How to install a temperature gauge in a '70 Chevelle?

[Lebowski]

I bought this car last November and drove it occasionally the last few months when the roads were clear and the weather was cool but now that it's warmed up I decided that it needs a temperature gauge. I drove it for two hours today in 90 degree heat and had no idea how hot the engine was. I looked at some videos on YouTube and they mentioned both electrical and mechanical gauges. What's the difference and which one should I use? I've never installed one before but I thought I would try to do it myself before looking for someone else to do it. I don't need a battery or oil gauge-just the temperature one. Thanks in advance for any comments and advice...

 

 

[oily rag]

The bulb type or mechanical are easier to install. They normally are installed  by removing a pipe plug. The electrical units install the same way and require a power source controlled by the ignition switch.

[capngrog]

While you're deciding on what kind of gauge to install and where to install it, you should get one of these:

 

https://www.walmart.com/ip/Etekcity-Digital-Thermometer-Laser-Infrared-Temperature-Gun-Lasergrip-1080/39881573?athcpid=39881573&athpgid=athenaItemPage&athcgid=null&athznid=PWVAV&athieid=v0&athstid=CS002&athguid=466001f5-c95c4f6b-a05cefbe7626a578&athena=true

 

These infrared temperature guns/sensors work really well, and at the price, every tool box (and glove box) should have one.

 

Cheers,

Grog

[caddyshack]

Lebowski, not knowing what you have is a problem. My 396 SS '70 Chevelle had a temp gauge problem, but it turned out to be an electrical sending unit that was shot, not the gauge itself. The sending unit was screwed into the block I believe and it had two electrical leads back to the gauge in the dash. Simple fix, but it was over 40 years ago and memory is fading. If its a bad gauge in the dash I can't help you there. Is the gauge definitely bad? There has to be a video out there that could help with that. Good luck, and beautiful engine by the way.

[bobg1951chevy]

LEWBOWSKI, you don't say here but am thinking you have the 1970 SS 396 Chevelle with the  RPO U 14  full gauge instrumentation, instead of the collection of idiot lights.

Seldom is the dash gauge the problem in a non reading or faulty reading temp. gauge.

Why not buy the engine  block sending unit ( electrical ),   then replace it,    instead of hanging after market gauges under the dash.

Not a tough job to do, at all.

[Lebowski]

33 minutes ago, caddyshack said:

Lebowski, not knowing what you have is a problem. My 396 SS '70 Chevelle had a temp gauge problem, but it turned out to be an electrical sending unit that was shot, not the gauge itself. The sending unit was screwed into the block I believe and it had two electrical leads back to the gauge in the dash. Simple fix, but it was over 40 years ago and memory is fading. If its a bad gauge in the dash I can't help you there. Is the gauge definitely bad? There has to be a video out there that could help with that. Good luck, and beautiful engine by the way.

 

The only gauge that came with the car was the gas gauge unless you count the speedometer and odometer. The other gauges were an option package which didn't come on the car as per the build sheet. I looked at some videos but couldn't find one for installing an aftermarket temp gauge in a '70 Chevelle with a big block. I'm going to go back to YouTube tomorrow and keep looking. Thanks for the kind words and here's what the rest of the car looks like....

 

 

[Lebowski]

4 minutes ago, bobg1951chevy said:

LEWBOWSKI, you don't say here but am thinking you have the 1970 SS 396 Chevelle with the  RPO U 14  full gauge instrumentation, instead of the collection of idiot lights.

Seldom is the dash gauge the problem in a non reading or faulty reading temp. gauge.

Why not buy the engine  block sending unit ( electrical ),   then replace it,    instead of hanging after market gauges under the dash.

Not a tough job to do, at all.

 

I have the idiot lights unfortunately. Please see my previous post.... 

[bobg1951chevy]

So you want to see actual temp., as in a digital gauge ...... or a "needle" display.

 

Beautiful car !

 

Edited May 21, 2018 by bobg1951chevy (see edit history)

[Lebowski]

31 minutes ago, bobg1951chevy said:

So you want to see actual temp., as in a digital gauge ...... or a "needle" display.

 

Beautiful car !

 

 

Thank you. The needle gauge would be fine....

[capngrog]

A popular addition back in those days was an under dash 3-gauge 'cluster' consisting of oil pressure, temperature and volts/amps.  I have such a gauge 'cluster' under dash in my '68 SS 396 Chevelle, and it looks and works fine.  By the way, the stock instruments in the '68 Chevelle are extremely difficult to read in bright sunlight, due to their being recessed a bit too far back in the panel.  That's just my opinion.  Oh yeah, and the stock tach in '68 is so useless that I'd not "hit a dog in the derriere" with it!

 

That being said, my '68 Chevelle SS 396 is one of my favorites ... not just to look at, but also to drive.

