Can I be too cool?

[tucsonjwt]

I had a leak in the water pump in my 454 C20 so I replaced the pump with a new Delco pump, found out I needed a fan clutch and replaced that with a Delco clutch ($$$), found a small leak in my 2 year old Ready Rad radiator and had that fixed, replaced all of the hoses and belts, and then took it for a short test drive.
No leaks, but the temp went up over 220 degrees after just a few minutes. So, I replaced the old thermostat (looked like it could have been factory original style) with a 180 degree thermostat from NAPA, and after a 10 minute drive in town it only got up to about 165 degrees. It was about 99 degrees outside, so it was quite cool for Tucson in July.
Is it possible that my big block could run too cool. I can't think of a problem with that, since I have no computer controls on this old truck, but I thought I would submit this question to the forum experts. For reference, this truck never got up to the 200 degree range in the past (stock thermostat should be 195 degrees for this truck). As I recall, the highest temp I got in the past was about 185 degrees, assuming the stock temp gauge is accurate.

[67_SS396]

165 is a little low IMO to ensure a good clean burn. I prefer to see 180+/- operating temp.
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[tucsonjwt]

So, if I lived in Alaska instead of the desert, would my winter engine temps run colder and cause insufficient burn? Just curious, since I see the big rigs run with those radiator covers in the winter - which I thought were to keep engine temps high enough to get heat in their cab.

[67_SS396]

That's why you see diesels in northern states run grill covers, too keep the engine temps higher. It's not just to keep the heater in the cab warm.
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[tucsonjwt]

I think I will drive around for awhile with my low temp engine and see what happens. I typically drive only a 3-10 miles at a time in town, so I never run the engine at high rpms. This truck get maybe 3000 miles of use per year max. I am assuming that my factory temp gauge is functioning properly, which is a big assumption in this old truck. I will give it a short run on the expressway this weekend and see how that affects engine temp. I am guessing that the new 180 degree thermostat is functioning properly.

[67_SS396]

It won't hurt anything running that cool and being an occasional cruiser, I'd run it and not worry about it.
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[TheApocalyptican]

Based on your temps I would think the temp gauge isn't perfect. However, if you have never had a problem with the temp going up in the past, and now that you have a brand new cooling system, there isn't a real reason(IMO)to run the lower temp t-stat. I would think tho that the temp gauge is off. From my experience, and reading others experiences, engines typically run either at, or over the t-stat's temp. Therefore you should see 180° or above with the current t-stat.

I wonder if maybe the new t-stat isn't working correctly and opening too soon and due to the new cooling system is overcooling, as it shouldn't let it run much cooler than the 180°. Just a guess at that tho.

[tucsonjwt]

Thanks for the info. As you guys might suspect, I am much more concerned about running an over temp engine, rather than an under temp engine, since I live in Hotzona. I will say that the engine seems to run a little smoother now at idle, although this big block, like the other big block I had, always idles better than the small blocks I have owned, even the new small block vehicles. I will probably only travel about another 600 miles until we get "cold" weather in Tucson, so I think I will see how this current thermostat works out then.

[rwhit57]

Running too cool won't cause any quick damage like running too hot, but I wouldn't do it for long. One of the biggest issues can occur with driving short distances like you described. Condensation can build up inside the motor, especially under the valve covers. Due to the fact the motor is not hot enough to burn this out. Have you ever pulled a valve cover and seen milky sludge stuff? The old 327's were notorious for it. By the way, come get your hot dry weather someone left it here in Okla and it won't go away. LOL

[tucsonjwt]

The real question for me is what is the actual temperature of my engine? Does anyone have positive experience with the accuracy of the HF infrared laser thermometers? This one has both positive and negative reviews.

http://www.harborfreight.com/non-con...r-header-96451

[dman1982]

ive never had any luck with the factory temp gauges in any old truck...im only 28 but have had alot of trucks over the years and only had 1 or 2 where the temp gauge actually worked correctly....about half were fords 86 to 96 and the others where chevys 79 to 92....not that they were all junk...just like to wheel and deal!!!!

