How can I keep my 2.9 cool?

[PetesPonies]

First of all . . wow, do we have some inaccurate info being slayed around as gospel. A properly designed cooling system will overcool an engine if allowed. If it cannot do that, then it is not properly sized. Fact, forget everything else, this is gospel.
Second, as junkie said, the thermostat will then control the operating temperature of the engine by controlling the temperature of the coolant. Typically the operating temperature will be about 7 degrees over the rating of the thermostat.
Adding a 4.0 radiator is a decent choice, however a proper operating 2.9 radiator should keep a proper operating 2.9 engine cool. So you decide where the problem is. The 4.0 radiator will certainly do the job and WILL NOT cause any temperature problems with the 2.9. I happen to be using a 4.0 radiator with my V8 swap and it does just fine.

 

[70roadrunner]

you said you go mudding a couple times a week. is the radiator clogged with mud? have a buddy shine a light through the radiator and see if you can see the light. if you cant see through it, air cant flow through it

 

[4.0B2]

I like the Taurus 3.8L e-fans... wire the low side on a temp switch and wire the high side on a toggle switch and to your a/c... The low will move enough air to keep it cool for normal driving in most cases and the high is great for trails or really really hot days.


but yes, you should be able to use the stock system and keep it cool. Try bypassing your heater core and doing it again, if it's partially stopped up... you'll see the difference. maybe have a radiator flush done... check all your hoses and stuff.

 

[Shran]

A properly designed cooling system will overcool an engine if allowed. If it cannot do that, then it is not properly sized. Fact, forget everything else, this is gospel.
Second, as junkie said, the thermostat will then control the operating temperature of the engine by controlling the temperature of the coolant

This is key information here - properly designed cooling system is the important part.

The 4.0 radiator swap ads a large volume of coolant, given fact. Therefore it takes longer to heat it to operating temperature. Because of this, the thermostat stays closed for longer intervals, allowing the water in the radiator to cool much more than it normally would. When the thermostat opens you get a huge rush of cold coolant.

Keep in mind we are talking about fuel injected engines that partially rely on coolant temperature to set the fuel/air mixture. We're not off in carburetor land where anything goes. That huge rush of coolant has a dramatic effect on your coolant temp sensor.

Y'all can tell me I'm wrong all you want, I've done the swap three times in three different vehicles with the same results. There is some science behind the reason why every vehicle doesn't have a huge radiator.

 

[PetesPonies]

I initial burst of cold coolant into the system may temporarily cause the thermostat to close, but this is normal. It happens anyway when they first open. And this goes away as the temperature settles in. Not an issue.

 

[kimcrwbr1]

Actually the thermostat performs two functions it allows the engine to reach operating temperature and it also restricts coolant flow through through the radiator for a heat exchange to take place. If it takes a long time for the engine to heat up the thermostat is likely to be stuck fully open. It dont matter how big a radiator is if the coolant is flowing too fast through it you will get a constant rise in temp especially with reduced air flow through the radiator. My 2.8 would overheat constantly even after a complete system, radiator, thermostat, water pump. What finally cured the problem was a good engine flush. I pulled the pump and thermostat and blasted the block out good with high pressure water it was amazing how much crap came out and have never had any problems even on the hottest days. The heater works faster and the temp stays more constant. Also check the bypass ports and clean them good my theory is if the bypass and block are good and clean the water pump circulates the coolant fast inside the block keeping it all the same temp and when the thermostat opens up the cool mixes better with the hot and your not gettin alot of extremes and the thermostat finds a balance point. The coolant will follow the easiest path so if the bypass is restricted the cool coolant is not allowed to circulate properly in the engine. In general if the engine is overheating check the temp of the lower radiator hose if it is cool the thermostat is likely stuck closed, if the hose is real hot the thermostat is stuck open or the radiator is plugged look for cold spots on the radiator. In my opinion you cant have too much radiator you just need to schroud it properly so the fan is pulling air through the entire area and the fan is moving enough cfm`s to transfer the heat. Thats the first time I have heard of a two speed fan maybe you could wire it to 4 low so it automatically turns on high when your wheelin. It`s monday so far the boss hasen`t called so I thought I would stir the pot

 

[PetesPonies]

Well this time, fortunately you "read" the correct information.

 

[Shran]

I initial burst of cold coolant into the system may temporarily cause the thermostat to close, but this is normal. It happens anyway when they first open. And this goes away as the temperature settles in. Not an issue.

It certainly is an issue when it's 5 degrees out, you have no defrost and you're getting 11mpg all day just because of a stupid radiator.

Maybe it's a total different thing down south where it's a little warmer, but for a daily driver vehicle in cold temperatures, it's pointless. Don't fix it if it ain't broke.

