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Old 07-13-2020, 06:35 PM   #1
Beach-Burban
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???Coolant Temperature Sending Unit???

I just got back with the Beach-Burban from a 3 1/2 hour drive (7 hour round-trip...longest distance since I've owned it) and I had a little anxiety because my temperature gauge would pin itself under certain conditions, causing me to pull over just to find that the engine was NOT overheating! The Burb drove beautifully in every other way: Plenty of power (454); speeds between 65 and 75; long uphill grades; TH400 never acted up; oil pressure held firm; no pre-ignition or detonation; no loss of coolant (not even in the overflow tank); no extreme heat radiating from the engine bay; and no crackling noises when shutting the engine down. This held true even when driving with air temperatures of 101 degrees! The gauge would float between the high mark to the pinned position depending on the grade I was on, but never affected drivability to the point that I had to say, screw it...there must be a communication problem between the sending unit and the gauge!?!? The radiator was flushed a couple years ago and fitted with a new pressure cap, as well as having a new sending unit installed because the old (original?) was dead...but during that time period, I had only been driving an hour or so at a time (and mostly coastal areas) so the gauge maxed out a little above the middle line. Do sending units have different ranges of temperature levels? Is it possible I installed the wrong unit...or is it more likely that the original gauge needs calibration? Baffled, yes...but very happy with the overall performance of the Beach-Burban! Any help would be appreciated!

Woody
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Old 07-13-2020, 06:51 PM   #2
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Re: ???Coolant Temperature Sending Unit???

Your problem is the reason most older vehicles end up with an aftermarket gauge pack. I hate staring at an OEM gauge and wondering if it is right or wrong. Stewart-Warner i still around for a reason. That being said, make sure your block, frame and cab all have good clean grounding straps. Then look at the sensor, and maybe swap it. If that doesn’t fix it, it means the gauge or voltage regulator for gauges is bad.
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Old 07-13-2020, 07:02 PM   #3
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Re: ???Coolant Temperature Sending Unit???

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Originally Posted by maynardogle View Post
Your problem is the reason most older vehicles end up with an aftermarket gauge pack. I hate staring at an OEM gauge and wondering if it is right or wrong. Stewart-Warner i still around for a reason. That being said, make sure your block, frame and cab all have good clean grounding straps. Then look at the sensor, and maybe swap it. If that doesnt fix it, it means the gauge or voltage regulator for gauges is bad.
Thanks maynardogle...I'll look into that! I felt like I was violating a major car-guy code by driving with a pinned temp gauge! It goes against everything I was ever taught!

Woody
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Old 07-13-2020, 10:14 PM   #4
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Re: ???Coolant Temperature Sending Unit???

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You might want to read through this thread.

http://67-72chevytrucks.com/vboard/s...d.php?t=808324

He was having the same problem recently....

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Old 07-14-2020, 03:19 PM   #5
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Re: ???Coolant Temperature Sending Unit???

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-
You might want to read through this thread.

http://67-72chevytrucks.com/vboard/s...d.php?t=808324

He was having the same problem recently....

LockDoc
Thanks for the link, Leon...very similar indeed! I copy and pasted my post into that thread and will be following along to see if I can learn more.

Woody
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Old 07-15-2020, 05:17 PM   #6
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Re: ???Coolant Temperature Sending Unit???

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Thanks for the link, Leon...very similar indeed! I copy and pasted my post into that thread and will be following along to see if I can learn more.

