General Discussion on Heat

[ludwig]

The goal I'm trying to achieve is to have the temp guage stop moving (without unplugging it) so far and often during the hottest of days with the A/C on all the time. (wish a bigger rad would fit)

Right there, that's your problem. It won't stop moving. It will go up when you creep in traffic and come back down when you increase the revs for the pump and more air across the radiator. It will spike when you stop and turn it off. You just won't see it. You will see it if you turn it right back on after five minutes or so. It will read high and then settle down shortly when cooler water comes in and flows past the temp sender. The engine temp will never get very hot in winter if you live where it is cold. You just want it not to get too hot to where it boils over or fails to cool the block.

 

[Lazy JW]

A buddy has a late 80's Ford Ranger (pickup) which just gives him fits in the summertime here. Dunno what shape the radiator is or the block for that matter, but it will actually vapor lock (EFI); you can hit the Schraeder valve and get bubbles out of it.

He put some wooden blocks in at the hinges to raise the rear of the hood about an inch, cured the vapor lock even when hauling firewood on hot days (100º). The hot air just BOILS up over the windshield!
Joe

 

[MPGmustang]

Okay, so I used my temp guage... checked at idle and driving (or after driving)
outside temp at 108*
Idle: this is without A/C
top = 180*
bottom = 161*
after driving with the A/C on: (had friend hold gas @ 2k rpm)
top = 191*
bottom = 181*

okay I've been told the top needs to be 40* less than the bottom, so this radiator isn't working for me. where should i go from here?

 

[JackFish]

I'd say ferget it, you have no problems. When you start boiling coolant you have a problem.
I don't know where you got the 40° differential, but it seems to me you'd want a system that maintains as close to a steady state as possible.
What temperature that steady state should be is my question. For example, the 2.3 engine has an electric fan. The sending unit is set to turn the fan on at 221°, which is very close I assume to the boiling point of the coolant. That would suggest that those kinds of temperatures are within normal operating parameters.

With regard to running without a t-stat, the device is there to help maintain as steady a temp as possible.
So removing it might make your coolant flow faster, thereby exposing itself less to the air it depends on to cool.

 

[AzCoupe]

put some wooden blocks in at the hinges to raise the rear of the hood about an inch

I've heard that works quite well. Even if it does look strange, it may be a temporary solution until you figure it out. You might also try turning the A/C off when you approach a stop light, then back on once you get up to speed. While this won't solve the problem, it will help keep the temps down. I also be curious to know what the temp readings are on the header, and/or the A/F ratio?

 

['68falconohio]

Stock thermostat for my '68 Falcon is 193*F, IIRC.

Just to add some more random bits to the mix.

 

[MPGmustang]

I'd say ferget it, you have no problems. When you start boiling coolant you have a problem.
I don't know where you got the 40° differential, but it seems to me you'd want a system that maintains as close to a steady state as possible.

I was skeptical too when I read it but no one argued with it...

Next use the infer red thermometer to measure the temperature of the upper and lower radiator tanks. The difference between them should be at least 40 degrees.

With regard to running without a t-stat, the device is there to help maintain as steady a temp as possible.
So removing it might make your coolant flow faster, thereby exposing itself less to the air it depends on to cool.

It makes more sense now that you put it that way...


hey Mike, what do you think on the temps? 190 down to 180 around the block (like a few miles) with the A/C on. (I'm asking cause your in my area)
I'll also get some readings on those headers for you mike, I'm sure that you would like to know what it is... I don't know the A/F ratio, I went from a 59F (14.1 WOT) jet to a 64 (calc'd @ 12.4 WOT) jet, i'm thinking about going back cause I really discolored my pipes... :arg: but dmg is already done. :x

 

[Frankenstang]

I was skeptical too when I read it but no one argued with it...
69.5Mav wrote:
Next use the infer red thermometer to measure the temperature of the upper and lower radiator tanks. The difference between them should be at least 40 degrees.

I take 69.5Mav's measure as a general parameter (ie other things being equal/all systems functional)...but don't think this is your case as he and mugsy laid out and you concluded...you've got an air flow problem at idle/stop&go. If your radiator were seeing ambient air flow of 85* then this differential might be expected but with 100*+ ambient temperature and a second heat exchanger (a/c condensing coil) throwing off more heat...I'm not surprised by the difference you measured.

