MG MGB and MGB GT Tech Talk
I just checked my coolant with an aftermarket temperature gauge. It was showing halfway between center and the red mark on my 77 B. With the aftermarket gauge it read 190 after about an hours run. By my way of thinking this should be dead center, if not a little cool. The loose gauge’s temp sensor was put down the hole on the thermostat cover with the system un pressurized.
Does anyone know what the temperatures are supposed to be?
190 in Atlanta after an hour's run? Sounds about right to me. I don't know if there's any "official factory" temps, but anything less than boiling should be OK.
You didn't say which thermostate you had in your car. If it's a 180, then you're doing great, but I wouldn't worry even if you had a 160 in the car.
Here in Dallas my 78 will normally sit right in the middle, but if I'm stuck in traffic (or stuck in line at the local McDonalds arrrrghhh!) then it will go up to where you mentioned.
At what point does your fans kick on?
For what it's worth, John Twist thinks 190° is the optimum running temp for Bs.
Mostly, as long as it's not boiling over, it's fine.
Dwain,
Your temp gauge sounds as though it's calibrated about like mine. I run 195º thermostat, and my needle sits anywhere from just a smidgen right of 'N' to midway between 'N' and 'H.' Out of curiosity, a few weeks ago when it was hot out, I stuck a thermometer in the filler neck whilst the needle was half-way between 'N' and 'H,' and the thermometer read 190º exactly....
Rob, why would you run a 195?? I have been running a 160, and it works great! When I was in Boise and Salt Lake, and had some 'issues' with my car, it got up to about 200', and I hated that!! At one poit, after a long climb, it said 212', and I really hated that!! I know that with a 7# cap, it won't boil until about 220' to 225' at sea level, but elevation comes into the equation, right???
Dwain, awhile back when my MG was having cooling problems the hubby and I did a great deal of research on this subject. Although the solution came from this board onene item of that you may find interesting though is our thermostat for the fans is factor set, and sealed, at 195 degrees. I called Moss and was told that was the correct temperature for the fans to come on.
Gary,
I run a 195º stat to make more power. I think most people try to overcool their cars. Energy is released from burning fuel, and that energy is either used to turn the crankshaft, or dumped into the environment as heat. I'd rather use more of it to turn the crankshaft!
I think the impulse to try to keep the temp way down stems from the fact that cars used to be equipped with low-rated thermostats. The reason manufacturers did that was because the engine oils of the day would break down quickly under heat. Present-day oils have much better heat stability.
Yes, elevation does influence boiling temperature. But if it's not boiling over, it hasn't influenced it enough to matter...
Just my 2¢
Gary, a lower temp thermostat will not make your car run cooler. It WILL open up sooner, but in summer temps it's going to STAY open anyway, and the car will run at whatever temperature your cooling system is capable of maintaining. Believe me, in the summer, that temperature will NOT be under 160!! It seems to me that MkI cars like to run about 100 degrees above ambient, so until the outside temps get down in the 50's, once that 'stat opens, it's gonna stay open!!
Makes sense Rob! Loma thought that I should put a 180' thermostat in, but I stuck with my 160'!!
Exactly what I found Ken!! When it was 103' outside, I was just over 200'! I guess in reality, a 160' thermostat only keeps it kooooool on cool days!!
Running a 160 thermo and 7# cap here in Colorado. Are you guys saying I should be using a different cap? Hadn't thought about it but it makes sense that it might need to be different. Water boiling temp here is 202F in Denver and lower in the mountains. Found a neat site <http://www.2-stroke-porting.com/altiden.htm> with altitude info on car performance.
I don't know, but a 10# cap would probably not be out of line if your cooling system is in good shape! I would guess that would bring your boiling temp up about 10 or 12 degrees!! But the other thing is, if it works fine, why worry??
Since the system is closed to the atmosphere with the 7lb cap, elevation/barometric pressure has nothing to do with coolant boiling point.
Richard
You don't need to change caps to compensate for altitude.
Richard
Actually,
THe 7# is the amount of overpressure (Pressure above the outside air pressure) needed to compress the spring and relieve the pressure of the closed system. So that is dependent on the elevation, barometric pressure.
At normal sea level, the air pressure is about 15 PSIA, (0 PSIG), the cap will lift at 22 PSIA at sea level, but at a lower pressure at higher alt.
FWIW
Ed
I hear what you're saying but you're wrong. In San Diego or in Santa Fe, it's still 7lbs.
Richard
Richard,
It's 7 lbs above ambient. So the relative pressure (7lbs relative to ambient) does not change, but the absolute pressure (7 lbs plus the local atmospheric pressure) does change....
This would (might) only matter if you change altitudes without exposing the cooling system to the changes in atmospheric pressure. But it really doesn't matter. Since you've undoubtedly opened the cooling system on your car at your location, the at-rest internal pressure of the cooling system is now equal to the atmospheric pressure. Now when the engine reaches operating temperature the system pressurizes. We aren't exposed to atmosphere anymore. The cap holds pressure on top of the coolant. As long as the cooling system will hold proper pressure, altitude isn't a factor.
Richard
I guess the consensus is 190-195 is normal operating temp in summer.
Therefore, I put a 15 ohm 1 watt resitor in line before the sending unit and now my guage reads dead in the middle at full operating temperature. In traffic it creeps up a little but it is still toward the middle.
By the way this adjustment cost me about 30 cents for the resistor and 2 plugs one male one female plus a 3inch piece of wire. So I can take it back out in 10 seconds.
Richard,
I realize we are argueing about how many camels can dance on the head of a pin, but "altitude does matter" THe temperature at which the coolant boils is determined by the total pressure of the system. THe system pressure with a 7# cap is atmospheric + 7 #'s so the boiling point of your coolant in Denver is lower than it is in San Diego, assuming you keep the same radiator cap and the same ratio of water to antifreeze.
However,
Coors does taste better in Denver than in San Diego, so lets concentrate on the really important matters :-)
Ed
Why is that Ed? I've never been to Denver, and never drank Coors in San Diego, but the Coors in WY tasted better than the same beer in OR.
I see Richards argument, but he is .... ummm. incorrect!! :o) It is 7 lbs above the outside pressure!! In Death Valley, that is a good thing!! I forget the exact number, but it boils around 215' F, or 101' C!! Good discussion!! Oh! everytime your car cools down, it would reset it's altitude! Right???
Chris,
The party line on why Coors taste better locally,( or the closer to the birthplace) is that it is cold brewed and has no preservatives. The farther it is trucked , even though they say it is in refrigerated trucks, the more the taste is adversely affected.
Now, personally, I have met very few beers that I would turn up my nose to, and none when someone else was buying. But the reason I liked it better in Denver, than San Diego, was I was on vacation in Co, and with good company. The sun is brighter, and the air is sweeter .... with good company.
Ed
If the pressure in your radiator is say 5psi at sea level and 5psi at 7500ft is the boiling point different?
Richard
Yes!! It is 5 lbs over the atmospheric pressure where you are!! Not 5 lbs over the atmospheric pressure is Death Valley!!
Richard,
To really ask the question, you have to use the correct units. The pressure in the radiator is 5 or 7 PSIG. PSIG is Pounds per Square Inch Gauge. That means that its five pound above the pressure of the atmosphere in that local. And yes, the boiling point is different. I don't have my steam tables handy, but at 7500 ft, the atmospheric pressure is noticably lower than at sea level.
One of the pilots on the BBS can probably give us the answer, and with the pressure at 7500, add the 7 pounds, look at a satuation steam table, and you got the boiling temperature.
Now, if you want to know the pressure below the surface of the ocean at any given depth, "That I know by heart"
Ed
