Inadequate Cooling

[MagicMexican]

So, I've always been the guy who just rolls his windows down and deals with the heat, but this year it's been so damn hot, I decided I'd splurge a little and turn on my AC.

Holy crap, it's nice. Especially for a '96, it blows the air ice cold. And now I'm spoiled. The only problem is that if I'm running the AC, and I happen to go up a hill, my engine temp starts to go up.

Usually, my temp gauge sits around 1/3, but with the AC on and going down the highway, the temps eventually go up to the halfway mark. Still no big deal. But then once I start going uphill, it starts to climb higher than that. I usually shut off the AC at that point.

Is this normal? I know both the AC and hills
put more strain on the engine, but is this something that just happens, or could my cooling system be running at less than 100%? I would just 'get over it' and turn the AC off when going uphill, but I plan to eventually add a supercharger or swap for a V8. If my radiator can't even handle AC, it won't do forced induction well, either. So, if that's not normal, what can I check? Or if it is normal, what are some recommendations for upgrades?

 

[Mark_88]

It is normal for this to happen...especially on really hot days. It's actually a matter of how accurate the temp gauge is and whether it is indicating the correct temperature to begin with.

The following was posted by RonD a few years ago and might help you understand how this works.

"There are two temp sensors on EFI engines, a 2 wire and a 1 wire sensor, the 2 wire temp sensor, also called the ECT, is for the PCM, it is in essence the "choke", it tells the PCM to run engine rich until it warms up.

The 1 wire sensor uses the engine as the ground, and the 1 wire just runs back to the dash gauge, the sensor itself is just a heat sensitive resistor as it warms up it has less resistance."

So the 1 wire is the one indicating your information on the dash gauge and unless there is a problem with the grounding or the wire running to the dash then it is, essentially, working properly.

The only problem I've ever had with these gauges is when I had an overheat on my first engine the temp gauge never worked properly after that and almost cost me another head replacement when it didn't indicate my engine was overheating. I only knew this was actually happening because when I stopped at a light I could smell it and the engine was running rough...I pulled over and found the coolant was almost completely gone.

So...my suggestion would be to flush and fill the rad with good anti-freeze if it hasn't been done for a while. Another suggestion would be to remove the water pump and check the impeller on the water pump because they have been known to simply break down over the years if the proper anti-freeze had not been used and this, of course, causes poor flow to the rad for heat reduction.

I also took the time to replace the two main hoses from the engine to the rad as well as the two running to the heater box.

Replacing the heater rad is also a good idea if you know it's never been replaced. On these trucks it is a bit more complicated because it requires removing the dash...but that is not actually as hard as it sounds...just a pain if you are not familiar with it.

If you live in a hot climate then you can also consider simply connecting the two hoses together under the hood and forgetting about it since it really only functions as a source of heat for the cab...although it can be used in a pinch to help reduce engine temp slightly...but is thwarted if your coolant has been lost due to broken hoses or whatever.

 

[RonD]

Was typing this and missed Marks post, +1 to what he said

Using AC does two things that cause engine temp to climb up, most obvious is the increased load on the engine when it is turning the AC compressor.

Second thing is the AC Condenser located in front of the radiator, it gets very hot, so the air passing thru the radiator for cooling is now bumped up to a higher temp, so less cooling for rad.

First thing I would check is that the cooling fins on the condenser and rad are clean, good air flow thru BOTH means better cooling.
Overtime you get debris clogging some fins, and it doesn't matter, goes unnoticed, until you need max cooling for the systems


If you have an automatic that adds another heat source to the rad, a second trans cooler is always a good idea with any automatic, it will add a few years to its life, whether you tow or not.
A factory, in radiator, trans cooler is "adequate" not best.
When you go up hill trans fluid starts to heat up as well

Changing coolant every 2 years and Cleaning/flushing cooling system is always good.
50/50 coolant/water is recommended but that is a general mix for all regions.
If you are in the south and regularly get +90 outside temp then 25% coolant and 75% water will give better cooling.
"Coolant" is added for corrosion protection, water pump lube and anti-freeze properties, water is a better "coolant" than coolant, lol.
Corrosion protection, and water pump lube is still good down to 10% coolant mix.

25/75 coolant/water has a freeze point of -10degF, 50/50 is -35degF
25/75 has boiling point of 215degF, 50/50 boils at 222degF

Radiator cap raises boiling point by 3degF for each pound of pressure
A 14psi rad cap = 42degF increase in boiling point
So 25/75 = 257degF
50/50 = 264degF

25/75 would be what I would run in southern US, and year round if I knew -10degF would be very unlikely

You should use distilled water to mix with coolant, tap water often has minerals(salts) mixed in, the salts counter act the corrosion protection of the coolant.
Distilled water isn't boiled water, that just kills germs

Distilled is evaporated water that is condensed back to water so it leaves the minerals/salts behind and just the H2O ends up in the catch can

 

[MagicMexican]

Thanks for the replies!

I actually replaced the whole system (radiator, 2 main hoses, thermostat and water pump) about 2 years ago, when I was leaking coolant from the lower intake.

