Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help

Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Vintage Mercedes Forum

LinkBack Thread Tools Display Modes
Old 07-05-2018, 12:32 PM
Registered User
Join Date: Jun 2010
Location: Miami Beach, Florida
Posts: 472
Water temp. sensor or temp. gauge, which one is it?

On my 76 280C, the temp needle fluctuates, from the midway mark down to about an eighth of an inch below that.
Sometimes even more. It seems that in the freeway it goes a little above the midway mark. I thought that on the freeway it should drive cooler.
Is my water temp sensor taking a dump or is it my gauge?
The car has new thermostat and new water pump and new coolant. Clutch fan was replaced about two months ago.

Thanks in advance

1976 280C
Reply With Quote
Old 07-05-2018, 02:12 PM
Registered User
Join Date: Jan 2012
Posts: 6,158
It's probably OK, is this movement new? You might be seeing the thermostat cycle at low / mid speed and the higher speed, higher load is keeping it open.

I have seen low coolant move the gauge around but it is usually more of a dramatic swing.

You could hang a ohm meter on the ( disconnected ) coolant sender and watch for movement.

A trick for determining thermostat opening point.

With an overnight cooling of the engine, start engine and let idle. Watch the temp climb, at some point it will drop a bit due to cold water in the radiator entering the engine, this is the thermostat opening temp. The temp will then climb back up, stat open again but the drop will be less than the first go around. At some point there will be a barely discernible fluctuation as the stat cycles.

This works for most cars however, radiators with a bleed line or heater hose returning to the return side tank ( 80's GM ) the drop in temp during stat opening will be less apparent.
Reply With Quote
Old 07-05-2018, 05:29 PM
Registered User
Join Date: Jun 2010
Location: Miami Beach, Florida
Posts: 472
Yes, this is new. There was always a fluctuation but now it seems that it's more aggressive. My needle never went up to the half way point and it never passed it.

1976 280C
Reply With Quote
Old 07-06-2018, 09:39 AM
meltedpanda's Avatar
Certified Benzaholic
Join Date: Mar 2003
Location: Central Ky
Posts: 6,090
mid point is fine, and under load it will get hotter even at highway speeds. I suspect you are now seeing normal operation after the new thermostat installed
2011 Porsche Cayman - Bond,James Bond
99 E320 THE Queen Mary
62 220b - Dolly - Finally my Finny!
72 450SL, Pearl-SOLD
16 F350 6.7 Diesel -THOR
07 Lexus RX 350 - Lexi
14 38HP John Deere 3038E Tractor -Mean Green
84 300SD, Benjamin -SOLD
71 220 - W115-Libby ( my first love) -SOLD
73 280 - W114 "Organspende" Rest in Peace
81 380 SL - Rest in Peace
Reply With Quote
Old 07-06-2018, 03:20 PM
Registered User
Join Date: Apr 2016
Location: CA
Posts: 106
My car does the same thing and I did everything you did as well as re-core the radiator. And on the highway, mine drives around 200F-212F and sometimes just slightly higher than the 212F mark. I want to get my timing set and see if that'll help.
Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

All times are GMT -4. The time now is 01:25 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page