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Cooling system info.

R

RootesRacer

Donation Time
I'd like to seek some opinions on general cooling system info.

My car is an SII alpine with a rootes 1725, but is of course modified to the teeth.

I have the early SII header tank, which uses an oddball (long) radiator cap, and I bought a new one from Rick a few years ago, and the darn thing never has held any pressure. The cap seems to be the longer variety, but it wont even hold back 1PSI of pressure.

Today I went out and put a radiator pressure tester on in place of the cap.
This is a tool that allows me to adjust a plunger so it seals against where the cap would in the radiator on in my case the header tank.
I pressured the tank with the included pump to 10PSIG.
No leaks and it held pressure for longer than I felt it needed to.

I then started the engine and let it get up to temp.
After about an hour of idling (I was jetting my carbs during this time), the temp on the dash showed a bit beyond 190.
I would have extrapolated the temp to read about 200.
The pressure gauge was reading about 6PSI and had been there for a long while as the engine ran.
Coolant was probably at 35% antifreeze 65% water mix.
Based on this pressure, the gauge must be reading low (I think).

Since the pressure didnt climb forever, I assume the head gasket is not blown and the engine cooling is marginal.
Opinions?

Question, does anyone have a resistance chart for what the temp transducer ought to read (in ohms) as a function of temperature?

Keep in mind this is an SII and uses the earlier gauges which DID NOT use the gauge voltage stabilizer.

TIA
 
Barry

Barry

Diamond Level Sponsor
Jarrid,

Rootes mostly used the Stewart-Warner standard which is 233 ohms at minimum reading and 40 ohms at maximum reading. The problem is that the SI-II and the SIII-V cars used a different sender and I don’t know why. ASSUMING that it was size / shape / connectors / etc. and not an electrical difference, then the sender in your S-II is PROBABLY 240 / 33 ohms.

The temperature gauge that came with my S-V reads from 50 / 85 / 120°C. which is roughly equivalent to 120 / 185 / 250°F.

My best SWAG for sender resistance versus temperature is:

°F. / Ohms

120 / 240

150 / 192

180 / 144

190 / 128

200 / 112

210 / 97

220 / 81

250 / 33​
 
R

RootesRacer

Donation Time
Barry said:
Jarrid,

Rootes mostly used the Stewart-Warner standard which is 233 ohms at minimum reading and 40 ohms at maximum reading. The problem is that the SI-II and the SIII-V cars used a different sender and I don’t know why. ASSUMING that it was size / shape / connectors / etc. and not an electrical difference, then the sender in your S-II is PROBABLY 240 / 33 ohms.

The temperature gauge that came with my S-V reads from 50 / 85 / 120°C. which is roughly equivalent to 120 / 185 / 250°F.

My best SWAG for sender resistance versus temperature is:

°F. / Ohms

120 / 240

150 / 192

180 / 144

190 / 128

200 / 112

210 / 97

220 / 81

250 / 33​
Click to expand...

Thx for the info, I can only assume that my transducer is not up to snuff.

If I knew for sure the resistance curve, I could use a new style RTD and build a conversion circuit.
 
R

RootesRacer

Donation Time
Hillman said:
Why not do the same but leave the cap off and put a thermometer in?
Click to expand...

Because due to the crappy cap whose plunger isnt long enough to pressurize the radiator, I have to leave my pressure tester connected (in place of the cap), and cant get at the water till the pressure is back down to 0 PSI.

Best I can do is put my infrared meter on the thermo housing and hope its accurate. I'll have to shut the motor off when I test it so the fan isnt cooling the casting throwing off the temp reading.

Based on the 6PSI the rad saw, it looks like the gauge must be WAY off, or someone needs to smack me around some on my understanding of vapor pressure.
My premise is that its going to take a temp well above 212deg F to generate 6psi vapor pressure with a 35% glycol mix.
No?
 
B

Bill Blue

Platinum Level Sponsor
Jarrid, I do too. While temperature-pressure charts are valid for boilers, I'm not so sure about applying them to a container filled with water. If a cooling system is filled "brim full", sealed, then heated, pressure will climb MUCH more rapidly than temperature as the expanding water has no place to go.

Even if that situation does not exist in your instance, let's suppose your engine is idling happily along, with a temp reading of 190* at the stat. Is that to say there is no place in the head where the temp will not be higher than 190, creating more pressure? Wouldn't the pressure be more related to the max temperature, located anywhere in the system, not just the thermostat temp?

Bill
 
R

RootesRacer

Donation Time
Bill Blue said:
Jarrid, I do too. While temperature-pressure charts are valid for boilers, I'm not so sure about applying them to a container filled with water. If a cooling system is filled "brim full", sealed, then heated, pressure will climb MUCH more rapidly than temperature as the expanding water has no place to go.

Even if that situation does not exist in your instance, let's suppose your engine is idling happily along, with a temp reading of 190* at the stat. Is that to say there is no place in the head where the temp will not be higher than 190, creating more pressure? Wouldn't the pressure be more related to the max temperature, located anywhere in the system, not just the thermostat temp?