Woody
***kind of an update***

The other thread Leon linked for me has more than just one person with the same issues...so I went looking at old threads on the subject. This problem has been going on for many years, and it appears that it could be related to the quality of replacement parts!? I also read that with the inferior replacement parts, they will be accurate from "cold" to 180 degrees...but above 180, they start reading way hotter than the actual temperature. This could be why I haven't had an issue for two years? This is what I posted on the other thread:

While searching for additional threads on this topic, I read a number of posts that "might" explain the problem that some of us are experiencing. Apparently there is a consensus that GM temperature gauges for our trucks "changed" in 1979 and the new resistance values of the gauges required a temperature sending unit that had a different resistance curve. That could explain some issues if the wrong year sending unit was used. Additionally, a number of members reported that even when they ordered a replacement sending unit for the right year of their gauge, there was no certainty that the replacement would have an accurate resistance curve...and I guess that this issue was so widespread, that American Autowire started making a reproduction of the GM #1513321 sending unit with a precise resistance curve to match the 1978 and older gauges. I read enough success stories to situations that sounded so much like our issues, that I payed the $27 to have one sent to me. I'll let you all know if it was worth it!

Woody
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Old 07-15-2020, 07:28 PM   #7
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Re: ???Coolant Temperature Sending Unit???

Hey Woody, just ran through this thread. For what its worth, my '72 big block had the exact problem you describe when I purchased it....

my solution however was to install a built 6.0L LS motor lol:

But seriously, that did "fix" the problem, but is definitely not why I did the LS swap. Hopefully your fix is equally effective while being far more economical!!
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Old 07-15-2020, 08:09 PM   #8
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Re: ???Coolant Temperature Sending Unit???

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Yes, it will be interesting to see if that cures it.

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Old 07-22-2020, 05:54 PM   #9
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Re: ???Coolant Temperature Sending Unit???

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Yes, it will be interesting to see if that cures it.

LockDoc
Well...I just got back from a 2 1/2 hour (one way) drive to monitor the readings with the new sending unit...and I would say that it was a "semi-successful" remedy!? If any members are familiar with "the 5 Freeway Grapevine" in So Cal, you'll know what a grueling test that is for a cooling system (more so for our older vehicles). This has been the site of countless "boil-overs" thoughout the years...to the point that there are radiator water spickets all along that section of the grade. Anyway...that's where I conducted my testing, and overall the answer is yes...the readings on the gauge more closely represent what's going on under the hood! The gauge never once pegged itself, even though it was indicating a very high temp reading...but then recovered quickly when the grade flattened out. I can live with that, however, I still want/need to know what the actual coolant temperature is when it gets that high...so I'm going to install an under dash gauge (and matching sending unit) that has gradient numbers in degrees. I'll report back after more testing!

Woody
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Old 07-22-2020, 11:35 PM   #10
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Re: ???Coolant Temperature Sending Unit???

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Originally Posted by Beach-Burban View Post
Well...I just got back from a 2 1/2 hour (one way) drive to monitor the readings with the new sending unit...and I would say that it was a "semi-successful" remedy!? If any members are familiar with "the 5 Freeway Grapevine" in So Cal, you'll know what a grueling test that is for a cooling system (more so for our older vehicles). This has been the site of countless "boil-overs" thoughout the years...to the point that there are radiator water spickets all along that section of the grade. Anyway...that's where I conducted my testing, and overall the answer is yes...the readings on the gauge more closely represent what's going on under the hood! The gauge never once pegged itself, even though it was indicating a very high temp reading...but then recovered quickly when the grade flattened out. I can live with that, however, I still want/need to know what the actual coolant temperature is when it gets that high...so I'm going to install an under dash gauge (and matching sending unit) that has gradient numbers in degrees. I'll report back after more testing!

Woody

Glad to hear things are more "normal". Not at all familiar with that highway but it sounds like that would be the supreme test.

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Old 07-31-2020, 07:54 PM   #11
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Re: ???Coolant Temperature Sending Unit???

***Update on Temperature Gauge***

So I ordered a couple of Stewart Warner gauges and a two hole under-dash panel bracket...an Ammeter, as my original hasn't worked since I bought the Burb, and a mechanical Temperature gauge to help analyze what my original gauge is telling me. I did a little research and found that these mechanical gauges will accurately measure the temperature of any liquid, so I plan on using this one to monitor my A/T fluid after I sort out things with my water temperature.

