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Old 09-03-2010, 05:23 PM
okyoureabeast's Avatar
Rogue T Tolerant
Join Date: Jul 2009
Location: North America
Posts: 1,675
New instrument cluster gauge and higher operating temp?

I've been at school for about 2 weeks now and I probably should have posted this about a month or two ago when I installed the new gauge.

My 85's original gauge had it's oil pressure gauge break internally from me not correctly tightening it. I found a man in town who had an 82 300D that he was parting out so I picked up the three way cluster instruments and reinstalled it into my 85.

Everything look ok, but I noticed that my temp gauge was running a little hotter than normal. Instead of running between 80-90*C it was running between 90 and 100*C.

I figured it was the gauge so I didn't think much of it however after recently coming back to hilly Ithaca in this unseasonably high heat the gauge has been peaking upwards to 100*C which has reasonably worried me. The temp drops quickly if I let off the go pedal.

I want to think everything is normal, but the over compulsive repairer in me has me thinking.

When I start the car, the gauge pegs up towards 60*C (roughly 136*F) which is nowhere near the ambient temperature or around 85*F which has me leading more towards bad sensors or an odd 3 way instrument cluster. Any ideas about this?

On a side note, I discovered my indy mixed in green coolant instead of normal white. When I look in the expansion tank the coolant is white. In the upper radiator hose the color is a distinct green. I'm a bit miffed about this so I will be doing a coolant flush and refill sooner rather than later.

-Typos courtesy of my mobile phone.
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Old 09-03-2010, 05:28 PM
Aquaticedge's Avatar
Bump on a log
Join Date: Nov 2009
Location: See Biography
Posts: 3,148
one thing to try if you can (idk much about your type of cluster) is to Swap out the temp part with the old one and see if it does the same thing or not if you can
1987 300TD 311,000M Stolen. Presumed destroyed
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Old 09-04-2010, 09:43 AM
Registered User
Join Date: May 2007
Location: Out in the Boonies of Hot, Dry, Dusty, Windy Nevada
Posts: 9,585
Ground Strap?

Do you have a IFR Lazer temp thermometer? Harbor Freight has them on sale not for $29.99. really handy for taking reading from different parts of the engine.

Your problem might just be a ground problem with the gauge. make sure the ground strap between the engine and body is clean and tight w/o corrosion/grease/paint causing a good contact.
I had a problem with the gauge spiking, and jumping around, turn off key turn back on and all was well. turn on a switch, and the gauge would jump. was the ground strap, took a while for me to work through this one. even changed the gauge.

I don`t believe the tri gauge can be taken apart with any success and have it work with parts from the other gauge.

there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works
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Old 09-05-2010, 11:13 AM
okyoureabeast's Avatar
Rogue T Tolerant
Join Date: Jul 2009
Location: North America
Posts: 1,675
I may just swap it out once I get back, but before I forget to ask:

Where is the ground strap to the chassis? Is it the one located directly behind the cluster?
-Typos courtesy of my mobile phone.
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Old 09-09-2010, 10:38 PM
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Join Date: Sep 2001
Location: Concord, MA
Posts: 603
Based on my experience....

I had the same thing happen...hotter running temps...or at least thats what the gauge says. I thought it could be the thermostat, so I replace it and I still get same hot operating temps. Then I pulled a temp sensor (mounts near glow plugs) from a local salvage yard, and installed into my car, and I got the same high reading on the gauge. Then I used my multi meter which has a thermocouple temperature sensor, and I put the sensor directly on the metal housing surrounding the temp sensor on the head, and while the gauge was reading 90 to 95 C, the actual measured temperature near the sensor was 80-81 C, just what it is supposed to be. My conclusion is that the temperature gauges on these cars, which are getting on in years, simply go out of calibration. I don't think there is an adjustment screw on the gauge, but the next time I have the dash cluster off, I will check. But at least I know the engine coolant temp is correct at operating temperature.

Also, that was a good suggestion to make sure the ground strap contacts are clean...this is a good general maintenance task anyway. The ground strap is located between engine and chassis, down low and under in the engine compartment forward of the driver footwell and beneath steering gear.

Good Luck,

1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)
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Old 09-10-2010, 01:39 PM
Oldwolf's Avatar
Join Date: Apr 2009
Location: Raleigh, NC
Posts: 1,017
Originally Posted by okyoureabeast View Post
I may just swap it out once I get back, but before I forget to ask:

Where is the ground strap to the chassis? Is it the one located directly behind the cluster?
Usually ground is pin #1.
1993 W124 300D 2.5L Turbo, OM602.962
2000 Chevrolet Cavalier, 2.4L DOHC
2002 Ford Explorer, 4.0L SOHC
2005 Toyota Prius, 1.5L
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Old 09-11-2010, 01:08 PM
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Join Date: Mar 2005
Location: Yountville, CA
Posts: 1,175
those thermal guns for measuring heat are worth every penny! My gauge was acting the same way, cleaned all grounds, still have erratic issues with gauge but gun confirmed correct operating temps for piece of mind . . . . yes, these cars are getting older and along with age comes certain age related electric idiosyncrasies . . .

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