jcomp

Hey everyone. It seems like we get a lot of questions about overheating in this forum so maybe we can answer the more common questions with this thread. I think we all now how frustrating overheating issues can be so lets try to make this thread into something that can help some people out. I think we should try to keep this discussion at the level where people who are just getting into the hobby can understand the discussion. Perhaps this information could eventually become a sticky.

First off, here's some basic reading about automotive cooling systems in general:
http://auto.howstuffworks.com/cooling-system.htm <-- This should be considered required reading for this thread

Radiator Information:
http://www.griffinradiator.com/faq.php

Fan Clutch Information:
http://www.haydenauto.com/products/f...fan-blades.htm

Here is some troubleshooting information:
http://www.gtoalley.com/ttcool.html
http://www.theautochannel.com/mania/repair/cooling.html


If your car is overheating, there are a few things that you need to know before you can begin troubleshooting:

1. Is it really overheating? Factory temperature gauges are notoriously inaccurate. I mean, they usually don't even indicate any values. Even a cheap aftermarket mechanical temperature gauge would be more useful. Get one and mount it where you can keep an eye on it. If you want to keep your car looking original, you could use an infrared thermometer to check the engine temperature (I'd shoot the thermostat housing with it). Or maybe mount the gauge out of sight in the glove box or wherever. I would consider a temperature of more than 10 degrees over the thermostat rating to be too hot. I would consider 220-230 to be getting too hot. However, I would like to get more opinions here.

2. WHEN does it overheat? Sitting in traffic? Cruising down the highway? All the time?

Now that you know when and how bad it's overheating you can begin the troubleshooting process:

1. Replace your thermostat.

I know, it might not be bad and you could test it instead (put it a pot of water on the stove, heat the water and note the temperature where the thermostat opens), but they are cheap and you would have to take it out to test it anyway. Running without a thermostat is a BAD idea. I use 180 degree thermostats, but this is a matter of personal opinion. Make sure the thermostat is not installed backwards or it won't work properly. A lot of people recommend drilling a 3/16" hole in the thermostat (near the outer edge) to allow trapped air to escape from the engine. When you look for a thermostat, try to find one of the "Balanced HP" units.

2. Inspect your radiator.

How many rows of tubes does it have? If you look down into the radiator you will see small rectangular openings in a grid pattern going down towards the ground. Count the number of openings in a horizontal row and that's the number of "rows" your radiator has. For a copper/brass radiator (stock style), it's common to see 2, 3, or 4 rows. In general, the more rows the more heat the radiator can dissipate and the better it is. However, each row heats the air as it passes over it so the rows behind it don't cool as well. This is why radiators with more than 4 rows are not common. An aluminum radiator is more efficient and is generally found in one or two rows. According to Griffin Radiators, "an aluminum radiator with 2 rows of 1" tubes is equivalent to a copper brass radiator with 5 rows of 1/2" tubes". If you've got a 3 or 4 row stock radiator or a 2 row aluminum radiator in good condition then your radiator is probably not your problem. Overheating on the highway is a sign that your radiator might be too small or dirty.

Is the radiator clean inside? A white crusty build up on the ends of the tubes means the radiator needs to be cleaned or replaced. Now might be a good time to upgrade to a direct-fit aluminum radiator.

Maybe someone can post a picture of a bad radiator?

3. Inspect the water pump.

Look for coolant coming out of a small hole in the water pump. Make sure the drive belt is tight and you don't hear it squealing when you accelerate. In my experience, the water pump is not often the cause of overheating but these quick checks don't take long.

4. Check your hoses

Squeeze the lower radiator hose while the engine is cool and the radiator cap is off. There should be a spring inside the hose that prevents you from pinching it very far. This is the suction side of the water pump and if the spring is missing the hose might collapse and prevent coolant from circulating through the engine. While you're at it, check the rest of the hoses for bulges, soft spots, worn areas, or leaks around the ends. Replace as necessary.

5. Let's talk about Fans
Engine cooling fans are a topic that is shrouded () in mystery and misinformation. There are many varying opinions on the subject and it's easy to be confused. We'll start with a description of the main types:

a. Solid Fan: This is a fan that bolts straight to the water pump (or to a spacer on the water pump) and has fixed, immovable blades. This is the kind of fan you see in house fans or even a ceiling fan.
b. Flex Fan: This one looks similar to a solid fan and bolts on in the same manner. The difference is that the trailing edges of the fan blades are flexible.
c. Clutch Fan: This fan has a solid fan blade attached to a clutch assembly that allows some slippage. This allows the fan to turn slower than a direct attachment.
d. Thermal Clutch Fan: Similar to the clutch fan but the clutch will disengage the fan below a certain temperature.
e. Electric Fan: A solid fan that is driven by an electric motor.