Bill
Click to expand...

Good thoughts.

Wish someone with some definite experience would pop in and enlighten.


EDIT:

And FYI I hadnt EVEN considered the expansion of the unbloiling water to the increase in pressure.
Could be a VERY valid point since the expansion tank was rather full since I had just filled
it prior to putting the pressure test cap on the tank.
 
65beam

65beam

Donation Time
cooling

my question is why are you only using 35% antifreeze? recommended percentage is 50%. all the premix that i have sold over the years is a 50/50 blend. and for what it's worth,i have a cap on the harrington that came from VB of all places and it works fine. never overflows,never overheats.
 
R

RootesRacer

Donation Time
65beam said:
my question is why are you only using 35% antifreeze? recommended percentage is 50%. all the premix that i have sold over the years is a 50/50 blend. and for what it's worth,i have a cap on the harrington that came from VB of all places and it works fine. never overflows,never overheats.
Click to expand...

Quite simple really, the damn thing wont hold coolant right now and I add water to it so I can test and tune it.

I have a specific gravity tester which allows me to gauge the %glycol to H2O, which is where the number comes from.

Now you do know that water cools better than antifreeze now dont you?

If I could get away with it, I'd run pure water and some water soluble oil, but the boiling point is just too low for that.


Oh and on your Harrington, does it use the rounded header tank like on the earlier alpine, or the square one with separate overflow valve?
 
serIIalpine

serIIalpine

Donation Time
After I redid my head I found that I blew a fair bit of coolant out of my expansion tank too. I assumed it was due to a failing head gasket but someone recommended putting a catch tank on the end of the drain tube from said tank and do you know what? While I may blow a little coolant off when the engine is hot it sucks right back in when it gets cool again.

It acts just like a modern system with catch tank. I know this isn't how it's supposed to work but it does and rarely do I get above an indicated 190-200 degrees even on the hottest days unless I'm running Arco gas in stop and go traffic on a really hot SoCal day.

My point being: Your car seems to be acting the same way as mine with the SS cap and old style catch tank and and I've put quite a few miles on it as it is with no problems you should try running yours as it is now as well.

Look at this pick. Is this the expansion tank and cap you are running?
P1000606.jpg


What you don't see is the 16oz. Gaterade bottle in front of the right fender that I'm using until I get a cool spun aluminum tank.

I can't imagine that your temp gauge is that far off and 6 lbs is nothing to worry about. With the cap that you do have and a catch tank you'd probably be fine. You'd want to make a few short runs to be sure but it seems to work just fine for me.

Hope this is of help.
 
R

RootesRacer

Donation Time
Thx Eric,

That is the exact same tank I have, the cap is not even vaguely right and wont hold back even one PSI of pressure, when I put the cap on, there is almost no force needed to push the plunger down, meaning practically zero seating pressure.

If I put an 1/8 inch rubber gasket between the caps plunger and the brass seat on the tank, only then can I keep it from weeping when the engine is running.
Its just the wrong cap, thats all there is to it.
Granted it is longer than normal caps, S.S. made a mistake that it is compatible with the SII tank distance.


Now I did try to do as you have and put a catch vessel on my car, but my cap doesnt have a sealing gasket on the top of the cap (like normal caps do).
As a result, it leaks to atmosphere and cant pull enough vacuum to lift the coolant back into the header tank when the tank cools.

My plan is to get a universal rad cap neck and have it tig'd to an alluminum plate which I can shape to match the stock plate that bolts to the header tank. That way I can install a higher pressure cap that really can be used in a closed system the way god intended.
 
R

RootesRacer

Donation Time
Eric,

BTW you installed your weber cable kit a bit backwards.

I know you can install it the way you did, but as you have it installed, the front carb actuates the back carb using the front carbs spindle as a torsional link.

This tends to twist the spindle due to all the spring pressure exerted by the rear carb.

A better way is to reverse the linkage (180 degrees) and have it act on the front carb, which links to the rear with your adjustable sync lever.

I did this and all it took was a minor welding mod the to the sync link mounted to the front carb which added a ball post for the push rod.

Just a thought.
 
bobw

bobw

Donation Time
RootesRacer said:
My premise is that its going to take a temp well above 212deg F to generate 6psi vapor pressure with a 35% glycol mix.
No?
Click to expand...

Try downloading this pdf
http://www.meglobal.biz/literature/product_guides/MEGlobal_MEG.pdf

There is a chart on page 17 of vapor pressure vs temperature for various concentrations of ethelene glycol and water. The closest I can interpolate it, at 75%, 300 mm Hg (5.8 psi) would be 84C, or 183F. At 6 psi, temp would be a little higher. It seems to me that your temps aren't that bad.

Bob W.

OK, I took another look (double checking my work) and this time it looks like 92C or 198F.
 
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