This has been going on for months. The situation is similar to this (http://www.elcaminocentral.com/showthread.php?t=41948) member's epic thread. Truck seems to have one of three "modes":



Normal water temp (~180)
Slightly hotter (~210)
Frighteningly hot (~230)

I never know which mode I'll get. Today going to work, I got mode 1; on the way home, mode 3. Mode does not seem to be influenced by outside air temperature or driving conditions. In all modes, car starts and runs fine. Radiator has never boiled over or anything dramatic like that.

Have replaced cap and thermostat. No leaks anywhere. Fan clutch is working correctly. Shroud is in place. Radiator hoses are in good shape as is the radiator itself (as far as I can tell).

So now I'm starting to suspect the gauge may be faulty. Today I popped the hood with the gauge reading ~230 and placed a digital thermometer on the thermostat housing. The highest temp I measured was 159. I know nothing about thermodynamics, but I find it hard to believe the thin steel of the housing would create a 71 degree difference in temperatures.

And so I turn to the wisdom of ECC. I think the next step should be to replace the sender. Any and all suggestions welcome.

Smart move to change gauges. By your description, sounds like a likely suspect. http://www.turbobuicks.com/forums/images/smilies/yup.gif

I fully appreciate your frustration, I also have been chasing the same scenario on a brand new build
(other than the # 1 mode...mine only lingers there for 10 minutes before going to 2 or 3)
When you say digital thermometer....are you talking about an Infrared "gun" or something else?

Does the engine actually "feel" hot? or seem hot? When it`s registering as hot (230) you should be able to turn on the heater / fan to high (I know....when it`s already 100 degrees...it`s crazy) and pull the gauge down considerably temporarily. That may tell you if your gauge is functional.

I`ve been using one of the gun type infrared thermometers, extremely easy, and I`ve been told extremely accurate, and I`m still having issues....but I`ll get it eventually. it`s driveable with ac on...for 30 miles (longest trip I`ve taken) in 100 degree heat....and I`ve been workin on the interior, so I stopped chasing the 220 degree problem.
Good luck..

Hasbeen

red5,
I apologize:dontknow: I re read your post and clicked on the link about the epic problem....
missed it the first time and didn`t realize you were talking about me.

Please disregard any suggestion, or advice from me.

It`s pretty obvious that a guy that can`t solve his own problems shouldn`t be taken seriously, while attempting to solve somebody elses:nanawrench:

that`s funny....had to laugh at myself.


again ...Good Luck...a lot of members chimed in on my original problem with good advice , and tests. I`m sure somebody will be able to help.

Hasbeen

I followed your adventure closely hoping for a solution that would apply to my situation as well. I cannot disregard your advice as I thought you tackled the problem in a rational and meticulous manner. It is an extremely frustrating problem; am I destroying this engine or stressing over nothing?:let_it_all_out:

The thermometer I used is this multimeter (http://www.lowes.com/pd_292758-12704-61-312_0__?productId=3201657&Ntt=multimeter&pl=1&currentURL=%2Fpl__0__s%3FNtt%3Dmultimeter&facetInfo=) in which supports a thermocouple. I have no reason to doubt its accuracy. With the engine running and the gauge at 230, I can palm the top of the radiator and cap without too much discomfort. If it was genuinely running at 230, I doubt I could do that without getting burned.

I'm going to replace the sender and report back here with the results. :dontknow:

Red5,, can you put in a temp mechanical gauge to get the true motor temp?? It does sound like a faulty gauge,, I would put in a temp gauge to rule out any over heating,,matty man

red5,

The fact that it doesn`t feel overheated to the touch is probably the best news I`ve heard.
I tried what Matty Man said...My company sells Stewart Warner Gauges, so I pulled one off the shelf and even left it partially in the package while hooking it into the intake.
It`s actually still under the hood for later reference.
http://www.kodakgallery.com/imaging-site/services/doc/5409:102851032213/jpeg/BG

http://www.kodakgallery.com/imaging-site/services/doc/5409:905871032213/jpeg/BG


There is a small desparity between it and my temp gun at the intake (I assume from heat transfer, or the actual water temp is slightly hotter than the intake)

Either way, back when I "worked for a living" I remember being able to hold a 180 degree hose....even if breifly. I`m pretty sure I couldn`t hold onto a 220 degree hose, so your description of being able to, on yours, is way encouraging.

We`re only as good as our tools and equipment, sounds like your sender or guage is giving bad information.

Keep us posted.

Hasbeen

From the nothing-is-easy-department: got a new sender. When I get home, I see the unit is different than what is in the car. The new unit has two prongs. The one in the car supports only a single wire:

http://i.imgur.com/Yud2e.jpg

After thinking about it for a minute, I may have a reason for the difference. The car is badged as an SS and has an SS dash (e.g. round gauges, no sweep), but I'm 99% sure its a clone (truck has a 350 which was not an option for the SS model in 1970).

So does anyone know if the SS sender is different than the non-SS sender?

I've only seen a one-wire temperature sender. It uses the head as a ground.
My '84 came with the gage package, and I had a problem with all gages being somewhat flaky, noticed it more with the voltmeter and water temp, oil pressure and gas gage were not bad. After a couple professional misdiagnoses, I found the actual problem to be the connector at the back of the instrument cluster. The connection is just copper tabs on the dash connector resting on bare spots on the gage printed circuit. Cleaned both sides with contact cleaner and gentle buff with scotch brite. Gages work fine after that.

My 68 has a factory gauge. It has only 1 wire, 2 wires are for idiot lites, the sending unit makes the connection between the 2 wires when it's hot bringing on the light. Unless someone else knows something different that might explain your reading being all over the map.:dontknow:
P.S. you hold your hand on something 220 degrees it will leave a mark!!!
Donny

I think the sensor you want is this one.
https://www.napaonline.com/Catalog/CatalogItemDetail.aspx?A=MPETS6469SB_0092672895&An=599001+101970+50014+2014016
There was a time before handheld multimeters when some would mount a set of gauges under the hood and usually on the firewall so we could monitor things while we were under there tuning.

Yeah that looks exactly like what is in the motor. I'll order one today and let everybody know the results. Thanks for the insight.

The problem I see (if I read it right) is that you have 2 wires? the sending unit and guage only uses one?
This is my guage (before new lens!!)
http://i324.photobucket.com/albums/k326/DONEDEALDONNY/PLASTIC008-1.jpg?t=1311635128 (javascript:void(0);)
This is the back, It looks like only one wire goes to it but I can't remember???
http://i324.photobucket.com/albums/k326/DONEDEALDONNY/PLASTIC009-2.jpg?t=1311635228 (javascript:void(0);)
I hope this helps!!!
Donny