I utilized a plugged 1/2" NPT hole on the drivers side head of my 454 so that I could still keep the electric sending unit operating...which makes comparing the two gauges much easier. As this tapped hole is located a little above the exhaust manifold, I used a couple feet of 1/4" ID X 1/2" OD rubber hose to insulate and protect the capillary tube (all the way past the firewall and into the cab), as well as some thin metal tape (crumpled up for a better insulation factor) from the Sender Bulb out past the manifold a ways (as a heat shield).

After refilling and "burping" the coolant to the best of my ability, I went out for a 45 minutes drive in our local hills of Palos Verdes. Not much of a test compared to the "Grapevine", but I mainly wanted to get any air pockets filled in with coolant, check for leaks and compare "around town" readings. At the halfway point of the drive, I stopped and found that the radiator had sucked coolant in from the recovery tank (it was at the "Full Hot" line when I left, and was now at the "Add" line) so I topped off the recovery tank and headed for home. Once home, I checked the recovery tank again, and as it was still at the "Full Hot" line, I believe all air pockets should be gone.

Results:
Spoiler alert...the two gauges did not read anything close to what I had expected, but I didn't take any pictures until I got home! While driving, the S/W gauge read between 200 and 210 almost the entire drive (after initial warm-up of course), but when I pulled into my driveway and sat with the motor running, it stabilized at what looked like 212 degrees. While driving, the factory gauge had been holding steady just about on top of the first mark past "C" (well technically, it's the second mark past "C"), but in my driveway with the motor running, it rose to about halfway between that first mark and straight up. I then decided to shut the motor off (with the key in the "ON" position) and see how much the temperature would rise without any circulation/fan. The S/W topped out at just above 230, and the factory gauge made it to just above straight up.

Now I do realize that there are "control issues" with the testing methods in place here...brand new mechanical gauge verses a 48 year old electric gauge (with a new American Autowire sending unit)...and...mechanical sender bulb installed in the water passage of the head verses electric sending unit installed in the water passage of the intake (right next to the T-Stat)...but I was expecting/hoping for something that I could say "well, that makes sense"...but I'm still puzzled! I guess I need to return to the "Grapevine" so I can compare what the S/W gauge reads when the factory gauge reads past the "H". Once again...I'll report my new findings!

Woody

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Old 07-31-2020, 10:38 PM   #12
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Re: ???Coolant Temperature Sending Unit???

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The more accurate reading would be where you have the mechanical sender bulb in the head, the intake port where you have the electric will read cooler....

210 is not out of line for a big block. There should be another one of the head ports on the passengers side at the back of the head by #8. The temp there usually reads a little higher than the one on the drivers side by #1.

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Old 08-01-2020, 10:03 AM   #13
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Re: ???Coolant Temperature Sending Unit???

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The more accurate reading would be where you have the mechanical sender bulb in the head, the intake port where you have the electric will read cooler....

210 is not out of line for a big block. There should be another one of the head ports on the passengers side at the back of the head by #8. The temp there usually reads a little higher than the one on the drivers side by #1.

LockDoc
Thanks Leon...what you said about Head port readings verses Intake port readings makes total sense, especially considering that the heads/block are what we are trying to protect (as opposed to the Intake)...but how much difference should we expect? If I was a little more "obsessed " with knowing that answer, I'd swap locations of the sender bulb and electric sending unit...then record those results...but I just got everything buttoned-up so nice, and what I really want to know is whether or not I am close to doing damage when the factory gauge is maxed out?

So if 210 isn't out of line for a big block...when should I start to worry?

Woody
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Old 08-01-2020, 05:34 PM   #14
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Re: ???Coolant Temperature Sending Unit???

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Originally Posted by Beach-Burban View Post
Thanks Leon...what you said about Head port readings verses Intake port readings makes total sense, especially considering that the heads/block are what we are trying to protect (as opposed to the Intake)...but how much difference should we expect? If I was a little more "obsessed " with knowing that answer, I'd swap locations of the sender bulb and electric sending unit...then record those results...but I just got everything buttoned-up so nice, and what I really want to know is whether or not I am close to doing damage when the factory gauge is maxed out?

