302 engine temperature too low?

[DirtDonk]

Nah, you really don’t…

 

[nvrstuk]

Thanks everyone for your help and suggestions. It was raining all day so I went ahead and pulled open the thermostat housing to investigate. I had completely forgotten that I purchased a “failed open” thermostat when I rebuilt the engine last year. As you can see from the link below, it did exactly what it was designed to do. I replaced it and it maintains 180 degrees now. Thanks again everyone.

Great news!!

 

[DeepC73]

So I ran my Bronco in the annual Christmas parade last night. It maintained 185 degrees for two hours, in gear, at a snails pace while it was 67 degrees outside. I would say my cooling is is solved. I have to say the slightly smaller pulley really did the trick. Thanks for all of the input and suggestions.

 

[DirtDonk]

The motor was rebuilt about 15,000 miles ago. I replaced the original radiator with an aluminum 3 core about a month ago. I also recently replaced the original 6 inch water pump pulley with a 5” to increase flow. It currently stays around 120-130, no matter what.

I had completely forgotten that I purchased a “failed open” thermostat when I rebuilt the engine last year. As you can see from the link below, it did exactly what it was designed to do. I replaced it and it maintains 180 degrees now.

I have to say the slightly smaller pulley really did the trick.

Uh, not necessarily. I'm sure it's not hurting slow speed cooling, but I see a few things here...
New-ish motor. They very often do run hot, but at 15k that should all have loosened up by now.
New hi-po radiator.
New hi-po pulley.
New correctly functioning thermostat.

Glad it's running correctly now. But you can't really say it was all due to the pulley change. Not until you change back and have the same issue of running hotter than you like.
Maybe someday when you're working on other things, you can swap the old one back in just to be sure. Or not... If it's not that important at this point to know.
Besides, if it's working, leave it alone!

Paul

 

[Steve83]

And for the purpose of destroying your hypothesis...let's assume it is installed in a Mastercraft Boat, floating in a Lake, with a reservoir temperature of 60F, and for the purpose of this analysis...let's assume that the lake is of infinite heat capacity.

If your goal is to "disprove" something, then your assumptions work.

My assumption was that this forum was for discussing early Broncos, so my statements presume a road vehicle with a recirculating liquid coolant system transferring heat from a common gasoline piston engine to an air-cooled radiator. If you want to discuss that, then explain what you think a wax thermostat that melts at 192°F will do differently at 220, 230 or even 195. How do you think it will regulate the cooling system differently at those temps.

...that's not real life for an automobile engine. HUGE difference between text book conditions and snow/ice in the mountains one day and crossing the desert the next.

IDK where you live your real life, but even when I lived in the desert in-sight (and driving distance) of the snow line, there was never a day (or a week) when it was above 70°F in the desert, and cold enough for visible snow (which does NOT mean antarctic temperatures). But there WERE several times that I drove from the desert up above the snow line without a thermostat, and the truck never had any coolant system problems. Plenty of cabin heat in the snow, and normal temperature on the desert floor. Maybe your reality is different.

...the water to pass thru quickly enough to NOT COOL...

That's VERY disingenuous to those who haven't studied thermodynamics. The speed of a liquid moving through an air heat exchanger is NOT a limiting factor on its ability to transfer heat to the air. It's much more complex, and nothing is constant in a real system. But in any case, a hot liquid moving at any speed through any heat exchanger (even the rubber hoses) WILL dissipate some heat to the air, so it will ALWAYS cool to some degree. And since you're a fan of reality, we don't need to consider liquid moving near the speed of sound, or heat exchangers with smaller volume than the hoses leading to & from them, or with less surface area than 100x that around the combustion chambers, where heat is flowing into the liquid. So that cooling will ALWAYS be more than semantic cooling. In a real eB, it will be significant cooling.

...the PASSIVE parts of the cooling system are doing THEIR job...

Remind me what those parts are. And then tell us what portion of engine cooling you think they account for, in reality.

...the clutch fan never needs to turn on...