 

[PetesPonies]

It's not an issue with engines period. It's not a design issue. What you are talking about is monetary. You are not understanding what fully happens and how long it happens. Don't guess.

If the thermostat will close when the cold coolant from a 2.9 radiator is let in, then whether or not a ( in this case slightly ) larger radiator lets coolant flow in, it is still going to close momentarily. And it will again open quickly and let in more cool coolant. Your engine will still be circulating the warmed coolant, letting it warm up as it should and send the warmed coolant to your heater core. No change at all.

 

[kimcrwbr1]

When it is that cold yes you want the engine to heat up cover half the radiator with a piece of cardboard and see if that helps bring it up to temp quicker. Just the coolant flowing through the heater core is probably able to keep up with the demand not allowing the thermostat to open. Maybe run the engine with the heater off and see what that does. It kinna sounds to me like the thermostat is not sealed properly allowing coolant to flow through the radiator before the engine is up to temp. The radiator is doing it`s job sounds to me.

 

[Shran]

I'm not guessing, I'm speaking from experience. I've done the swap three times with the same results. I had three vehicles - '86 Ranger, '87 Bronco II and '90 Bronco II. The cooling systems in all three were in good shape, no issues. The radiator swaps were done simply because it seemed like a good idea and the parts were free. All three resulted in very long warm up time and poor gas mileage. Night and day change.

I am not a scientist nor an engineer, I am just a guy who works on stuff with a basic understanding of how this stuff is supposed to function. I get that there is some science behind what you're saying, and you are right, but based on my real life observations, I am too.

 

[kimcrwbr1]

To show you how heat exchanges one thing to know is heat allways travels from hot to cold. Fill the bathtub with hot water and add cold until you can get in. Note the amount of cold you added. Then fill the tub half full of cold water and add the same amount of hot you will see it takes alot more hot water to change the temp. The same is happening with the coolant system. Guys have drilled too big of weep hole in the thermostat to burp the system and when you start the motor it is allowing a constant flow of coolant through the radiator and the coolant in the engine takes alot longer to heat up. If you add a weep hole to the thermostat it only needs to be 1/32 or smaller to allow the air to pass by when the thermostat is closed.

 

[bfiakas]

Have you installed a back flush kit in the heater hose to flush out the block? 192 deg. is stock for the T-stat.Install a new water pump and radiator cap and hoses (Gates reenforced type)

 

[4x4junkie]

I'm not guessing, I'm speaking from experience. I've done the swap three times with the same results. I had three vehicles - '86 Ranger, '87 Bronco II and '90 Bronco II. The cooling systems in all three were in good shape, no issues. The radiator swaps were done simply because it seemed like a good idea and the parts were free. All three resulted in very long warm up time and poor gas mileage. Night and day change.

When I'm up in Oregon during the winter when it's anywhere from single-digits to low-20s at best in the mornings I still get 19-20 MPG (and have nice warm air coming from the vents maybe 5 minutes after starting it).
I still say you had a thermostat issue (using the wrong temp or brand or something) or there was another issue with the vehicle.

Also, thermostats open gradually, they don't click open and closed allowing sudden cold rush of coolant into the engine like you're saying (at least that's what the Stant one I have here does).

I do agree however you wouldn't need as big a radiator in the colder north than in the hot southwest, but again, the thermostat is what should be regulating the engine's temp, not the radiator.

 

[Tedybear]

I'm a bit surprised no one has asked about the fan cooling clutch. If the truck goes down the highway at normal temps (50mph+) and is good? But you get it into town for stop and go driving or idle...and the temp goes to high? That's a clear sign the cooling fan clutch is on the way out. It's designed to tighten a 'clutch' on the pully/fan unit to increase the RPM as the temp increases. It's a simple spring kinda like the old school carb's use for the choke. This one just tightens/loosens a clutch pack for the fan.

If that's going bad? The fan won't spin fast enough when at low speeds and the engine could overheat/run hot. Quick and dirty test. (not 100% accurate, but it gives a good idea). Idle the truck until it's hot and the thermostat is open and at temp. (no--don't overheat the engine). Watch the cooling fan. Now the whole thing is at temp, and you do not have a stream of cold air hitting the clutch spring at the front of the fan (which is what happens at highway speeds....cold air is already being rammed into the front of the engine/radiator...so why use a lot of fan RPM's when it's not needed?)

Now when it's running at the normal temp....shut the engine off and watch the fan blades. They shouldn't free spin that much. (The clutch should be just about fully engaged...and running the blades at about the same RPM as the engine belts are spinning it) So when the engine is shut down? If the fan blades just sit there and free spin quite a bit? You should consider a new clutch for the fan. (You'll have a little spin....as it's not a direct 1 to 1 ratio...But if you can grab the fan blades with the engine off and it seems to be quite free spinning after doing this test? Your clutch is shot.)

Just my .02cents

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