Canary in the coal mine for my water pump?

[StreetCreeper]

I know this is splitting hairs and in no way cause for concern on my part — I'm just natural curious about things I see and wondering if my logic on this is sound or not.

So I monitor my coolant temps religiously and I take note whenever temps deviate from the norm (which is pretty much never). These days I usually putter around at 191-193*, but today I noticed that at idle while waiting on the women folk in the store, I noticed I was sitting at 195* with the A/C off — which is a first.

The truck hadn't been driven hard just before parking, so it wasn't just cooling down from a spirited run. This was something new.

I proceeded to go down a mental checklist of possible causes — but none held up under scrutiny. My radiator is less than a year old, my coolant is the same age as the radiator, my coolant level is normal because I check it about every three days and it was fine yesterday. There are no leaks that I can detect, I just replaced all drive belts about a month ago with OEM belts and I tensioned them properly and my fan clutch is about year old and is also OEM and seems to engage/disengage appropriately.

There are no codes, no pending codes and no abnormal behavior of any sort.

So, I'm wondering if I'm not seeing the beginning of the death of my water pump? My truck idles right at 700rpm and the coolant was 195*, if I increased my engine speed to 1000rpm, the coolant immediately goes back to its normal 191*. When I decrease engine speed, it returns to 195*.

Ordinarily my first thought would be the fan clutch, but since that is new and unlikely to be failing, the only other thing I can think of is the water pump is starting to fail at idle speeds and needs a little extra RPM to maintain the normal 191*.

Am I smoking too much green stuff and just imagining things, or is the the canary in the water pump coal mine letting me know that shits on the decline?

Thoughts?

Pics cause why not...

​

 

[JayRolla]

Really? 195* and your concerned.

 

[Roamed YT]

I think you might just be hyper-aware... pull the timing cover and check to see if it's weeping. Other than that I wouldn't let 2 degrees get to you. In metric, it's not even one degree!

 

[JayRolla]

I think you might just be hyper-aware... pull the timing cover and check to see if it's weeping. Other than that I wouldn't let 2 degrees get to you. In metric, it's not even one degree!

That's ridiculous. It's 2*

 

[JZiggy]

Creeper,

The water pump does its job of pushing a certain amount of coolant all the time, even as it starts to wear out. What really wears out is the bearing or the seals (which then kills the bearing). Even with a bad bearing the impeller should be working just the same.

I suppose if there was a detectable wobble in the water pump shaft that could contribute. But I think its more likely, if this temp deviation is really real, that its the thermostat changing a bit. Maybe it stuck in one position a teensy bit.

Was your heater on at all? Sometimes the heater core can dump a little extra cold coolant onto the thermostat making it close a bit. This was at least true in the 22RE -- Toyota made an updated dual-plunger style to eliminate the "runs hotter with the heat on" effect.

 

[StreetCreeper]

Hmm, maybe the first paragraph is invisible....

I'm not concerned in the least bit. I know my truck and I know what my truck runs at coolant-wise. So I notice even the slightest deviations from normal and make note of them. That's all this is — I'm not concerned and I'm not paranoid, I'm simply curious if my water pump might be on its way out and this is the first indication of such.

 

[StreetCreeper]

Creeper,

The water pump does its job of pushing a certain amount of coolant all the time, even as it starts to wear out. What really wears out is the bearing or the seals (which then kills the bearing). Even with a bad bearing the impeller should be working just the same.

I suppose if there was a detectable wobble in the water pump shaft that could contribute. But I think its more likely, if this temp deviation is really real, that its the thermostat changing a bit. Maybe it stuck in one position a teensy bit.

Was your heater on at all? Sometimes the heater core can dump a little extra cold coolant onto the thermostat making it close a bit. This was at least true in the 22RE -- Toyota made an updated dual-plunger style to eliminate the "runs hotter with the heat on" effect.

I see your logic there regarding the pump itself. As to the T-stat, I replaced it about a year ago with OEM, so while possible to be sticking but probably not likely.

No heater, in fact the only other thing that was abnormal for me was not having the a/c on since it has been cool here today. Perhaps the decreased engine speed without the a/c on could be the source of this.

 

[giovannie23]

mine also was 191 to 193 never went higher
in till about2 months ago it crept to 195 and does every now and then
But figure it's nothing to worry about I been thru lots of hard driving and haven't had a issue it's just normal now

 

[ltsr]

Hmm, maybe the first paragraph is invisible....

I'm not concerned in the least bit. I know my truck and I know what my truck runs at coolant-wise. So I notice even the slightest deviations from normal and make note of them. That's all this is — I'm not concerned and I'm not paranoid, I'm simply curious if my water pump might be on its way out and this is the first indication of such.

It's your attention to small details that your truck has that many miles. It's not by accident. I'm kind of the same way as you are. When did you last change your fan clutch?