The three most common of the above list are the flex fan, the thermal clutch fan, and the electric fan. For the sake of brevity, I'll just sum up their pros and cons:

A flex fan is cheapest. It is driven by the water pump pulley. It may not move enough air at any engine speeds to cool the engine. It is less efficient at moving air than the other two and requires a fan shroud.
A thermal clutch fan will move the most air of the three at anything but low engine speeds. It is driven by the water pump pulley. It may not move enough air at low engine speeds to cool the engine. The cost greater than a flex fan but far less than an electric fan. It requires a fan shroud and more space between the radiator and the water pump than the other two.
An electric fan is the most expensive but does not necessarily require a shroud so it may be the easiest to install. It is not directly driven by the engine so it will move the same amount of air at all engine speeds. It may require a larger alternator. They are given airflow ratings by the manufacturers (in CFM or cubic feet per minute) but there is no standardized test for the ratings.

OK, now that that's out of the way, let's look at your fan. We've already checked that the belt driving the water pump is tight so if you have an engine driven fan we're set in that department. Now here's where things get a somewhat controversial due to the different opinions out there:
Do you have a flex fan? If so, look into getting a thermal clutch fan after you've checked everything in this post.
You have a thermal clutch fan? Run the engine until it's HOT and turn it off. Immediately open the hood and spin the fan blade by hand. If it keeps spinning after you let go, the clutch is bad and should be replaced. If it stops right away, your fan is not your problem unless you've got an underdrive pulley on the water pump that is spinning the fan too slowly.
Electric

lucastrex

Alright, here it goes: I've been researching the cooling system for some time here in the forums, and I appreciate the time everyone has put into this problem. I'm still not sure how I want to procede so please let me know what you think, and thank you all in advance for your input. I also apologize in advance for my limited mechanical knowledge and will do the best I can to describe the situation.

My ride: 1966 Mustang coupe, rebuilt 302 bored .030 over,radical cam (575 solid lifter), 4.10 gear,C4 trans withtrans. cooler

Cooling system: aftermarketcopper/brass3 row radiator, 8-blade electric puller fan with shroud(no mechanical fan), stock water pump, thermostat with guts removed (constant, but restricted flow), rubber lower hose with no spring inside

Observations:
1. No visible leaks in system, no loss of coolant, however, coolant was dirty brown with small debris inside.
2. Radiator shop brief examination while in operating range: Measured temp. of top radiator hose at 200 degrees and lower hose at 150 degrees. Alsothought lower hose was fine even withoutspring.
3. Maximum temperature to date: 220 degrees, most often obtained at sustained highway driving. Car cruises 60mph at 3000 rpm. Sustained cruising STEADILY RAISES water temp even when 70 degrees outside. Exiting highway and driving between 2000 and 3000 rpm DECREASES water temp.

What I've done so far:
1. Flushed radiatorwith liquid flush, followed instructions to the letter. Fluid still not crystal clean.
2. Lessened anti-freeze amount: now mostly distilled water, a little anti-freeze, and 1 bottle water wetter.
3. Changed timing from 12 to 10 degrees.
These may have helped delay heating up, but not prevented it from seeing 220.

Questions:
1. Radiator shop said 50 degree difference between the hoses proves radiator is cooling the fluid, however may benefit from rodding out ($80) as fluid is not clean. Will this improve cooling? What is the desired temp. of the lower hose? Will aluminum radiator fix or mask problem, or do nothing?

2.My "old school" friend who built the car claimed the "guts out" thermostat provides the proper restricted flow to ensure the thermostat never gets stuck and causes a tragedy. I've heard of others doing it, but several people have suggested trying a 180 or even 160 degree thrermostat with the 1/8" hole drilled in it. I've seen enough negative postings on the 160 to make me nervous about it. Opinions please.

3. Should I be heating up during highway driving like I am? Lower hose: Do I need one with a spring? Will that keep the temp. lower during those highway runs? If so, do all the parts stores have it, or do I need a Mustang specialty store?

4. Stock water pump ok? Do I really need an aftermarket one, or not at this point yet?

5. What type and ratio of coolant should I go with. I'm leaning toward the 50/50 mix as changing it didn't help me enough to warrant the potential headaches of not having enoughanti-freeze in the winter.

Solution to which I'm leaning:
1. Rod radiator, and replace lower hose (to one with spring) whileradiator's out.
2. Run 50/50 green coolant & distilled water with 1 bottle water wetter.
3. If unsuccessful, try 180 degree thermostat.