I'd recommend a Fan Shroud. I believe pulling a greater volume of outside air across the heat exchangers at idle would cure your problem (as forced air going down the road does). It seems you don't have nearly the issues if you're not running the a/c. A/C's were an after thought in this era and the fan shroud that did accompany them is the same. Also may not hurt to clean the condensor coil like they do on home units, as mentioned(free efficiency gain and lot more debris/bugs/dirt being directed at car ones)...use a wide fan spray pattern of water with light pressure...no power blasters. I intend on using this build your own fan shroud approach MustangSix posted when I get my a/c online (currently I have a disabled condensor coil in front of my 2 row aluminum radiator, with 195* stat on a 30 over engine with 100K+ and it did fine in 100* temps this week):
http://www.jalopyjournal.com/forum/show ... fan+shroud

Is there other way's of cooling the car to have it run no hotter than 190*? even in +110* degree weather with the A/C on? (without electric)

Not w/o using refrigerant , but if you wanna get closer, fan shroud. I don't think fan shrouds are often thought of as necessary on these older models, but I had a '77 Explorer with a 302 that never overheated till the fan shroud was destroyed in a front end collision and left off after repairs were made. Every summer here in Texas it ran hot. Eventually replaced the shroud...never ran hot again...same thing happened in an old '72 skylark I owned before I got a shroud for it. Extreme temp air flow is the difference if you ask me.

I'd also check your cap and make sure it's holding pressure. Water boils at a higher temperature under pressure depending on altitude (approx 3* per lb of pressure...220-230 on some 16lb 'closed' systems' will not boil over).

Make sure you've got a 6 blade fan...four blade is insufficient for a/c equipped IMO.

But the very first thing I'd do IIWIYS (as mentioned) although can't be over emphasized. Get a t-stat housing with a bung for a temp sender (if you don't already have one) and put decent aftermarket 'mechanical' gauge under the dash at least temporarily. Cheap insurance to protect that investment.
Good luck!

 

[CobraSix]

Okay, so I used my temp guage... checked at idle and driving (or after driving)
outside temp at 108*
Idle: this is without A/C
top = 180*
bottom = 161*
after driving with the A/C on: (had friend hold gas @ 2k rpm)
top = 191*
bottom = 181*

okay I've been told the top needs to be 40* less than the bottom, so this radiator isn't working for me. where should i go from here?

If you have a 180* T-stat, those numbers are not bad at all for the driving conditions you describe. Never heard of the 40* differential requirement. Bottom line, the water temp at the top is the maximum water temp the engine is seeing. Running 10* over the T-stat set temperature is not a sign of cooling system problems. Remember, these T-stats are not highly accurate pieces of equipment. They are a temperature calibrated spring. One way to test a thermostat is to place it in a pot of water and see when the valve is fully open and measure the temperature of the water. It is not uncommon for a 180* T-stat to not full open until 185-190*.

As far as removing the T-stat, you do have to be careful with that. While it may help on really hot days, it will cause bad conditions on cold winter nights (I guess depending on where in AZ you are that may not be an issue). The increased flow rate through the radiator will reduce the amount of heat dissipated per unit of water per cycle, but at the same time the water will be absorbing less heat from the block per cycle. But, more water is flowing per unit of time, so the total cycles of water increases, thus making the total heat exchange the same as a partially restricted flow. While the T-stat does restrict flow somewhat through the engine, the Radiator itself is a larger restriction to flow than the T-stat. But, if you ever try to drive on a cold day, your engine will probably never warm up beyond 130-140* which is arguably worse for an engine than running at 200-210*.

The set up on my mustang is all new stock components with exception of the radiator which is a 3-row (not aluminum though) and a 180* T-stat. While I don't have a problem at all during the summer (even in 95-100* days, which are rare here) I don't have AC. Now during the winter, the engine barely warms up to 160*. If I drive it on cold days, I actually have to block part of the radiator.

Other things to check is to make sure your timing is set better. Try retarding the timing some. I'm not sure what you are running now. Check the carb tuning. If you run too lean, the engine will run hot. Vacuum leaks can also result in a hot running engine (leaning the mixture out). I once turned an exhaust manifold glowing red all because the timing was so far off. I don't know how far off because I adjusted it on the side of the road. But my mistake was driving the car after I tuned it but had forgotten to tighten the dizzy bolt down.

 

[JackFish]

I'm wondering what sort of temperature differential one would see be by changing jet sizes?
How much of an effect does this have?
I went up two sizes from stock on my 1bbl with the modified engine. It runs pretty cool, but I didn't have the guage installed at the time to compare.

 

[MPGmustang]

okay, drove to work then read temps
top: 180*
bottom: 165*
with the A/C on the whole way

it was roughly 95* this morning (cooler than norm)
just for referance, I'm measuring the top inlet to the rad and the bottom exit (what the engine gives and gets). I don't have a cooling issue, I have a I'm in AZ issue...