 

By the way, Lebowski, that's a really great looking Chevelle.   You'll have fun driving her this summer.

 

There should be a heat gauge sensor already in the engine (block or head) that would have supported the over-temperature "idiot light".  I'm not sure if such a sensor would provide accurate signals to a 'real' gauge, however.

 

Cheers,

Grog

[bobg1951chevy]

One block sensor for the light, another sensor  for the gauge version.

[padgett]

The most desirable is the factory gauge cluser but can be pricy. AFAIR the '70 has a conventional dial tach. Back then just about everything was an option: clock, speedminder speedo, gauges, gauges and tach, clock and gauges, clock gauges and tach....

 

Aftermarket set usually come with everything you need but the mechanical oil pressure comes with a teensy tube that can be slow to respond. Best ones have a 270 sweep, cheap ones a 90 degree. And then there are digital gauges and pods that go on the A pillar.

 

I prefer to run cars cooler than stock - 160 to 170F with a carb, everything seems to last longer and the passenger compartment stays cooler.

 

Just some thoughts.

[Lebowski]

46 minutes ago, padgett said:

The most desirable is the factory gauge cluser but can be pricy. AFAIR the '70 has a conventional dial tach. Back then just about everything was an option: clock, speedminder speedo, gauges, gauges and tach, clock and gauges, clock gauges and tach....

 

Aftermarket set usually come with everything you need but the mechanical oil pressure comes with a teensy tube that can be slow to respond. Best ones have a 270 sweep, cheap ones a 90 degree. And then there are digital gauges and pods that go on the A pillar.

 

I prefer to run cars cooler than stock - 160 to 170F with a carb, everything seems to last longer and the passenger compartment stays cooler.

 

Just some thoughts.

 

It doesn't have a tach. Like I said in my first post, all I want is a temperature gauge. I don't want a digital gauge on the A pillar. I would like to mount a sweep gauge at the far end of the console where most people can't see it. Thanks to you and the others for the comments and kind words....

[padgett]

OK just make sure what you buy is what you need. I prefer a 270 sweep. These gauges need three things: gauge, connectors and tube or wiring, & mounting bracket. Some come as an all-in-one package, others are a la carte. Make sure you buy what you need.

 

ps period correct would be Sun, B-W, and a few others.

Edited May 21, 2018 by padgett (see edit history)

[Matt Harwood]

The first post gets it right--use a mechanical gauge with a bulb-type sender. They tend to be more accurate and I personally like the 270 degree sweep of the needle rather than the 120-degree sweep on the electrical gauges. Some gauge manufacturers also offer two scales--get the one with the lower maximum reading. The ones that read to like 300 degrees don't really do you any good (what engine gets that hot before you notice?) and as a result, the operating range is a smaller portion of the dial. Mine reads to 250 degrees and gives me a much better view of the engine's temperature at a glance and is much more accurate--I can watch the thermostat open and close on it.

 

Temperature gauges will come already assembled so you don't need tubing or anything else, although you might need some kind of reducer bushing depending on where you install it. There should be some threaded plugs, probably in the intake manifold, that you can use to install the gauge bulb into the coolant flow. Failing that, you can always buy an adapter that fits into the upper radiator hose and has a threaded bung that will also put it right into the flow of coolant. Some thermostat housings also have a threaded plug you can use. I can't give you an exact location, but there should be multiple options. On my Mustang where I changed to a mechanical gauge but wanted to keep the original gauge working, I put the mechanical gauge bulb in the original gauge's spot, thinking it was the most appropriate place, then relocated the sender for the factory gauge to another one that may or may not have been as accurate. Since you just have a warning light, that might be a good alternative. The sending unit will be easy to find, just a brass plug with one wire coming out threaded into the intake somewhere, probably on the driver's side. 

 

Electrical gauges aren't any easier to install although I guess the wire is easier to route than the bulb and tubing, which can be fragile. I don't think electrical gauges are as accurate, however.

 

Hope this helps!

[Lebowski]

How about something like this? It doesn't say what else is in the box besides the gauge but it's a Stewart-Warner and it's mechanical. It's on eBay for $45 including shipping. If you don't like this one then which one would you recommend? Thanks....

 

https://www.ebay.com/itm/Stewart-Warner-82326-60-Water-Temp-Gauge-/123097788521?_trksid=p2349526.m4383.l4275.c10

 

 

[Matt Harwood]

That's a mechanical gauge and will have a period-correct look. Price is right, too. There shouldn't be anything else included unless there's some kind of mounting bracket. It should have the bulb and capillary tube already attached and probably a light bulb with either one or two wires--one wire means it grounds through the housing, two wires are power and ground. You can tap into the existing gauge lights and it will dim with the rest of the instruments. Some guys just attach the wire to the fuse, but that seems lazy to me.