Ok, a mouthful I know. Your turn, let her rip.

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Jakaru

I have a question. Why would it be bad to run without a thermostat? If it's because it can keep cold or even frozen coolent out of the engine what about those like me running in az and keep their ponnies in the garage? I would rather run without a themostate if there is no detriment because that would leave one less thing to malfunction.

It's still 110 or more here and I think it got below 32 degrees once for an hour or so last winter.

73 Sportroof

2 things on running without a thermostat. Running cold can be as hard on an engine as running hot, and without it the water will flow to fast and if it does heat up the radiator will not have time to cool the water.

67mustang302

There's also a metallurgy aspect to engine tempurature. The iron in the block, the aluminum in the heads and pistons, it's designed to operate under a certain tempurature. Without a stat the cylinder walls and rings will wear more and your engine won't last as long. Also, the warmer an engine is the more efficient combustion is. I run a 195 and have no problems. A cooler stat is good for a blown application where lower combustion chamber temps may help control detonation.

As far as the overheating issue, don't retard the ignition timing, it'll run hotter. If it has a prettylumpy cam than most likely it's gonna need more than 12deg initial, possibly as much as 16 or 18 depending on manifold, cam and exhaust. How much power is it putting down? You may not have enough cooling system for the engine, but I doubt that's the problem. Rodding it out will definately help, and you may wanna think about an aluminum high flow water pump. I run a high flow pump on mine with a 195 stat and a 3 row copper/brass radiator and even in Bakersfield summer temps of 110deg or higher it doesn't overheat, either at cruise or idle

jcomp

Those are some good observations, very detailed. Do you know how much HP you are making?

2. I've never made measurements of the temps out of the radiator so I can't really comment there. I don't know if 150 is average or not. However, the fact that you are still running hot would suggest that it is too high.

3. 220 isn't going to hurt your engine but it does show that your cooling system is having trouble keeping up. A reason your car is getting hot during sustained cruising is that your engine is continuously making more power to keep the car moving at that speed. More power = more heat. Airflow should not be an issue because of the "ram" effect pushing air through the radiator. However, your electric fan with shroud may be causing a restriction and preventing the air to pass through the radiator in sufficient volume. You could try putting on a thermal clutch fan (without shroud if necessary) and removing the electric fan. Take it for a cruise on the highway and see if it helps. Common knowledge is that you don't need a fan on the highway but I would still want something. You can pick up a thermal clutch fan at a junkyard for cheap, make sure the clutch isn't leaking fluid and doesn't have any wobble or play in it, and that the fan blades are not cracked or bent.

You also mentioned that the coolant was dirty, it is also possible that the radiator has some deposit buildup inside. When you look inside, do the ends of the tubes have any crusty white buildup? Even though it's likely big enough, it may no longer be able to dissipate as much heat as it used to.

It's my understanding that the liquid flush is OK but will not take the place of having the radiator rodded out. Have you considered installing a coolant filter?
I'm glad you mentioned distilled water, it is something I forgot to mention above.
Is your vacuum and/or mechanical advance working?

1. Like I said above, I'm not sure about the radiator outlet temp measurement. I think rodding out the radiator will improve cooling due to the dirty coolant you had. I think an aluminum radiator would be a better choice. I believe in getting the biggest radiator that will fit, if for no other reason than to rule it out as a problem when I'm having overheating issues.

2. Most of what I've read says that you need to be running a proper balanced high-flow thermostat. I'm glad you mentioned drilling the hole in them, it is something I forgot to include above. I use 180 degree thermostats.

3. Your lower hose may be collapsing, but I don't think it's your entire problem. You mention that you are overheating at 3K RPM on the highway but not at 3K otherwise. The water pump speed and coolant pumping will be the same in both instances. However, getting a proper hose would eliminate it as a possibility. All parts stores carry them.

4. Maybe someone else will help out with this one. I would think the stock pump would be fine but I don't know what its limitations are. Are you using underdrive pulleys?