I think I'm going to try that fiberglass fan shroud, It'll be intresting on how it turns out in hotter weather.

 

[69.5Mav]

Okay, so I used my temp guage... checked at idle and driving (or after driving)
outside temp at 108*
Idle: this is without A/C
top = 180*
bottom = 161*

The Temperature difference between the top and bottom tank is a measure of how much heat is being extracted from the radiator. At 108 degrees air temperature the coolest you could get the coolant temperature to is 108. With a top tank temperature of 180 that would be a difference of 72 degrees. But this would be really difficult to do and the car would be too cumbersome to drive. As the coolant temperature approaches the air temperature heat flow slows down. So to get the last few degrees would take heroic and unnecessary measures. I got the 40 degree temp. dif. from measurement of many automotive cooling systems in various climates. It's just a rule of thumb and needs to be used judisously. Still with a good radiator and good coolant and air flow at a coolant temp.of 180 and air temp of 108 you have no trouble pulling 40 degrees out of the coolant. That would leave you at 140 degree coolant temp. Which should be quite capable of absorbing excess engine heat bringing the coolant temp back up to 180 or above. Coolant temp. will rise to the point where the heat being generated by the engine is equal to the heat being extracted from the radiator.

The thermostat. A long debated subject. Should one leave it in or take it out. It depends. Most cooling systems in good shape have enough margin that the thermostat being in poses no problem. Removing it delays heat build up and adds a small amount of extra flow to the system. I would say leave it in as it sets the lower limit of coolant temp. the engine will see and helps the engine warm up faster. Warming up faster saves gas. My 08 Prius runs coolant around the exhaust manifold to speed warm up. In some climates people change thermostats twice a year, using a summer one and a higher winter one.

This time try the same test after the car is warmed up and at idle. After taking your first set of reading use a household fan of at least 20" in diameter held in front of the radiator don't rev the engin to increase airflow because this also increases heat production in the engine and water pump out put, you want to keep everything the same except for increasing the air flow. If your bottom tank temperature drops then you don't have enough air flow. If you don't have a shroud get one.

Any way a bit rambling but that’s my opinion.

 

[66 Fastback]

Temps don't sound out of line to me. My Pointiac has a stock 192 deg thermostat. With a new aluminum radiator it maintains about 208 deg, about what my 94 Olds has always done.

As has been mentioned, check timing and verify the vac advance is functioning correctly. You mention you might have about 30 deg at idle. That may be a bit much and is likely contributing to the Pinging.

CobraSix mentioned the fan. Do you have an upgraded fan? The 4 blade fan was for non-AC cars and is inadequate.

Question about higher coolant flow helping? Yes, any time you increase either the coolant flow or the air flow, you are helping the heat exchange rate. More coolant flow brings more heated coolant mass across the radiator tubes and maintains a higher internal tube temp which increases the temp differential across the radiator. Same is true of more air flow. More air flow will keep the exterior surface of the radiator at a lower temp and increase the temp differential. The temp differential is the voltage or pressure that is driving the heat flow across the materials.

You can increase the coolant flow and air flow by changing the pulley diameter. Some cars that had A/C came equipped with smaller diameter pulleys on the water pump / fan. A smaller diameter pulley will spin faster at the same engine crank rpm increasing both coolant and air flow.

One thing to keep in mind about the AC is that once the air passes through the AC condensor, it has been warmed up well above the 105 deg ambient temp, so the temp differential at the radiator is less. Also check the fins on the condensor. They take the majority of the hits from the rocks bugs etc and they fold over easily or get plugged with bugs and rocks. I have spent hours with radiator fin combs and a couple of screw drivers picking out the debris and straightening bent fins on condensors and radiators to restore the air flow.
Doug

 

[69.5Mav]

Yes, any time you increase either the coolant flow or the air flow, you are helping the heat exchange rate. More coolant flow brings more heated coolant mass across the radiator tubes and maintains a higher internal tube temp which increases the temp differential across the radiator. Same is true of more air flow. More air flow will keep the exterior surface of the radiator at a lower temp and increase the temp differential. The temp differential is the voltage or pressure that is driving the heat flow across the materials.

Couldn't hve said it better myself. Wish I had. You sound like an electrical engineer.

 

[1bad6t]

any time you increase either the coolant flow or the air flow, you are helping the heat exchange rate. More coolant flow brings more heated coolant mass across the radiator tubes and maintains a higher internal tube temp which increases the temp differential across the radiator.

It is possible to have too much flow and the coolant will not have time to suck the heat. This is why they make restrictors to absorb heat.

