Overheating Diesel?

[rmmagow]

When I first bought my 83 300D last June or so it ran at a very steady 90C on the guage. This past winter it would occasionally get within about a needle's width of 100C. Usually turning the heat up would make it go down again. Today it started running a bit warm again, this time about a needle's width above 100C. Cranking the heat up all the way would drop it back down some. When I got home I let it idle in the driveway while popping the hood to have a look-see and the temp dropped back to normal, about 90C. Someone told me they heard a belt squealing when I started it up the other day at work. Anyway, some questions, the electric fan in the front, is that supposed to come on even if the A/C system doesn't work? What temp roughly should it come on at. Could a little belt slippage cause it to go up like this ? Maybe it slips a lot at higher engine speeds? I'm going to put in 4 new belts this weekend. No drop in fluid levels and no dripping anti freeze in the d'way. Can someone confirm for me that 100C isn't all that too hot for this engine? Regardless, it still runs well and hopefully it's just some maintenance being needed.

[Stevo]

rmmagow

You, most likely will get lots of help on this one, common problem. 100c is running too hot. Not hot enough to hurt the engine but something is not right. Also a slipping belt could very well cause problems. I suggest you do a search in the archives if you still have a problem after replacing your belts as a bit of detective work will be needed. Not sure about the A/C fan but Im sure someone will help you with that. .....Good luck

I just finished up today with cooling issues on two of my cars.

[BoostnBenz]

That is DEFENITELY too hot for winter time, let alone summer. In the winter I won't even touch 80*C, in the summer I stay around 85*C, 100*C isn't doing the motor any favors better look into that.

[rmmagow]

Some more careful observations. I checked the belts and tension and although belts aren't perfect they (actually it, the one for the alt and water pump) is in fairly good shape. This morning while driving to work I left the heat at full max. I drove at about 70~75 and it started to run a little hot, just under 100C on the guage. Traffic essentially stopped and the thing cooled right down to about 1/4" above the 80C indicator. I "think" I smelled hot rubber but I was also in back of a big truck so I'm not sure if it was me. As traffic started to move again one of the idiot lights went on. Not being too familiar with the lights, I freaked and got off the hi-way to see if I had tossed a belt. Turns out the light I was seeing was the brake wear indicator. Figured fine, I'll fix that too, pulled back on the hi-way, brake indicator flickered a couple of times and went out and stayed out for the remained of the drive, about 30 miles. No apparent change in brake function or anything. Now, I strongly doubt these two problems are related but......
The Aux fan, is it supposed to go on if no A/C is in use? Via a wire trace, can I just join the wires together to make the fan run all the time? Since the hot running seems to only occur at speed am I experiencing cavitation due to a maybe worn Water Pump? Any advise is greatly appreciated as I wade through the archives. Thanks.

[edge]

I am also having that flickering brake light problem when accelerating. My brak fluid seems to be fine and the parking brake is not engaged....?

[Ken300D]

Take a look in the coolant overflow tank for any oil spots or bubbles. It's a relatively easy check to look for an indication of a leaking head gasket.

Not that I think that's what you have. By far the more likely cause is a radiator clogged up from plain oldness. I always use distilled water now in the radiator, because my tap water is full of minerals that stay behind as the water evaporates - thus leaving those lime deposits inside the radiator.

The electric fan should come on at some point without the A/C being on. A quick way to test the fan motor is to disconnect the two fan relay leads from the A/C accumulator/receiver, and short them together to throw the relay. (Note, there are two sets of leads, one for the fan and one for the A/C compressor - it's OK to try both sets, one should start the fan.)

However, you should not be needing the electric fan in RI yet - it's not hot enough. So you have a basic cooling problem somewhere.

Ken300D

[Ken300D]

Edge:

There are two brake warning lights.

One says "BRAKE" in red and indicates something seriously wrong, like low fluid or some other failure. It also comes on when you set the parking brake.

The other one is yellow and looks like a (O) and that is the front brake pad wear indicator. It is less serious but deserves some attention. If it is flickering now, as the pads wear further it should come on steadily when you brake. Then its time for new pads.

Ken300D

[edge]

It's the "BRAKE" light and it comes on when accelerating, not when I am braking. I guess, I'll bleed the brakes next weekend and see it that helps. Although I can't see why it would change anything.

[dave1shere]

Hello all. I am having the same problem. My temp. gauge stays about a needle's width below the 100c mark this has just happened in the last few weeks. It use to stay at the 80c mark have changed the thermostat but no change. The former owner that I bought this car from told me that he had put a new radiator in it looked new? Also my fan now comes on when I first turn on the key and stays on . This just started a night ago. My question is where do I go from here. Does anyone know where the relay for the fan is seems that it has kicked on and is stuck. I did a search but most seem to indicate the thermostat or radiator for overheating don’t know what to try next.

[edge]

Did I read somewhere that someone said to put a pinhole in the thermostat to get it to drain properly and hence lower the temp to the low 80's area.

If the red brake light comes on when accelerating that is an indicator your brake fluid is a little low. Once it gets lower that light will come on all the time.

[Ken300D]

Also be aware that the brake reservoir (if your car is not from the 60's) is divided into two sections, with a sensor in each section.

So, you have to carefully look in each section of the reservoir to make sure it has fluid. You might think you have enough if you are only looking at one of the two fluid chambers.

Best way to do this is remove the cap and take a look.

Ken300D

[edge]

Oh, I didn't know, Ill check it, thanks

[jhal]

I believe the aux fan relay is on the driver side fender under a black cover. It has a tab that you push in and then lift off.

[jhal]

The a/c temp switch located on the reciever/drier can go bad making the aux fan stay on also. Just don't use your a/c if you disconnect the fan, it can cause your compressor to overheat and fail.