does 100c hurt the motor? - PeachParts Mercedes-Benz Forum

andmoon · #1 03-31-2006, 04:39 PM

I have searched and read the threads.

My 90 sdl runs at 85 most of the time but will go to 100 in stop and go...and then drop to 97 or so then repeat the cycle.

On the highway it's never gone above 90.

Brian Carlton · #2 03-31-2006, 05:41 PM

The '86 SDL does the same thing.......especially when it's warmer out. It won't ever go over 105°C., even under an extended load, and I'm certainly not concerned about 105°C.

Ali Al-Chalabi · #3 03-31-2006, 05:53 PM

100C is normal in traffic.

RUN-EM · #4 03-31-2006, 07:18 PM

Think of this: 100 degrees centigrade is boiling point of water or 212 degrees F. Zero degrees C. is water freeze point or 32 degrees F. The difference between the two is 180 degrees F. Therefore 50 degrees C equals (90 + 32)
122 degrees F.

O d.C = 32 d.F
50 d.C = 122 d.F
100 d.C = 212 d.F

That will give you some reference. And no -- 100 d. C. is not too hot.....many engines are designed to run much higher than boiling (212 d.F) in order to maintain engine tuning for emissions purposes. With a 50/50 mix of antifreeze/water and a good radiator pressure cap, you car will not "boil" until much higher.....oh, say, 240 degrees F.

Regards

Run-em
1983 300SD - aka - SPARKY THE DIESEL

pawoSD · #5 03-31-2006, 07:49 PM

I bet it'd go even higher than 240 degs....especially with 50/50 mix, 240 is only 28 higher than normal boiling temp.....then again, I don't really want to find out.

Highest mine's ever gone was uphill in 85 degree weather in pennsylvania, floored in third gear with 1100lbs of cargo and people up a hill, it was only making about 35-45mph tops depending on the grade, those were such steep hills!

It got up to near 110C for a little bit, but fell right away when going down hill.

#6 03-31-2006, 07:54 PM

Quote:

Originally Posted by pawoSD

I bet it'd go even higher than 240 degs....especially with 50/50 mix, 240 is only 28 higher than normal boiling temp.....

Well, the red line is 120C (or 248F), so I'm sure it is good to at least that without boiling.

BodhiBenz1987 · #7 03-31-2006, 08:00 PM

I went through months of mental turmoil over my 1987 300D's temps last summer. It did about the same thing ... would run around 90, go up to 100 sometimes, occasionally climb above 100.
Aside from finding out my temp gauge is 5 degrees too high, I have also found that it seems these cars are designed to run there. As you can see from other responses, a lot of folks' 603s hang out in that range. You just want to be sure that your t-stat works, you have plenty of coolant, your fan clutch engages and you aux fans kick in (should you reach 110). If all that is in order, as far as I know, 100 on climbs or in stop-n-go is not cause for worry.

Brian Carlton · #8 03-31-2006, 08:50 PM

Quote:

Originally Posted by BodhiBenz1987

Motorsport columnist supreme ...

........that's terrific.........a bit of a departure from sports.......that's for sure..........do they know that we edumacated you here.............

pawoSD · #9 04-16-2006, 01:03 AM

I am paranoid now because when its warmer out....(the 70's

) my car ran up to almost 110C on my 65 mile trip at 80-85mph yesterday, it never went higher, and my gauge blips around a bit (jumps up and down in a 5C range) so I have no idea how accurate it is....my car has never overheated or caused it to boil, always seems to run fine, it cools back off once off the freeway. Going home last night I did 73-76mph and it was cooler out, and it ran about 87-92C the whole way. It seems to vary a lot. Our '83 never gets above 83-84C or so, ever. Even at 100+mph under full load. Should I replace my thermostat? Its never been looked at.....and my radiator is from 1987, but the last time I drained it about 2 years ago there wasn't any junk in the fluid....its nice 50/50 MB coolant mix....though the ratio's may be off now because I've added some here and there due to losses from my old cracked expansion tank, so it may be more antifreeze than water at this point....

Maybe I will completely drain it out and put in a proper 50/50 mix to make sure its not overly anti-freeze thats in there....would that lead to higher temps? If I do that I may as well change out the old t-stat too though.

Also, with my new expansion tank in, I've lost no coolant anymore, that solved that problem, but the other day it was hot out and I came home, popped the hood, and looked around (with it running at about 90C) it turned on its aux fan shortly after parking (usually does this) and I noticed in the nice clear expansion tank that fluid was pouring into it on top from that little skinny "bridge" hose from the radiator....I rev'd it and it was pumping through there pretty hard, rev'd it higher, then let off, and it went away, no more flow through there....

Even when I rev'd it again.... Is all this normal? I just want to make sure my cooling system is working ok. Another tidbit...these high temps on the freeway were using a blend of RUG/soy/diesel if that would cause higher temps....can't see why it would....it did the same thing (110C on the freeway and in sitting traffic) on my huge trip to/from washington DC last summer, it was HOT out, upper 80's/low 90's on that trip, and I was hauling 1000+lbs of junk in the car at 70+ mph....never overheated or had a problem then either....

sailor15015 · #10 04-16-2006, 01:13 AM

I'm having the same problems. I bought a couple of bottles of cooling system flush and now that there's no danger of freezing, I'm going to pour it in and let it run through for a couple of days. I also have a mysterious leak right beneath my upper radiator hose, possibly a cracked neck thing, that's keeping me from putting my cap on all the way and presurizing the system.

pawoSD · #11 04-16-2006, 02:30 AM

Any other suggesstions on what might be the prob? Should I change the thermostat and flush it out???

Brian Carlton · #12 04-16-2006, 10:02 AM

Quote:

Originally Posted by pawoSD

Any other suggesstions on what might be the prob? Should I change the thermostat and flush it out???

When was the last time you had the radiator out of the vehicle and thoroughly cleaned the fins with condenser cleaner and compressed air?

P.E.Haiges · #13 04-16-2006, 10:41 AM

pawoSD,

With all the trouble I see others are having with new thermostats, I think U should stick with the one that's in there. Mine are 26+ years old, work well and I'm not about to replace them as long as they work OK.

When your temp is over 100*C or 212*F, the thermostat is wide open and replaceing it with a new one will not change anything.

"If it ain't broke, don't fix it.

Best way to have your engine run cooler is to have the radiator cleaned professionally and a radiator shop. Scale builds up inside the radiator tubes and reduces the heat transfer.

P E H

P.E.Haiges · #14 04-16-2006, 10:46 AM

andmoon,

No, 100*C or 212*F will not hurt your motor and it won't hurt your engine either. Look at the red mark on you temperature gage. As long as the engine temperature stays below that when the engine is pulling hard, such as when ascending a long hill, engine is OK.

P E H

#15 04-16-2006, 10:56 AM

Keep in mind that thermostats have absolutely NO effect on your systems ability to cool, it's simply a regulator of the temperature range the engine operates in.

I'm not saying that you should not replace the t-stat if you have an overheating problem. It's only 1 part of a whole list of things that need to be checked. 100* is fine every now and then. It's when the temps creep into the 105-110 range that you need to stop and cool down. If you do allow it to 120*, especially with a 601/2/3, just hope you have no permanent issues later on.