 

[woodbutcher]

The only new car that I ever owned was a 1971 Toyota Corolla 1600 with all options.
The AC compressor had a really neat feature.Under 1600 RPM the compressor would disengage.Such as at a stop light or in heavy traffic.Wonder if all the newer vehicles have this feature?I thought it was pretty neat.The car had a 4 speed manual tranny.
Leo

 

[PhantomAce]

An idea...
If you have the room for it, try putting some 1/2" stand-offs between the radiator and the condensor.
The A/C may not work as well, but you'll allow the fan to pull a little "extra" air around the edges of the condensor and through the radiator.
What's the worst it could cost? Four bolts 1/2" longer and a little bit of steel tube to make the stand-offs...
Might be enough to balance out the engine temp without sacrificing too much A/C efficiency.
Just a thought, IMHO.

 

[JackFish]

any time you increase either the coolant flow or the air flow, you are helping the heat exchange rate. More coolant flow brings more heated coolant mass across the radiator tubes and maintains a higher internal tube temp which increases the temp differential across the radiator.

It is possible to have too much flow and the coolant will not have time to suck the heat. This is why they make restrictors to absorb heat.

Exactly, the thermostat is a regulator.
From the 4x4 pirate site:

The thermostat is the "brains" of the cooling system. Recall how we said that the job of the "cooling" system was actually to regulate or control the temperature of the engine to keep it as close as possible to the designed normal operating temperature at all times? It is the thermostat that accomplishes this.

Here's a good read, although it's GM related:
http://www.pirate4x4.com/tech/billavista/Cooling/

Because the old-style thermostats were located at the top of the engine where coolant temperatures are highest, and because any vapour or trapped air always seeks the highest point in a system and therefore could get trapped beneath the thermostat, this design can lead to unwanted thermal cycling as the area of the thermostat heats and cools causing the thermostat to repeatedly open and close.

A small air pocket could account for the type of temperature cycling that some people see.

 

[66 Fastback]

You sound like an electrical engineer.

Petroleum Engineer, so I probably understand fluid flow a bit better than I understand "magical" "invisible" electron flow. I just wish the electrical engineering and thermodynamic courses had made more sense in college. In my career, I have had a stint as a facilities engineer with generators, turbine powered pumps and refrigeration gas plants. I had to re-educate myself on electrical and thermo.

It is possible to have too much flow and the coolant will not have time to suck the heat. This is why they make restrictors to absorb heat.

That is an old myth that people argue for the coolant side of the equation. But I never hear anyone state that you need to reduce the air flow across the radiator in order to get better cooling because the air is moving too fast. Intuitively everyone knows more air flow will increase cooling. It is the same on the coolant side of the radiator too. More coolant flow will aid cooling.

In some cases the flow restrictors see success, but it is typically on race engines where the water pump is running at high rpm's, outside of the intial desing envelope that the pump was designed to operate at. If a stock engine is hopped up with go fast goodies and the engine makes more HP and heat and the engine rpm's are running high, then water pump can cavitate because the coolant is operating closer to the boiling point and the higher pump speed pulls the suction down. So the coolant flashes and reduces pump output. Adding a restrictor plate increases the back pressure on the pump. This reduces the cavitation and although pump output is restricted, it pumps more fluid than if it is suffering cavitation. The restrictor plates treated a sympton, not the problem. Back when the plates were more common, you could not run down to the parts store and buy high performance water pumps or larger pumps like you can now. It was a way of making what you had work. Racers used to remove vanes from the water pumps to get them to work better on their race engines. Again that is because they were operating pumps under conditions that they were not designed for.

The only new car that I ever owned was a 1971 Toyota Corolla 1600 with all options.
The AC compressor had a really neat feature.Under 1600 RPM the compressor would disengage.Such as at a stop light or in heavy traffic.Wonder if all the newer vehicles have this feature?

My Mom's Lumina used to cut out the AC when you accelerated hard. It had a fairly gutless engine.
Doug

 

[Lazy JW]

.....
That is an old myth that people argue for the coolant side of the equation. But I never hear anyone state that you need to reduce the air flow across the radiator in order to get better cooling because the air is moving too fast. Intuitively everyone knows more air flow will increase cooling. It is the same on the coolant side of the radiator too. More coolant flow will aid cooling.


......... This reduces the cavitation and although pump output is restricted, it pumps more fluid than if it is suffering cavitation. The restrictor plates treated a sympton, not the problem....

Amen to that, Bro
Removing the thermostat has ALWAYS resulted in lower coolant temps for me; my experiences have always been at "normal" speeds though, never a racing application.