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#1
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Engine operating temperature too low
All,
My 1985 300D KaliKar has always run "too low" on the temperature gauge since I got it back in August. The highest it ever read was just below the mark between 40° and 80° (is that 60° C?) So I got a new thermostat, noticed it had 80° stamped on it. Pulled the thermostat housing; out popped and nearly brand-new thermostat marked 80°. Was oriented correctly. So I went ahead and installed the new thermostat. Put everything back together and refilled the system. Drove for two days with the same result; gauge never gets above what I interpret as 55° C. Heater gets plenty hot; I also recently replaced the monovalue plunger. So what do I investigate next? I'd rather not spend a lot more $$s on this if I don't have to. Engine runs well on the highway. Low speed/idle is still problematic--rough idle when cold (starts immediately when cold). Thanks for any advice.
__________________
Mike Frederick 1986 300SDL, 240K+ miles 1985 300D KaliKar, 270K+ miles |
#2
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Sounds like your temp guage is malfunctioning. Also a bad glow plug or two.
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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC] ..I also have a 427 Cobra replica with an aluminum chassis. |
#3
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OK, so I do go for the gauge or the temp sender?
__________________
Mike Frederick 1986 300SDL, 240K+ miles 1985 300D KaliKar, 270K+ miles |
#4
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Do the sending unit. It's much easier than the guage. I had to try three senders before I found one that was accurate on my '83.
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#5
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Use a multimeter to measure cold ohms and hot ohms at the sender, then compare these reading to specifications. This should tell you if the sender is OK, or not, BEFORE you start replacing parts.
Sorry, I don't know what the readings should be, but someone here does... |
#6
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Quote:
__________________
Mike Frederick 1986 300SDL, 240K+ miles 1985 300D KaliKar, 270K+ miles |
#7
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What I would do is check the temp with a infra-rd temp gun and see what the engine temp actually is.
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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" |
#8
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OK, but I already have a multimeter and I don't have/don't really want to buy a temp gun if I don't have to.
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Mike Frederick 1986 300SDL, 240K+ miles 1985 300D KaliKar, 270K+ miles |
#9
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You might also just check to make sure the plug connector on the temp sensor is clean and fitting tightly. Probably not the issue, but good thing to check.
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Andrew '04 Jetta TDI Wagon '82 300TD ~ Winnie ~ Sold '77 300D ~ Sold
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#10
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Yes; unfortunately I crushed the plastic connector housing during my recent glow plug reaming work. So the cylindrical metal connector is still there and connected, but there is no nice plastic housing any more. I guess the easiest way to sort-of fix this is putting heat shrinkable tubing over the end.
__________________
Mike Frederick 1986 300SDL, 240K+ miles 1985 300D KaliKar, 270K+ miles |
#11
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Quote:
Once you have one, you'll find many uses for it, including bar-b-cue grilling.
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RM Smith 1988 560SL "Where is it again that we are going, and why are we in this handbasket"? |
#12
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OMG! I've read many ways to justify buying a new tool, but this one is GREAT! Fix the Mercedes and bar-b-cue!
__________________
Mike Frederick 1986 300SDL, 240K+ miles 1985 300D KaliKar, 270K+ miles |
#13
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Quote:
__________________
Andrew '04 Jetta TDI Wagon '82 300TD ~ Winnie ~ Sold '77 300D ~ Sold
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#14
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a man's gotta have his priorities...
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RM Smith 1988 560SL "Where is it again that we are going, and why are we in this handbasket"? |
#15
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Got the temp sender ohm readings
Quote:
cold: 3.4K ohms hot: 7.2 ohms By cold I mean not started yet first thing in the morning; by hot I mean just parked after a 30 minute commute at 60 mph. And yes, I meant 3.4K ohms vs 7.2 ohms; I didn't forget one of the "K"s. This was measured across the contact coming out of the center of the sender and the hex body of the sender. Thanks to anyone that can help with what these readings should be for a given temperature. For you guys wanting me to check glow plugs because of my engine's cold stumbling idle, I checked each glow plug wire and installed a set of new glow plugs (yes, each of these checked). I did the testing by screwing the glow plug wire onto the glow plug and laying the plug on the engine/head/somewhere so it would make metal-to-metal contact and turned the key to illuminate the glow plug light on the dashboard. They all got hot and glowed red. All of this was to no avail; I still have stumbling idle when cold.
__________________
Mike Frederick 1986 300SDL, 240K+ miles 1985 300D KaliKar, 270K+ miles |
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