5. I would go with 50/50 and find out what the real problem is.

All three of these sound good. I would do the thermostat regardless. If these steps don't help, then take a hard look at the fan like I described above.

valley firearms

For those of you who like to do your own work, cleaning a radiator is simple. When I was younger, I used to flush my own radiators with great success. Two words, muratic acid. Remove your radiator from your mustang. Leave the cap on. Lay it in a wheel barrell with the inlet and outlet facing up. Pour enough muratic acid in one of the outlets and rock the wheel barrell from side to side so the acid flows through the tubes. After a few minutes fill the radiator with water and dilute the acid enough so it's not harmful. Repeat if neccessary. After you have flushed the radiator. take a old bike inner tube and cut it in half. Clamp each end of the tube to the inlet and outlet and charge with air. Next take a spray bottle with a water/soap mixture and spray the entire radiator. The acid would have eaten away any stop leak or debre that may have plugged any pin holes in the past. You are looking for leaks that may have appeared during the acid flush. If you find any leaks, drain the radiator off any water and solder the pin holes with a small torch, flux, and 50/50 solder. When soldering pin holes using 50/50 you don't need to get the spot too hot. Heat the area, hit it with flux brush to clean off the old paint. Heat it a little more and give it a little solder. Test again.

I have seen great results doing this myself. I have soldered top and bottom caps and outlets using a torch. It's not that difficult. Save your $80 and do what they would do for $5.

It is very important to do this outdoors in a well ventillated area. I never used safety equipment back then and never had any problems. I suggest you wear protective gear (respirator, gloves, face shield) just in case(my disclaimer). You don't want to look like jcomps avatar if you slip up.
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Arcticspook

Jcomp,

Thanks for taking the time to put that much effort into your post. I learned a lot.

lucastrex

Thank you all for your replies.

valley: thanks for the tip.


Jcomp:

1. Sorry, I don't know the horsepower. Ballpark estimate 300.

2. That's the first I heard that my elec. puller fan/shroud could be causing restricted airflowon highway...interesting.

3. I didn't think I had a lot of crud in radiator & reservoir, but heard that ANY is too much...should be CLEAN. I have crud, so will definitely rod radiator and flush everything else too. Reference filter, once system is clean, should i need filter? Filter has gotten some negative press in my online research. Your link did not work jcomp, sorry.

4. Is vacuum/mechanical advance working? Sorry, I don't know how or whether this works.

5. LOWER HOSE !@#*? (headache): Can't find one with spring. Is "flex hose" what guys are referring to with the spring, because I can't find any other. This is what i find:
http://www.partsamerica.com/ProductD...64&PTSet=A
I've reada ton of posts from guys claiming they've purchased lower hose with spring, but would appreciate a direct link right to the part please!
The mustang specialty stores don't list the hoses as having springs in them...i have calls in to a couple,and am waiting for reply.
Also, is the lower hosethe only one i should change if the others look fine and don't leak?


67 mustang 302:

1. What is your max operating temp with that 195 stat?

2. Does my 575 lift cam need more than 12 deg. initial timing, and if so, why? FYI, I have Cobra intake manifold, Hooker super comp long tubes, and 3" exhaust. Again, horsepower is unknown...best (un)educated guess is around 300hp. If cleaning my system does not solve problem, should I advance timing in small steps to see if it helps? Please lay this out for me.

3.What high-flo water pump do you have? Is your motor worked, rear gear, etc.similar to mine?


ALL:

1. How do I flush the enginewhen I have the radiator out? Is it as simple as spraying a garden hose into the top hose until water comes out the bottom clean?

2. I read that improper valve adjustmentcould cause overheat. Previous owner said he intended to do a valve adjustment, but i don't know the reason for this.Is valve adjustment something related to havingsolid lifter cams? If so, how often should it be done or why?? Could it be the problem?

Important to note I think is:
1. Other than heating up, the car performs great (no hesitation, detonation). She's an animal.

2. I seem to burn oil when it runs hot also. No smoke or leaks, just have to add some every now and then. Mobile 1 15W50 too!

3. I just get the feeling I wasn't meant to be on the highway or at 3000 rpm for any length of time. Does anyone feel that no matter what cooling changes i make, my setup will not run cool enough at sustained highway driving. Any other worked motors/4.10 gears out there enjoying unlimited cruising w/o heating up? Should i consider another rear gear. What gear is a balancefor bothhighway and good acceleration. I love when i mash it, she jumps...but hate my top cruising speed of 60 mph! Yeah i know, want my cake and eat it too.

lucastrex

I've been reading a ton of other people's experience, and I think this might help:

My car doesn't overheat within a few minutes of starting up. It takes a while, unless driving at high rpm (3000). People whose timing is off seem to heat up very quickly.They also seem to usually have other signs such as backfire or other lack of performance problem other than overheating. I don't, so I'm not convincedthat timing is the problem.

With ambient temp in the 80's Idrove for 30 minutes at variable speeds 3000 rpm & under and didn't break 200 degrees. The other night after she hit 210 on highway (still climbing, but i got off), she dropped to 190 while driving local roads home. After that I let her idle for 10 minutes and she stayed at 190.Does this mean my problem is only withsustained driving at 3000 or more rpm?