You seem to think that a fan clutch is similar to an e-fan relay. It's not. It can AND DOES progressively regulate the fan speed based on the temperature of the air it's pulling through the radiator. And unless you're doing donuts with solid-rubber tires for 15 minutes straight, even if the fan speed was 0RPM, there WILL be air flowing through the radiator when the engine is loaded enough to produce a significant amount of heat. If the engine is at idle, it will ALMOST (but not actually) air-cool. If the engine is at high RPM for more than a few seconds, the vehicle is moving through the air enough to push heat across the fan clutch.

But back to the main point of my previous post: the PCV system...
Air flowing through the crankcase literally fulfills the semantic definition of "PCV". But in reality, we know it's more than that, right? For the PCV system to actually accomplish its function, the engine (and its oil) must be significantly above room-temperature; it must be CLOSE TO the boiling point of water. If you have a grasp of thermodynamics, you should certainly understand the chemistry of internal combustion, the mechanics of pistons/rings/cylinders, and the effects of water in the oil. If you don't, read this:

(click this text)

4. Once the engine is above the t'stat temp, the t'stat has very little purpose. (Concur, because if the engine is above t'stat temp, then the t'stat is already completely open...

Absolutely correct, which is why it doesn't affect the engine's temperature any more - so it can't affect the engine's highest temp, or regulate any temperature above its rated temp.

...if the engine is above t'stat temp, then...the thermal transfer of the radiator/ heat exchanger is already inadequate.)

This is how I read your AND statement, but I have to be reading it wrong because that's NONSENSE. You can't really think that no real vehicle engine ever goes above its thermostat temp, or that those that do have some malfunction or design defect.

 

[nvrstuk]

So far off I don't even want to spend the time... but I will address the inability for Steve to understand what a t-stat does on a cold day. I'll let the rest of the world with time address all his other inaccurate statements.

What Steve83 is writing and using as an example about the desert floor and snow driving is a total lack of understanding what happens in an automobile in the example he states here: (his statement) "when it was above 70°F in the desert, and cold enough for visible snow (which does NOT mean antarctic temperatures). But there WERE several times that I drove from the desert up above the snow line without a thermostat, and the truck never had any coolant system problems. Plenty of cabin heat in the snow, and normal temperature on the desert floor. Maybe your reality is different."

Of course you didn't have any cooling system problems when driving into snow covered hills from the desert floor (with or w/o a t-stat) with an adequately sized radiator cooling system. I never said it wouldn't. However, you will NOT get any heat from the heater w/o a t-stat to "hold" the water back into the engine to warm it up enough so you will have cabin heat! Wow, EVERYBODY knows this! In our Valley everyone runs t-stats and cardboard to try to restrict the airflow so there will be cabin heat. Without doing so you will NOT have cabin heat. Come on up here all last week (not even cold yet) without a t-stat and show me how well that windshield is going to clear w/o a t-stat regulating the water/coolant flow so the engine can warm up enough to supply hot enough water for the heater core. I can run all winter without a clutch fan as I'm cruising down the highway over 45 mph but if I didn't have a t-stat and if I was cruising down that same highway the windshield would be frozen over and the water temp gauge would be reading waaaaay low. How do I know? We've done it.

Here's another example of you not understanding my very simple explanation from several days ago...
We routinely have 80+deg F days with snow on the Valley's hills at 6K ft (and within 8mile of the Valley floor) for over at least a month every spring.... but the very simple fact that you aren't grasping here is if you leave the Valley floor in your example with your t-stat missing at 70+ deg F (our temps are commonly in the 80's) and your water temp is probably warm but not hot, then drive into the snowy hills only 8miles away which we do here every spring where we live you are saying and I quote once again "Plenty of cabin heat in the snow, and normal temperature on the desert floor. Maybe your reality is different." (this is your quote)

You are trying to say that w/o a t-stat that you have plenty of cabin heat?! IPolitely said- I gotta laugh out loud- sorry, but you've missed the boat by a mile! You missed that chapter in your thermodynamics book. I'm just an Electrical Engineering grad and obviously know zip about how passive cooling, clutch fans and how a t-stat regulates water flow so it will allow the water in the block to heat enough so the block, water, oil, etc will reach operating temperature. When it does the t-stat opens allowing the .blah, blah, blah... yeah, most of us know the rest... ( I should probably proof read this but I've wasted waaaaaay too much time already and won't even try)

 

[Steve83]

...a t-stat to "hold" the water back into the engine to warm it up...

