Couple of Questions on 1980 300D
 

New to me, 1980 300d and a couple of more questions.

What is the normal operating temp on this car? It seems to run at 100c and sometimes a little above that when cruising down the highway at 75mph. It will sometimes drop below 100c while stopped at light, etc. . . It has been hot in Texas, 106 today. Is this the normal operating temp, AC works great as well. AUX fan works to.

I don't have an RPM gauge, but my RPM seem high at 75, it is shifting into 4th gear. Is this normal?

Last night pulled the car in the garage to inspect more stuff under the hood, noticed smoke coming from below the air filter housing. Removed housing and the Crankcase or PCV was disconnected. Should there have been a clamp on this hose? I went ahead and added it.

Is the MB coolant or Z-05 green in color or is this just regular old coolant?

New to this car, so just still trying to figure it out.

Thanks,

Tex

If it's going above 100 that is a bit high, nothing to cause alarm however in that sort of heat with the AC on. Check to make sure you have a thermostat in there... putting in a new one is always cheap insurance on a newly acquired old car.

If the AC and aux fan work great, you're doing really good :D.

Oh at 75 she'll be singing to you for sure. Normal.

The Zerex isn't green it's, uh, I guess amber/clear sort of? My memory sucks. But if it's green, it isn't right.

Temp is a little high. Could be a bad fan clutch or debris clogging the radiator.

Temp is a little high. Clean radiator fins, and if that doesnt help replace thermostat with 80C unit.

Car shouldnt have green coolant, Zerex G-05 is yellow as is the MB coolant.

Its normal for the car to seem like its revving to high at 75 MPH, its spinning about 3700 RPM

My 1st thought is a partially blocked radiator or condenser fins. The fan clutch works at idle and city speeds, so it seems to be fine. Use a garden hose with a strong spaying nozzle on the engine side of the radiator to force out any debris. Replace the radiator cap with a new MB one. A weak cap can raise eng. temp. 100 C is not too hot but ideally it should be stable around 85 to 90 degrees C.

There's a MB approved product called waterweter that is intended to improve the performance of your coolant system. It's made by RedLine the same that makes the 85 plus. www.redlineoil.com. As a User, i would recommend both.

Thanks for the input, today I drove 180 miles starting in the morning with the outside temperature at 86°F, driving 65-75mph the car was running just below 100°C. As the outside temp went up to a high of 106°F, the temp would run just above 100°C at 70mph. Never moved above that mark, would drop below when stopped in traffic. I think this might just be the normal temp for this car. The radiator is new within the last 3 years with maybe 3K miles on it and the fluid is good and clean. I might just for preventative maintenance replaced the water pump and thermostat, looks pretty simple and maybe add the redline water wetter. Any thoughts on this?

Forgot to add, the A/C was running.

The water pump is cheap and easy to replace. But I usually wait until it leaks/weeps from the hole in bottom. I have never been stranded by a bad water pump.

I have had my 1980 300D since 1984. I really do love this car.

In these hot temps (your Texas 106) I do not think that the 100C is bad.

Go ahead and check the thermostat before replacing. If that car got a radiator then who would not do a thermostat ???

Good luck on your new find.

Oh, one more thing. The 1980 I own has a yellow 55 on the speedo because
at the time 55 was the national maximum speed.
I also think mine winds a little high at 75.
But remember, a non-turbo diesel has a maximum speed of 80 .
Except in extreme situations (downhill with a tailwind drafting a semi).
Of course in Texas there are no hills, so simple NASCAR style drafting will have to do.

I had a good run over the weekend in my 80 non turbo 300D from Jacksonville to East Orlando and back. I was cruising 85-90+ almost the whole way there and back. I like to keep a distance from the cars that tend to "pack" up on the interstates. Had a/c blowing 45 degrees at center vents and never saw over 100c. Ambient outside temp had to be at least mid 90's.

I see 100 as the average running temp in mine. Been in the high 90's with hugh humidity here in GA. Yes, your screaming at 75... there is always the option of tossing in a later rear end... (I have one out of an 83 I thought about putting in mine). I don't thing it would do the car any favors as far as it being able to climb hills so I have not done it.

SAve yourself some grief and just go ahead and remove the radiator from the car and clean it. You'll be shocked at the amount of crap between the 2 even after you have "cleaned" it the other way. Besides, it will give you a good reason to go ahead and replace the hoses too...