Always at 100* - Page 2 - PeachParts Mercedes-Benz Forum

winmutt · #16 02-25-2009, 04:28 PM

Whats the best place to measure with IR temp?

What about leak testers?

Think I am on the third coolant cap

UriahT · #17 02-25-2009, 05:11 PM

Quote:

Originally Posted by winmutt

Whats the best place to measure with IR temp?

I'd say right at the head where the temp sender is... Then maybe a quick check underneath on the block, but coolant flow should be even throughout.

81veggiebenz · #18 02-25-2009, 05:12 PM

Hey winmutt, I am having the same exact issue.

I have changed the thermostat and hoses, remanufactured radiator, and some other stuff but my car always runs around 90 or 100 degrees.

I thought about getting the laser thermometer too but have not yet.

The actual temp sending unit i have been told is on the engine block but I sware that mine is right behind the thermostat. I cant figure this out either.

Not much help but I will watch this thread closely.

81veggiebenz · #19 02-25-2009, 05:30 PM

Correction above I meant sending unit in the head.

This is not a permanent fix but it is very interesting.
I have not tried it but after changing a bunch of stuff I think it is an option. If diesel giant has done it I dont think it can be all bad.

It kinda boggles the mind and will be interesting to see what poeple here think about it.

But you can count on someone saying fix it the right way.

http://www.dieselgiant.com/thermostatreplacementandmodif.htm

JonL · #20 02-25-2009, 05:49 PM

Quote:

Originally Posted by winmutt

Whats the best place to measure with IR temp?

What about leak testers?

Think I am on the third coolant cap

Never saw confirmation that you have a good thermostat in the car. Did you ever change it, and are you sure it is the correct one?

IMO, the symptoms you've described could be caused only by a thermostat that is the wrong temperature (but still functioning properly), or a fault in the gauge circuit (sender, wiring, gauge).

Mark DiSilvestro · #21 02-25-2009, 06:24 PM

I have this same issue with my '84 NA Euro 300TD and wound up installing a new radiator and thermostat, with no significant improvement in my gauge, which still hovers around the 100 C mark. As it turned out, my old radiator did have signs of very slight seepage from one corner, and having seen a couple '80s Mercedes radiators develop 'broken-neck syndrome', where the upper hose fitting snapped off without warning, I'm glad I replaced mine. Since then I've tested the coolant temp with an old-fashioned dial thermometer and my coolant temp seems to be running around 18 degees below 212 (100C). It's been almost a year now with no evidence of puking antifreeze or other cooling-system distress, even with the AC going, so I stopped worrying.

Happy Motoring, Mark

vox_incognita · #22 02-26-2009, 07:18 AM

Hi,
The temperature sender would measure ohm resistance @ temp.Celsius as follows (roughly,+/-5ohm):
60C-110 ohm
80C-67 ohm
90C-51 ohm
100C-38 ohm
Give it a try+the IR therm.test.

Shawn D. · #23 02-26-2009, 08:15 AM

Quote:

Originally Posted by 81veggiebenz

This is not a permanent fix but it is very interesting.

I have not tried it but after changing a bunch of stuff I think it is an option. If diesel giant has done it I dont think it can be all bad.

The only way that would be "helpful" is if there is air stuck in place by a closed thermostat, which will be irrelevant once it opens the first time. If you must modify it, a 1/16" hole will do the same thing, but will preserve the main function of the thermostat and still allow the car to warm up more quickly.

Jeremy5848 · #24 02-26-2009, 10:58 AM

If both engines have the same problem and given the other work that has been done, I would next suspect the gauge. It may be as simple as a needle that has gotten rotated on its shaft a little.

Graplr · #25 02-26-2009, 11:15 AM

Quote:

Originally Posted by Jeremy5848

If both engines have the same problem and given the other work that has been done, I would next suspect the gauge. It may be as simple as a needle that has gotten rotated on its shaft a little.

Yes, that makes sense. But if I were messing with/recalibrating my needle, I would want 100% verification with a heat gun that it was now reading accurate.

UriahT · #26 02-26-2009, 11:16 AM

Quote:

Originally Posted by Shawn D.

The only way that would be "helpful" is if there is air stuck in place by a closed thermostat, which will be irrelevant once it opens the first time. If you must modify it, a 1/16" hole will do the same thing, but will preserve the main function of the thermostat and still allow the car to warm up more quickly.

I agree, this is not something anyone would want to do, as it negates the good things a thermostat does (aka. regulating temperature).
It'd only really make a difference on short drives, since on longer drives, the thermostat should fully open anyhow. Just makes the engine colder for longer, which will result in a less efficient engine.
I really don't think this would alleviate winmutt's symptoms, since his car maintains temp well. 100* isn't too hot for the car, and it's probably 1) a higher temp thermostat in place, or 2) my guess, an incorrect temp sender. The original owners manual also doesn't urge caution unless the temp goes into the red.

jt20 · #27 02-26-2009, 11:24 AM

anything you did not swap with the engine needs to be inspected first.

temp gauge / sender circuit

pressure cap

Oracle12345 · #28 02-26-2009, 11:47 AM

do you install the thermostat backwards?

installing the tstat backwards will causes issues.

Stevo · #29 02-26-2009, 12:39 PM

You know about the arrow which needs to point up, right? Some T-stats may not have it.

Sbean · #30 02-26-2009, 12:56 PM

Low pressure doesn't cause high temperature; it allows coolant to boil at a lower temperature. Higher pressure allows running at a higher temperature without boiling (vaporizing) coolant.
Steve