 

[St Runner]

Yes you are smoking too much green stuff but your car is not. If it goes to the usual temp when you give it a little gas I suspect the problem is airflow. Did you replace your fan clutch with a new or used one? Adjust the fan belts after a week of breaking them in? Radiator and ac clean with no restrictions? But then maybe you can blow a little of that green stuff through the radiator and see if it will chill. I am not responsible for any other side effects

 

[catrains]

your brain is not working properly on why the engine temp is not in the normal range as it usually is. #1 T stat regulates the temp . at idle the temp should be very close to the T stat spec.

now if you had ac on and it was a 100F air day going up grades and the temp spiked then that would be coolant leaks/pressure cap/fan belt slip/ clutch/radiator crap etc.

the T stat may have stuck intermittently if it continues then replace it.
I have purchased several NEW T stats that were defective .

I NOW have the opposite problem you have @idle the temp drops down to 170F.. when driving under load goes back up to 190F..

I will have to replace this before winter or NO heat...

 

[Mark_BC]

I'm no expert in fact I know hardly anything about this at all. But I did stay at a Holiday Inn Express last night. My guess is a combination of the car not moving so less airflow over radiator and a slightly sticky thermostat that has a bit of a delayed opening (called "hysteresis", when something opens / closes at a different value depending if it is going up or down) when there isn't much water pressure from the water pump spinning at 700 rpm or whatever the equivalent rpm would be for the water pump. When your rpm's go up the pump has more oomph and the T stat flips.

 

[4Reak Show]

Alright sure why not....

Sooo the digital numerical temperature value you're seeing is a calculated one. The truck's ECM interprets a value, and then your scangauge interprets that value and spits out a number in the form of degrees.

That means there's a set ranged value of inputs corresponding to every CALCULATED degree number it displays. This all comes from the temp sensor for the ECM. Likely voltage or resistance value is measured and changing as the sensor heats up.

So let's say the range to display calculated temp of "193 degrees F" is 1000-1500 ohms or whatever. And "195 degrees F" displayed is for the sensor range of 1501-1750 ohms. What happens when it dances around between 1500/1501 ohms? The ECM will be dancing as well.

So what I'm saying is it only takes one fraction of a unit to give you the results you're seeing. Idling generally makes the cooling system work pretty hard. (Low coolant flow from low RPMs, low air flow, poor engine room circulation etc) Even AC on kicks up the idle a hair and helps to pump more juice.

But I might not know what I'm talking about either.

 

[davidch]

Just thinking out loud here: could a small change - a very small change , to be sure - in the engine's operating temperature be due to oil refineries switching to a "summer blend"? Or perhaps some other modification to what's in the fuel?

What is the Difference between Summer- and Winter-Blend Gasoline? | AAA NewsRoom

From that article:

The US Environmental Protection Agency (EPA) says conventional summer-blend gasoline contains 1.7 percent more energy than winter-blend gas, which is one reason why gas mileage is slightly better in the summer. ​

 

[LittleCaesar]

I have to ask if you have made that trip to Lowes yet?

You check the coolant level every three days? I wouldn't worry one bit.

It does sound like you may need a new water pump but I'd ask first how well you burped the cooling system after the radiator replacement last year. New cap as well?

Tell the ladies next time to hurry it up....

 

[19963.4lsr5]

Raising the rpm and the temp drops to 191 and then back up to 195 to me means the T-Stat is wide open. So the temp regulation is now water flow through the rad and airflow through the rad. It's one or the other or a combination of both.


Sent from my iPhone using Tapatalk

 

[StreetCreeper]

It's your attention to small details that your truck has that many miles. It's not by accident. I'm kind of the same way as you are. When did you last change your fan clutch?

In all fairness I've only had the vehicle since 350,000 miles when it was left for dead and was about to be towed away for the junk yard. I snatched the ol'girl right out from the greasy claws of death and have been rebuilding her ever since.

So yeah, I monitor everything and take note when things change. I fully believe that a lot more 4runners would still be on the road if people noticed the little things and addressed them before they turn into big things – like blown head gaskets and fried trannies.

To me, coolant temps are a decent marker for current engine health. That's not to say that if your coolant temps are fine then so is the rest of the engine, but if coolant temps rise and there are no obvious reasons for it – then something else has changed and it may be the first symptom of a larger problem. In a similar vain, you notice a tiny bump on your forearm one day that seems unusual and it doesn't go away, you could easily rationalize it as just a bump (and maybe it is) , but maybe it's not either. No harm comes from taking note of it and mentioning it to your Dr – it might just save your life.

Yes you are smoking too much green stuff but your car is not. If it goes to the usual temp when you give it a little gas I suspect the problem is airflow. Did you replace your fan clutch with a new or used one? Adjust the fan belts after a week of breaking them in? Radiator and ac clean with no restrictions? But then maybe you can blow a little of that green stuff through the radiator and see if it will chill. I am not responsible for any other side effects

My brain thinks better the more pot I smoke, but sometimes I can become so laser-focused that I lose sight of the bigger picture – so I sometimes question my own logic.

