Normal operating temp 300sd
 

I have a 93 300sd,today the temp gauge seemed to be running higher than I think it should. It was just over 100* here today and with the A/C on it was reading between 100 and 110 degrees celcius.I changed the w/p and the fan clutch last year,but I don't remember if I changed the thermostat. Is it running too hot or am I worried about nothing.I don't think it ran this hot last year but I'm not sure.

A properly operating system should never get much over 100C even with the A/C on in very hot weather. If it does you probably need to flush the system and ideally replace the radiator/t-stat/fan clutch, and check the aux fans to see if they are coming on.

82

careful of the rodbender!
the good news is your head is much stronger than the older 603's. still, a radiator and block flush and check of the fan clutch is called for.
your thermostat could be sticking, and lastly your waterpump could be failing internally. is MB gold or zerex G05 in there?

since you've already taken care of the big items, besides the radiator, consider replacing the thermostat on principle.

verify the accuracy of your coolant gauge before purchasing any big ticket items.

I think most on this forum would prefer that your engine not go above 100*c on a regular basis, as mentioned above.

Thanks for the replies,I am going to replace the thermostat and see what happens.Since it just started doing this all the sudden I'm thinking this will correct the problem.

Mine ran hot till I made sure the AC control was not a MAX Detent. I'd say 100C is fine if it is that hot out. I've seen 110 on my on HWY pulling long steep hills. If I see this I just back off the trottle some. I wouldn't be too concerned with what you are experiencing.

I also never run my AC fan on Max either, I use the Auto fan button. This keeps the fan from going to speed 5. I think it goes to speed 4.This will also help. Still keeps cabin cool.

Lots of material in engine and little radiator and sometimes temperature lags the load. You see this in the Winter; on the other end.

Oh yeah, my electric fans up front runs fine. Yours should cut in with AC on after 5-10 min with AC on and car idling on a warm day. Does yours?

If U have 50/50 antifreeae-water mixture you are good to boil over at 265F or aproximately 129C.

See #5. Always start with verification.

Just read some more replies,the twin fans in the front are both working and the clutch fan is pulling good. We did have the a/c turned down low though.Last week my wife was driving home from OKC and she said it got a little warm in stop and go traffic but she thought it was running about 80-90*c on the highway.

would be good also to check and make sure there isn't any debris trapped between AC condenser and the rad or the aux cooling fans and the ac condenser.

my .02

steve a

FWIW Mine always cools down in city stop and go with AC on Hi or Low.

If it were me I'd replace the thermostatic fan clutch since yours seems to warm up in stop and go.

I replaced mine when I got the car, it had 150K on it.

When you spin them fans cold they should offer allot of Resistance and not go far after U let go. Grab the hub and wiggle it. There should be no clearance or wobbling whatsoever.

I think U can get a new one for less than $100 and they are not that hard to replace.

Hope this helps, good luck.

As a side note mine runs about 80-82c on the gauge.

steve a

Thanks everybody for the advice/replies. I pulled the thermostat out tonight. I then got out my little single burner propane stove and put it in some water and proceeded to heat things up. I finally gave up on it opening at 99.7*c. I am going to try to find one in the morning,hoping I can find something local,the nearest dealer is in OKC about 140 miles one way. need to get it fixed for a trip to Dallas on tues. I have never felt comfortable removing them and running without one. On a couple occasions I have gutted them and used them till I could get a replacement.