Running 200 °F with ambient temp 65 °F - PeachParts Mercedes-Benz Forum

cewyattjr · #1 06-01-2010, 08:48 AM

I think something is up with the coolant system for my '82 300D. Normally I see temps around 150-170 on a day like today, but definitely running hotter. Coolant level seems OK. However, when I popped the hood, I didn't see the radiator fan running. What's the best way to test it? Is it typical the fan to fail before the thermostat?

Thanks,

Chuck

vstech · #2 06-01-2010, 09:00 AM

you mean the belt driven fan mounted on the water pump? or the electric fan mounted in front of the ac condenser?

cewyattjr · #3 06-01-2010, 09:04 AM

The electric fan. Perhaps that doesn't come on unless running the compressor?

tangofox007 · #4 06-01-2010, 09:11 AM

Quote:

Originally Posted by cewyattjr

The electric fan. Perhaps that doesn't come on unless running the compressor?

The electric fan doesn't come on until an a/c refrigerant temp switch is satisfied. Simply having the compressor engaged won't do it.

cewyattjr · #5 06-01-2010, 09:13 AM

OK, so not running the AC at all. Just running a little hot on a mild day, which seems odd to me. What's the first possible culprit to look at? OK, so now I'm kind of thinking thermostat, since the mechanical fan seems to be operating fine and coolant level is fine.

vstech · #6 06-01-2010, 09:14 AM

the electric fan will also come on if the water temp rises above 105C/220F (why does your 82D have american temp scale? is your dash from an older vehicle?

cewyattjr · #7 06-01-2010, 09:17 AM

It actually doesn't have a US temp scale, I'm just "converting" it for discussion.

I have a WVO temp gauge that catches the fuel temp on the return line, and it is completely coolant-heated. Both on-board and WVO temp readings are higher than normal on a "normal" day.

tangofox007 · #8 06-01-2010, 10:40 AM

Quote:

Originally Posted by vstech

the electric fan will also come on if the water temp rises above 105C/220F

Not on an '82 300D. The aux fan on that model is actuated solely by the refrigerant temp switch.

Graplr · #9 06-01-2010, 11:23 AM

Possible issues could be-

Bad thermostat
Blockage somewhere in the coolant lines
Low/no coolant
Bad gauge/sender
Water pump bad

Since you have a greasecar system installed you also may be affecting the flow somehow with that system. Is your system plumbed parallel or series? Do you have any valves to shutoff flow anywhere?

Since you state both WVO gauges and stock gauges read high it is most likely not a gauge/sender issue. You stated coolant level was fine. Next I would check to see if the radiator gets hot after the car is up to temp.

cewyattjr · #10 06-04-2010, 03:29 PM

Definitely will check these items this weekend. No valves shut of the flow of coolant. I am now seeing some difference between the WVO temp gauge and the one on board. So am suspicious that the WVO one is reading high. Still, I did buy a thermostat to replace the existing one as that is kind of "low hanging fruit" anyway.

engatwork · #11 06-04-2010, 03:57 PM

Is it doing it at highway speed on the interstate or at idle while stuck in traffic?

cewyattjr · #12 06-04-2010, 03:59 PM

Most of my daily driving is highway, and that's definitely where I'm seeing it. It's not awful, but at least 20-30 degrees (F) higher than I am accustomed to seeing it, and I've had the car for about 3 1/2 years now, and with the WVO kit that whole time.

Jeremy5848 · #13 06-04-2010, 04:22 PM

Since you have two gauges that more or less agree, it's probably not quite as important to double-check with a hand-held IR temp gauge but still a good excuse to buy one.

One test that you can do on the highway is to turn off the a/c and turn the heater on full blast for a few minutes (as long as you can stand it). Does the coolant temperature come down a little? If so, it confirms that the cooling system is not removing as much heat as it is supposed to.

One of the easier things to check and service is to make sure you have good air flow through the radiator and condenser. An ordinary garden hose or (better) a high-pressure sprayer, applied at the back of the radiator, can be used to blast dirt and bugs out of the fins.

Failure of the thermostat is another good possibility and fairly easy to replace.

Finally, an internally-clogged radiator is a possibility but check the easy stuff first.

Jeremy

cewyattjr · #14 06-04-2010, 04:27 PM

Thanks, Jeremy. I did in fact notice this winter. When I would turn on the heat, the temp of the on board gauge would drop, and just enough to notice. Will try the easy stuff first, thanks!!

cewyattjr · #15 06-13-2010, 06:46 PM

I did end up replacing the thermostat and followed this guide:

http://www.dieselgiant.com/thermostatreplacementandmodif.htm

I ended up doing his mod, but only with one hole. I do notice that it DOES take longer to warm up from a cold start. Also, it is fine temp around town, though gets up to about 190 F on the highway after some 15 -20 miles. Curious that it would be higher on the highway (??).

Chuck