PROBLEM SOLVED! Why is my motor running cool? Help!

I recently had the same issue with a SBC cooled by a re-cored 1939 pickup radiator.

It ran incredible but moved along around 150 degrees. When not moving it would heat up to 190-200. Start moving again, it would cool right down.

I had it dyno'd and they made some changes to the timing and jetting. It now runs even better, is more efficient (little better mileage) and stays right around 180 all the time.

To me it was worth the extra bucks to know it's dialed in correctly and I know exactly what HP it's making. Correcting the cool / heating issue was a nice, unexpected bonus.

 

Higher temps are not solely for emissions. If an engine runs too cool you get some unburned fuel that will become carbon deposits in the combustion chambers. Modern engines run even hotter than the magic 180 we hot rodders like. My daily driver runs at 213 and that is where the dealer tells me it should run.

Don

 

Dang, I hate to be the lone ranger on this but 140-150 degrees is to damn cold ... a lot of unnecessary wear is happening to your internals. It is my understanding that 185 degrees is the optimum operating timp and that range is where you get the highest power.

I would be concerned about premature engine wear.

EDIT: Don, your fast!

 

i would want my motor running at 190 all the time.

lots of reasons.

many have been mentioned.

 

I found a little writeup about engine temperatures and the effect they have on longevity and performance. I think it is pretty informative:

Proper Coolant Temperature and Camshaft Life!

Have you ever tried to find what proper coolant temperature is for most automotive engines? There are a lot of people who think they know, but it is difficult to find specifics, even in textbooks. We know we want the intake air to be as cold as possible (for best power) because cold air is denser (there are more oxygen atoms per cubic foot). The coolant temperature, however, is a different matter. The internal combustion engine changes chemical energy stored in gasoline into heat energy that is focused on the piston tops. If the cylinder heads and engine block are too cold, they will absorb much of the combustion heat before it can be used to push the piston down the cylinder. If the engine gets too hot, engine lubricants can break down, as well as overheating of the intake charge can lead to detonation, etc.

It turns out that coolant (usually a 50/50 mixture of coolant and water) has some fantastic properties that are ideal for use in engines. With a properly pressurized cooling system, coolant will not freeze until –30°F, and it won’t boil until +270°F (new oils don’t start to break down until well over 270°F). With these characteristics, engine designers have decided that engines should operate at approximately 210-215°F. Why, you ask? Well, it has to do with operating the engine at a high enough temperature to boil water out of the oil after the engine is cold started. If you have dew on the grass, it is certain that you have water in your oil, as the crankcase is open to atmospheric pressure! You can either remove the water by draining it out the bottom of the oil pan (remember the oil floats on water) or run the engine long enough and hot enough to boil the water out of the lubrication system. Years ago, coolants weren’t as sophisticated and engines were run at 165-180F, but the oil was changed every 1000 miles or so. That’s why many old timers think engines should run at 165-180F. Have you ever noticed that Ford doesn’t put temperature marks on their gauges? They just mark C for cold and H for hot and write “normal” through the center. If you hook up a scan tool to a GM, you will often find that the gauge reads much lower than the coolant temp sensor. That is because they know most drivers don’t understand how hot an engine should run.

So what does this have to do with camshafts? Many enthusiasts erroneously think that the colder their engine runs the better! If they are not running the engine hot enough to boil the water out of the oil, the oil becomes contaminated and the lifter/cam lobe interface is the highest load point in the engine. Engines running too cool can contribute significantly to camshaft and lifter failure. Think about it: What good does it do to use the most expensive synthetic oil and then run the engine so cold that it is contaminated by water vapor??!! Another point, piston manufacturers’ piston-to-wall clearance recommendations assume you will be running the fully warmed engine at 200°+F. Run the engine too cold, and you could see some scuffed pistons because the cylinders had not expanded enough to provide clearance.

