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

[Lebowski]

1 hour ago, JACK M said:

 

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.

 

Who sells the recovery tank? Do I have to get one for a different car since the '70 Chevelle didn't come with one or is there a generic one? Thanks....

[playswithbrass]

Different pound rad caps do matter.For every pound increase in the rad cap pressure the boiling point of the cooling system is raised by three degrees.

[JACK M]

All you need is a reservoir of some sort.

Some guys just zip tie a beer can near the overflow hose stick the hose in the beer can so that it is to the bottom.

When the coolant comes out of the hose it is saved until the system cools the the coolant is sucked back into the radiator.

 

But there are these. 

https://www.speedwaymotors.com/Speedway-Polished-Radiator-Coolant-Overflow-Expansion-Tank-3-x-10-In-,2953.html

If you understand the theory they are easy to hook up.

[JACK M]

3 hours ago, playswithbrass said:

Different pound rad caps do matter.For every pound increase in the rad cap pressure the boiling point of the cooling system is raised by three degrees.

 

Agreed, but the car will still run at the same temperature.

I am not a big fan of using high pressure caps ever since I had an aluminum radiator that the tubes swelled from to much pressure and wouldn't ley enough air thru to cool.

Took me awhile to figure that one out.

[Lebowski]

6 hours ago, playswithbrass said:

Different pound rad caps do matter.For every pound increase in the rad cap pressure the boiling point of the cooling system is raised by three degrees.

 

So if I use a 20# cap there's less of a chance that the coolant will overflow after I drive the car on a hot day? Do they make a 30 or 40# cap or is that too much pressure? Thanks....

[DAVES89]

Go back and read post #44. You run the risk of blowing out your radiator coils.

[Lebowski]

1 hour ago, DAVES89 said:

Go back and read post #44. You run the risk of blowing out your radiator coils.

 

I don't have an aluminum radiator. I bought a 20# cap and am going to put it on and go for a drive after dinner in 87 degree heat and see what happens....

[Matt Harwood]

Just remember that the 20-pound cap will not lower operating temperatures and if it does start to overheat, that 20-pound cap will reveal the other parts of your cooling system that are not able to handle 20 pounds of pressure (heater cores and water pump seals come to mind). 

 

The idea of an overflow can is a good one. Just mount something subtle and appropriate and drop the overflow hose into it, making sure that it is submerged below the fluid level, even if you have to add a little fluid to the overflow can to make this happen. It'll overflow when it gets hot and then pull the coolant back into the radiator as it cools off. Totally normal. 

 

I think running at 200 degrees on warm days is just fine and will not cause problems. If it starts to go above that while you're moving, then there's a problem. If not, there's not. The higher-pressure cap will only mask the problem, not prevent it--temperature is temperature, but pressure is different. It will raise the boiling point but all that pressure is going to have to go somewhere if the car overheats.

 

However, I am confident that the car is not overheating. 200 degrees is normal. Losing coolant is normal (this is why we had full-service filling stations with guys who would add coolant to your radiator whenever you filled the tank). Next time, try filling it just to the top of the core and leave the top tank empty--don't fill it to the neck. That will give the coolant plenty of room for expansion and it should not overflow as much. I think you're losing so much coolant simply because when it overflows, it keeps pulling more coolant out as a function of capillary action. Get the level right and it will greatly reduce this tendency. A catch can will be very helpful here.

 

Don't over-think this now that you can see temperatures with a gauge. If it ran fine and didn't overheat before you knew what the temperature was, you're in no danger now. It's all OK, I promise!

[Aaron65]

Run whatever cap came with the car originally, which was PROBABLY a 15 lb. cap.  As others have mentioned, a higher pressure cap will do nothing more than find a weak heater core or hose fitting.  

 

You say that the radiator is half empty.  Is your cap on the left or right side of the radiator?  If so, it's a crossflow radiator and the tank under the cap will probably look like the water is roughly 4-6 inches down from the cap.  This is fine.  If you add more antifreeze, it will puke it out if it is too high, as you have found.  Now if it is truly half empty, you will be adding a gallon of antifreeze mix each time.  If you are doing THAT, then you have another problem.

[Lebowski]

I drove it for about 45 minutes at 50-55 mph in 87 degree weather and it stayed below 200 degrees with the 20# cap. When I got home absolutely no coolant overflowed from the radiator even though it was almost full when I left. The overflow tank that Jack suggested in post #43 looks like it would be more appropriate for a car with a frame-off restoration than a beer can and zip ties. LOL....

[Lebowski]

1 hour ago, Aaron65 said:

 Is your cap on the left or right side of the radiator?  If so, it's a crossflow radiator and the tank under the cap will probably look like the water is roughly 4-6 inches down from the cap.  This is fine.  If you add more antifreeze, it will puke it out if it is too high, as you have found.  Now if it is truly half empty, you will be adding a gallon of antifreeze mix each time.  If you are doing THAT, then you have another problem.

 

The cap is on the right (passenger) side which is the same side as the battery so there is no room there for an overflow tank. However, on the driver's side if I removed the plastic container that holds the windshield washer fluid it would fit there nicely. Would it be ok to run the overflow hose over the top of the fan shroud or does it need to be on the same side of the car as the radiator cap?

[Aaron65]

Honestly, if you keep the fluid level a good 6 inches down from the cap, you shouldn't NEED an overflow, but it wouldn't hurt to run an overflow line across the top of the radiator as long as it doesn't get pinched by the hood or anything.

[ted sweet]

exactly. it should be only be fiiled to the top of the fins on a system with no recovery tank

[JACK M]

I would be very uncomfortable with a 20 pound cap.

Even though I do a lot of custom and home made stuff I have found for a daily driver stock works best.

Go to what ever is stock for a cap (and they do go bad on occasion like many other parts), it is understandable that you are uncomfortable with the low coolant level, I would be too.

An add on recovery system would cure this problem and not be to far from stock.

Try a test run with the beer can, this would at minimum answer some of your concerns.

 

[mike6024]

24 ounce Coors, not the 12 oz - too small

[Lebowski]

I've been driving it for the last couple of weeks in 85-90 degree heat with the 20# cap and noticed that when I park it in the garage afterwards there is no coolant puddle under the car. Today I topped off the radiator with antifreeze and drove it for over an hour nonstop in 91 degree heat and there was still no overflow whatsoever when I parked it. The temp gauge showed 190-200 the whole time so it definitely wasn't overheating so my question is why would the radiator always spit out coolant with the 15# cap but it spits out nothing with the 20# cap?

[TerryB]

Physics says raising the pressure of water increases the temperature at which it boils.