Engine speed / car speed - engine temp
 

Some newbie questions:

I bought a 1985 300TD a few months ago, in great shape. However, since this is my first Mercedes Diesel, I have nothing to compare it to, so I want to make sure that it's running okay. Specifically, it seems like it should have overdrive or something of a top gear from where it tops out at. At 70MPH it's running about 3k rpm. Is this normal?

Also, normal operating temp is to be about 85 deg. C, but when punching it (above 70 mph) it gets up to 90 deg C.

That seems kinda high to me... Can anyone verify these things on their automobile?

Thanks,

John

3000rpm at 70 is right where it should be. 4th gear is 1:1.

85 is normal-ish (80-82 is what it should run at) and 90 is kind of high but both are acceptable. You should try cleaning out the radiator with compressed air or a pressure washer, over the years dirt and bugs will clog the core and block air flow.

Both numbers are pretty much what I have seen on my '85 300D for the last two years. There will be differences from one thermostat to another so you will see different people reporting different numbers. In hot weather, city traffic or high speed uphill driving, with a/c running, temps could easily reach 100C and no harm done. Cleaning the radiators is a good idea that is seldom done; it's amazing how much junk gets in there.

ok great, thanks!

You can get several different thermostats that open at different temps. It could have very well been changed by the PO.

One thing I do every time I buy a car is flush the coolant, brakes, etc. It definitely couldn't hurt.