If your engine will only run its best at the drag strip with the engine at 165°F, you probably have too cold of a spark plug heat range and you are probably jetted way too rich! If you keep the engine hot (not the intake charge), you will be using more of the heat energy in the gasoline to make power instead of just heating up your block. It does take “tuning know-how” to run an engine at 200-210°F, but you might be surprised how well and how long it runs when you do!! One final point - running a computer managed engine at 165°F compared to the factory 210°F will often cost you as much as 4 MPG. The reason for this is that the computer thinks that the engine is not off the “choke cycle” and it is still putting out a rich mixture! Check the science on this and don’t pay attention to the “old wives tales” of the past. Materials and lubricants are much better and different today than they were in the past!!


Don

 

On Thermostat s the temp rating is for full open they always start to open at lower temps
Colin

 

To warm things up, you can switch to a copper/brass radiator. My '32 had an aluminum radiator with an electric fan on a thermostat. No matter traffic, or how hot it was, the fan never came on. It always ran at 180. When the aluminum radiator sprung a leak, I switched to a copper/brass radiator. If the car was moving, it ran at 180. If traffic was stopped, the fan would come on to maintain the 180 temp.

 

you can always put a pot on the stove and put your T-stat in the water with a thermometer to check that its not opening prematurely.

Or do what was mentioned earlier, cover some radiator up.

 

Yup!

Don,
The gauge sensor is right beside the thermostat housing.

 

Did that. Check.
Jay

 

My small block will usually run cool according to the gauge when the coolant level is low. The heater will not blow warm air. I would check the elevations of the new radiator with the original radiator. I would break the connection of your temperature sensor on the block of the engine to see if you have an air pocket. If the temperature sending unit is not submerged in coolant, the temperature will read cooler than actual temperature.

 

Just drive it? Just sayin'!

 

Well this would be my first guess at changing your operating temp .

The thermostat in your car regulates the operating temperature, much like the thermostat on the wall regulates the house temp.

The reason going from 180 tstat to 190 would help raise the operating temp is it will not open until the coolant gets 10* hotter. This would delay the opening of it and retain the coolant until it was warmer.

What I find interesting is that even with a 180* you are running at 140* and stay there. This can only be possible if there is coolant flow back to the radiator that isn't controlled by the t stat. Enough flow that the t stat never needs to open while driving. If this is indeed the case - it wouldn't matter if you put a 190 , 200 or 210
Are there holes drilled in the t stat ? A few big holes?
The other explanation is the gauge is wonky.

I'd like to study your system and see what's happening because what ever you have going on could help guys who run too hot.

 

Please correct me if I'm wrong, but isn't oil temperature more important for "engine longevity" than water temp?
I think it's all hooey about cooler water temps, anyway. Once the engine is up to whatever operating temperature is operates at, you're good to go. I mean how much do water temperatures affect combustion? I know my car definitely feel stronger when it's running cooler. If everything is healthy and works right with no driveability issues, I wouldn't worry about it.
The 11:1 SBC in my 55 runs down the road at 160, and will creep to 180-190 on warm days in traffic. I run a 180* thermostat, Edelbrock water pump, Champion aluminum radiator, plastic flex fan with a shroud, and a overflow tank. Been running just fine for 6 years now. The big old cam in it slobbers down low anyway, so even if I were not burning every little molecule of fuel, I'd never know it. A little situational, I'm sure, but that's my story.

 

Have you verified that your gauge is accurate?

 

No holes drilled in the T stat! Made sure of that!

The gauge is good! Checked that and double checked it.

Here is one thing that I have been thinking about today...

I have an overdrive in this car. So without the overdrive the RPM was around the 3000 RPM mark. With the overdrive I now run at 1900 RPM. cruising down the road. Would that reduce my engine temp???? With a motor that is turning at lower RPM it maybe reduce my operating temp???

 

No, the Rpms have nothing to do with it .

How are your bypass hoses or heater hoses ran.