But I used water from my garden hose to make 50/50 coolant... so I'll probably flush that out soon. Mine is a stick shift. I live in southern Colorado so we get both 90+ days in the summer, and some really cold -10 weather in the winter.

What I got from your post, Mark, is that if the gauge is on, and moving, then the 1-wire sensor is 'working' but may not be accurate?

So, my plan for now would be, clean out the radiator and condenser, flush and refill coolant, then maybe replacing temp gague and higher PSI rad cap.

That doesn't really help with my later plans though, since the temps climbing is 'normal', it'll be even worse when/if I add a supercharger.
Also, more short term, I was also planning on going to 31' tires (I'm on 30's now) when these wear out. Wouldn't that strain the engine even more while going uphill? What about an all aluminum/race radiator? I've always thought they were pretty cool but could never justify buying one.

 

[RonD]

Yes, I would stick with 50/50 at your location, thin air doesn't help with cooling either, lol.

1" larger tires shouldn't matter as long as you stay in the best torque RPM band for the engine, the Lima 4cyl engines are higher RPM engines so you need to keep the RPMs up unless you are on flat ground.

You shouldn't "need" a larger rad, the Limas generally run fairly cool, most temp related things I read about them is how to keep them warm in the winter, lol, heater blows cold because they can't generate enough heat when outside temp gets too low.

The temp sender on your engine is on drivers side rear of head I believe, above oil pressure sender

 

[alwaysFlOoReD]

Don't use Teflon tape with the gauge temp sensor as the threads are the ground for current flow.

Sent from my XT1032 using Tapatalk

 

[MagicMexican]

Yes, I would stick with 50/50 at your location, thin air doesn't help with cooling either, lol.

1" larger tires shouldn't matter as long as you stay in the best torque RPM band for the engine, the Lima 4cyl engines are higher RPM engines so you need to keep the RPMs up unless you are on flat ground.

You shouldn't "need" a larger rad, the Limas generally run fairly cool, most temp related things I read about them is how to keep them warm in the winter, lol, heater blows cold because they can't generate enough heat when outside temp gets too low.

The temp sender on your engine is on drivers side rear of head I believe, above oil pressure sender

Ohhhh, crap. I posted this in the 4-cyclinder thread, I misread that as 4-Liter. I have the 4.0 OHV engine. *facepalm*

Don't use Teflon tape with the gauge temp sensor as the threads are the ground for current flow.

Sent from my XT1032 using Tapatalk

This is good to know. Thanks.

 

[Mark_88]

Ohhhh, crap. I posted this in the 4-cyclinder thread, I misread that as 4-Liter. I have the 4.0 OHV engine. *facepalm*



This is good to know. Thanks.

That's OK...just about the same principles apply to any engine...but when I see "4 banger" -- "AC" and "Big Tires" I often think you probably should have a 4.0 in there...and...like Magic...you do!

I like happy endings...

 

[Tedybear]

Don't use Teflon tape with the gauge temp sensor as the threads are the ground for current flow.

Sent from my XT1032 using Tapatalk

Opps. I've always done it that way and never had an issue? Then again I torque stuff down and that normally strips off a goodly layer of the teflon tape so it gets a good connection.

S-

 

[tomw]

Teflon tape is fine for the sensors. The tape ends up shredded, filling only the 'gaps' so that you do not have to torque down the pipe threads. I leave a bit of the threads on the sensor exposed, but I do not think it matters as long as there is conduction.
If you install a sensor, using Teflon tape, and then remove it you'll see how much metal-to-metal contact is made, and it is more than sufficient. Gooey plumbers sealant or dope, or the stick type are not as neat an application. If you remove the factory sensor, you won't find sealant on the threads. At least I didn't.
tom


Added: The general rule for overheating is:
If it overheats on the highway, your radiator is not working properly.
If it overheats in traffic, your pump is not working, though I would check that the fan(s) work also. (when the rule was written, fans were all on the nose of the water pump - well, 99.999%)

I would not get concerned about the temp rising while climbing a hill. That is normal. What is NOT normal is the temp continuing to climb... until something catastrophic happens. Temp variation is actually a sign the thermostat is working.
tom

 

[MagicMexican]

I would not get concerned about the temp rising while climbing a hill. That is normal. What is NOT normal is the temp continuing to climb... until something catastrophic happens. Temp variation is actually a sign the thermostat is working.
tom

You shouldn't "need" a larger rad, the Limas generally run fairly cool, most temp related things I read about them is how to keep them warm in the winter, lol, heater blows cold because they can't generate enough heat when outside temp gets too low.

So, Ron, knowing now that I have the 4.0, and that temps climbing a bit while going uphill is 'normal', could a larger/aluminum radiator help with that? I live in Colorado and I go into the mountains a lot, usually in the winter for snowboarding, so it's not a big deal. But in the summer, for camping, now that I've converted over to the AC side, I'd rather not worry about my temps at all.

 

[tomw]

Take a look in your owners manual for comments on the temperature gauge. As I remember, the words indicated 'not to worry, fluctuation is normal, but if it gets to the H, check things out.'
If you really want reassurance, get a non-contact thermometer and read the temperature of the upper radiator hose. Get it cooking, climbing to Berthoud Pass for example, and pull over in a rest-stop to check the temperature.
tom