Which operating temperatures are OK for 617 engine? - PeachParts Mercedes-Benz Forum

deniss · #1 07-09-2007, 05:15 PM

Today is the warmest day of the summer here in NJ - around 93 degrees F. Usually, my 617 engine operates at just above the 80-degree C mark. Today, I was parked waiting for someone for about 10 mins in the sun, with the car idling and A/C (R-12) on max, and the temperature dial went above the 100-degree C mark. Now, I didn't wait long enough to see if it would make it to the 120-degree C mark (it got to slightly above 100 but not 110), but the A/C certainly wasn't cooling the car all that well during idling, which is understandable...

Driving around town, with the A/C, the temp gauge today was hovering around the 100 C mark, falling as I was driving down a stretch of the highway.

Is this sort of behavior expected for this engine? This makes me wonder what some of you living in, for instance, Phoenix see on your temperature gauges every summer! I doubt this is a thermostat issue, since the engine does otherwise operate just above 80 C, but the A/C does seem to put a considerable heat load on the engine at ambient temps around 90 F and higher.

Jeremy5848 · #2 07-09-2007, 06:35 PM

My 617 used to operate at just above 80C, getting up towards 100C with load, high temps, and a/c. Recently, my indy changed the thermostat. The engine now stays around 100 and doesn't move much regardless of what I do. I've even come home and let the car stand running in the driveway (80-90F outside, coolant temp about 100C, a/c = ON) until the aux fan kicks on. When that occurs, the coolant temp actually drops a few degrees!. I've seen this several times.

Your temps sound normal to me. You must allow a good deal of leeway for variations from one engine to another, of course.

Jeremy

sailor15015 · #3 07-09-2007, 10:26 PM

I have a 75*C stat in my car and it keeps the temps at around 82-85C. A few days ago the temps were just above 90F here and I left the car idling with the a/c on max for about ten minutes while I went inside to pick up the gf just to see what it would do. I came back and it was about 90C on the gauge and the vent temps were about 48F, with the aux fan on.

t walgamuth · #4 07-10-2007, 02:41 AM

From what you have described I would suspect either the auxiliary cooling fans or the clutch fan is not working correctly.

Not to be mr obvious here, but did you check your coolant level?

Tom W

deniss · #5 07-10-2007, 10:09 AM

The Aux fan on the condenser is brand new, and it engages normally during A/C operation.

The coolant is slightly below the KaltWasser arrow mark, but I wouldn't think that would have this much of an effect? I'll put more in.

I don't know about the main fan... How is it "supposed" to operate? It's running all the time in my case - I haven't seen my engine idling without that fan turning. Since I assume it's driven by the water pump pulley, I doubt it can go any faster at idle speed than the drive speed it's getting from the water pump... Right?

Maybe my A/C condenser itself is tired and the fins aren't cooling it like they should...

DubMutant · #6 07-10-2007, 03:51 PM

I was having this issue with my om617 as well. Since i was heading on a long road trip, and want the car to last, I decided to take preemptive action.
In order to make sure the cooling system was operating at maximal capacity I took the following actions:

1. I replaced the aging fan clutch,
2. I power washed the radiator (out of the car obviously),
3. I straightened ALL radiator fins with 2 small screwdrivers for max air flow
4.I replaced most of the radiator fluid with 50% MB coolant and distilled H2O
5. I replaced the thermostat with OE MB t-stat direct from stealer-ship
6. Added 1 bottle of Redline "Water Wetter"

After 1100 miles, long hills high speeds and high ambient air temps, the internal t-stat never climbed past 90 deg. (these are highly inaccurate BTW and if you smash the top of the gauge cluster and the t-stat bounces, it is time for a rebuild)

I had removed the aux fan( no A/C working) for *****s and giggles) It was a risky move as the aux fan switches on automatically at 120 deg, but with that aux fan siezed, it wouldn't have made a difference!
All in all, it was $200.00 in parts and 3 hours of work but I'm glad I did it.

POS · #7 07-10-2007, 03:58 PM

We're 92 down here in Texas all summer long and when driving I'm hovering just above 80, and when standing still I'm just below 100. It never seems to move much other than that.

deniss · #8 07-10-2007, 05:02 PM

The temperatures seem to behave just fine without the AC, which makes me want to blame the condenser. There are quite a few fins bent on the condenser following my deer accident from last fall, when the condenser fan housing was pushed somewhat into the condenser fins. I'll try straightening them tomorrow.

I had a mechanic change coolant in May, but i didnt have him replace the thermostat... I do have a Wahler thermostat sitting at home - I'm not sure if this is what the Benz dealers sell... I might change it if I have time, but I doubt it's a thermostat issue.

What is the function of the fan clutch exactly?

DubMutant · #9 07-11-2007, 12:58 PM

I had a wahler in there but I switched it over to a MB part. The t-stats have a different design- same size but slight design differences.

The fan clutch turns the fan at a constantly increasing speed depending on engine RPM. It is located in the fan housing. Fan is held onto the H20 Pump pulley by 4 bolts. To remove, use open ended 10mm or grind down a 10 mm closed wrench to fit it in there. Leave 1 bolt on for alignment purposes.
Remove fan clutch from fan by removing 4 - 12mm bolts. (not sure on size)

Make sure all fins on radiator are straight. I power washed mine out of car and straighentned fins out of car. Easy to remove.

1.Unclip fan shroud.
2.Remove 8mm oil cooler bracket bolts.
3. Release coolant from petcock. ***first cool the car down use blower/fans if hot
4.remove all radiator hoses.
5. unbolt transmission cooler lines. Do not get these wet. If rusted into radiator like mine, unbolt at oil pan.
6.un-clip radiator from car frame. Lift out carefully.

If the car has many miles on it, fan clutch is suspect. Expensive part but well worth weight in gold. Does Aux fan work when A/C is on? Possible rebuild in order for that part. This should come on with A/C. Straighten all condenser fins ASAP. Bent fins = decreased air flow.