The fan clutched I replaced with a new Asin clutch last year when I overhauled my cooling system. I replaced the t-stat, radiator, upper/lower/overflow hoses, fan clutch, radiator cap and flushed/cleaned the coolant lines for three days with distilled water and flush chems before adding fresh coolant. Everything was OEM except for the radiator and coolant.

I'm no expert in fact I know hardly anything about this at all. But I did stay at a Holiday Inn Express last night. My guess is a combination of the car not moving so less airflow over radiator and a slightly sticky thermostat that has a bit of a delayed opening (called "hysteresis", when something opens / closes at a different value depending if it is going up or down) when there isn't much water pressure from the water pump spinning at 700 rpm or whatever the equivalent rpm would be for the water pump. When your rpm's go up the pump has more oomph and the T stat flips.

All theories are viable at this point!

Alright sure why not....

Sooo the digital numerical temperature value you're seeing is a calculated one. The truck's ECM interprets a value, and then your scangauge interprets that value and spits out a number in the form of degrees.

That means there's a set ranged value of inputs corresponding to every CALCULATED degree number it displays. This all comes from the temp sensor for the ECM. Likely voltage or resistance value is measured and changing as the sensor heats up.

So let's say the range to display calculated temp of "193 degrees F" is 1000-1500 ohms or whatever. And "195 degrees F" displayed is for the sensor range of 1501-1750 ohms. What happens when it dances around between 1500/1501 ohms? The ECM will be dancing as well.

So what I'm saying is it only takes one fraction of a unit to give you the results you're seeing. Idling generally makes the cooling system work pretty hard. (Low coolant flow from low RPMs, low air flow, poor engine room circulation etc) Even AC on kicks up the idle a hair and helps to pump more juice.

But I might not know what I'm talking about either.

This makes sense to me, my only thoughts are why now? Perhaps it was just truly random and a mere hiccup. Guess I'll just have to keep watching and see if it continues or not.

Just thinking out loud here: could a small change - a very small change , to be sure - in the engine's operating temperature be due to oil refineries switching to a "summer blend"? Or perhaps some other modification to what's in the fuel?

What is the Difference between Summer- and Winter-Blend Gasoline? | AAA NewsRoom

From that article:

The US Environmental Protection Agency (EPA) says conventional summer-blend gasoline contains 1.7 percent more energy than winter-blend gas, which is one reason why gas mileage is slightly better in the summer. ​

Anything is possible I suppose but it seems like if it were the fuel, it would be consistent – time will tell I suppose.

I have to ask if you have made that trip to Lowes yet?

You check the coolant level every three days? I wouldn't worry one bit.

It does sound like you may need a new water pump but I'd ask first how well you burped the cooling system after the radiator replacement last year. New cap as well?

Tell the ladies next time to hurry it up....

I don't want to tell them to hurry up or else they might ask me to go in with them and hold things like purses!

Which trip to Lowe's? For the tourqe wrench or is it something else I'm forgetting?

I burped the cooling system well and have had no issues whatsoever since I did it a year ago. I used Rhino Ramps so my truck was at a perfect incline to get any air out out of the system.

Radiator cap is OEM .9 bar and was replaced during the overhaul.

 

[St Runner]

What is the time lag when you raise the rpm to when the temp drops? The t-stat will have a bit of a delay so if it is quick its probably not the t-stat. Also as someone else pointed out the gauges are not graduated perfectly.My ultraguage will jump a degree or a degree and a half or maybe two. If you are on the high side of 91 it might not be making that big of a jump. Still think it is lower coolant flow and air flow at idle, not out of the ordinary

 

[LittleCaesar]

Yep, for the torque wrench. I know they were having a Memorial Day sale that included some wrenches and the like.

Personally I would roll one with Jimmi and not worry about it. If it jumped to 205, then maybe you have some merit to inquire further.

It's a satchel, not a purse.....

 

[StreetCreeper]

What is the time lag when you raise the rpm to when the temp drops? The t-stat will have a bit of a delay so if it is quick its probably not the t-stat. Also as someone else pointed out the gauges are not graduated perfectly.My ultraguage will jump a degree or a degree and a half or maybe two. If you are on the high side of 91 it might not be making that big of a jump. Still think it is lower coolant flow and air flow at idle, not out of the ordinary

From the time I increased engine speed to the time it dropped to 191° is about 10-15 seconds. The reverse was the same from the time I decreased engine speed to a return to 195°.

Yep, for the torque wrench. I know they were having a Memorial Day sale that included some wrenches and the like.

Personally I would roll one with Jimmi and not worry about it. If it jumped to 205, then maybe you have some merit to inquire further.

It's a satchel, not a purse.....

Yeah I need to pick that wrench up especially for the upcoming timing belt job. I'll check to see if they are running any specials on it

Me an Jimmi will have a pow-wow tonight and "herb-up" so we can think clearly on this issue imp:

Damn skippy it's a satchel!