Physics must be really different in your world. In mine, there's coolant in the engine regardless of the presence of the t-stat. The hoses & other components hold coolant in the engine. And in mine, if the engine gets hot (which it does every time it burns fuel), the coolant in the engine gets hot. And in mine, t'stat or no, the WP pushes coolant into the bottom of the engine, which pushes the hot coolant out the top, into the radiator & heater core.

So there is no situation in which a t'stat is necessary to get hot coolant out of the running engine.

Wow, EVERYBODY knows this!

Like everybody knows the world is flat? And that the sun revolves around the Earth? And that electricity is black magic?

You need to take more time reading, instead of skimming over stuff. I said there were SEVERAL times I drove up the mountain. SOMETIMES when the desert floor was BELOW 70 and there was snow above.

As to what happens in a cold engine with a t'stat: the WP pumps coolant, but only through the heater core, until the t'stat opens, at 192°F. Then it also flows through the radiator, where some heat reaches the fan clutch (which has been free-spinning) causing it to progressively speed up. The t'stat may close & open several times as the engine warms up, sending pulses of hot water through the radiator. Each time it lets more cold water come in, that might close the t'stat again temporarily.

Without a t'stat, coolant is always flowing, so it takes longer to warm up. But if the engine produces enough heat to keep the t'stat open, then it will produce the SAME amount of heat without a t'stat, and the cabin will have the SAME heat available. It'll just TAKE LONGER to get up to that temp.

 

[nvrstuk]

Your original t-stat tatement is still incorrect. Now you're modifying it. You either need a t-stat to regulate engine temperature or you don't. I think semantics is possibly getting involved. too. T-stat's job- regulate engine temp or coolant temp or both or in your example- not even needed.

Your quote "But if everything else is working right, the engine will run fine without the t'stat. " Not true, never has been-except under controlled atmospheric testing conditions that could never change.. as I'm sitting here surrounded by snow and will have single digit temps again soon.

Hence my post and then your reply about "plenty of cabin heat" without a t-stat- which if you ever drove a truck in Alaska or Canada or where I live for 6 months a year your windshield would never defrost even if you drove an hour at a time because the "coolant and the engine" would never warm up to optimum temp. Yes, passive cooling exists in automotive engines. Passive cooling in this enviroment does work. Passive cooling occurs from startup on an auto engine. Can't believe the difficulty understanding this. IF passive cooling didn't work in cold climates, why then aren't electric fans spinning or clutch fans engaging Because they never have to turn on in cold weather for days/weeks/months most of the time even with a t-stat. Have you you opened the hood on a car where the engine has just been shut off? Any heat radiating from it?-maybe just a little? We put food wrapped in alum foil on the manifolds when we go in the mountains and no water, no cooling fans, nothing but passive radiant heat warms it up so hot you can't touch it for a while.

Without the t-stat you will never reach close to 192 or higher in my examples.

Now that you amended your drive to the mountains statement & you are changing your statement by saying that a t-stat is needed (by saying it will just take longer), your quote still reads: " But if the engine produces enough heat to keep the t'stat open, then it will produce the SAME amount of heat without a t'stat, and the cabin will have the SAME heat available. It'll just TAKE LONGER to get up to that temp." Nonsense- the same energy in btu's might be produced by the combustion process (I won't include any tech tip articles for you) but those btu's aren't ever going to be available for the heater core w/o a t-stat-.

What I have said mulitple times is that the coolant will NEVER reach those temps in cold climates and I stand by that. Might get somewhat warm if the engine is operated at maximum output rating continually & without the help of mechanical fans or as you tried to insinuate a electromagnetic operated fan relay. (Most electric fans on newer autos are variable speed for many reasons.)