[tucsonjwt]

So, anybody with experience on the HF infrared thermometers?

I am thinking that the temperature of an engine will ultimately be governed by the efficiency of the cooling system, rather than the temperature rating of the thermostat. I have read that the temperature rating of the thermostat only determines the temperature at which it will open - after that temperature is reached the thermostat remains open. I have to think that my engine will quickly reach 195 degrees (factory thermostat temperature), especially in the summer, so wouldn't the temperature rating of the thermostat be irrelevant, except in a very cold climate?

[rwhit57]

Originally Posted by tucsonjwt

So, anybody with experience on the HF infrared thermometers?

I am thinking that the temperature of an engine will ultimately be governed by the efficiency of the cooling system, rather than the temperature rating of the thermostat. I have read that the temperature rating of the thermostat only determines the temperature at which it will open - after that temperature is reached the thermostat remains open. I have to think that my engine will quickly reach 195 degrees (factory thermostat temperature), especially in the summer, so wouldn't the temperature rating of the thermostat be irrelevant, except in a very cold climate?

This is a true statement. With all the improvements you made to your cooling system you dropped the temp about 20 degrees according to your old fact. gauge. I would say the gauge is off and before you were probably in the 200 range and now your in the 180 range. You might try replacing the sending unit for the gauge and see if it improves the reading.

[tucsonjwt]

I think you are correct. I just drove the truck about 15 miles, mostly highway, and the temp gauge is still sitting around 160-165. Since the original thermostat was definitely not opening (or not opening properly), I suppose I was running hot for a long time previously, but the gauge just showed about 185 tops.
The engine does run a lot smoother, especially at idle. I used to have a bit of rough idle with the A/C on, but now it is smooth as glass, so I hate to "improve" it anymore and risk another problem. I can feel significant heat off the engine at idle, but not as much as prior to all of the cooling parts replacements.
I might give that temp sending unit a shot. However, mine seems to have a shielding gasket around it, and my experience with this old truck is that stuff like that breaks when you touch it, and finding those kind of replacement parts is almost impossible.

[rwhit57]

I have to agree, leave it like it is. You know the gauge is working well enough to warn you if something goes wrong and if it's acting better why fool with it. Thats actually the exhaust manifold gasket bent around it whoever installed it should have trimmed it a bit to clear the sending unit.

[INSIDIOUS '86]

180 should be fine, if your not hotrodding around then your all good, as long as nothing is acting up

[tucsonjwt]

No hotrodding - hot is what I was trying to get rid of

[rfmaster]

Originally Posted by tucsonjwt

I think you are correct. I just drove the truck about 15 miles, mostly highway, and the temp gauge is still sitting around 160-165. Since the original thermostat was definitely not opening (or not opening properly), I suppose I was running hot for a long time previously, but the gauge just showed about 185 tops.
The engine does run a lot smoother, especially at idle. I used to have a bit of rough idle with the A/C on, but now it is smooth as glass, so I hate to "improve" it anymore and risk another problem. I can feel significant heat off the engine at idle, but not as much as prior to all of the cooling parts replacements.
I might give that temp sending unit a shot. However, mine seems to have a shielding gasket around it, and my experience with this old truck is that stuff like that breaks when you touch it, and finding those kind of replacement parts is almost impossible.

Looking at your photo you may have non OE single wire temp sensor. These sensors are at best crude indicators. I had similar problem (way too cold) in my '75 - the problem was due to mis matched sensor - factory gauge. Over the years GM used a number of these single wire sensors and aftermarket replacements are at best approximations ( in terms of resistance vs. coolant temperature). To verify your coolant temperature temporarily install quality aftermarket gauge - Autometer or S&W gauge. Usually, most stock engines will stabilize around 185 to 195F on a 75 F day.

//RF

[bigd65]

If everything is the same, no real problem but the oil is not real effective until it reaches over 192-200 degrees
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[Dan1969]

Mine stays on the far left, around 165. It works fine and the outside temps are around 108 everyday.