 

Go for it!

[capngrog]

Attached are some photos of the three-gauge below-dash panel installation on my 1968 Chevelle.  A friend of mine who owns a numbers-matching 1968 Chevelle has a similar after market gauge set up and says that they are "period correct".  I don't worry too much about the "period correct/numbers matching" stuff, but I like the look of the panel installation.  They work fine and are easy to read.  I think that a similar below-dash setup would be the way to go.  Oh, by the way, I agree with Matt on the advice on the full sweep (270°) mechanical temperature gauge.  The temperature sensor for my gauge is in the left (driver's side) cylinder head of the 396 engine.  As Matt stated above, I think the best location for a temperature gauge sensor would be in the vicinity of the thermostat.

 

Below are some photos of the gauge cluster in my Chevelle.

 

Cheers,

Grog

[Lebowski]

I ordered the gauge pictured above in post #16 and will let you guys know how the installation goes one way or the other. Thanks again for the advice, comments and kind words regarding the Chevelle.... 

[ted sweet]

170 is too cold. engine wear increases

[cheezestaak2000]

off topic, but kind of relative.in the late 70's, we got a service/recall buletin for the olds omega with the v6 engine. it seems the oil light would come on sometimes when hot at idle. the braintrust at GM said replace the sending unit with an "updated" one. the replacement wouldn't light the idiot light until pressure dipped below 8 psi. nice fix huh?

 

[Lebowski]

The temperature gauge arrived yesterday and I don't see any places to shove the tubing through the firewall so is there a certain plug or whatever I should remove or do I just need to drill a hole about 1/2" in diameter? Thanks....

[Matt Harwood]

The steering column boot is a popular place, it might have enough room to squeak the bulb through. Or maybe over by the heater box? I'm trying to remember the firewall of our last Chevelle and think of other possible spots. I do object to drilling fresh holes in a firewall, but perhaps there's a place where there could have been a hole that you can find and use. Try to use a grommet if you find a clean hole that the bulb will fit through, it will seal up better and protect the somewhat fragile sensor line.

 

I'll try to go over to the shop this weekend and look at the 1970 El Camino we have sitting there and see if I can spot a suitable spot for you.

Edited May 26, 2018 by Matt Harwood (see edit history)

[Lebowski]

2 hours ago, Matt Harwood said:

The steering column boot is a popular place, it might have enough room to squeak the bulb through. Or maybe over by the heater box? I'm trying to remember the firewall of our last Chevelle and think of other possible spots. I do object to drilling fresh holes in a firewall, but perhaps there's a place where there could have been a hole that you can find and use. Try to use a grommet if you find a clean hole that the bulb will fit through, it will seal up better and protect the somewhat fragile sensor line.

 

I'll try to go over to the shop this weekend and look at the 1970 El Camino we have sitting there and see if I can spot a suitable spot for you.

 

I found a small screw hole below the steering column which comes out below the master cylinder which I drilled out but my largest drill bit is only 1/2" and I need to make the hole about an inch in diameter to fit the tube and other piece (that screws into the top of the sending unit) through. I'm going to call a couple of people to see if they have a one inch drill bit so we'll see what happens....

[Matt Harwood]

I might recommend one of those step bits rather than a 1-inch drill bit. That will grab and shred sheetmetal, while with the step bit, you can sneak up on it and not have a big jagged hole. Plus your drill won't fight you in such close quarters. Remember the grommet, too!

[Lebowski]

7 minutes ago, Matt Harwood said:

I might recommend one of those step bits rather than a 1-inch drill bit. That will grab and shred sheetmetal, while with the step bit, you can sneak up on it and not have a big jagged hole. Plus your drill won't fight you in such close quarters. Remember the grommet, too!

 

I figured it out. I used a small bit and drilled a couple of holes next to the big hole and made them bigger until they merged with the big hole and I could get the piece through. I hooked up the sending unit and let the engine run for 5 minutes and it went up to 180 degrees which is about right since it was about a gallon low on coolant. I'm cooling off now since it's 88 degrees here with the humidity at about 110%. After dinner I'm going to put some electrical tape around the tube where it goes through the hole and jam a small rag into the hole and then mount the gauge at the front end of the console. I'll post a pic later if everything goes according to plan. Thanks for the help.... 

[capngrog]

Where do you plan to mount the sensor?  Looking at the photo in your Post #1, it appears that the sensor for the electrical "idiot light" is located in the driver's side cylinder head, just below the valve cover between cylinders 3 and 5.  You should be able to install the mechanical sensor into the same spot, unless you want to keep the "idiot light", in which case you'd want to install the mechanical sensor as discussed in Posts #15 and #18.

