box?

Yup

Here is that area behind the drivers headlight.

See the thermo housing attached to the end of the top radiator hose ??? The sw 1/2 " to the right with two wires is the high fan sw.[ blue sw]

See the two connectors encased in clear plastic sleeves 1/2 way between the power steering pump and the reciever drier .. that is the leads for the low fan pressure sw. [ just to the right of the pump res.]

Looking at pic, of course....