So if 210 isn't out of line for a big block...when should I start to worry?

Woody

I never did a scientific test on it but I think 10 - 15 higher at the head.

220 - 225 all the time on the open road I would start to worry. Others may disagree.

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Old 08-02-2020, 07:14 AM   #15
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Re: ???Coolant Temperature Sending Unit???

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I never did a scientific test on it but I think 10 - 15 higher at the head.

220 - 225 all the time on the open road I would start to worry. Others may disagree.

LockDoc
Thanks Leon...When I do the next "Grapevine" test, the results should be very telling!

Woody
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Old 08-02-2020, 10:49 PM   #16
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Re: ???Coolant Temperature Sending Unit???

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Thanks Leon...When I do the next "Grapevine" test, the results should be very telling!

Woody
Let us know how it goes.

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Old 08-05-2020, 12:37 PM   #17
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Re: ???Coolant Temperature Sending Unit???

Got back yesterday from another "Grapevine" road-test...and the results are indeed "very telling"! Bottomline is: my radiator needs an old fashion boil-out, rodding...or core replacement. The block and head water passages might need some "descaling" as well. It's my intention to stick with the copper/brass original style 4 core, which is why I'm going to a friend recommended shop, as they actually work with your radiator instead of the quick "scrap and replace with new junk" approach. I hear a lot of pros and cons regarding aluminum radiators...but I'm not sold on that idea (yet).

Temperature gauge results:

Photos one and two: my normal around town and freeway temps when fully warmed-up.
Photos three and four: my "new" normal freeway temp with just a slight grade.
Photos five and six: Going up the Grapevine!!! Truth is, right before I hit the summit, the gauge was kissing 250 (no photo), but over the summit on the down side, it did back off to the 230ish range!
Photo seven: The recovery tank was doing it's part on this drive, where it wasn't needed on the last one (without knowing the numbers). My fresh green coolant is now a rusty brown color, but I still didn't lose any coolant and the motor did not "act" as though it was over-heating...but I can tell things are going in the wrong direction!

I stopped at the bottom of the grade and had a "Dave's Double" at Wendy's...and sat for a while. When I finally started it back up, the radiator started guzzling up the coolant from the recovery tank...but no more than it expelled into it (as far as I can tell?). Nothing significant to report on the way home, but of course, my "new" normal freeway temp stayed in the 230 range. I stopped for a while at my best friend's house when I was about an hour from home...and got stuck in traffic (an accident) when I left, but things stayed pretty much the same at the slower speeds. Off the freeway and in beach city driving conditions, the "new" normal stayed around 220ish, so a stop at my friend's repair shop confirmed what I already suspected...dirt/rust/debris clogging the radiator is the prime suspect. A flushing will be the first step, but it's doubtful that this will be a cure...but when it's all sorted out, I will once again compare the readings between the Stewart Warner mechanical gauge and the factory gauge utilizing both of the electrical sending units (TS6S and American Autowire). Report will be coming...but don't hold your breath...it's going to take me a while!

Woody

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Old 08-05-2020, 12:39 PM   #18
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Re: ???Coolant Temperature Sending Unit???

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Old 08-05-2020, 01:04 PM   #19
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Re: ???Coolant Temperature Sending Unit???

I've got both aluminum and copper radiators in vintage vehicles. The cost of a completely rebuilt copper radiator is more.
In my experience copper lasts longer and are repairable. The only way an aluminum radiator can be repaired is with epoxy.
A friend of mine just tried to have his brand new aluminum radiator epoxied and it didn't work. He is going to try it again doing it himself this time. They took their newly (LS) repowered Nova out for a test run with no grille installed and took a rock dead center in the new radiator and broke 2 tubes. And I thought I had bad luck!
Anyway long stupid post, but yeah copper is good. That's what I have in my Burban. The aluminum radiators I have used are generic roundy round ones that are dirt cheap but require making mounts.
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