Think of your thermostat as a valve -
A valve that doesn't open until the temp gets to 180*.
When it opens, it allows hot water out of the block into the radiator -while the water pump pushes cool water out of the radiator back into the block that the t stat just let out.
Yours never gets to 180, so it theoretically never opens .
Yet your engine runs cool. Some how water is circulating without the temperature governing of the thermostat.

 

No heater core! Bypass hoses or anything. Lower rad hose and upper rad hose that is it. That is all.
Jay

 

Buick runs the same way, never see the high side of 170 degrees unless I get stuck in traffic, fan comes on at 190 and cools right down. I have the 1/8" hole drilled in my 180 degree Tstat, always done it that way to help get the air out of the system when filling it up. I have no problem with it, runs great and gets good mileage, and the temp gauge isnt the "panic" gauge that I have to check every few minutes. LT1 in the caddy that has the factory 180 stat without the hole runs at 190 degrees all the time, so maybe the slight bleeding of coolant across the Tstat keeps it cooler? Maybe yours is sticking open since you have no holes drilled in it? I have had that happen before on OT late model FI cars, puts a dent in the gas mileage. Regardless I have no issue with either of mine, and both run great with their cheapo ebay aluminum radiators.

 

Checked it and rechecked to make sure that it isn't sticking open.


Maybe you guys are right. Just live with it I guess. There are a lot of knowledgable guys that have been giving some really good advice. Maybe in the end I just live with it. If it is really cool out. Shove a air blocker in front of the rad when it is super cool out.

I am tempted to stick a 190 thermostat in it just to see. I am definately curious now.

Jay

 

Why don't you think a 190 (195 actually) thermostat won't warm things up? That's what they're made to do.

BTW, I drill a hole in thermostats before I install them in customer (and my) cars. It seems to level out the temp spikes when the thermostat opens and shuts. I tried 1/8" to start with, but I think it's too big. Takes an engine a long time to warm up with it. 1/16" hole works better.

 

I still think your sending unit is not being submerged in the coolant. The top of the new radiator might be sitting too low. Aluminum radiators do not cool as good as a brass radiator. The "R" value of aluminum is about half of brass. Stick a thermometer in the top of the radiator in the coolant and read the temperature. If you do not have a thermometer use an old mechanical temperature gauge. Either the temperature gauge is wrong ( and not submerged) or the thermostat is not working. This is not a quantum phyisics problem.

 

Sometimes, trying to make something better, makes it worse. Just sayin'.

 

Where do you mount the temperature sending unit. Pictures would be nice.

 

Haven't read the whole thread - but is your 180 t-stat opening then - and not at only 90 or something?

 

Isnt a "too cool" engine temp kinda like a "four hour errection"?....a problem that we all wish for? Do an experiment and put a 210 deg t-stat in and see what happens. It just may fix the problem by raising the temp a bit.

 

You have not explained how you tested the temperature gauge or the thermostat. This could help some people figure out the problem.

What temperature gauge are you using. The sensors are usually matched to a certain gauge. If you are using the stock gauge in the car and an aftermarket senor or a non matched pair you could have false readings. How did you check and recheck the gauge and sending unit.

I am sure you realize the cool coolant is at the bottom of the radiator and goes in the bottom hose on the engine. The hot coolant comes out of the top on the engine unless you have a reverse circulating pump. The serpentine drive pumps rotate in the opposite direction of the v belt driven pumps. Some people buy the wrong pump not realizing the rotation is different.

The usual temperature difference between the coolant leaving the bottom of the radiator and entering the top is 15 to 20 degrees F.

 

SMALL BLOCK CHEVY!!!! BABY!!!!!!! That's all I could come up with. And I read the whole thing

 

Agreed !!!

 

You guy are funny. Aluminum Intake/radiator/water pump/etc., heat sheilds, headers, stick trans, heat wrap, . . . . . ,SBC, And . . . "Why is my is my car running cool"?