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Old 12-06-2000, 09:14 PM
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Join Date: Oct 2000
Location: Oakland, CA USA
Posts: 221
Ever since I purchased my '87 560SEL (approx. 6 months ago) the engine temp gauge has never worked, it would just sit at "40" unless I got the engine up above 2500 rpm, which would cause it to wiggle up and down a bit. Since this has been a relatively minor problem, I haven't gotten around to getting it fixed. I have been slowly replacing/repairing the minor problems with this car. Last week I replaced the air filter and aux. breather (purchased here, of course). Since doing this the temp gauge now works up to 80, and then begins flickering if the temp rises above 80. My question is, is it possible that replacing the air filter is in any way connected to this (I don't see how...), and if so, what would be the next step in getting it to work completely? Thanks for any help!
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Old 12-07-2000, 07:16 AM
Posts: n/a

I wonder if there is a flaky connector or connection near the air filter that you bumped. Why don't you do a thorough visual inspection of all wires in this area. Most likely the sensor is in one of the cylinder heads and you should be able to easily find it.

Good luck,
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Old 12-07-2000, 07:58 AM
Join Date: Aug 2000
Location: Holland, MI
Posts: 1,316
Justin, congratulations on your "new" 560SEL. How is it to drive the 1987 "Flagship" of the line?

I'll second Larry's thought; it may be a loose or corroded connector which adds resistance and thus looks like lower temperature. When you find the connector(s) have a good look at them. Shiny, or dull copper is good, green gunk is not good. Nicked, cracked or pinched wires could make an intermittent connection.

I'll guess that the temperature sensor is located near the thermostat, which is near the upper radiator hose. Good luck and good hunting.

Related, but not in an MB...

I have a "possessed" temperature gauge on the Suburban; after a normal climb during warm-up it will read 210 for a while, the drop really fast to 140 and creep back up to 210. It does this a lot, and it's distracting, so I decided to have the techs have a look.

So far I've found out that:

1. The temperature sensor is not connected to the temperature gauge.

2. The temperature sensor is connected to the engine computer.

3. Disconnecting the sensor (to check it) with the engine running causes an immediate increase in rpm. NOW I know it's because the computer now thinks the coolant temperature is low, but it is a surprise!

4. The techs have determined that thermostat operation is normal. SCAN I diagnostic shows coolant at 200, the a small drop to 190 and back to 200.

5. They can't explain why a 10 degree coolant drop results in the gauge dropping 60 degrees. I don't quite like their first answer of "it's a bad gauge" because I can't figure out how a gauge would read like this! The sending unit isn't jumping, so what would tell the gauge to jump?

Good luck with your troubleshooting. I don't know if your sensor goes to the gauge, or to a computer.

BCingU, Jim
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Old 12-07-2000, 08:38 AM
Posts: n/a

It just so happens I helped a neighbor work through this exact same problem on a GMC pickup, which is the same as a Chevy pickup, regardless of my Dad's insistence that a GMC is a better truck.

We replaced sensor first, then thermostat, checked connections until we were blue in the face. Ended up replacing the guage itself and fixed it.

This, of course, may not have anything to do with your problem, but I thought I'd let you know of our experience. I was very surprised that it turned out to be the guage drifting.

I'm now over my monthly quota for General Motors related comments, I was referring to something about my Vette earlier this morning.

Best of luck,
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Old 12-07-2000, 05:34 PM
Ashman's Avatar
Service Advisor
Join Date: Sep 2000
Location: Sherman Oaks, CA
Posts: 4,748
I had an older 83 GMC Jimmy K5, and it had some gauge problems too. After removing the gauge panel and all, I noticed the gauges made their connections via some metal clips that attch to pins ont he back of the gauges. Well I had a fuel gauge that was inaccurate. it would not show a full tank when there was one. I found out when taking apart the cluster, that the fuel gauge was not seated correctly in its pin sockets.

After i made that little adjustment, the gauge worked perfectly.

Perhaps it is just a loose gauge..

'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.
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Old 12-07-2000, 07:26 PM
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Join Date: Apr 2000
Location: So. Cal
Posts: 4,430
Always learning something new

Like I've said many times, I always seem to learn something on this BB. Today, reading on MB's, I learn about Chevy/GMC's. Now I have clues to start hunting down the source of my inaccurate fuel gauge on the Suburban.

When full, the needle goes way beyond the "F", and I really worry about where the "E" really is. Now, at my next convenience, I'll take a looksie at the gauge cluster.

Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon least its a diesel

Non illegitemae carborundum.
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Old 12-08-2000, 06:59 AM
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I hope all this American vehicle talk doesn't contaminate our Forum somehow. I just got through talking about a Ford truck in another thread, now Chevy/GMC's. This could cause all our MB's to start rattling and staying broken down all the time. It also might make us have to go buy English size wrenches.

My dry and corny humor for the day,
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Old 12-08-2000, 05:16 PM
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Join Date: Apr 2000
Posts: 166

It is my understanding that Chevrolet and GMC pickups are built on the same assembly line. I have also been told that the GMC's get the lock washers.

Your not the only one with corny humor.
1979 240D
165,000 miles
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Old 12-09-2000, 06:31 PM
Posts: n/a

I have done some work in the Chevy/GMC pickup assembly plant in Shreveport. I was telling those guys that my Dad insists that a GMC truck is better built than a Chevy. They thought it was the funniest thing that they ever heard. They said the ONLY difference is the trim that they put on them.

Have a great day,
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