Thermostat in 230SL

[Naj ✝︎]

The temp sender unit sits in a side pod on the left of the cylinder head.
There is a sieve-like adaptor on the head which lets water into the pod.
I wonder if the sieve is silted up not allowing enough waterflow?

Naj

[alchemist]

If you send your gauge for a rebuild, it may cost you about $150. Call Palto Alto Speedometer at 650-323-0243, they might be able to fix it, if not, they will suggest someone. They are experienced in repairing MB gauges.

[ctaylor738]

Earlier, I posted that vintageeuroparts.com was selling new gauge assemblies for $325.  I was told by Babak that they would work in a 250SL.  Two of us in the DC area bought these gauges.  They do not work when installed in the car because the "bourdon tube" hits the side of the instrument pod, and does not allow the needle to move.  My friend Ray was able to get his to work by enlarging the mounting holes enough to move the tube away from the pod's side. 

The unit pictured on Babak's web site would work, but the units shipped have the bourdon tubes protruding from the right side.

Babak agreed to a refund.

Cheers,

CT

[Jonny B]

To clarify, the sending unit is filled with ether (don't know which one). I did some poking around the site (with the search function ) on google, and my mechanic to verify. The thing to be careful of is trying anything with flames around the tube, or potentially broken tube.

[ctaylor738]

One other interesting thing from this exercise.  One of the gauges worked, but read low.  It turned out to have a kink in the tube.  When the tube was straightened, it started reading normally.  Decided on replacement out of concern that the kink had weakened the tube and that it would break.

[Harry]

I am about to have some time to get back to the temperature gage on my 230SL but it's behavior has me a little puzzled.  As I have said before, it is functional but does not seem to reading the correct temperature.  It never shows above 140F (or so) even though I have confirmed with two separate IR guns that the temperature at the engine and radiator is around 180F.  The puzzling part of this is that the gage would work at all if there were a leak in the capillary or otherwise.  It would seem that a leak anywhere would render the gage inoperable - there would be no corresponding pressure buildup.  Does this logic stand to reason or has anyone else had experience where the gage was functional but had a leak?  Curious.

Thanks,
Harry

[ja17]

Seems like your gauge is just out of calibration. It usually works or it doesn't work (no in-between). So maybe the needle on the gauge got bumped out of calibration when the dash was apart. Should be an easy fix for someone if this is the case. I think these units are filled with alcohol not mercury? When the system is accidentally cracked open all the vaporized alcohol escapes. I heard that the units are repaired by fixing the leak, re-filling the bulb with alcohol and resealing it (soldered at the bulb end), then re-calibrating the gauge. The unit is chilled while during  the soldering process to keep the alcohol from turning to vapor an escaping.  I am not sure that this is an accurate description of the process , but it sounds logical. Al Liefring is our resident instrument specialist. Maybe he can shed some light on this? Hey Al, are you out there?

[Naj ✝︎]

Could it be that the pod where the sensor bulb fits is silted up and not allowing a full flow of the coolant

Naj

[Harry]

Please excuse me if you're seeing this post twice.  It's clear that the most recent prior post was March 12.  I expect that was my last post but that content isn't visible (to me) on the forum - so I will post again.

This pertains to the temperature gage that is still showing 140F with a warm engine, when I have verified through two separate IR guns that the actual temperature is 180F.  The consensus seemed to be that the gage must have a leak but I question that because it would seen a leak would manifest itself with a totally inoperable gage instead of one that is partially operable.  If there is a leak, how can any pressure build up?  I was wondering if there has been similar experience with a temperature gage simply indicating the wrong temperature?

Thanks,
Harry

[Peter van Es]

Harry... what do you mean that you cannot see the two replies to your original post?

[Harry]

Peter - thanks for the prompt inquiry.  "Operator error" on my part.  I failed to see that there were multiple pages and the first page happened to end with a post of my own.  Sorry.