A mystery:

So, in the last month I did two things on my 82 240D. I replaced the radiator with a used one out of a friend's car. I also replaced the temp/oil/fuel portion of my cluster (the old one was leaking oil) and transferred my working dimmer switch to the new cluster.

Now it appears that my car is frequently overheating, but I don't trust the temp gauge. When the car's lights are on, the temp and fuel gauge both jump up considerably, and they bounce when the blinker is on. However, the radiator has had mysterious fluid disappearance- it seems to be down by an inch or two every time I check it. Though I am not smelling coolant or seeing leaks under it when I stop.

The gauge behaves more or less consistently with what I'm doing with the car- heats up on the uphills, cools on the downhills, and starts reading as overheating when I've been driving it an hour or so. (But not all the time) However, when I stop to let it cool, it doesn't feel hotter then normal to me. FYI: The thermostat was recently changed.

It's making me crazy- I'm so afraid I'm going to melt the engine. What's going on here?

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1976 300D 217k...an old car needin some love. (GONE OFF TO RUSTY CAR HEAVEN)

1982 240D probably something like 190,000 miles...was Old Yeller, but I changed the name to Buttercup

You can check the temperatures with a non-contact thermometer to confirm the guage. However since your coolant is dropping, I vote for overheating.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Allot of the time a "jumpy' gauge indicates a bad ground. Check out my post 'good shop found on road trip' I had a gauge problem with my 240D but yours sounds like a bad ground also check for coolant dripping from the "weep hole' in your water pump.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

i had a problem similar to this with my fuel gauge, turned out it was a fuse that was barely making a connection causing some wierd readings.

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Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

Jumpy gauge is usually a bad sensor.

An extra ground has fixed the "jumpy" gauge problem in the past for me. My last episode with what appeared to be over heating was the gauge itself.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Ditto. My gauge was jumping around too and I solved it by adding two new ground wires on the back of the instrument cluster. You can search my name to find the exact details if you wish.

Scott

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Scott
1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
1965 Pontiac GTO 15,000 restored (sold)

with mine, I found a jumpy gauge was related to a connection set disconnected. it must have gotten a wierd signal through the wiring somehow...
once I reconnected the harness, the gauges went right back to working.
try looking for a loose bundle under the dash.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

..

My guess is a bad ground on the gauge. The "missing" coolant could be from the cooling system naturally working the bubbles out after the radiator change. If it's not obviously boiling over steaming or forcing out coolant I doubt you will hurt your engine while you are figuring it out.

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82 300SD AKA The Dieter Beater

85 GMC Jimmy AKA #$%((@

Both on WVO

Where are you located? What's the usual ambient temperature where you live?
I live in Phoenix and drove a 240D for a while with ambient temperatures around 114 for days on end during the summer and I never had it out of the 85 to 90 range, so these cars can run correctly if everything is working right.

1) Why did you put your friends radiator in your car? Was there already a temperature problem you were trying to fix?

2) Jumping gauges is likely an electrical issue, you are probably best following others advice on that.

3) I'd suggest getting new radiator and heater hoses, as well as a new radiator itself if you can spring for that, and a new thermostat. These are all available right here on the forum from Phil at Fastlane and are all pretty easy things to replace.

4) Look closely for leaks if you are losing water including the weep hole on the water pump as has been mentioned.

- Peter.

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2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S

So I put a ground on the cluster and that more or less solved the problem of the jumpy gauges. They still move slightly when the blinker is on, but the seem to be much more reliable now (not jumping all over the place at all).

And the car is still running hot, although now the temperature is pretty much consistent at 100 or just a little less/more.

Question: How do I know if I need to replace the water pump? Just replace the hoses first and see if the problem goes away?

Also, I don't have the shroud on there, though it's in my garage. I should probably put that on too, eh?

Thanks!

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1976 300D 217k...an old car needin some love. (GONE OFF TO RUSTY CAR HEAVEN)

1982 240D probably something like 190,000 miles...was Old Yeller, but I changed the name to Buttercup

Yes, you do need the fan shroud in place. Also check your alternator and battery. Guages that move with the turn signal suggest less than optimal voltage or amps.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K