 

Cheers,

Grog

[Lebowski]

1 hour ago, capngrog said:

Where do you plan to mount the sensor?  Looking at the photo in your Post #1, it appears that the sensor for the electrical "idiot light" is located in the driver's side cylinder head

 

That's where I put the sensor. I put the gauge at the end of the console and took it for a drive and it works great.... 

 

 

[Lebowski]

I drove the car for about 45 minutes in 90 degree heat and it was at 200 degrees when I got home. I know the boiling point of water is 212 degrees so is 200 degrees acceptable? If not what can I do to get it to run cooler? I have a mixture of antifreeze and water in the radiator....

[Matt Harwood]

200 isn't anything to worry about in hot weather. The cooling system is pressurized, so it should be good to 225 or so before it actually starts to steam and I bet if you had gotten it out on the road with air moving through it at about 45-50 MPH, it would have chilled down a bit. It also depends on what thermostat you have in it. I'm not sure what the Chevelles came with, but I wouldn't be surprised if it was a 192 degree unit, which is pretty common in production cars. So you're not too far off that mark. It does the car no harm and if it held at that temperature, you have nothing to worry about. If it starts to climb past that then maybe there is some investigating to be done, but what you're describing sounds normal to me. As long as it's consistent, it's all good. You might try a 180 degree thermostat, but remember that the thermostat only controls the minimum temperature at which the engine will run, not the max. It merely gives you a bigger reserve and if it's seeing 200 degrees, I don't know that a cooler thermostat will make much of a difference. It might take a little longer to get to 200, but it will get there eventually. The important thing is that it stays there and doesn't keep climbing.

 

With a gauge that's accurate, you're going to be tempted to watch and worry. You'll eventually get a good idea of what's "normal" for your car. They're all different and as long as it isn't blowing steam or losing coolant, you're not in any danger. If it didn't overheat before the gauge, it won't overheat afterwards--you just know where it is now. Don't worry, have fun!

Edited May 31, 2018 by Matt Harwood (see edit history)

[Lebowski]

After driving it on hot days it usually leaves a puddle on the garage floor from the radiator overflow hose. Every 2-3 weeks I add some water or antifreeze the next day after the engine is cool. It doesn't make a knocking sound like it's overheating so I figured that's normal. Thanks for the input....

[Bill Stoneberg]

Yes, my Buicks do the same thing. Eventually, if I dont add water, the radiator finds the level it likes.  Try not filling it and see what happens next time.

[Lebowski]

4 hours ago, Bill Stoneberg said:

Yes, my Buicks do the same thing. Eventually, if I dont add water, the radiator finds the level it likes.  Try not filling it and see what happens next time.

 

I've tried that but the radiator is more than half empty. Won't the engine run hotter if there isn't enough coolant in it?

[Bill Stoneberg]

4 minutes ago, Lebowski said:

 

I've tried that but the radiator is more than half empty. Won't the engine run hotter if there isn't enough coolant in it?

 

Thats a lot   Buicks fall to just over the cores   half empty is a lot.

[capngrog]

3 minutes ago, Lebowski said:

 

I've tried that but the radiator is more than half empty. Won't the engine run hotter if there isn't enough coolant in it?

 

Well, try the easy things first.  I'd take a look at your radiator cap, because it may be opening at too low of a pressure.  The radiator cap on my 1968 SS 396 is rated at 16 psi.

 

Good luck and let us know how it works out.

 

Cheers,

Grog

[mike6024]

Also consider retrofitting a recovery tank, in place of the simple overflow tube.

[Lebowski]

Mine has a 15# cap. Would a higher or lower number help it to run cooler? 

 

I'm trying to keep the car as original as possible but would a recovery tank help it to run cooler? I would consider installing one if it would. 

 

Thanks to both of you for your input.... 

[capngrog]

2 hours ago, Lebowski said:

Mine has a 15# cap. Would a higher or lower number help it to run cooler? 

 

My point was that your cap may be defective.  If it is venting out of the radiator overflow hose and your engine is only running at a maximum temperature of 200° F, then something is wrong.  My guess is that the spring on your 15 psi cap is a little weak.

 

Cheers,

Grog

[Lebowski]

1 hour ago, capngrog said:

 

My point was that your cap may be defective.  If it is venting out of the radiator overflow hose and your engine is only running at a maximum temperature of 200° F, then something is wrong.  My guess is that the spring on your 15 psi cap is a little weak.

 

Cheers,

Grog

 

The cap is brand new but I know it could still be defective. So would you recommend a 20# cap or a 10# cap or what? Thanks....

[JACK M]

A different cap would probably not effect the temperature much.

 As suggested your cap could be bad and not living up to its advertising. 

But a recovery system would save you some grief.

Works on a blow me suck me principle, as the coolant expands it will bypass the cap and be saved it the reservoir, then when it cools it will get sucked back in to the radiator, so you should not lose coolant anymore.