Non-turbo 617 runs hot...!

[babyjames]

My '84 W123 300D (n/a 617 motor) seems to be running a little hot. It hasn't overheated, yet, but consistently is above 80C on the temp gauge. I haven't driven this car a whole lot, so I'm not sure if this is de rigeur for this motor. My TD and SD (both turbocharged) stayed right at the 80 mark, occasionally creeping a bit higher. I changed the coolant and flushed the radiator... think I should pull the water pump and inspect the impeller? The car was garaged for a few months this winter, so I, honestly, can't remember where the needle on the gauge sat before. Anything to be (overly) concerned about??

[Lycoming-8]

So, how much above 80' does it run? Half way to the next mark is only 90', at least on my gauge. My 300D turbo runs at about 83' or 84' when warmed up. When the thermostat was new, a year or two ago, it would run closer to 80'; but I am not a bit worried about the slightly higher temp. There are several reasons that could cause a higher reading. Gauge or sender out of calibration, thermostat bit off of calibr, somewhat old coolant with resulting scum on the interior heat exchange surfaces, low fan efficiency, dragging brakes, and several others.

You have already done the coolant, but bottom line is it seems OK to me.

[babyjames]

If I keep the motor revving, it will stay down in that 83 or 84 degree range. In traffic, traffic, though, it creeps up to the 100 mark. Still not that hot, but....

[pawoSD]

Mine is the same way, it will occassionally go up when its hot out and I am sitting in traffic, but the aux fan comes on, and it falls a bit, then once I am driving again it falls more and is fine, has never come close to overheating so far, highest its been was around 92 deg C on a very hot day in sitting traffic after I got off the freeway....

[Maki]

Two things to consider: first, the sender may not be accurate. I have an '82 300cd-t that tops the 100c mark regularly in the summer. One day I ran the temp gauge to 105 and (carefully) removed the EGR thermovalve from the head to expose the water jacket (warning: don't try this at home if you can't avoid the surge of hot coolant).

I stuck a candy thermometer in the head and took a reading: 180 degrees.

The circuitry in a W123 instrument panel is at least 20 years old. It's not complex, but it's taken a beating. I've driven around in the summer (just a Wisconsin summer, though) with the cap depressurized after the expansion tank cracked. Coolant loss was minimal.

That said, one of the mbz.org listers theorizes that elevated coolant temperatures are the result of aluminum erosion in the OM617 thermostat housing. Again, it's an issue of 20 years of wear, just like the hydraulic erosion that turns a riverbed rock into a wafer..

This fellow argued that erosion in the thermostat housing permitted excessive heated coolant to bypass a trip through the radiator. He drilled a small hole through the thermostat housing, and claims it reduced his coolant temperature. I have not tried this but I think you could find a summation of his experience with a little web surfing.

Of course, there are all the usual caveats: make sure your radiator fins are clean, ensure there are no air pockets in the coolant jacket. This post is starting to sound like one long disclaimer. Sorry about that.

One more thing: if you have a car that gets hot while standing still, check your viscous fan clutch.

Russ M

[babyjames]

What I really want to do is eliminate the crank-driven fan entirely, and "sandwich" the radiator with electric fans; one that comes on at 80C and another that comes on at 85C or so. Know where I can get a 12-volt thermostatically controlled switch? Radio Shack?
Otherwise, what you're saying is that I'm getting all worked up about nothing. Heat is the enemy, though, and I want this thing to run cooler! I just replaced the water pump on my TD the other day. Man, it had one with a REALLY cheesy stamped-steel impeller on it. Now that car runs a couple degrees cooler... guess maybe I'll try the same thing on the sedan.

Jay.

[pawoSD]

You'd have to do an alternator and wiring upgrade if you went to electric fans, personally I don't see it as worth it, MB chose a mechanical fan for a reason, they even use them on the newer cars, its just more reliable.

[babyjames]

I'm going to wire the main electric fan directly from the battery. As there is, essentially, no other drain on the electrical system except headlights, I think the 55ah alt ought to be able to handle the load.

[t walgamuth]

the diesels also run a little warmer when being run hard such as on a hill or fast on the highway. if that is when it is hot, maybe not any problem at all.

[kmaysob]

why not fix it right? flush the radiator,check the thermostat,make sure the lower radiator hose isnt collapsing and check the accuracy of the temp gauge. also make sure its full of water(not just the aux tank) and make sure your coolant ratio to water is proper

[babyjames]

Euro model, so no overflow tank. Already flushed the radiator, and it is FULL of 50/50. As for the thermostat, I've never had a car OVERheat due to a bad thermostat, usually just the opposite? My aux. fan has not come on yet, how would I go about checking the relay that triggers it? I checked the fan itself with my battery charger, and it is fine. All the wiring looks good, too. I'm starting to question the accuracy of the gauge.

[babyjames]

What would an ohm meter read if connected to the temp sender and a ground if the engine were at 80C??

[babyjames]

For anyone who's curious:

60C - - 110 ohm
80C - - 67 ohm
100C - - 38 ohm

At least those are the values I found by doing a search.

Where's the temp sender for the aux. fan??

[tangofox007]

There is a temp switch for the aux fan on the receiver/dryer. If you disconnect the temp switch leads and connect them together (ignition switch on) the fan should come on. On most W123's, the aux fan is not actuated by coolant temp, only refrigerant temp.

[P.E.Haiges]

Babyjames,

You are making a big ado about nothing.

If it ain't broke, don't fix it. (and it ain't broke).

P E H