Just a thought here- read what is being posted, not what you are thinking is being posted- example below:

An example of that is in your quote... "So there is no situation in which a t'stat is necessary to get hot coolant out of the running engine."

Correct, find my quote where I said a t-stat was needed to remove hot coolant out of an engine.



What we (everyone except you) are saying is that a t-stat is needed to hold back the water in the engine UNTIL the water temp in the block reaches whatever temp the engineers deemed necessary for emissions, longevtivty, etc then and ONLY then does the t-stat open to allow the soon to be over heated water out to the radiator so now your clutch fan can do it's job which is to keep the coolant at the temp that the engineers want the engine to operate at.

Your quote again.... "but if everything else is working right, the engine will run fine without the t'stat. The fan clutch has FAR MORE contraol ... " Wrong, when talking about my example of minimum cabin heat in cold climates & keeping the coolant in the engine block at it's proper temperature as you can read in my post above or ask anybody in Canada or Alaska because without a t-stat those engines will NEVER reach proper operating temperature. Same with oil temps.

You really need to go drive a truck in zero degree temps for a week w/o a t-stat then you can understand what life in a cold climate is, how passive cooling contributes in cooling an engine in cold weather and understand what that reality is when your windshield will NEVER defrost even after an hour of driving and then agree with many of us here because an engine will NOT run FINE without the t-stat during the examples I am repeatedly trying to help you understand. Sometimes repetition helps??

Your quote is not true- btu's are lost, fans are not needed and the heater will never transfer enough heat from the water to the heater core- your quote-
"Without a t'stat, coolant is always flowing, so it takes longer to warm up. But if the engine produces enough heat to keep the t'stat open, then it will produce the SAME amount of heat without a t'stat, and the cabin will have the SAME heat available. It'll just TAKE LONGER to get up to that temp." BTU's are lost everywhere, mainly thru passive loss and the heater will never work. Repetitive but maybe?

I agree that a cooling fan- clutch or electric or full lockup mechanical helps regulates max temp (who doesn't here) because w/o one in the summer as an example you would be over heated quite quickly, but it's a different set of parameters in cold weather which you aren't agreeing with or bothering to understand-hence again, the need for a t-stat

So unless you resort to character attacks here then it's time to move on from our ClassicBroncos tech forum. as I am done, have a good day all.

 

[Speedrdr]

Oh, I don’t know if it’s time to move on. I have really enjoyed the back and forth between posts. Not sure if I can say there’s anything in my background (farming, economics, construction and nursing) to allow my contributions to the topic at hand, but I have certainly been entertained.

Randy

 

[Steve83]

Well, it's too bad he left the discussion before ever explaining what he meant by "passive cooling", or which parts accomplish that. But he did talk himself in so many circles that he eventually agreed with my original statement that the t'stat is for emissions (the PCV system).

 

[bmc69]

What we (everyone except you) are saying is that a t-stat is needed to hold back the water in the engine UNTIL the water temp in the block reaches whatever temp the engineers deemed necessary for emissions, longevtivty, etc then and ONLY then does the t-stat open to allow the soon to be over heated water out to the radiator so now your clutch fan can do it's job which is to keep the coolant at the temp that the engineers want the engine to operate at.

This old thermodynamics engineer has to agree with that....noting that not all cooling systems use a clutched fan though. ;-)

Speaking of passive cooling...when I was a poor lad with a young family, I drove a beater 1974 Volvo wagon that an uncle gave me. It had about 350K miles on it. During its final year or so, the radiator was so shot that it wouldn't hold water...but the engine was so loose that if I ran it real easy, I could make it back and forth to work running it as an air cooled engine. ;-)

 

[blade]

I've always thought of a thermostat as a switch. In a properly working system it will cycle on and off allowing the engine to first reach operating temperature and then as the cool water from the radiator flows into the engine it causes the thermostat to close again which allows the water to be cooled in the radiator. My understanding is that it should never stay open constantly, if it does you will at some point have overheating, such as was the case of the OP with overheating when driving slow.